AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
420 AM PST SUN FEB 17 2008
.SYNOPSIS...
THE MARINE LAYER AND ONSHORE FLOW WILL CAUSE COASTAL LOW CLOUDS AND
FOG IN THE NIGHTS AND MORNINGS. OTHERWISE...FAIR THROUGH MONDAY
UNDER WEAKENING HIGH PRESSURE. A SERIES OF UPPER LEVEL LOW PRESSURE
SYSTEMS WILL BRING MORE CLOUDS AND COOLING WITH PERIODIC CHANCES OF
PRECIPITATION FOR TUESDAY THROUGH NEXT WEEKEND.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM (TODAY THROUGH TUESDAY)...
SATELLITE IMAGERY SHOWS AN EXTENSIVE STRATUS FIELD OVER THE
CALIFORNIA COASTAL WATERS EXTENDING LOCALLY INLAND INTO PORTIONS OF
SOUTHWEST CALIFORNIA. ACARS SOUNDINGS SHOW ONLY A VERY WEAK MARINE
INVERSION AROUND 1500 FEET...HELPING TO EXPLAIN THE PATCHY COVERAGE
OVER LAND AREAS. THE STRATUS SHOULD FILL IN SOME OVER LAND AREAS
THROUGH SUNRISE WITH THE MARINE LAYER DEPTH SUFFICIENT FOR SOME
STRATUS TO EXTEND INLAND AS FAR AS THE LOWER COASTAL VALLEYS. WITH
HIGH PRESSURE OVER SOUTHERN CALIFORNIA SLOWLY WEAKENING OVER THE
NEXT 24 HOURS...STRATUS MAY EXTEND A LITTLE FARTHER INLAND BY MONDAY
MORNING. OTHERWISE...FAIR WITH TEMPERATURES A LITTLE ABOVE SEASONAL
AVERAGES THROUGH MONDAY. FOR MONDAY NIGHT AND TUESDAY...A WEAK UPPER
LOW...CURRENTLY A FEW HUNDRED MILES OFF THE CALIFORNIA COAST
CENTERED NEAR 33N/135W...WILL MOVE INLAND ACROSS SOUTHERN
CALIFORNIA. THIS WILL BRING ADDITIONAL DEEPENING OF THE MARINE LAYER
AND A SLIGHT CHANCE OF LIGHT PRECIPITATION ALONG AND WEST OF THE
MOUNTAINS AS SHOWN IN THE ECMWF QPF. THIS TROUGH OF WILL ALSO BRING
SOME COOLING AND GREATER CLOUD COVER FOR MOST AREAS.
&&
.LONG TERM (WEDNESDAY THROUGH SATURDAY)...
A STRONG PACIFIC JET WILL SAG SLOWLY SOUTHWARD ACROSS CALIFORNIA
DURING THE PERIOD INCREASING CHANCES FOR PRECIPITATION IN SOUTHWEST
CALIFORNIA WITH GREATER CHANCES FOR MORE SIGNIFICANT PRECIPITATION
LATER IN THE WEEK. TO THE EXTENT ONE WANTS TO TIME SHORTWAVES IN
SUCH A FAST FLOW PATTERN...WEAKLY FAVOR THE ECMWF WHICH BRINGS ONE
SOMEWHAT STRONGER SHORTWAVE THROUGH THURSDAY NIGHT AND FRIDAY AND
ANOTHER ON SUNDAY. IN GENERAL...THERE WILL BE COOLER TEMPERATURES
AND MORE CLOUDS DURING THIS PERIOD WITH GUSTY WINDS IN THE MOUNTAINS
AND DESERTS AT TIMES AND SOME CHANCE FOR MAINLY LIGHT PRECIPITATION
AT TIMES ALMOST ANY TIME DURING THIS PERIOD. THERE`S ALSO THE
POSSIBILITY OF ONE OR TWO PERIODS OF SOMEWHAT HEAVIER PRECIPITATION
DURING THIS PERIOD...BUT TIMING IS VERY DIFFICULT THIS FAR OUT WITH
A HIGH DECREE OF UNCERTAINTY IN THE FORECAST DETAILS.
&&
.AVIATION...
171100Z...STRATUS HAS CONTINUED TO FILL IN OFFSHORE DURING THE
OVERNIGHT AND MAY BE BETTER ORGANIZED OVER COASTAL ORANGE COUNTY
EARLY THIS MORN...POSSIBLY REACHING INTO THE INLAND EMPIRE AS FAR AS
KONT AS WELL. EXPECT SCATTERED TO BROKEN CEILINGS TO IMPACT COASTAL
SAN DIEGO CO. STRATUS BASES APPROX 1000-1600 FT MSL AND TOPS NEAR
FL020. THE STRATUS SHOULD SCATTER OUT BY 18Z. ALSO PATCHY FOG WILL
AFFECT INLAND VALLEYS EARLY THIS MORN WITH AREAS 3SM VISIBILITY AND
LOCAL DENSE FOG 1/2 MILE OR LESS MAINLY UNTIL 16Z. OTHERWISE VFR
CONDITIONS WILL PREVAIL TODAY. THEN THIS EVENING SOME AREAS OF
STRATUS SHOULD REFORM OVER COASTAL SECTIONS WITH BASES APPROX
1400 FT MSL.
&&
.MARINE...
ABOVE NORMAL LONG-PERIOD WEST NORTHWEST SWELL CONTINUES INTO TODAY
BUT WITH A GRADUAL DECREASING TREND DURING THE DAY. LOOKING AT
YESTERDAY/S SURF REPORTS AND LATEST BUOY/SWELL DATA EXPECT THE
HIGH SURF CONDITIONS TO SLOWLY SUBSIDE THRU THIS AFTN. WILL KEEP
SURF ADVISORY IN EFFECT TIL 2 PM PST.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...HIGH SURF ADVISORY UNTIL 2 PM PST THIS AFTERNOON FOR ORANGE
COUNTY COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS.
PZ...NONE.
&&
$$
PUBLIC...MARTIN
AVIATION/MARINE...LAVIS
NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
820 PM PST SAT FEB 16 2008
.SHORT TERM (TONIGHT-TUE)...LATEST AMDAR SOUNDINGS FROM KLAX
INDICATED A COUPLE WEAK INVERSIONS. ONE AT 1500 FT AND ANOTHER NEAR
4500 FT. CURRENT LAX-DAG SFC GRAD IS +4.5MB. THIS COMBO SHOULD ALLOW
LOW CLOUDS TO FORM AND PUSH INTO THE VALLEYS OVERNIGHT. CURRENT
SATELLITE IMAGERY SHOWS SEVERAL AREAS OF PATCHY LOW CLOUDS. ALTHOUGH
MOST INLAND AREAS REMAIN CLEAR THIS EVENING...THE IMMEDIATE COASTAL
AREAS OF LA/VTU/SBA COUNTIES HAVE BEEN UNDER LOW CLOUDS THROUGH MOST
OF THIS EVENING. LOW CLOUDS ARE ALREADY MOVING INLAND ACROSS THE
SANTA YNEZ VALLEY AS WELL AS THE EASTERN SAN GABRIEL VALLEY. EXPECT
MOST OF LA/VTU COUNTY VALLEYS TO BE MOSTLY CLOUDY OVERNIGHT AND
SUNDAY MORNING BEFORE BURNING OFF TO HAZY SUNSHINE. ALTHOUGH
THICKNESS LVLS RISE SLIGHTLY TOMORROW. THE COASTAL AREAS SHOULD SEE
TEMPS SIMILAR TO TODAY WITH A COUPLE DEGREES OF WARMING INLAND.
A WEAK UPPER LVL CLOSED LOW WILL MOVE CLOSE TO THE CENTRAL COAST BY
MONDAY. AT THE LOWER LEVELS...WRF SHOWS WEAK ONSHORE FLOW...WHICH I
FIND A BIT SURPRISING. TEMPS SHOULD BE A FEW DEGREES COOLER AND
EXPECT INCREASING CLOUDS ACROSS THE COASTAL AND INLAND
AREAS...ESPECIALLY N OF POINT CONCEPTION. THERE IS STILL A SLIGHT
CHANCE OF SHOWERS N OF POINT CONCEPTION...BUT NOT VERY CONFIDENT
THAT THIS WILL OCCUR. MOST OF THE MOISTURE STAYS OFFSHORE UNTIL TUE
EVENING THEN DOMINANT NW FLOW WILL BRING IN COOLER THAN NORMAL TEMPS
TO THE AREA. WITH NORTHWEST TO NORTH FLOW COMING DOWN THE SAN
JOAQUIN VALLEY...SOME CLOUDS COULD PILE UP ACROSS THE NRN SLOPES OF
SBA/VTU AND WESTERN LA COUNTY. THIS COULD BRING THE BEST CHANCE OF
SHOWERS TO THE NRN SLOPES MENTIONED...INCLUDING THE I-5 CORRIDOR. IF
A FEW SHOWERS DO DEVELOP ACROSS THIS AREA TUE AFTERNOON THROUGH
EARLY WED...SNOW LEVELS WILL BE ABOVE 5500 FT SO DRIVING CONDITIONS
SHOULD BE OK THROUGH THE GRAPEVINE.
...FROM PREVIOUS DISCUSSION...
.LONG TERM (WED-SAT)...COOL BUT DRY WEATHER EXPECTED WED. THEN THE
NEXT SYSTEM WILL START SPREADING CLOUDS INTO THE AREA WED NIGHT WITH
RAIN CHANCES DEVELOPING MAINLY ALONG THE CENTRAL COAST THU
AFTERNOON. LEFT IN LOW POPS EVERYWHERE THU AS TIMING ISSUES STILL
EXIST BETWEEN THE GFS AND ECMWF. THIS SYSTEM STILL APPEARS TO BE THE
STRONGEST THIS WEEK, WITH THE BEST CHANCE OF RAIN ACROSS THE AREA
THU NIGHT. AT THIS POINT IT LOOKS LIKE YOUR TYPICAL HALF INCH AT THE
COAST AND 1-2 INCH IN THE MTNS SORT OF STORM, BUT THAT COULD CHANGE
EITHER HIGHER OR LOWER. THE ECMWF IS SHARPER WITH THE TROF AND
GENERALLY HIGHER WITH RAINFALL TOTALS. CONDITIONS WILL DRY OUT
FRIDAY AND SATURDAY WITH TEMPS STILL ON THE COOL SIDE.
&&
.AVIATION...AT 0430Z...OR 830 PM PST...
WEAK INVERSION WILL ALLOW LOW CLOUDS TO FORM RANDOMLY ACROSS THE
COASTAL AND VALLEY LOCATIONS THIS EVENING THROUGH OVERNIGHT HOURS.
EXPECT CIGS MAINLY MVFR BUT LOCAL IFR CIGS WILL BE
POSSIBLE...ESPECIALLY N OF POINT CONCEPTION. LOW CLOUDS WILL PERSIST
SUNDAY MORNING...WITH BURNOFF BY LATE MORNING.
.KLAX...MVFR CIGS WILL INCREASE OVERNIGHT WITH LIGHT WINDS EXPECTED
OVERNIGHT. MVFR CIGS SHOULD BURN OFF BY MID MORNING HOURS. WITH WEAK
INVERSION IN PLACE...CONFIDENCE IS NOT HIGH WITH CURRENT TAF. NO
WIND ISSUES FOR SUNDAY.
.KBUR... MVFR TO LOCAL IFR CIGS SHOULD DEVELOP OVERNIGHT. LOW CLOUDS
WILL BURN OFF BY MID MORNING. WITH WEAK INVERSION IN PLACE...NOT
CONFIDENT WITH CURRENT TAF. NO WIND ISSUES THROUGH SUNDAY.
$$
.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXCWFLOX).
HIGH SURF ADVISORY (SEE LAXCFWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
&&
$$
PUBLIC...KAPLAN/WOFFORD
AVIATION...KAPLAN
WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
1018 AM EST SUN FEB 17 2008
.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OVER THE REGION TODAY AS A STRONG COLD
FRONT APPROACHES FROM THE WEST. THE COLD FRONT WILL ADVANCE ACROSS
THE AREA LATE TONIGHT AND MONDAY MORNING. HIGH PRESSURE WILL THEN BUILD
IN BEHIND THE FRONT...AND PERSIST THROUGH THE MIDDLE OF THE WEEK.
ANOTHER STORM SYSTEM COULD IMPACT THE REGION BY LATE WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LOW CLOUDS AND FOG HAVE RAPIDLY BURNING THIS MORNING ALONG AND
S OF A METTER-SPRINGFIELD-BEAUFORT LINE. N OF THERE WHERE A WEAK
WEDGE IS IN PLACE...LOW CLOUDS ARE HOLDING TOUGH...PARTICULARLY
IN THE CHARLESTON AREA. RUC AND NAM-12 FCST SOUNDINGS INDICATE
MOSTLY SUNNY SKIES WILL CONTINUE ACROSS MAINLY THE SRN HALF OF THE
FCST AREA FOR THE NEXT SEVERAL HRS BEFORE CLOUDS ACROSS SW GA AND
CLOSED CELL STRATOCUMULUS OVER THE ATLC MOVE THROUGH. SUSPECT
THESE CLOUDS WILL TEND TO SCATTERED OUT AS MIXING HEIGHTS INCR BUT
ENOUGH CLOUD COVER SHOULD BE IN PLACE TO JUSTIFY A PARTLY CLOUDY
FCST. TEMPS WILL BE QUITE WARM WITH SOUNDINGS SUPPORTING MID-UPR
70S WITH A FEW LWR 80S POSSIBLE ALONG THE ALTAMAHA RIVER. FARTHER
N IN THE WEDGE...TEMPS WILL BE A BIT COOLER /LWR-MID 70S/ WHERE
CLOUDS WILL LINGER THE LONGEST. ALL BETS ARE OFF OF COURSE IF THE
CLOUDS BREAK IN THE WEDGE SOONER THAN EXPECTED. THE COOLER SHELF
WATERS WILL KEEP COASTAL LOCATIONS IN THE UPR 50S TO LWR 60S.
PCPN CHANCES WILL REMAIN VERY LOW TODAY. THE RUC DOES HINT AT SOME
ISOLD SHOWER ACTIVITY DVLPG ACROSS THE CHARLESTON COUNTY COASTAL
WATERS WHICH MAY BRUSH THE COAST FROM SULLIVANS ISLAND N. WILL
MAINTAIN SLGT CHANCE POPS IN THIS AREA SINCE ITS ALREADY IN THE
FCST...ALTHOUGH WE REALLY DO NOT EXPECT MUCH. PCPN ASSOC WITH THE
COLD FRONT APRCHG FROM THE WILL GENERALLY REMAIN WELL TO THE W
TODAY. STILL EXPECT MOST OF THE RAIN WILL OCCUR TONIGHT AND MON
MRNG BUT A FEW SHOWERS COULD APRCH THE FAR WRN ZONES BY LATE
AFTN...THUS 15-20 PCNT POPS WILL BE MAINTAINED THERE. WE CONTINUE
TO EVALUATE THE OVERNIGHT SEVERE WEATHER THREAT.
FINALLY...WINDS COULD BECOME RATHER GUSTY AT TIMES THIS AFTN AS
MIXING HEIGHT INCR AND TAP INTO THE STRENGTHENING LLJ ALOFT. WINDS
COULD GUST AS HIGH AS 25 MPH...ESPECIALLY IN GA WHERE THE WARMER
TEMPS WILL BE FOUND.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
MODELS CONTINUE TO DELAY THE EASTWARD PROGRESSION OF THE ADVANCING
COLD FRONT...WITH MODEL CONSENSUS NOW SHOWING A FRONTAL PASSAGE LATE
TONIGHT AND MONDAY MORNING. A ROBUST LOW LEVEL JET...REACHING
UPWARDS OF 45-50 KT AT 925 MB TONIGHT INTO MONDAY...WILL ALLOW FOR
A GOOD TAP OF GULF/ATLANTIC MOISTURE TO OCCUR WITH PRECIPITABLE WATER
VALUES RISING OVER 1.5 INCHES. THIS...IN ADDITION TO STRONG
FORCING...WILL RESULT IN CATEGORICAL SHOWERS AT SOME POINT EITHER
LATE TONIGHT OR MONDAY MORNING AHEAD OF THE APPROACHING COLD
FRONT.
SURFACE BASED INSTABILITY WILL BE LIMITED OVER THE AREA...BUT
THUNDERSTORMS STILL APPEAR POSSIBLE AHEAD OF THE FRONT GIVEN
STRONG FORCING...ABUNDANT MOISTURE AND DECENT MID LEVEL LAPSE
RATES. THE STORM PREDICTION CENTER STILL DEPICTS A SLIGHT CHANCE
OF SEVERE THUNDERSTORMS ACROSS THE AREA...AND THIS SEEMS PRUDENT
GIVEN THE IMPRESSIVE LOW LEVEL WIND FIELD THAT WILL BE IN PLACE.
THE GREATEST SEVERE WEATHER THREAT WILL BE DAMAGING WIND
GUSTS...ALTHOUGH AN ISOLATED TORNADO CANNOT BE RULED OUT.
DRIER CONDITIONS WILL BEGIN TO SPREAD INTO THE AREA FROM THE WEST
FOLLOWING THE DEPARTURE OF THE COLD FRONT MONDAY AFTERNOON.
TEMPERATURES WILL BE WELL ABOVE NORMAL TONIGHT DUE TO THE STRONG
SOUTHERLY FLOW AND ABUNDANT CLOUD COVER...WITH LOWS GENERALLY IN
THE LOWER 60S ACROSS THE AREA. HIGHS MONDAY WILL BE DEPENDANT ON
THE EXACT TIMING OF THE FRONT...BUT EXPECT MID 60S WELL INLAND AND
AROUND 70 CLOSER TO THE COAST. TEMPERATURES MAY BEGIN TO FALL
DURING THE MID-LATE AFTERNOON AS STRONG COLD AIR ADVECTION DEVELOPS.
BREEZY CONDITIONS WILL REMAIN IN PLACE SUNDAY NIGHT AND MONDAY...WITH
GUSTS UP TO 30 MPH POSSIBLE AT TIMES.
LAKE WINDS...A LAKE WIND ADVISORY HAS BEEN ISSUED FOR LAKE
MOULTRIE BEGINNING LATE THIS EVENING AND CONTINUING THROUGH
MONDAY. WHILE MIXING OVER THE OPEN LAKE WATERS WILL NOT BE
FAVORABLE IN THE WARM AIR ADVECTION PATTERN AHEAD OF THE
FRONT...IT IS HARD TO IGNORE THE 50 KT LOW LEVEL JET THAT
DEVELOPS. THE STRONGEST WINDS SHOULD OCCUR CLOSER TO THE LAKE
SHORE DUE TO BETTER MIXING...WHERE SUSTAINED WIND SPEEDS SHOULD
REACH UP AROUND 20 KT WITH THE POTENTIAL FOR HIGHER GUSTS.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
COOLER AND DRIER HIGH PRESSURE WILL BUILD INTO THE AREA MON NIGHT
BEHIND A COLD FRONT. TEMPS WILL RETURN TO SLIGHTLY BELOW NORMAL TO
NEAR NORMAL LEVELS THROUGH WED NIGHT BEFORE GETTING BACK TO ABOVE
NORMAL THU. TUE WILL LIKELY BE THE COOLEST DAY WITH DECENT COLD
AIR ADVECTION KEEPING HIGHS IN THE MID 50S...AND POSSIBLY EVEN
COOLER. TUE NIGHT WILL BE THE COLDEST NIGHT AS DECENT RADIATIONAL
COOLING CONDS SET UP WITH HIGH PRES SLIDING OVER THE AREA. MOST
PLACES AWAY FROM THE COAST WILL BE NEAR TO BELOW FREEZING.
FORECAST UNCERTAINTY INCREASES BEGINNING THU AS THE MODELS ARE
DISAGREEING ON THE NEXT SYSTEM APPROACHING FROM THE W. WILL MAINTAIN
20/30 POPS STARTING THU NIGHT AND CONTINUING THROUGH THE END OF THE
WEEK AS AT LEAST ONE WAVE OF LOW PRESSURE WILL AFFECT THE REGION.
LAKE WINDS...WILL LIKELY SEE ADVISORY CONDS INTO TUE OVER LAKE
MOULTRIE AS STRONG COLD AIR ADVECTION KICKS IN BEHIND A COLD FRONT
ALLOWING FOR AT LEAST GUSTS TO 20 KT.
&&
.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
A PERSISTENT ONSHORE FLOW IS RESPONSIBLE FOR MOISTENING THE LOW
LEVELS OF THE ATMOSPHERE EARLY THIS MORNING...WITH BOTH TERMINALS
REPORTING LIFR CEILINGS AS OF 12Z. IN ADDITION...PATCHY FOG HAS
DEVELOPED...REDUCING VISIBILITIES TO MVFR LEVELS AT KCHS AND LIFR
LEVELS AT KSAV. THERE IS CERTAINLY THE POTENTIAL FOR VISIBILITIES
TO LOWER FURTHER AT KCHS THROUGH ABOUT 14Z.
CONDITIONS WILL BEGIN TO IMPROVE AT BOTH TERMINALS AFTER
14-15Z...ALTHOUGH MVFR/LOW VFR CEILINGS ARE POSSIBLE THROUGH ABOUT
21Z. MVFR OR LOWER CONDITIONS ARE POSSIBLE AFTER ABOUT 09Z AS
SHOWERS AND PERHAPS SOME THUNDERSTORMS DEVELOP AHEAD OF AN
APPROACHING COLD FRONT.
WINDS WILL VEER TO THE SOUTHEAST AND EVENTUALLY SOUTH THIS
AFTERNOON AND EVENING DUE TO A STRENGTHENING LOW LEVEL JET AHEAD
OF THE APPROACHING COLD FRONT. GUSTS COULD REACH 20-25 KT DURING
MUCH OF THIS TIME PERIOD...ALTHOUGH MAY DIMINISH SOME LATE TONIGHT
WITH LESS FAVORABLE MIXING PROFILES. DESPITE THESE STRONG AND
GUSTY WINDS AT THE SURFACE...LOW LEVEL WIND SHEAR HAS BEEN ADDED
AT BOTH TERMINALS AFTER 02Z AS WINDS AT THE 2K FT LEVEL INCREASE
UP TO 50 KT OVER KCHS AND 40 KT OVER KSAV. HOWEVER...THIS SHOULD
BE A GRADUAL/STEADY INCREASE WITH HEIGHT...LESSENING THE OVERALL
IMPACT ON AIRCRAFT.
EXTENDED AVIATION OUTLOOK...EXPECT MVFR OR LOWER CONDITIONS MON
MORNING THROUGH EARLY AFTERNOON IN SHOWERS/THUNDERSTORMS. VFR
CONDITIONS RETURN LATE MON THROUGH THU. MAY ALSO SEE LOW LEVEL
WIND SHEAR MON NIGHT/EARLY TUE AS STRONG WINDS CONTINUE OFF THE
SURFACE.
&&
.MARINE...
NO CHANGES WILL BE MADE THE CURRENT STARTING TIMES FOR THE VARIOUS
SMALL CRAFT ADVISORIES ACROSS THE MARINE AREA. A GALE WATCH HWVR
WILL BE ISSUED FOR THE GA OFFSHORE WATERS FROM 06Z-15Z MON...MAINLY
FOR THE WATERS 40-60 NM...AS BOUNDARY LAYER WINDS ARE FCST OFF THE
17/12Z NAM TO INCR TO 35 KT IN THIS AREA. HIGH RESOLUTION SEA
SURFACE ANALYSIS FROM RUTGERS UNIVERSITY INDICATE 70+ DEG WATER
TEMPS CURRENTLY EXTEND FROM 45 NM E OF THE ALTAMAHA SOUND ENTRANCE
TO NEAR THE R8 TOWER. SUSPECT ENOUGH MIXING WILL OCCUR IN THIS
AREA TO PRODUCE FREQUENT GUSTS TO 35 KT GALES. WITH THE EVENT IS
STILL IN THE SECOND PERIOD...A GALE WATCH WILL BE ISSUED PER COORD
WITH JAX AND THE OPC. THE WATCH MAY BE UPGRADED TO A GALE WARNING
WITH THE AFTN FCST PKG.
&&
.FIRE WEATHER...
A STRONG COLD FRONT WILL MOVE THROUGH THE REGION MON BRINGING MUCH
DRIER AIR FOR TUE WITH MIN RH/S AROUND 20 PERCENT AWAY FROM THE COAST.
IT WILL ALSO BE BREEZY WITH SUSTAINED WINDS NEAR 20 MPH AND GUSTS 25
TO 30 MPH...ESPECIALLY ACROSS SERN SC. THUS...CRITICAL FIRE WX CONDS
ARE LIKELY...MAINLY ACROSS SERN SC...AND RED FLAG WARNINGS MAY
EVENTUALLY BE NEEDED.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY FROM 10 PM THIS EVENING TO 5 PM EST TUESDAY
FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 4 PM EST MONDAY
FOR AMZ352-354.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 10 PM EST
TUESDAY FOR AMZ350.
GALE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR AMZ374.
SMALL CRAFT ADVISORY UNTIL 1 AM EST MONDAY FOR AMZ374.
SMALL CRAFT ADVISORY UNTIL 10 PM EST TUESDAY FOR AMZ330.
&&
$$
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
730 AM EST SUN FEB 17 2008
.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OVER THE REGION TODAY AS A STRONG COLD
FRONT APPROACHES FROM THE WEST. THE COLD FRONT WILL ADVANCE ACROSS
THE AREA LATE TONIGHT AND MONDAY MORNING. HIGH PRESSURE WILL THEN BUILD
IN BEHIND THE FRONT...AND PERSIST THROUGH THE MIDDLE OF THE WEEK.
ANOTHER STORM SYSTEM COULD IMPACT THE REGION BY LATE WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE AT THE SURFACE WILL SHIFT AWAY FROM THE NEW ENGLAND
COAST TODAY...ALLOWING A RETURN FLOW TO BECOME WELL ESTABLISHED
ACROSS THE REGION. MEANWHILE...WEAK RIDGING WILL PERSIST ALOFT AND
A STRENGTHENING LOW LEVEL JET WILL ALLOW FOR STRONG ADVECTION OF
WARM AND MOIST AIR TO TAKE PLACE.
AN ONSHORE FLOW WILL KEEP THE LOW LEVELS OF THE ATMOSPHERE RATHER
MOIST...RESULTING IN A GOOD DEAL OF CLOUD COVER THIS MORNING. THERE
IS THE POTENTIAL FOR SOME PATCHY FOG AND DRIZZLE AS WELL THIS
MORNING. THERE COULD BE SOME THINNING OF THIS CLOUD COVER IN THE
AFTERNOON...BUT HIGH LEVEL CLOUDS SHOULD BE ON THE INCREASE BY
THEN...GENERALLY KEEPING SKIES MOSTLY CLOUDY.
DESPITE THE CLOUD COVER...TEMPERATURES SHOULD WARM NICELY INTO THE
MID TO PERHAPS UPPER 70S ACROSS THE AREA THIS AFTERNOON. THE
ONSHORE FLOW WILL MAKE FOR A TIGHT GRADIENT IN TEMPERATURES ALONG
THE IMMEDIATE COAST...WHERE THE COOL ATLANTIC SHELF WATERS SHOULD
KEEP TEMPERATURES FROM RISING MUCH ABOVE 60 DEGREES.
BREEZY CONDITIONS ARE EXPECTED TO DEVELOP THIS AFTERNOON GIVEN THE
UNSEASONABLY WARM TEMPERATURES AND STRENGTHENING LOW LEVEL
JET...ESPECIALLY IF ANY BREAKS OCCUR IN THE CLOUD COVER. THERE IS
THE POTENTIAL FOR GUSTS TO REACH INTO THE 25 TO 30 MPH RANGE.
WITH THE FRONT STILL A GOOD DISTANCE AWAY...MODELS ARE IN FAIRLY
GOOD AGREEMENT WITH KEEPING THE BULK OF THE PRECIPITATION WEST OF THE
AREA. WHILE MOST OF THE FORECAST AREA SHOULD REMAIN DRY THROUGH
THIS AFTERNOON...WILL INDICATE A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS ACROSS EXTREME INLAND SOUTHEAST GEORGIA LATE IN THE
AFTERNOON. ALSO...GIVEN THE MOIST SOUTHERLY FLOW AND FAVORABLE
TRAJECTORIES...THERE APPEARS TO BE THE POTENTIAL FOR A BAND OF
ISOLATED CONVECTION TO DEVELOP OVER THE COASTAL WATERS AND AFFECT
PORTIONS OF THE ADJACENT SOUTH CAROLINA COAST LATE IN THE DAY.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
MODELS CONTINUE TO DELAY THE EASTWARD PROGRESSION OF THE ADVANCING
COLD FRONT...WITH MODEL CONSENSUS NOW SHOWING A FRONTAL PASSAGE LATE
TONIGHT AND MONDAY MORNING. A ROBUST LOW LEVEL JET...REACHING
UPWARDS OF 45-50 KT AT 925 MB TONIGHT INTO MONDAY...WILL ALLOW FOR
A GOOD TAP OF GULF/ATLANTIC MOISTURE TO OCCUR WITH PRECIPITABLE WATER
VALUES RISING OVER 1.5 INCHES. THIS...IN ADDITION TO STRONG
FORCING...WILL RESULT IN CATEGORICAL SHOWERS AT SOME POINT EITHER
LATE TONIGHT OR MONDAY MORNING AHEAD OF THE APPROACHING COLD
FRONT.
SURFACE BASED INSTABILITY WILL BE LIMITED OVER THE AREA...BUT
THUNDERSTORMS STILL APPEAR POSSIBLE AHEAD OF THE FRONT GIVEN
STRONG FORCING...ABUNDANT MOISTURE AND DECENT MID LEVEL LAPSE
RATES. THE STORM PREDICTION CENTER STILL DEPICTS A SLIGHT CHANCE
OF SEVERE THUNDERSTORMS ACROSS THE AREA...AND THIS SEEMS PRUDENT
GIVEN THE IMPRESSIVE LOW LEVEL WIND FIELD THAT WILL BE IN PLACE.
THE GREATEST SEVERE WEATHER THREAT WILL BE DAMAGING WIND
GUSTS...ALTHOUGH AN ISOLATED TORNADO CANNOT BE RULED OUT.
DRIER CONDITIONS WILL BEGIN TO SPREAD INTO THE AREA FROM THE WEST
FOLLOWING THE DEPARTURE OF THE COLD FRONT MONDAY AFTERNOON.
TEMPERATURES WILL BE WELL ABOVE NORMAL TONIGHT DUE TO THE STRONG
SOUTHERLY FLOW AND ABUNDANT CLOUD COVER...WITH LOWS GENERALLY IN
THE LOWER 60S ACROSS THE AREA. HIGHS MONDAY WILL BE DEPENDANT ON
THE EXACT TIMING OF THE FRONT...BUT EXPECT MID 60S WELL INLAND AND
AROUND 70 CLOSER TO THE COAST. TEMPERATURES MAY BEGIN TO FALL
DURING THE MID-LATE AFTERNOON AS STRONG COLD AIR ADVECTION DEVELOPS.
BREEZY CONDITIONS WILL REMAIN IN PLACE SUNDAY NIGHT AND MONDAY...WITH
GUSTS UP TO 30 MPH POSSIBLE AT TIMES.
LAKE WINDS...
A LAKE WIND ADVISORY HAS BEEN ISSUED FOR LAKE MOULTRIE BEGINNING
LATE THIS EVENING AND CONTINUING THROUGH MONDAY. WHILE MIXING OVER
THE OPEN LAKE WATERS WILL NOT BE FAVORABLE IN THE WARM AIR
ADVECTION PATTERN AHEAD OF THE FRONT...IT IS HARD TO IGNORE THE 50
KT LOW LEVEL JET THAT DEVELOPS. THE STRONGEST WINDS SHOULD OCCUR
CLOSER TO THE LAKE SHORE DUE TO BETTER MIXING...WHERE SUSTAINED
WIND SPEEDS SHOULD REACH UP AROUND 20 KT WITH THE POTENTIAL FOR
HIGHER GUSTS.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
COOLER AND DRIER HIGH
PRESSURE WILL BUILD INTO THE AREA MON NIGHT BEHIND A COLD FRONT.
TEMPS WILL RETURN TO SLIGHTLY BELOW NORMAL TO NEAR NORMAL LEVELS
THROUGH WED NIGHT BEFORE GETTING BACK TO ABOVE NORMAL THU. TUE WILL
LIKELY BE THE COOLEST DAY WITH DECENT COLD AIR ADVECTION KEEPING
HIGHS IN THE MID 50S...AND POSSIBLY EVEN COOLER. TUE NIGHT WILL BE
THE COLDEST NIGHT AS DECENT RADIATIONAL COOLING CONDS SET UP WITH
HIGH PRES SLIDING OVER THE AREA. MOST PLACES AWAY FROM THE COAST
WILL BE NEAR TO BELOW FREEZING.
FORECAST UNCERTAINTY INCREASES BEGINNING THU AS THE MODELS ARE
DISAGREEING ON THE NEXT SYSTEM APPROACHING FROM THE W. WILL MAINTAIN
20/30 POPS STARTING THU NIGHT AND CONTINUING THROUGH THE END OF THE
WEEK AS AT LEAST ONE WAVE OF LOW PRESSURE WILL AFFECT THE REGION.
LAKE WINDS...WILL LIKELY SEE ADVISORY CONDS INTO TUE OVER LAKE
MOULTRIE AS STRONG COLD AIR ADVECTION KICKS IN BEHIND A COLD FRONT
ALLOWING FOR AT LEAST GUSTS TO 20 KT.
&&
.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
A PERSISTENT ONSHORE FLOW IS RESPONSIBLE FOR MOISTENING THE LOW
LEVELS OF THE ATMOSPHERE EARLY THIS MORNING...WITH BOTH TERMINALS
REPORTING LIFR CEILINGS AS OF 12Z. IN ADDITION...PATCHY FOG HAS
DEVELOPED...REDUCING VISIBILITIES TO MVFR LEVELS AT KCHS AND LIFR
LEVELS AT KSAV. THERE IS CERTAINLY THE POTENTIAL FOR VISIBILITIES
TO LOWER FURTHER AT KCHS THROUGH ABOUT 14Z.
CONDITIONS WILL BEGIN TO IMPROVE AT BOTH TERMINALS AFTER
14-15Z...ALTHOUGH MVFR/LOW VFR CEILINGS ARE POSSIBLE THROUGH ABOUT
21Z. MVFR OR LOWER CONDITIONS ARE POSSIBLE AFTER ABOUT 09Z AS
SHOWERS AND PERHAPS SOME THUNDERSTORMS DEVELOP AHEAD OF AN
APPROACHING COLD FRONT.
WINDS WILL VEER TO THE SOUTHEAST AND EVENTUALLY SOUTH THIS
AFTERNOON AND EVENING DUE TO A STRENGTHENING LOW LEVEL JET AHEAD
OF THE APPROACHING COLD FRONT. GUSTS COULD REACH 20-25 KT DURING
MUCH OF THIS TIME PERIOD...ALTHOUGH MAY DIMINISH SOME LATE TONIGHT
WITH LESS FAVORABLE MIXING PROFILES. DESPITE THESE STRONG AND
GUSTY WINDS AT THE SURFACE...LOW LEVEL WIND SHEAR HAS BEEN ADDED
AT BOTH TERMINALS AFTER 02Z AS WINDS AT THE 2K FT LEVEL INCREASE
UP TO 50 KT OVER KCHS AND 40 KT OVER KSAV. HOWEVER...THIS SHOULD
BE A GRADUAL/STEADY INCREASE WITH HEIGHT...LESSENING THE OVERALL
IMPACT ON AIRCRAFT.
EXTENDED AVIATION OUTLOOK...EXPECT MVFR OR LOWER CONDITIONS MON
MORNING THROUGH EARLY AFTERNOON IN SHOWERS/THUNDERSTORMS. VFR
CONDITIONS RETURN LATE MON THROUGH THU. MAY ALSO SEE LOW LEVEL
WIND SHEAR MON NIGHT/EARLY TUE AS STRONG WINDS CONTINUE OFF THE
SURFACE.
&&
.MARINE...
A RETURN FLOW WILL BECOME ESTABLISHED ACROSS THE COASTAL WATERS
TODAY AS HIGH PRESSURE SHIFTS FARTHER FROM THE NEW ENGLAND COAST.
A STRENGTHENING LOW LEVEL JET AHEAD OF AN APPROACHING COLD FRONT
WILL ALLOW FOR STEADILY INCREASING WINDS AT THE SURFACE THROUGH
THIS EVENING. A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR CHARLESTON
HARBOR...AND SMALL CRAFT ADVISORIES WILL TAKE EFFECT BEGINNING
LATE THIS MORNING FOR THE OUTER GEORGIA WATERS...THEN FOR THE NEAR
SHORE COASTAL WATERS LATE THIS AFTERNOON AND EARLY THIS EVENING.
WINDS AT 925 MB COULD REACH 45-50 KT LATE THIS EVENING THROUGH
MONDAY MORNING. HOWEVER...MIXING PROFILES WILL REMAIN POOR OVER THE
COASTAL WATERS DUE TO THE COOL SEA SURFACE TEMPERATURES. WINDS
COULD APPROACH GALE FORCE AT TIMES IN THE OUTER GEORGIA WATERS AND
NEAR SHORE WATERS NORTH OF EDISTO BEACH...BUT CONFIDENCE IS NOT
HIGH ENOUGH TO ISSUE EITHER A GALE WATCH/WARNING.
THE COLD FRONT WILL MOVE ACROSS THE COASTAL WATERS LATE MONDAY
MORNING...WITH STRONG COLD AIR ADVECTION DEVELOPING LATER IN THE
AFTERNOON. THIS WILL KEEP GUSTY CONDITIONS IN PLACE AND WILL
THEREFORE NEED TO KEEP ALL SMALL CRAFT ADVISORIES GOING.
MONDAY NIGHT THROUGH THURSDAY...A STRONG COLD FRONT WILL BE PUSHING
THROUGH AT THE START OF THE PERIOD. STRONG COLD AIR ADVECTION BEHIND
THE FRONT WILL YIELD SMALL CRAFT ADVISORY CONDS CONTINUING INTO TUE
FOR ALL OF THE WATERS EXCEPT POSSIBLY THE GA WATERS OUT TO 20 NM.
CONDS IMPROVE BY WED AS HIGH PRES MOVES INTO THE AREA...WHICH THEN
SHIFTS OFFSHORE THU. THE FCST BECOMES A BIT MORE UNCERTAIN BEGINNING
THU AS THE MODELS DIFFER ON THE TIMING OF THE NEXT SYSTEM
APPROACHING FROM THE W. FOR NOW WILL KEEP CONDS BELOW ADVISORY
CRITERIA.
&&
.FIRE WEATHER...
A STRONG COLD FRONT WILL MOVE THROUGH THE REGION MON BRINGING MUCH
DRIER AIR FOR TUE WITH MIN RH/S AROUND 20 PERCENT AWAY FROM THE COAST.
IT WILL ALSO BE BREEZY WITH SUSTAINED WINDS NEAR 20 MPH AND GUSTS 25
TO 30 MPH...ESPECIALLY ACROSS SERN SC. THUS...CRITICAL FIRE WX CONDS
ARE LIKELY...MAINLY ACROSS SERN SC...AND RED FLAG WARNINGS MAY
EVENTUALLY BE NEEDED.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY FROM 10 PM THIS EVENING TO 5 PM EST TUESDAY
FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 4 PM EST MONDAY
FOR AMZ352-354.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 10 PM EST
TUESDAY FOR AMZ350.
SMALL CRAFT ADVISORY UNTIL 10 PM EST TUESDAY FOR AMZ374.
SMALL CRAFT ADVISORY UNTIL 10 PM EST TUESDAY FOR AMZ330.
&&
$$
JAQ/RJB
AREA FORECAST DISCUSSION
NWS CHARLESTON SC
649 AM EST SUN FEB 17 2008
.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OVER THE REGION TODAY AS A STRONG COLD
FRONT APPROACHES FROM THE WEST. THE COLD FRONT WILL ADVANCE ACROSS
THE AREA LATE TONIGHT AND MONDAY MORNING. HIGH PRESSURE WILL THEN BUILD
IN BEHIND THE FRONT...AND PERSIST THROUGH THE MIDDLE OF THE WEEK.
ANOTHER STORM SYSTEM COULD IMPACT THE REGION BY LATE WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE AT THE SURFACE WILL SHIFT AWAY FROM THE NEW ENGLAND
COAST TODAY...ALLOWING A RETURN FLOW TO BECOME WELL ESTABLISHED
ACROSS THE REGION. MEANWHILE...WEAK RIDGING WILL PERSIST ALOFT AND
A STRENGTHENING LOW LEVEL JET WILL ALLOW FOR STRONG ADVECTION OF
WARM AND MOIST AIR TO TAKE PLACE.
AN ONSHORE FLOW WILL KEEP THE LOW LEVELS OF THE ATMOSPHERE RATHER
MOIST...RESULTING IN A GOOD DEAL OF CLOUD COVER THIS MORNING.
THERE COULD BE SOME THINNING OF THIS CLOUD COVER IN THE
AFTERNOON...BUT HIGH LEVEL CLOUDS SHOULD BE ON THE INCREASE BY
THEN...GENERALLY KEEPING SKIES MOSTLY CLOUDY.
DESPITE THE CLOUD COVER...TEMPERATURES SHOULD WARM NICELY INTO THE
MID TO PERHAPS UPPER 70S ACROSS THE AREA THIS AFTERNOON. THE
ONSHORE FLOW WILL MAKE FOR A TIGHT GRADIENT IN TEMPERATURES ALONG
THE IMMEDIATE COAST...WHERE THE COOL ATLANTIC SHELF WATERS SHOULD
KEEP TEMPERATURES FROM RISING MUCH ABOVE 60 DEGREES.
BREEZY CONDITIONS ARE EXPECTED TO DEVELOP THIS AFTERNOON GIVEN THE
UNSEASONABLY WARM TEMPERATURES AND STRENGTHENING LOW LEVEL
JET...ESPECIALLY IF ANY BREAKS OCCUR IN THE CLOUD COVER. THERE IS
THE POTENTIAL FOR GUSTS TO REACH INTO THE 25 TO 30 MPH RANGE.
WITH THE FRONT STILL A GOOD DISTANCE AWAY...MODELS ARE IN FAIRLY
GOOD AGREEMENT WITH KEEPING THE BULK OF THE PRECIPITATION WEST OF THE
AREA. WHILE MOST OF THE FORECAST AREA SHOULD REMAIN DRY THROUGH
THIS AFTERNOON...WILL INDICATE A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS ACROSS EXTREME INLAND SOUTHEAST GEORGIA LATE IN THE
AFTERNOON. ALSO...GIVEN THE MOIST SOUTHERLY FLOW AND FAVORABLE
TRAJECTORIES...THERE APPEARS TO BE THE POTENTIAL FOR A BAND OF
ISOLATED CONVECTION TO DEVELOP OVER THE COASTAL WATERS AND AFFECT
PORTIONS OF THE ADJACENT SOUTH CAROLINA COAST LATE IN THE DAY.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
MODELS CONTINUE TO DELAY THE EASTWARD PROGRESSION OF THE ADVANCING
COLD FRONT...WITH MODEL CONSENSUS NOW SHOWING A FRONTAL PASSAGE LATE
TONIGHT AND MONDAY MORNING. A ROBUST LOW LEVEL JET...REACHING
UPWARDS OF 45-50 KT AT 925 MB TONIGHT INTO MONDAY...WILL ALLOW FOR
A GOOD TAP OF GULF/ATLANTIC MOISTURE TO OCCUR WITH PRECIPITABLE WATER
VALUES RISING OVER 1.5 INCHES. THIS...IN ADDITION TO STRONG
FORCING...WILL RESULT IN CATEGORICAL SHOWERS AT SOME POINT EITHER
LATE TONIGHT OR MONDAY MORNING AHEAD OF THE APPROACHING COLD
FRONT.
SURFACE BASED INSTABILITY WILL BE LIMITED OVER THE AREA...BUT
THUNDERSTORMS STILL APPEAR POSSIBLE AHEAD OF THE FRONT GIVEN
STRONG FORCING...ABUNDANT MOISTURE AND DECENT MID LEVEL LAPSE
RATES. THE STORM PREDICTION CENTER STILL DEPICTS A SLIGHT CHANCE
OF SEVERE THUNDERSTORMS ACROSS THE AREA...AND THIS SEEMS PRUDENT
GIVEN THE IMPRESSIVE LOW LEVEL WIND FIELD THAT WILL BE IN PLACE.
THE GREATEST SEVERE WEATHER THREAT WILL BE DAMAGING WIND
GUSTS...ALTHOUGH AN ISOLATED TORNADO CANNOT BE RULED OUT.
DRIER CONDITIONS WILL BEGIN TO SPREAD INTO THE AREA FROM THE WEST
FOLLOWING THE DEPARTURE OF THE COLD FRONT MONDAY AFTERNOON.
TEMPERATURES WILL BE WELL ABOVE NORMAL TONIGHT DUE TO THE STRONG
SOUTHERLY FLOW AND ABUNDANT CLOUD COVER...WITH LOWS GENERALLY IN
THE LOWER 60S ACROSS THE AREA. HIGHS MONDAY WILL BE DEPENDANT ON
THE EXACT TIMING OF THE FRONT...BUT EXPECT MID 60S WELL INLAND AND
AROUND 70 CLOSER TO THE COAST. TEMPERATURES MAY BEGIN TO FALL
DURING THE MID-LATE AFTERNOON AS STRONG COLD AIR ADVECTION DEVELOPS.
BREEZY CONDITIONS WILL REMAIN IN PLACE SUNDAY NIGHT AND MONDAY...WITH
GUSTS UP TO 30 MPH POSSIBLE AT TIMES.
LAKE WINDS...
A LAKE WIND ADVISORY HAS BEEN ISSUED FOR LAKE MOULTRIE BEGINNING
LATE THIS EVENING AND CONTINUING THROUGH MONDAY. WHILE MIXING OVER
THE OPEN LAKE WATERS WILL NOT BE FAVORABLE IN THE WARM AIR
ADVECTION PATTERN AHEAD OF THE FRONT...IT IS HARD TO IGNORE THE 50
KT LOW LEVEL JET THAT DEVELOPS. THE STRONGEST WINDS SHOULD OCCUR
CLOSER TO THE LAKE SHORE DUE TO BETTER MIXING...WHERE SUSTAINED
WIND SPEEDS SHOULD REACH UP AROUND 20 KT WITH THE POTENTIAL FOR
HIGHER GUSTS.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
COOLER AND DRIER HIGH
PRESSURE WILL BUILD INTO THE AREA MON NIGHT BEHIND A COLD FRONT.
TEMPS WILL RETURN TO SLIGHTLY BELOW NORMAL TO NEAR NORMAL LEVELS
THROUGH WED NIGHT BEFORE GETTING BACK TO ABOVE NORMAL THU. TUE WILL
LIKELY BE THE COOLEST DAY WITH DECENT COLD AIR ADVECTION KEEPING
HIGHS IN THE MID 50S...AND POSSIBLY EVEN COOLER. TUE NIGHT WILL BE
THE COLDEST NIGHT AS DECENT RADIATIONAL COOLING CONDS SET UP WITH
HIGH PRES SLIDING OVER THE AREA. MOST PLACES AWAY FROM THE COAST
WILL BE NEAR TO BELOW FREEZING.
FORECAST UNCERTAINTY INCREASES BEGINNING THU AS THE MODELS ARE
DISAGREEING ON THE NEXT SYSTEM APPROACHING FROM THE W. WILL MAINTAIN
20/30 POPS STARTING THU NIGHT AND CONTINUING THROUGH THE END OF THE
WEEK AS AT LEAST ONE WAVE OF LOW PRESSURE WILL AFFECT THE REGION.
LAKE WINDS...WILL LIKELY SEE ADVISORY CONDS INTO TUE OVER LAKE
MOULTRIE AS STRONG COLD AIR ADVECTION KICKS IN BEHIND A COLD FRONT
ALLOWING FOR AT LEAST GUSTS TO 20 KT.
&&
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
A PERSISTENT ONSHORE FLOW IS RESPONSIBLE FOR MOISTENING THE LOW
LEVELS OF THE ATMOSPHERE EARLY THIS MORNING...WITH BOTH TERMINALS
REPORTING LIFR CEILINGS AS OF 12Z. IN ADDITION...PATCHY FOG HAS
DEVELOPED...REDUCING VISIBILITIES TO MVFR LEVELS AT KCHS AND LIFR
LEVELS AT KSAV. THERE IS CERTAINLY THE POTENTIAL FOR VISIBILITIES
TO LOWER FURTHER AT KCHS THROUGH ABOUT 14Z.
CONDITIONS WILL BEGIN TO IMPROVE AT BOTH TERMINALS AFTER
14-15Z...ALTHOUGH MVFR/LOW VFR CEILINGS ARE POSSIBLE THROUGH ABOUT
21Z. MVFR OR LOWER CONDITIONS ARE POSSIBLE AFTER ABOUT 09Z AS
SHOWERS AND PERHAPS SOME THUNDERSTORMS DEVELOP AHEAD OF AN
APPROACHING COLD FRONT.
WINDS WILL VEER TO THE SOUTHEAST AND EVENTUALLY SOUTH THIS
AFTERNOON AND EVENING DUE TO A STRENGTHENING LOW LEVEL JET AHEAD
OF THE APPROACHING COLD FRONT. GUSTS COULD REACH 20-25 KT DURING
MUCH OF THIS TIME PERIOD...ALTHOUGH MAY DIMINISH SOME LATE TONIGHT
WITH LESS FAVORABLE MIXING PROFILES. DESPITE THESE STRONG AND
GUSTY WINDS AT THE SURFACE...LOW LEVEL WIND SHEAR HAS BEEN ADDED
AT BOTH TERMINALS AFTER 02Z AS WINDS AT THE 2K FT LEVEL INCREASE
UP TO 50 KT OVER KCHS AND 40 KT OVER KSAV. HOWEVER...THIS SHOULD
BE A GRADUAL/STEADY INCREASE WITH HEIGHT...LESSENING THE OVERALL
IMPACT ON AIRCRAFT.
EXTENDED AVIATION OUTLOOK...EXPECT MVFR OR LOWER CONDITIONS MON
MORNING THROUGH EARLY AFTERNOON IN SHOWERS/THUNDERSTORMS. VFR
CONDITIONS RETURN LATE MON THROUGH THU. MAY ALSO SEE LOW LEVEL
WIND SHEAR MON NIGHT/EARLY TUE AS STRONG WINDS CONTINUE OFF THE
SURFACE.
&&
.MARINE...
A RETURN FLOW WILL BECOME ESTABLISHED ACROSS THE COASTAL WATERS
TODAY AS HIGH PRESSURE SHIFTS FARTHER FROM THE NEW ENGLAND COAST.
A STRENGTHENING LOW LEVEL JET AHEAD OF AN APPROACHING COLD FRONT
WILL ALLOW FOR STEADILY INCREASING WINDS AT THE SURFACE THROUGH
THIS EVENING. SMALL CRAFT ADVISORIES WILL TAKE EFFECT BEGINNING
LATE THIS MORNING FOR THE OUTER GEORGIA WATERS AND FOR THE
CHARLESTON HARBOR...THEN FOR THE NEAR SHORE COASTAL WATERS LATE
THIS AFTERNOON AND EARLY THIS EVENING.
WINDS AT 925 MB COULD REACH 45-50 KT LATE THIS EVENING THROUGH
MONDAY MORNING. HOWEVER...MIXING PROFILES WILL REMAIN POOR OVER THE
COASTAL WATERS DUE TO THE COOL SEA SURFACE TEMPERATURES. WINDS
COULD APPROACH GALE FORCE AT TIMES IN THE OUTER GEORGIA WATERS AND
NEAR SHORE WATERS NORTH OF EDISTO BEACH...BUT CONFIDENCE IS NOT
HIGH ENOUGH TO ISSUE EITHER A GALE WATCH/WARNING.
THE COLD FRONT WILL MOVE ACROSS THE COASTAL WATERS LATE MONDAY
MORNING...WITH STRONG COLD AIR ADVECTION DEVELOPING LATER IN THE
AFTERNOON. THIS WILL KEEP GUSTY CONDITIONS IN PLACE AND WILL
THEREFORE NEED TO KEEP ALL SMALL CRAFT ADVISORIES GOING.
MONDAY NIGHT THROUGH THURSDAY...A STRONG COLD FRONT WILL BE PUSHING
THROUGH AT THE START OF THE PERIOD. STRONG COLD AIR ADVECTION BEHIND
THE FRONT WILL YIELD SMALL CRAFT ADVISORY CONDS CONTINUING INTO TUE
FOR ALL OF THE WATERS EXCEPT POSSIBLY THE GA WATERS OUT TO 20 NM.
CONDS IMPROVE BY WED AS HIGH PRES MOVES INTO THE AREA...WHICH THEN
SHIFTS OFFSHORE THU. THE FCST BECOMES A BIT MORE UNCERTAIN BEGINNING
THU AS THE MODELS DIFFER ON THE TIMING OF THE NEXT SYSTEM
APPROACHING FROM THE W. FOR NOW WILL KEEP CONDS BELOW ADVISORY
CRITERIA.
&&
.FIRE WEATHER...
A STRONG COLD FRONT WILL MOVE THROUGH THE REGION MON BRINGING MUCH
DRIER AIR FOR TUE WITH MIN RH/S AROUND 20 PERCENT AWAY FROM THE COAST.
IT WILL ALSO BE BREEZY WITH SUSTAINED WINDS NEAR 20 MPH AND GUSTS 25
TO 30 MPH...ESPECIALLY ACROSS SERN SC. THUS...CRITICAL FIRE WX CONDS
ARE LIKELY...MAINLY ACROSS SERN SC...AND RED FLAG WARNINGS MAY
EVENTUALLY BE NEEDED.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY FROM 10 PM THIS EVENING TO 5 PM EST TUESDAY
FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 4 PM EST MONDAY
FOR AMZ352-354.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 10 PM EST
TUESDAY FOR AMZ350.
SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 10 PM EST
TUESDAY FOR AMZ330-374.
&&
$$
JAQ/RJB
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
1243 AM EST SUN FEB 17 2008
.UPDATE...
ADJUSTMENTS TO GOING FREEZING RAIN ADVISORY TO START SOONER
SOUTHERN TIER AND END SRN/WRN ZONES MUCH SOONER WITH STRONG LOW
LEVEL WARM AIR ADVECTION EVIDENT PER TAMDAR SOUNDINGS LATE THIS
EVENING ON SE DESCENT INTO KMDW. DEEP WARM LAYER ASSOCIATED WITH
THICK BLANKET OF SC IS ATYPICAL OF TRADITIONAL WARM
FRONTAL/LAYERED MOISTURE ZR EVENT WITH MORE EVAP COOLING TOP DOWN
WITH VIRGA INTO SUBSTANTIVE 8H-7HDEWPOINT DEPRESSION. I290-295K
MOISTURE AND THERMAL TRANSPORT INTO CWA QUITE STRONG AS WELL...AS
I290K SFC AT KFWA LOWERED 80 MB FROM 00-06 UTC AND AND WALL OF
MOISTURE MOVED IN WITH SFC MOISTENING FROM 1.7 TO 6.7 G/KG IN SAME
6 HR PERIOD. TEMP AT OFFICE ROSE 7 DEGREES IN LITTLE OVER PAST 2
1/2 HOURS...THOUGH WITH KASW DP STILL AT 25F AND COOP/APRS
STATIONS INVOF STN STILL IN UPPER 20S HAVE ADJUSTED TIMING OF
FREEZING RAIN ADVISORY BUT HELD ONTO PREVIOUS ADVISORY
CONFIGURATION AND STARTED NOW BUT ADJUSTED ENDING TIME IN
SRN/SWRN/WRN AREAS TO EXPIRE EARLIER 4 AM EST. NORTHEASTERN CWA
WHERE COLDEST SFC DPS REMAIN...HILLSDALE AT 18F AND WALDRON AT
15F TO CONTINUE LONGEST UNTIL 8 AM EST. HEAVIEST AND MOST WIDESPREAD
PRECIP SHIELD STILL WELL SW BACK TO CENTRAL IL AND ENTIRE CWA WILL
BE ABOVE FZG BY ARRIVAL...THEREFORE AMOUNT OF ZR ACCUM LOWERED TO
LESS THAN ONE- TENTH..SAVE FOR NORTHEAST CORNER WHERE PROLONGED
EVENT COULD SEE ACRETIONS NEAR ONE- TENTH...ESPECIALLY ELEVATED
SFCS.
&&
.AVIATION...
CHANGES MADE TO INITIAL 3 TO 6 HOUR PERIOD TO REMOVE FZRA MENTION AT
KFWA AND TONE DOWN AT KSBN. KFWA NOW ABOVE FREEZING AND DIAL IN TO
SBN ASOS SHOWS TEMP NOW AT 32 DEGREES SO EXPECT TEMPS TO CONTINUE
THEIR CLIMB. MAY BE A BRIEF DROP AS RAIN STARTS BUT WILL BE SHORT
LIVED. HAVE DECIDED TO GO WITH A BRIEF 1 HR TEMPO GROUP FOR FREEZING
RAIN...BUT SUSPECT THIS MAY NOT EVEN OCCUR.
AFTER THAT...LARGE AREA OF RAIN CONTINUED TO EXPAND WITH INCREASING
LIFT AND MOISTURE FLUX ACROSS THE AREA. HAVE KEPT TAFS AS IS FOR
MUCH OF THE REMAINDER OF THE PERIOD WITH THREAT FOR CONVECTION STILL
AROUND FOR THE AFTERNOON HOURS. COLD FRONT LOOKS TO COME THROUGH
SOMEWHERE AROUND 5Z MONDAY AT KSBN SO HAVE WENT WITH WIND SHIFT AND
RASN FOR PRECIP STARTING AT THAT TIME AND WILL ADD FURTHER DETAIL
WITH 12Z TAFS.
&&
.PREV DISCUSSION... /ISSUED 407 PM EST SAT FEB 16 2008/
SHORT TERM...
TONIGHT THROUGH SUNDAY NIGHT...
SEVERAL CONCERNS FOR TONIGHT WITH ONSET OF PRECIPITATION AND
PRECIPITATION TYPE GIVEN THERMAL PROFILES. USING BLEND OF NAM WRF
AND PATTERN RECOGNITION FOR SHORT TERM FORECAST.
WATER VAPOR SHOWS COMPLICATED PATTERN OVER NORTH AMERICA AND PACIFIC
OCEAN THIS AFTERNOON. SOUTHERN STREAM LOW MOVING ACROSS WEST TEXAS
WHILE POTENT NORTHERN STREAM ENERGY DIVING THROUGH WESTERN CONUS.
PHASING OF THESE SYSTEMS ALREADY IN PROGRESS WHICH WILL LEAD TO
STRONG CYCLOGENESIS OVER THE PLAINS. MODELS NOW IN GOOD AGREEMENT ON
TRACK OF SURFACE LOW THROUGH NORTHEAST ILLINOIS WHICH LEAVES OUR
AREA IN WARM SECTOR THROUGH THE EVENT. STRONG WARM AIR ADVECTION
WILL OCCUR ALOFT THIS EVENING AND OVERNIGHT. NAM SHOWING INCREDIBLE
SATURATION OF VERY DRY AIRMASS WITH 30F DEW POINT DEPRESSION BEING
WIPED OUT IN 3 HOURS OVER NORTHERN INDIANA. CONCERNED THIS IS MUCH
TOO FAST FOR SATURATION BUT GRANTED THERE IS NO STRONG EASTERLY FLOW
TO LOCK THE DRY AIR IN PLACE. OTHER CONCERN IS LACK OF COOLING NOTED
IN FORECAST SOUNDINGS FROM THIS EVAPORATIVE COOLING PROCESS. SURFACE
OBSERVATIONS SHOW SURFACE DEW POINTS IN TEENS OVER MOST OF AREA
WHILE NAM 18Z DEW POINTS PROGGED TO BE IN LOWER 20S. CONCERNED THAT
NAM IS NOT ACCOUNTING FOR ENOUGH EVAP COOLING NOR IS IT TAKING INTO
ACCOUNT SHALLOW ARCTIC WEDGE OVER SNOW PACK. THUS IT MAY BE WARMING
SURFACE TEMPS AND BOUNDARY TOO FAST OVERNIGHT...AS IT TENDS TO DO
WITH
RETREATING ARCTIC AIRMASSES. ON THE OTHER HAND...WARM AIR ADVECTION
IS QUITE STRONG JUST ABOVE SURFACE AND ONCE SATURATION DOES
OCCUR...WARM RAIN COULD QUICKLY WARM LOWER LEVELS.
AT THIS POINT...PLAN TO HEDGE BETWEEN BOTH PLAUSIBLE SCENARIOS AND
KEEP FREEZING RAIN ACROSS FAR NORTH INTO SUNDAY MORNING. GIVEN RAPID
SATURATION AND MODERATE PRECIPITATION...SOME ICE ACCUMULATIONS
EXPECTED SO WILL ISSUE A FREEZING RAIN ADVISORY FOR NORTHERN THIRD
OF FORECAST AREA WHERE POTENTIAL FOR SUB FREEZING TEMPS WILL BE
GREATEST. WILL RUN FROM NEAR 07Z TO 14Z IN COLLABORATION WITH
NEIGHBORING OFFICES. SOME SLEET POSSIBLE INITIALLY BUT WITH STRONG
WARMING AND VERY SHALLOW SFC COLD LAYER...EXPECT FREEZING RAIN TO
BE PRIMARY HAZARD. THUNDER ALSO REMAINS A POSSIBILITY OVERNIGHT WITH
INCREASING ELEVATED INSTABILITY AND STRONG JET DYNAMICS MOVING INTO
AREA. IMPRESSIVE UPPER LEVEL DIVERGENCE NOTED ON NAM IN CONJUNCTION
WITH STRONG ISENTROPIC LIFT AND WARM AIR ADVECTION.
ONCE TEMPS RISE ABOVE FREEZING ON SUNDAY...FOCUS SHIFTS TO HEAVY
RAIN THREAT INTO EARLY AFTERNOON BEFORE DRY SLOT MOVES IN. PWATS
NEAR 1 INCH AND K INDEX TO NEAR 30 WITH STRONG LOW LEVEL JET AND
MOISTURE ADVECTION. THREE QUARTERS OF AN INCH TO OVER AN INCH
PRECIPITATION VERY POSSIBLE AND SO FLOOD WATCH TO CONTINUE. WITH
FURTHER WEST LOW TRACK AND OCCLUDING SYSTEM...EASTERN AREAS TO SEE
LESS RAINFALL BUT STILL ENOUGH TO CAUSE POSSIBLE FLOODING CONCERNS.
ALSO A CONCERN FOR LINE OF ELEVATED STRONG THUNDERSTORMS AHEAD OF
MAIN COLD FRONT LATE SUNDAY AFTERNOON AND EVENING. EACH OF THESE
STRONG LOWS EJECTING FROM SOUTHWEST THIS WINTER HAS PRODUCED SEVERE
WEATHER IN THE OHIO VALLEY. WITH OUR AREA IN WARM SECTOR THIS NOT
OUT OF QUESTION...ESPECIALLY SOUTH OF HIGHWAY 30. NO INCREASED
MENTION IN FORECAST AT THIS TIME BUT CERTAINLY SOMETHING TO WATCH
WITH LOW FREEZING LEVELS. COLD AIR THEN QUICKLY FOLLOWS WITH
CHANCES FOR LIGHT SNOW IN RESIDUAL MOISTURE AND POSSIBLE LAKE
ENHANCEMENT.
LONG TERM... MONDAY THROUGH SATURDAY
MAIN HIGHLIGHTS IN THE LONG TERM WILL BE LAKE SNOW CHANCES MONDAY
THROUGH TUESDAY...BRIEF MODIFIED ARCTIC SPELL AND TRANSITION TO
ACTIVE PROGRESSIVE FLOW BY LATE WEEK. MODELS /NAM/GFS/ECMWF/GEM ARE
IN GOOD AGREEMENT THROUGH WEDNESDAY AND HAVE THE SUPPORT OF THE MEAN
NAEFS AND GFS ENSEMBLE. DISCREPANCIES ARISE TOWARD THE LATER HALF OF
THE PERIOD WHERE HANDLING OF NORTHERN PLAINS RIDGING AND RESULTING
NORTHWEST FLOW OVER THE GREAT LAKES BECOME OBVIOUS...WITH RUN TO RUN
ISSUES APPARENT IN THE GFS AND ECMWF. 12Z PACIFIC HEIGHT AND
MOMENTUM ANALYSIS REVEALS A POWERFUL 100-200 KNOT UPPER JET
STRETCHING FROM NEAR JAPAN TO NEAR 170W. TWO NEGATIVE ANOMALIES WERE
LOCATED TO THE NORTH OF THIS FEATURE. ASSUMED ROBUST DIVERGENT LEFT
EXIT REGION OF THE JET WILL HELP FORCE HEIGHT FALLS IN THE NE
PACIFIC AS THE SYSTEM PROGRESSES EAST. SFC PRESSURE REFLECTION WILL
INTENSIFY AND ALLOW STRONGER LL WAA FLOW TO IMPINGE UPON THE
NORTHERN ROCKIES WHERE WARMING DOWNSLOPE FLOW WILL HELP SUPPORT
INCREASING UPPER RIDGING OVER THE CANADIAN PLAINS THROUGH MID WEEK.
END RESULT...AMPLIFIED UPPER RIDGE WILL ALLOW STRENGTHENING NW UPPER
FLOW INTO THE GREAT LAKES. SEMI PERMANENT HUDSON BAY VORTEX IN PLACE
WILL PROVIDE A SOURCE REGION FOR A FEW REINFORCING MID LEVEL
IMPULSES INTO THE GREAT LAKES...ALLOWING CAA TO CONTINUE THROUGH
MUCH OF THE WEEK BEFORE PATTERN BREAK DOWN OCCURS AS THE
AFOREMENTIONED PACIFIC JET ENTERS THE WESTERN US...ALLOWING
UNSETTLED FAST WESTERN FLOW TO DEVELOP PER PV CONSERVATION AND
RESULTANT WAVE TRAINING OVER THE CENTRAL ROCKIES. CLASSIC LONG
EXTENSION OF THE UPPER JET INTO THE EASTERN PACIFIC IS ONE OF THE
STRONG INDICATORS OF A POSITIVE PNA PHASE. MEAN GFS ENSEMBLE PNA
PROGS INDICATE A SHARP POSITIVE PHASE BY NEXT WEEK SUPPORTING
CONTINUE COLD NORTHWEST FLOW...WITH MAIN STORM TRACK RESIDING SOUTH
OF THE REGION. HAVE OPTED FOR THE GEM/MEAN NAEFS/12Z GFS/12Z ECWMF
PROGS AS THEY ALL CALL FOR CONTINUED COLD DISTURBED NW FLOW THROUGH
THURSDAY.
MONDAY THROUGH TUESDAY...COLD NW CYCLONIC UPPER FLOW WITH WEAK
EMBEDDED IMPULSES WILL HELP SUPPORT SNOW SHOWER CHANCES WITH
INCREASING LAKE EFFECT POTENTIAL BY MONDAY NIGHT. HAVE INCREASED
LAKE EFFECT SNOW CHANCES DUE TO INCREASED INVERSION HEIGHTS PER
ADVANCING MID LEVEL SPEED MAX/INCREASED LAKE CAPES TO NEARLY 500
J/KG/H85 DELTA T/S OVER 20 C/AND RELATIVELY MOIST BL. THINKING THAT
2 TO 4 INCHES SEEMS REASONABLE WITH LOCALLY HIGHER AMOUNTS THROUGH
TUESDAY IN NW LAKE BELT ZONES. HAVE CONTINUED TO TREND TEMPS DOWN A
LITTLE WITH VERY STRONG CAA EXPECTED PER H85 TEMPS DROPPING TO -20 C
BY 06Z TUESDAY. WIND WILL ALSO BE STRONG DURING THIS PERIOD PER
MODERATE PRESSURE GRADIENT/CAA/WELL LINKED SFC-BL WINDS...CREATING
VERY COLD WIND CHILL VALUES.
WEDNESDAY...ACTIVE NW FLOW WILL SUPPORT YET ANOTHER CLIPPER SYSTEM
TUESDAY NIGHT INTO WED. GIVEN DRY MODIFIED ARCTIC AIR AND LACK OF
MOISTURE NOT ANTICIPATING MUCH QPF. HOWEVER..HIGH SNOW RATIOS MAY
SUPPORT 1-2 INCHES.
THURSDAY THROUGH FRIDAY...GEM/GFS/AND THE NAEFS ARE ALL SUPPORTING
THE DEVELOPMENT OF VERY STRONG SFC HIGH PRESSURE PER ADVANCING UPPER
RIDGE. SUBSIDENT DRYING/COLD AIR IN PLACE/AND LL NE THROUGH NEARLY 5
KFT WILL BE ONGOING AS A WEAK SOUTHERN STREAM IMPULSE EJECTS EAST
ACROSS THE SOUTHERN CONUS. MODELS ARE SUPPORTING PRECIP DEVELOPMENT
JUST NORTH INTO THE CWA THROUGH THIS PERIOD. HOWEVER...WITH ABOVE
CONCERNS AND EXPECTED DOMINATE NW FLOW...THINKING THIS MAY CONTINUE
TO TREND FARTHER SOUTH. HAVE LEFT LOW POP IN FOR NOW DUE TO SOME
UNCERTAINTY...BUT AGAIN THE TREND HAS BEEN DRIER IN LINE WITH A
STRONGLY POSITIVE PNA.
SATURDAY...MODELS AND ENSEMBLES HAVE BEEN CONSISTENTLY PROGGING
ANOTHER ORGANIZED STORM SYSTEM TO PUSH INTO THE CENTRAL MISSISSIPPI
VALLEY BY NEXT WEEKEND. HAVE INTRODUCED LOW POPS GIVEN CONSISTENT
6-7 DAY REPEAT PATTERN THIS WINTER...COUPLED WITH MEAN ENSEMBLE
SUPPORT. THIS SYSTEM WILL HAVE TO WATCHED AS HEAVY RAIN WOULD
DEFINITELY BE A REAL POSSIBILITY ONCE AGAIN.
HYDROLOGY...
MANY RIVERS ALREADY BEING FORECAST TO RISE ABOVE FLOOD STAGE WITH
EXPECTED RAINFALL AS INPUT. EXCEPT FOR POINTS ALREADY IN
FLOOD...WILL ALLOW FLOOD WATCH TO COVER THESE POTENTIAL RISES ABOVE
FLOOD FOR NOW. EXPECT WARNINGS TO BE ISSUED OVER NEXT 24 HOURS AS
HEAVY RAINFALL BECOMES BETTER DEFINED. ALSO ALLOWED CURRENT
WARNINGS TO CONTINUE ON A FEW RIVERS EXPECTED TO FALL JUST BELOW
FLOOD STAGE BEFORE RISING BACK ABOVE LATER SUNDAY INTO MONDAY.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...FLOOD WATCH THROUGH THIS EVENING FOR INZ003>009-012>018-020-
022>027-032>034.
FREEZING RAIN ADVISORY UNTIL 4 AM EST /3 AM CST/ EARLY THIS
MORNING FOR INZ003>005-012-014-016>018.
FREEZING RAIN ADVISORY UNTIL 8 AM EST THIS MORNING FOR INZ007.
FREEZING RAIN ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR
INZ006-008-009.
MI...FLOOD WATCH THROUGH THIS EVENING FOR MIZ077>081.
FREEZING RAIN ADVISORY UNTIL 4 AM EST EARLY THIS MORNING FOR
MIZ077-078.
FREEZING RAIN ADVISORY UNTIL 8 AM EST THIS MORNING FOR MIZ080-
081.
FREEZING RAIN ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR
MIZ079.
OH...FLOOD WATCH THROUGH THIS EVENING FOR OHZ001-002-004-005-015-016-
024-025.
FREEZING RAIN ADVISORY UNTIL 4 AM EST EARLY THIS MORNING FOR
OHZ004-005-015-016.
FREEZING RAIN ADVISORY UNTIL 8 AM EST THIS MORNING FOR OHZ001-
002.
LM...NONE.
&&
$$
SHORT TERM...LASHLEY
LONG TERM...CHAMBERLAIN
AVIATION...FISHER
UPDATE...MURPHY
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
1045 PM EST MON FEB 18 2008
.UPDATE...
MAIN FCST CONCERNS ARE LES TRENDS.
NNW FLOW MULTIPLE WIND PARALLEL BAND LES CONTINUED SUPPORTED BY 850
MB TEMPS NEAR -20C AND DEEP MOISTURE (TO AROUND 15K FT...PER TAMDAR
SOUNDINGS) OVER THE AREA WITH A MID LEVEL TROUGH.
SNOWFALL TODAY OF AROUND 6 INCHES WAS REPORTED AT IRONWOOD WITH
THE HEAVIEST SNOWFALL RATES DURING THE PERIOD WHEN SYNOPTIC SUPPORT
FROM A MID LEVEL SHORTWAVE MOVED THROUGH LATE THIS AFTERNOON AND
EARLY THIS EVENING.
EXPECT WINDS TO BACK ENOUGH AT KIWD SO THAT SNOWFALL RATES WILL
GENERALLLY BE LIGHT...ADDITIONAL ACCUMULATIONS OF AN INCH OR TWO.
THE KEWEENAW WAS ADDED TO THE ADVISORY AS OCNLY HEAVY SNOW SHOWERS
MOVED THROUGH DURING THE EVENING AND WITH DEEPER MOISTURE LINGERING
THROUGH 12Z...12 HOUR ACCUMULATIONS IN THE 2 TO 5 INCH RANGE ARE
POSSIBLE. OVER THE EAST...EXPECT LIGHT TO MODERATE LES WILL ALSO
CONTINUE WITH LES ADVISORIES REMAINING IN EFFECT.
.SYNOPSIS...
WATER VAPOR LOOP AND RUC ANALYSIS INDICATES AMPLIFIED MID-UPR FLOW
OVER NORTH AMERICA WITH RIDGING OVER THE WEST COAST AND A BROAD
TROUGH OVER CENTRAL CANADA AND THE CENTRAL CONUS. NNW FLOW AT SFC
BETWEEN LOW PRES OVER QUEBEC AND HIGH PRES CENTERED OVER THE HIGH
PLAINS HAS SUSTAINED LAKE EFFECT SNOW SHOWERS OVER UPR MI FOR
FAVORED NW FETCH AREAS. DESPITE FAIRLY DEEP MOISTURE AT UPSTREAM
CWPL AND KINL 12Z SNDGS...INFLUX OF DRIER AIR BLO THE INVERSION HAS
RESULTED IN WIDELY-SPACED MULTI-PARALLEL LES BANDS AS OBSERVED ON
RADAR EAST OF KMQT.
&&
.SHORT TERM (TONIGHT AND TUESDAY)...
WITH BROAD UPR TROUGH LINGERING OVER THE UPPER GREAT LAKES...MODEL
SNDGS INDICATE DEEP MOISTURE WILL HANG OVER THE AREA. DESPITE DEEP
MOISTURE...FAIRLY FAVORABLE DENDRITIC SNOW GROWTH LAYER NEAR THE
SURFACE AND INCREASING CONVERGENCE WITH LAND BREEZE DEVELOPMENT
TONIGHT...LACK OF SYNOPTIC ENHANCEMENT SHOULD KEEP SNOW TOTALS IN
CHECK OVER FOR LAKE SUPERIOR NW SNOWBELT COUNTIES. THUS...HAVE
DECIDED TO DROP WARNING FOR ERN COUNTIES (ALGER-LUCE AND NRN
SCHOOLCRAFT) AND GO WITH A SNOW ADVISORY TONIGHT INTO TUE. ALGER
ADVISORY WILL BE EXTENDED INTO TUE NIGHT AS FLOW STRENGTHENS WITH
PASSAGE OF TROUGH AND WIND DIRECTION BECOMES MORE NRLY.
ALSO KEPT ADVISORY GOING FOR GOGEBIC COUNTY TONIGHT BUT EXTENDED
ADVISORY FOR ONTONAGON THROUGH TUESDAY NIGHT AS WEAK CONVERGENT WNW
FLOW ON TUE COULD KEEP A DOMINANT LES BAND OVER ONTONAGON-WHITE PINE
AREA. SHIFT TO STRONGER NRLY FLOW BEHIND TROF PASSAGE SHOULD KEEP
LES GOING FOR ONTONAGON COUNTY TUE NIGHT. NRLY FLOW WILL ALSO FAVOR
GOGEBIC COUNTY AGAIN FOR A HEADLINE TUE NIGHT BUT THIS WILL HAVE TO
BE DETERMINED BY LATER SHIFTS AS IT SHOULD BE NO MORE THAN ADVISORY
SNOW AMTS. SNOW GROWTH BECOMES LESS FAVORABLE LATE TUE NIGHT AS 850
MB TEMPS DROP TO NEAR -24/-25C. EXPECT SNOW AMTS IN THE ADVISORY
AREA TO GENERALLY RECEIVE 2 TO LOCALLY 5 INCHES OF SNOW PER 12 HRS.
ELSEWHERE ALONG THE REST OF THE LAKE SUPERIOR COUNTIES WHERE THE
FLOW WILL BE LESS FAVORABLE...EXPECT GENERAL AMTS OF 1-2"/12 HRS.
FLURRIES CAN BE EXPECTED OVER SCNTRL COUNTIES UNDER PARTLY TO MOSTLY
CLOUDY SKIES.
MIN TEMPS COULD STILL DIP INTO THE SINGLE DIGITS BLO ZERO TONIGHT
OVER THE WRN INTERIOR WITH SINGLE DIGITS ABV ZERO FOR AREAS
DOWNSTREAM OF THE MODERATING INFLUENCE OF LAKE SUPERIOR. HIGHS TUE
WILL STAY CHILLY WITH LITTLE REBOUND FROM OVERNIGHT MINS AS 850 MB
TEMPS ARE FCST TO BE -20 TO -23C OVER THE AREA. EXPECT HIGHS IN THE
SINGLE DIGITS ABV ZERO WRN HALF WITH LOW TEENS EAST HALF.
.LONG TERM (TUESDAY NIGHT THROUGH NEXT MONDAY)...
STABLE PATTERN WTIH RIDGE OVER WESTERN CONUS AND TROUGH OVER EAST
HALF OF THE CONUS DOMINATES THROUGH MUCH OF THE PERIOD. A COUPLE OF
PUSHES OF ARCTIC AIR SPILL ACROSS THE UPR GREAT LAKES WED AND AGAIN
THU/FRI. MAJORITY OF THE TIME...LK EFFECT SNOW SHOWERS ARE EXPECTED
IN AREAS FAVORED BY NW WINDS. MAY BRIEFLY SEE SNOW SHOWERS AFFECT
AREAS FAVORED BY NORTH WINDS IN FAR WEST AND NORTH CENTRAL CWA TUE
NIGHT AS SFC TROUGH PUSHES ACROSS LK SUPERIOR INTO THE NORTH HALF OF
THE CWA. PREFER THE SHARPER NAM DEPICTION OF THE TROUGH AS IT HAS
SUPPORT FM THE REGIONAL CANADIAN AND LOCALLY RUN WRF AND LOOKS MORE
REASONABLE CONSIDERING THE COLDER ARCTIC AIR INTERACTING WITH THE
OPEN WATERS OF LK SUPERIOR. SHARP WIND SHIFT RESULTS IN CONVERGENCE
MAXIMIZING FM GOGEBIC INTO ONTONAGON AND IN EASTERN MARQUETTE AND
WESTERN ALGER COUNTIES.
SO...IN ADDITION TO WHERE THE LK EFFECT ADVISORIES WERE EXTENDED
INTO TUE NIGHT...COULD ALSO SEE NEED FOR ADDITIONAL ADVISORIES FOR
GOGEBIC AND MARQUETTE COUNTIES. FAVORABLE SETUP IS FOR LESS THAN 12
HRS AND THAT SHOULD KEEP SNOWFALL AMOUNTS IN CHECK. THOUGH WOULD NOT
BE SURPRISED TO SEE SNOWFALL RATES TUE EVENING UP TO INCH/HOUR WITH
MOST FAVORABLE CONVERGENCE AND SOME UPPER LEVEL SUPPORT SKIRTING THE
AREA TO THE SOUTHWEST. MOVING INTO WED MORNING WINDS BACK MORE TO NW
WHICH ALLOWS THE LK EFFECT TO MOVE BACK INTO THE NW FLOW AREAS OF NW
UPR MI AND ALONG LK SUPERIOR EAST OF MARQUETTE. DESPITE VERY CHILLY
H85 TEMPS BLO -20C...LOWERING INVERSIONS WILL BEGIN TO PUT CRIMP
INTO ADDITIONAL ACCUMS. OTHER ITEM TO WATCH IS WIND CHILL VALUES
LATER TUE NIGHT INTO WED MORNING. STRONGEST WINDS LOOK TO BE PINNED
ALONG THE LK SUPERIOR SHORE WHERE AIR TEMPS WILL BE HIGHEST. TEMPS
INLAND WILL PLUMMET UNDER 10 BELOW ZERO...BUT THERE...WINDS WILL BE
MARGINAL TO SATISFY CRITERIA (10 MPH). IF WINDS LOOK TO BE A BIT
STRONGER...THEN LATER SHIFTS MAY NEED TO POST WIND CHILL ADVY FOR
PORTIONS OF WEST HALF OF CWA TUE NIGHT INTO WED MORNING. SHALLOW
ARCTIC AIR REMAINS ENTRENCHED THROUGH END OF THE WEEK. COLDEST NIGHT
WILL BE WED NIGHT AS WINDS BECOME LIGHT WITH APPROACH OF SFC RIDGE.
20 BLO READINGS NOT OUT OF QUESTION.
PROCEEDED TO GO ON LOW END OF GUIDANCE FOR HIGHS AND LOWS RIGHT INTO
SAT AS ARCTIC AIR SLOWLY DEPARTS. LATE THIS UPCOMING WEEKEND INTO
EARLY NEXT WEEK HEIGHTS FALL ALONG THE WEST COAST AND THE RIDGE OVER
THE WEST CONUS BEGINS SHIFTING EAST. THIS SHIFT ALLOWS THE TROUGH TO
LIFT INTO THE ATLANTIC AND SHOULD ALLOW FOR TEMPS OVER THE UPR GREAT
LAKES TO MODERATE TO MORE NORMAL VALUES FOR LATE FEB (UPR 20S FOR
HIGHS AND 5 TO 10 ABOVE FOR LOWS).
&&
.AVIATION (FOR 00Z TAF ISSUANCE)...
AT KCMX...EXPECT PERSISTENT LAKE EFFECT -SHSN. NNW WIND LES
SHOULD KEEP PREVAILING VSBY IN THE IFR CATEGORY THROUGH MUCH OF
TONIGHT. THERE COULD EVEN BE SOME OCCASIONAL IFR CIGS.
WINDS BACKING TO THE NW TUE MORNING WOULD BE LESS FAVORABLE
FOR LES BANDS SO EXPECT PREVAILING CONDITIONS WILL IMPROVE TO MVFR
AT THAT TIME.
NW FLOW WILL KEEP MAINLY MVFR CIGS INTO TUE MORNING WITH VFR VSBY IN
LIGHT LAKE EFFECT SNOW SHOWERS. VEERING WINDS TO NNW WILL BRING AN
INCREASE IN LES TUE AFTERNOON WITH POTENTIAL FOR IFR VSBY.
&&
.MARINE...
ARCTIC AIR SETTLING OVER THE AREA WILL RESULT IN AN EXTENDED PERIOD
OF WINDS FREQUENTLY IN THE 20 TO 30KT RANGE THRU WED. IN ADDITION...
HEAVY FREEZING SPRAY WILL CONTINUE THRU THU.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
LAKE EFFECT SNOW ADVISORY UNTIL 11 AM EST TUESDAY FOR MIZ001-003.
LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST TUESDAY FOR MIZ007-085.
LAKE EFFECT SNOW ADVISORY UNTIL 4 AM CST TUESDAY FOR MIZ009.
LAKE EFFECT SNOW ADVISORY UNTIL 7 AM EST WEDNESDAY FOR MIZ002-
006.
LAKE SUPERIOR...
HEAVY FREEZING SPRAY WARNING UNTIL 7 PM EST THURSDAY FOR LSZ162-
263>267.
LAKE MICHIGAN...
HEAVY FREEZING SPRAY WARNING UNTIL 7 PM EST WEDNESDAY FOR LMZ248-
250.
&&
$$
UPDATE...JLB
SYNOPSIS/SHORT TERM...VOSS
LONG TERM...JLA
MARINE...VOSS
AVIATION...JLB
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
1045 AM EST SUN FEB 17 2008
.UPDATE...
THE FREEZING RAIN ADVISORY WORKED OUT WELL...WITH SEVERAL REPORTS
OF AN 1/8 INCH OF ICE ACROSS THE MUCH OF THE AREA. TEMPERATURES
HAVE RISEN INTO THE MID TO 30S ACROSS MOST OF THE CWA...AND LOOK
TO BE ON THEIR WAY INTO THE 40S BASED ON UPSTREAM OBS OVER THE
NORTHERN OHIO VALLEY AND WITH THE EXPECTED LOW TRACK THROUGH
NORTHERN LOWER MICHIGAN THIS EVENING. SURFACE ANALYSIS SHOWED A
987 MB LOW OVER WEST CENTRAL ILLINOIS AT PRESENT TIME. HAVE
REMOVED THE HEAVY RAIN MENTION...AS HEAVIEST RAIN IS MOVING OUT OF
THE AREA AND WE WILL BE IN THE INFLUENCE OF THE MID LEVEL DRY SLOT
FOR MUCH OF THE AFTERNOON. STILL ENOUGH LOW LEVEL MOISTURE/UP GLIDE
TO SUPPORT RAIN/DRIZZLE/FOG WITH HIGHER DEW POINTS COMING OVER THE
SNOW PACK.
&&
.PREV DISCUSSION...ISSUED 629 AM EST SUN FEB 17 2008
AVIATION...
FREEZING RAIN IN IFR CONDITIONS WILL CONTINUE AT ALL TERMINALS
OVER THE NEXT SEVERAL HOURS...BEFORE TRANSITIONING TO RAIN FROM
SOUTH TO NORTH BETWEEN 14-17Z. PERIODS OF MODERATE RAINFALL WILL
CONTINUE THROUGH THE DAY...MAINTAINING IFR CEILINGS AND
VISIBILITY. AS MOIST LOW LEVEL AIR LIFTS ATOP THE SNOWPACK...WILL
SEE AREAS OF FOG DEVELOP DURING THE AFTERNOON AND EVENING...AND
WILL CONTINUE WITH LOWER RESTRICTIONS ON VISIBILITY DURING THIS
TIME. SOUTHERLY WINDS WILL BECOME GUSTY AT TIMES TO AROUND 25
KNOTS THIS AFTERNOON AS THE PRESSURE GRADIENT TIGHTENS AHEAD OF
STRONG LOW PRESSURE LIFTING ACROSS WESTERN GREAT LAKES. WINDS WILL
SHIFT TOWARD THE NORTHWEST BEHIND THIS SYSTEM OVERNIGHT.
PREV DISCUSSION...ISSUED 408 AM EST SUN FEB 17 2008
SHORT TERM...TODAY
STRONG MOISTURE TRANSPORT AND WARM AIR ADVECTION ONGOING JUST
UPSTREAM THIS MORNING...IN RESPONSE TO A 60+ KNOT SOUTHERLY LOW
LEVEL JET WRAPPING AROUND A DYNAMIC MID/UPPER LOW CURRENTLY ROTATING
ACROSS NORTHERN TEXAS. THIS COMBINED WITH GOOD UPPER LEVEL
DIFFLUENCE SUPPORTING AN EXPANSIVE AREA OF PRECIPITATION THROUGHOUT
THE MISSISSIPPI VALLEY/MIDWEST...WITH LATEST RADAR/SFC OBS SHOWING
THE LEADING EDGE NOW ENCROACHING UPON SOUTHERN MICHIGAN. INITIAL
SURGE OF LIGHTER PRECIPITATION WILL OVERSPREAD THE ENTIRE AREA EARLY
THIS MORNING. LATEST MODEL SOUNDINGS...ALONG WITH RECENT TAMDAR
SOUNDING DATA NEAR DTW...STILL SHOW A FREEZING RAIN PROFILE AT ONSET
AS A SHALLOW SUB-FREEZING LAYER REMAINS BENEATH AN INCREASINGLY
PRONOUNCED WARM LAYER. TRENDS UPSTREAM INDICATE IT WILL TAKE LITTLE
TIME TO SCOUR OUT THIS SHALLOW COLD LAYER...ESPECIALLY ACROSS THE
SOUTHERN HALF OF THE CWA. SFC TEMPERATURES AS OF 08Z ARE NOW AT OR
ABOVE FREEZING FROM SOUTH BEND TO FINDLAY OHIO. THUS...LOOKING AT
PRIMARILY A 2-4 HOUR WINDOW OF -FZRA...BEFORE TRANSITIONING TO JUST
RAIN BETWEEN 12-15Z ALONG/SOUTH OF THE M-59 CORRIDOR...AND BY LATE
MORNING TOWARD THE NORTH.
BEST LARGE SCALE ACCENT WILL OCCUR FROM 15-21Z...LEADING TO A PERIOD
OF MODERATE/HEAVY RAINFALL AS PW VALUES APPROACH 1 INCH. QPF OF
AROUND 0.5"...COMBINED WITH A MODEST AMOUNT OF SNOWMELT...WILL
ELEVATE SOME AREA RIVERS/STREAMS. HOWEVER...OVERALL FLOODING
CONCERNS APPEAR TO BE MINIMAL...WITH THIS WARMUP APPEARING TOO BRIEF
TO MELT THE ENTIRE SNOWPACK. THE PRONOUNCED WARM AIR ADVECTION WILL
HELP PUSH TEMPERATURES BY LATE AFTERNOON/EARLY EVENING INTO THE
LOW/MID 40S. THE RAPID INCREASE IN LOW LEVEL MOISTURE...WITH
DEWPOINTS IN THE UPPER 30S...MOVING OVER THE SNOWPACK WILL LIKELY
LEAD TO AREAS OF FOG BY AFTERNOON/EVENING. A STRONG LOW LEVEL
GRADIENT WOULD SEEM TO REDUCE THE CHANCES FOR CONDITIONS TO
DETERIORATE ENOUGH TO NECESSITATE AN ADVISORY...BUT WILL NEED TO
MONITOR THIS THROUGH THE DAY.
LONG TERM...TONIGHT THROUGH SATURDAY
CONTINUED PRECIPITATION CHANCES IS THE FOCUS OF THE LONG TERM.
STRONG SURFACE LOW PRESSURE OF APPROXIMATELY 984MB WILL BE
CENTERED IN WEST CENTRAL LOWER MICHIGAN AT THE START OF THE LONG
TERM. A WELL COUPLED JET STRUCTURE ACROSS EASTERN ONTARIO AND A
NEUTRAL TO NEGATIVE TILTING OF THE LONGWAVE TROUGH WILL KEEP A
PROGRESSIVE MOVEMENT TO THE SURFACE LOW. THE LOWER ATMOSPHERE
REMAINS QUITE WARM THROUGH 6Z...AND HAVE KEPT THE ALL RAIN
MENTION (EXPECTING THE MAJORITY OF THE QPF TONIGHT TO FALL IN
THIS TIMEFRAME). THEREAFTER...THE FRONT SLIDES THROUGH CRASHING
TEMPERATURES...CHANGING LIQUID OVER TO ALL SNOW. THE POTENTIAL FOR
PRECIPITATION WILL LINGER THROUGHOUT THE NIGHT WITH THE FOLLOWING
FORCING BEYOND 00Z...TRIPLE POINT SURFACE CONVERGENCE/CYCLONIC
VORTICITY ADVECTION...A TRAILING DEFORMATION AXIS...AND DEEP
FRONTOGENESIS. PRECIPITATION AFTER 6Z IS TRICKY. CURRENT THINKING
HAS SUBSIDENCE AND FRONTOLYSIS SHUTTING DOWN OR WIDELY SCATTERING
THE SNOW SHOWERS ACROSS THE SOUTHERN HALF OF THE FA (LITTLE TO NO
ACCUMULATIONS SOUTH OF I69). FOR THE SAGINAW BAY AND THUMB
VICINITIES PESKY DEFORMATION SNOW BANDING MAY SET UP A BIT LONGER.
ADDITIONALLY...ABUNDANT RESIDUAL LOW LEVEL MOISTURE WILL NEED TO
BE SCOURED AND FEEL FRONTAL PASSAGE AND COLD AIR ADVECTION COULD
BE EFFECTIVE IN WRINGING THIS OUT. IF BANDING PERSISTS LATE ACROSS
THE NORTH...1 TO 2 INCHES WILL BE POSSIBLE.
THE GREAT LAKES REGION WILL SHIFT TO A LAKE EFFECT PATTERN AS
COLD CYCLONIC FLOW BUILDS IN THROUGH MIDWEEK. HAVE TRENDED POPS
DOWNWARD ON MONDAY WITH WEAK SYNOPTIC SUPPORT AND EXTREMELY
MARGINAL LES PARAMETERS (INVERSION HEIGHTS OF AROUND 3.5 KFT AND
DELTA T/S OF -15C). MONDAY NIGHT...PROSPECTS FOR LAKE MICHIGAN
LES MAKING IT OVER PICK UP. A REINFORCING COLD SHOT OF SUB -20C
850MB TEMPS AND STRONG PV ANOMALY WILL SETTLE INTO LOWER MICHIGAN
TUESDAY MORNING. THIS ALLOWS A FLARING OF LAKE SNOWS THROUGHOUT
THE DAY WITH DELTA T/S CLIMBING TO -20C AND EQUILIBRIUM HEIGHTS
REACHING NEAR 10KFT. TWO NEGATIVE ARE THE DRY MIDLEVELS...AND THE
NORTHWESTERLY COMPONENT IN SURFACE WINDS. A SUBSIDENCE INVERSION
WORKS DOWN THE COLUMN WEDNESDAY NIGHT REDUCING PRECIPITATION
CHANCES ONCE AGAIN. ATTM...ACCUMULATIONS ARE EXPECTED TO REMAIN
LIGHT.
GUIDANCE IS NOW ADVERTISING A SOLUTION THAT WOULD BRING A
WELCOMED QUIET PERIOD FOR SOUTHEASTERN MICHIGAN. THE LATEST
GFS/ECMWF SUGGEST ARCTIC HIGH PRESSURE SETTLES IN THURSDAY AND
LASTS INTO THE WEEKEND. HOWEVER...ROOM FOR ERROR DOES EXIST AS A
STRONG BAROCLINIC ZONE SETS UP JUST TO THE SOUTH IN UNFAMILIAR
ZONAL FLOW. ENERGY ZIPPING ALONG THE FRONT MAY ALLOW A NORTHWARD
JOG BRINGING PRECIPITATION BACK INTO THE PICTURE. HOWEVER...WITH
BOTH MODELS IN AGREEMENT ON THE DOMINANT SPRAWLING ARCTIC HIGH
THIS SOLUTION WOULD BE A NICE CHANGE. FOR NOW WILL CONTINUE THE
INHERITED PRECIPITATION CHANCES FOR THE BEGINNING OF THE WEEKEND.
TRENDED TEMPERATURES DOWNWARD THROUGH FRIDAY...GIVEN THE COLDER
GUIDANCE SOLUTIONS. DAYTIME TEMPERATURES MONDAY THROUGH THURSDAY
ARE EXPECTED TO RANGE FROM THE UPPER TEENS TO MID 20S...SOME 10
TO 15 DEGREES BELOW NORMAL. LOWS WILL GENERALLY FALL INTO THE
SINGLE DIGITS ABOVE ZERO.
MARINE...
STRENGTHENING PRESSURE GRADIENT AHEAD OF A STRONG LOW PRESSURE
SYSTEM TRACKING NORTHEAST FROM SOUTHERN LAKE MICHIGAN ACROSS LAKE
HURON WILL BRING INCREASING SOUTHERLY WINDS TODAY AND TONIGHT.
WINDS THIS AFTERNOON AND EVENING WILL APPROACH GALE FORCE OVER THE
OPEN WATERS OF LAKE HURON...WITH GUSTS OF 25 TO 30 KNOTS OVER MUCH
OF THE NEARSHORE WATERS. AFTER A BRIEF LULL OVERNIGHT AS THE LOW
MOVES THROUGH...WINDS WILL SHIFT TOWARD THE NORTHWEST AND INCREASE
AGAIN ON MONDAY AS COLDER AIR MOVES IN BEHIND THE SYSTEM. THIS
WILL BRING ANOTHER PERIOD OF WINDS TO GALE FORCE OVER THE LAKE
HURON OPEN WATERS...AND GUSTS UP TO 30 KNOTS ALONG THE NEARSHORE.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...FREEZING RAIN ADVISORY...MIZ047-MIZ048...UNTIL 1 PM SUNDAY.
LAKE HURON...
GALE WARNING...LHZ362-LHZ363-LHZ462-LHZ463-LHZ464...UNTIL 4 PM
MONDAY.
BRISK WIND ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
HURON INCLUDING OUTER SAGINAW BAY...UNTIL 4 PM MONDAY.
LAKE ST CLAIR...
BRISK WIND ADVISORY...UNTIL 4 PM MONDAY.
MI WATERS OF LAKE ERIE...
BRISK WIND ADVISORY...UNTIL 4 PM MONDAY.
&&
$$
UPDATE.......SF
AVIATION.....MR
SHORT TERM...MR
LONG TERM....CB
MARINE.......MR
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
629 AM EST SUN FEB 17 2008
.AVIATION...
FREEZING RAIN IN IFR CONDITIONS WILL CONTINUE AT ALL TERMINALS
OVER THE NEXT SEVERAL HOURS...BEFORE TRANSITIONING TO RAIN FROM
SOUTH TO NORTH BETWEEN 14-17Z. PERIODS OF MODERATE RAINFALL WILL
CONTINUE THROUGH THE DAY...MAINTAINING IFR CEILINGS AND
VISIBILITY. AS MOIST LOW LEVEL AIR LIFTS ATOP THE SNOWPACK...WILL
SEE AREAS OF FOG DEVELOP DURING THE AFTERNOON AND EVENING...AND
WILL CONTINUE WITH LOWER RESTRICTIONS ON VISIBILITY DURING THIS
TIME. SOUTHERLY WINDS WILL BECOME GUSTY AT TIMES TO AROUND 25
KNOTS THIS AFTERNOON AS THE PRESSURE GRADIENT TIGHTENS AHEAD OF
STRONG LOW PRESSURE LIFTING ACROSS WESTERN GREAT LAKES. WINDS WILL
SHIFT TOWARD THE NORTHWEST BEHIND THIS SYSTEM OVERNIGHT.
&&
.PREV DISCUSSION...ISSUED 408 AM EST SUN FEB 17 2008
SHORT TERM...TODAY
STRONG MOISTURE TRANSPORT AND WARM AIR ADVECTION ONGOING JUST
UPSTREAM THIS MORNING...IN RESPONSE TO A 60+ KNOT SOUTHERLY LOW
LEVEL JET WRAPPING AROUND A DYNAMIC MID/UPPER LOW CURRENTLY ROTATING
ACROSS NORTHERN TEXAS. THIS COMBINED WITH GOOD UPPER LEVEL
DIFFLUENCE SUPPORTING AN EXPANSIVE AREA OF PRECIPITATION THROUGHOUT
THE MISSISSIPPI VALLEY/MIDWEST...WITH LATEST RADAR/SFC OBS SHOWING
THE LEADING EDGE NOW ENCROACHING UPON SOUTHERN MICHIGAN. INITIAL
SURGE OF LIGHTER PRECIPITATION WILL OVERSPREAD THE ENTIRE AREA EARLY
THIS MORNING. LATEST MODEL SOUNDINGS...ALONG WITH RECENT TAMDAR
SOUNDING DATA NEAR DTW...STILL SHOW A FREEZING RAIN PROFILE AT ONSET
AS A SHALLOW SUB-FREEZING LAYER REMAINS BENEATH AN INCREASINGLY
PRONOUNCED WARM LAYER. TRENDS UPSTREAM INDICATE IT WILL TAKE LITTLE
TIME TO SCOUR OUT THIS SHALLOW COLD LAYER...ESPECIALLY ACROSS THE
SOUTHERN HALF OF THE CWA. SFC TEMPERATURES AS OF 08Z ARE NOW AT OR
ABOVE FREEZING FROM SOUTH BEND TO FINDLAY OHIO. THUS...LOOKING AT
PRIMARILY A 2-4 HOUR WINDOW OF -FZRA...BEFORE TRANSITIONING TO JUST
RAIN BETWEEN 12-15Z ALONG/SOUTH OF THE M-59 CORRIDOR...AND BY LATE
MORNING TOWARD THE NORTH.
BEST LARGE SCALE ACCENT WILL OCCUR FROM 15-21Z...LEADING TO A PERIOD
OF MODERATE/HEAVY RAINFALL AS PW VALUES APPROACH 1 INCH. QPF OF
AROUND 0.5"...COMBINED WITH A MODEST AMOUNT OF SNOWMELT...WILL
ELEVATE SOME AREA RIVERS/STREAMS. HOWEVER...OVERALL FLOODING
CONCERNS APPEAR TO BE MINIMAL...WITH THIS WARMUP APPEARING TOO BRIEF
TO MELT THE ENTIRE SNOWPACK. THE PRONOUNCED WARM AIR ADVECTION WILL
HELP PUSH TEMPERATURES BY LATE AFTERNOON/EARLY EVENING INTO THE
LOW/MID 40S. THE RAPID INCREASE IN LOW LEVEL MOISTURE...WITH
DEWPOINTS IN THE UPPER 30S...MOVING OVER THE SNOWPACK WILL LIKELY
LEAD TO AREAS OF FOG BY AFTERNOON/EVENING. A STRONG LOW LEVEL
GRADIENT WOULD SEEM TO REDUCE THE CHANCES FOR CONDITIONS TO
DETERIORATE ENOUGH TO NECESSITATE AN ADVISORY...BUT WILL NEED TO
MONITOR THIS THROUGH THE DAY.
LONG TERM...TONIGHT THROUGH SATURDAY
CONTINUED PRECIPITATION CHANCES IS THE FOCUS OF THE LONG TERM.
STRONG SURFACE LOW PRESSURE OF APPROXIMATELY 984MB WILL BE
CENTERED IN WEST CENTRAL LOWER MICHIGAN AT THE START OF THE LONG
TERM. A WELL COUPLED JET STRUCTURE ACROSS EASTERN ONTARIO AND A
NEUTRAL TO NEGATIVE TILTING OF THE LONGWAVE TROUGH WILL KEEP A
PROGRESSIVE MOVEMENT TO THE SURFACE LOW. THE LOWER ATMOSPHERE
REMAINS QUITE WARM THROUGH 6Z...AND HAVE KEPT THE ALL RAIN
MENTION (EXPECTING THE MAJORITY OF THE QPF TONIGHT TO FALL IN
THIS TIMEFRAME). THEREAFTER...THE FRONT SLIDES THROUGH CRASHING
TEMPERATURES...CHANGING LIQUID OVER TO ALL SNOW. THE POTENTIAL FOR
PRECIPITATION WILL LINGER THROUGHOUT THE NIGHT WITH THE FOLLOWING
FORCING BEYOND 00Z...TRIPLE POINT SURFACE CONVERGENCE/CYCLONIC
VORTICITY ADVECTION...A TRAILING DEFORMATION AXIS...AND DEEP
FRONTOGENESIS. PRECIPITATION AFTER 6Z IS TRICKY. CURRENT THINKING
HAS SUBSIDENCE AND FRONTOLYSIS SHUTTING DOWN OR WIDELY SCATTERING
THE SNOW SHOWERS ACROSS THE SOUTHERN HALF OF THE FA (LITTLE TO NO
ACCUMULATIONS SOUTH OF I69). FOR THE SAGINAW BAY AND THUMB
VICINITIES PESKY DEFORMATION SNOW BANDING MAY SET UP A BIT LONGER.
ADDITIONALLY...ABUNDANT RESIDUAL LOW LEVEL MOISTURE WILL NEED TO
BE SCOURED AND FEEL FRONTAL PASSAGE AND COLD AIR ADVECTION COULD
BE EFFECTIVE IN WRINGING THIS OUT. IF BANDING PERSISTS LATE ACROSS
THE NORTH...1 TO 2 INCHES WILL BE POSSIBLE.
THE GREAT LAKES REGION WILL SHIFT TO A LAKE EFFECT PATTERN AS
COLD CYCLONIC FLOW BUILDS IN THROUGH MIDWEEK. HAVE TRENDED POPS
DOWNWARD ON MONDAY WITH WEAK SYNOPTIC SUPPORT AND EXTREMELY
MARGINAL LES PARAMETERS (INVERSION HEIGHTS OF AROUND 3.5 KFT AND
DELTA T/S OF -15C). MONDAY NIGHT...PROSPECTS FOR LAKE MICHIGAN
LES MAKING IT OVER PICK UP. A REINFORCING COLD SHOT OF SUB -20C
850MB TEMPS AND STRONG PV ANOMALY WILL SETTLE INTO LOWER MICHIGAN
TUESDAY MORNING. THIS ALLOWS A FLARING OF LAKE SNOWS THROUGHOUT
THE DAY WITH DELTA T/S CLIMBING TO -20C AND EQUILIBRIUM HEIGHTS
REACHING NEAR 10KFT. TWO NEGATIVE ARE THE DRY MIDLEVELS...AND THE
NORTHWESTERLY COMPONENT IN SURFACE WINDS. A SUBSIDENCE INVERSION
WORKS DOWN THE COLUMN WEDNESDAY NIGHT REDUCING PRECIPITATION
CHANCES ONCE AGAIN. ATTM...ACCUMULATIONS ARE EXPECTED TO REMAIN
LIGHT.
GUIDANCE IS NOW ADVERTISING A SOLUTION THAT WOULD BRING A
WELCOMED QUIET PERIOD FOR SOUTHEASTERN MICHIGAN. THE LATEST
GFS/ECMWF SUGGEST ARCTIC HIGH PRESSURE SETTLES IN THURSDAY AND
LASTS INTO THE WEEKEND. HOWEVER...ROOM FOR ERROR DOES EXIST AS A
STRONG BAROCLINIC ZONE SETS UP JUST TO THE SOUTH IN UNFAMILIAR
ZONAL FLOW. ENERGY ZIPPING ALONG THE FRONT MAY ALLOW A NORTHWARD
JOG BRINGING PRECIPITATION BACK INTO THE PICTURE. HOWEVER...WITH
BOTH MODELS IN AGREEMENT ON THE DOMINANT SPRAWLING ARCTIC HIGH
THIS SOLUTION WOULD BE A NICE CHANGE. FOR NOW WILL CONTINUE THE
INHERITED PRECIPITATION CHANCES FOR THE BEGINNING OF THE WEEKEND.
TRENDED TEMPERATURES DOWNWARD THROUGH FRIDAY...GIVEN THE COLDER
GUIDANCE SOLUTIONS. DAYTIME TEMPERATURES MONDAY THROUGH THURSDAY
ARE EXPECTED TO RANGE FROM THE UPPER TEENS TO MID 20S...SOME 10
TO 15 DEGREES BELOW NORMAL. LOWS WILL GENERALLY FALL INTO THE
SINGLE DIGITS ABOVE ZERO.
MARINE...
STRENGTHENING PRESSURE GRADIENT AHEAD OF A STRONG LOW PRESSURE
SYSTEM TRACKING NORTHEAST FROM SOUTHERN LAKE MICHIGAN ACROSS LAKE
HURON WILL BRING INCREASING SOUTHERLY WINDS TODAY AND TONIGHT.
WINDS THIS AFTERNOON AND EVENING WILL APPROACH GALE FORCE OVER THE
OPEN WATERS OF LAKE HURON...WITH GUSTS OF 25 TO 30 KNOTS OVER MUCH
OF THE NEARSHORE WATERS. AFTER A BRIEF LULL OVERNIGHT AS THE LOW
MOVES THROUGH...WINDS WILL SHIFT TOWARD THE NORTHWEST AND INCREASE
AGAIN ON MONDAY AS COLDER AIR MOVES IN BEHIND THE SYSTEM. THIS
WILL BRING ANOTHER PERIOD OF WINDS TO GALE FORCE OVER THE LAKE
HURON OPEN WATERS...AND GUSTS UP TO 30 KNOTS ALONG THE NEARSHORE.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...FREEZING RAIN ADVISORY...MIZ068-MIZ069-MIZ070-MIZ075-MIZ076-MIZ082-
MIZ083...UNTIL 10 AM SUNDAY.
FREEZING RAIN ADVISORY...MIZ047-MIZ048-MIZ049-MIZ053-MIZ054-MIZ055-
MIZ060-MIZ061-MIZ062-MIZ063...UNTIL 1 PM SUNDAY.
LAKE HURON...
GALE WARNING...LHZ362-LHZ363-LHZ462-LHZ463-LHZ464...FROM 1 PM
SUNDAY TO 4 PM MONDAY.
BRISK WIND ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
HURON INCLUDING OUTER SAGINAW BAY...FROM NOON SUNDAY TO 4 PM
MONDAY.
LAKE ST CLAIR...
BRISK WIND ADVISORY...FROM NOON SUNDAY TO 4 PM MONDAY.
MI WATERS OF LAKE ERIE...
BRISK WIND ADVISORY...FROM NOON SUNDAY TO 4 PM MONDAY.
&&
$$
AVIATION.....MR
SHORT TERM...MR
LONG TERM....CB
MARINE.......MR
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
408 AM EST SUN FEB 17 2008
.SHORT TERM...TODAY
STRONG MOISTURE TRANSPORT AND WARM AIR ADVECTION ONGOING JUST
UPSTREAM THIS MORNING...IN RESPONSE TO A 60+ KNOT SOUTHERLY LOW
LEVEL JET WRAPPING AROUND A DYNAMIC MID/UPPER LOW CURRENTLY ROTATING
ACROSS NORTHERN TEXAS. THIS COMBINED WITH GOOD UPPER LEVEL
DIFFLUENCE SUPPORTING AN EXPANSIVE AREA OF PRECIPITATION THROUGHOUT
THE MISSISSIPPI VALLEY/MIDWEST...WITH LATEST RADAR/SFC OBS SHOWING
THE LEADING EDGE NOW ENCROACHING UPON SOUTHERN MICHIGAN. INITIAL
SURGE OF LIGHTER PRECIPITATION WILL OVERSPREAD THE ENTIRE AREA EARLY
THIS MORNING. LATEST MODEL SOUNDINGS...ALONG WITH RECENT TAMDAR
SOUNDING DATA NEAR DTW...STILL SHOW A FREEZING RAIN PROFILE AT ONSET
AS A SHALLOW SUB-FREEZING LAYER REMAINS BENEATH AN INCREASINGLY
PRONOUNCED WARM LAYER. TRENDS UPSTREAM INDICATE IT WILL TAKE LITTLE
TIME TO SCOUR OUT THIS SHALLOW COLD LAYER...ESPECIALLY ACROSS THE
SOUTHERN HALF OF THE CWA. SFC TEMPERATURES AS OF 08Z ARE NOW AT OR
ABOVE FREEZING FROM SOUTH BEND TO FINDLAY OHIO. THUS...LOOKING AT
PRIMARILY A 2-4 HOUR WINDOW OF -FZRA...BEFORE TRANSITIONING TO JUST
RAIN BETWEEN 12-15Z ALONG/SOUTH OF THE M-59 CORRIDOR...AND BY LATE
MORNING TOWARD THE NORTH.
BEST LARGE SCALE ACCENT WILL OCCUR FROM 15-21Z...LEADING TO A PERIOD
OF MODERATE/HEAVY RAINFALL AS PW VALUES APPROACH 1 INCH. QPF OF
AROUND 0.5"...COMBINED WITH A MODEST AMOUNT OF SNOWMELT...WILL
ELEVATE SOME AREA RIVERS/STREAMS. HOWEVER...OVERALL FLOODING
CONCERNS APPEAR TO BE MINIMAL...WITH THIS WARMUP APPEARING TOO BRIEF
TO MELT THE ENTIRE SNOWPACK. THE PRONOUNCED WARM AIR ADVECTION WILL
HELP PUSH TEMPERATURES BY LATE AFTERNOON/EARLY EVENING INTO THE
LOW/MID 40S. THE RAPID INCREASE IN LOW LEVEL MOISTURE...WITH
DEWPOINTS IN THE UPPER 30S...MOVING OVER THE SNOWPACK WILL LIKELY
LEAD TO AREAS OF FOG BY AFTERNOON/EVENING. A STRONG LOW LEVEL
GRADIENT WOULD SEEM TO REDUCE THE CHANCES FOR CONDITIONS TO
DETERIORATE ENOUGH TO NECESSITATE AN ADVISORY...BUT WILL NEED TO
MONITOR THIS THROUGH THE DAY.
&&
.LONG TERM...TONIGHT THROUGH SATURDAY
CONTINUED PRECIPITATION CHANCES IS THE FOCUS OF THE LONG TERM.
STRONG SURFACE LOW PRESSURE OF APPROXIMATELY 984MB WILL BE
CENTERED IN WEST CENTRAL LOWER MICHIGAN AT THE START OF THE LONG
TERM. A WELL COUPLED JET STRUCTURE ACROSS EASTERN ONTARIO AND A
NEUTRAL TO NEGATIVE TILTING OF THE LONGWAVE TROUGH WILL KEEP A
PROGRESSIVE MOVEMENT TO THE SURFACE LOW. THE LOWER ATMOSPHERE
REMAINS QUITE WARM THROUGH 6Z...AND HAVE KEPT THE ALL RAIN
MENTION (EXPECTING THE MAJORITY OF THE QPF TONIGHT TO FALL IN
THIS TIMEFRAME). THEREAFTER...THE FRONT SLIDES THROUGH CRASHING
TEMPERATURES...CHANGING LIQUID OVER TO ALL SNOW. THE POTENTIAL FOR
PRECIPITATION WILL LINGER THROUGHOUT THE NIGHT WITH THE FOLLOWING
FORCING BEYOND 00Z...TRIPLE POINT SURFACE CONVERGENCE/CYCLONIC
VORTICITY ADVECTION...A TRAILING DEFORMATION AXIS...AND DEEP
FRONTOGENESIS. PRECIPITATION AFTER 6Z IS TRICKY. CURRENT THINKING
HAS SUBSIDENCE AND FRONTOLYSIS SHUTTING DOWN OR WIDELY SCATTERING
THE SNOW SHOWERS ACROSS THE SOUTHERN HALF OF THE FA (LITTLE TO NO
ACCUMULATIONS SOUTH OF I69). FOR THE SAGINAW BAY AND THUMB
VICINITIES PESKY DEFORMATION SNOW BANDING MAY SET UP A BIT LONGER.
ADDITIONALLY...ABUNDANT RESIDUAL LOW LEVEL MOISTURE WILL NEED TO
BE SCOURED AND FEEL FRONTAL PASSAGE AND COLD AIR ADVECTION COULD
BE EFFECTIVE IN WRINGING THIS OUT. IF BANDING PERSISTS LATE ACROSS
THE NORTH...1 TO 2 INCHES WILL BE POSSIBLE.
THE GREAT LAKES REGION WILL SHIFT TO A LAKE EFFECT PATTERN AS
COLD CYCLONIC FLOW BUILDS IN THROUGH MIDWEEK. HAVE TRENDED POPS
DOWNWARD ON MONDAY WITH WEAK SYNOPTIC SUPPORT AND EXTREMELY
MARGINAL LES PARAMETERS (INVERSION HEIGHTS OF AROUND 3.5 KFT AND
DELTA T/S OF -15C). MONDAY NIGHT...PROSPECTS FOR LAKE MICHIGAN
LES MAKING IT OVER PICK UP. A REINFORCING COLD SHOT OF SUB -20C
850MB TEMPS AND STRONG PV ANOMALY WILL SETTLE INTO LOWER MICHIGAN
TUESDAY MORNING. THIS ALLOWS A FLARING OF LAKE SNOWS THROUGHOUT
THE DAY WITH DELTA T/S CLIMBING TO -20C AND EQUILIBRIUM HEIGHTS
REACHING NEAR 10KFT. TWO NEGATIVE ARE THE DRY MIDLEVELS...AND THE
NORTHWESTERLY COMPONENT IN SURFACE WINDS. A SUBSIDENCE INVERSION
WORKS DOWN THE COLUMN WEDNESDAY NIGHT REDUCING PRECIPITATION
CHANCES ONCE AGAIN. ATTM...ACCUMULATIONS ARE EXPECTED TO REMAIN
LIGHT.
GUIDANCE IS NOW ADVERTISING A SOLUTION THAT WOULD BRING A
WELCOMED QUIET PERIOD FOR SOUTHEASTERN MICHIGAN. THE LATEST
GFS/ECMWF SUGGEST ARCTIC HIGH PRESSURE SETTLES IN THURSDAY AND
LASTS INTO THE WEEKEND. HOWEVER...ROOM FOR ERROR DOES EXIST AS A
STRONG BAROCLINIC ZONE SETS UP JUST TO THE SOUTH IN UNFAMILIAR
ZONAL FLOW. ENERGY ZIPPING ALONG THE FRONT MAY ALLOW A NORTHWARD
JOG BRINGING PRECIPITATION BACK INTO THE PICTURE. HOWEVER...WITH
BOTH MODELS IN AGREEMENT ON THE DOMINANT SPRAWLING ARCTIC HIGH
THIS SOLUTION WOULD BE A NICE CHANGE. FOR NOW WILL CONTINUE THE
INHERITED PRECIPITATION CHANCES FOR THE BEGINNING OF THE WEEKEND.
TRENDED TEMPERATURES DOWNWARD THROUGH FRIDAY...GIVEN THE COLDER
GUIDANCE SOLUTIONS. DAYTIME TEMPERATURES MONDAY THROUGH THURSDAY
ARE EXPECTED TO RANGE FROM THE UPPER TEENS TO MID 20S...SOME 10
TO 15 DEGREES BELOW NORMAL. LOWS WILL GENERALLY FALL INTO THE
SINGLE DIGITS ABOVE ZERO.
&&
.MARINE...
STRENGTHENING PRESSURE GRADIENT AHEAD OF A STRONG LOW PRESSURE
SYSTEM TRACKING NORTHEAST FROM SOUTHERN LAKE MICHIGAN ACROSS LAKE
HURON WILL BRING INCREASING SOUTHERLY WINDS TODAY AND TONIGHT.
WINDS THIS AFTERNOON AND EVENING WILL APPROACH GALE FORCE OVER THE
OPEN WATERS OF LAKE HURON...WITH GUSTS OF 25 TO 30 KNOTS OVER MUCH
OF THE NEARSHORE WATERS. AFTER A BRIEF LULL OVERNIGHT AS THE LOW
MOVES THROUGH...WINDS WILL SHIFT TOWARD THE NORTHWEST AND INCREASE
AGAIN ON MONDAY AS COLDER AIR MOVES IN BEHIND THE SYSTEM. THIS
WILL BRING ANOTHER PERIOD OF WINDS TO GALE FORCE OVER THE LAKE
HURON OPEN WATERS...AND GUSTS UP TO 30 KNOTS ALONG THE NEARSHORE.
&&
.PREV DISCUSSION...ISSUED 1143 PM EST SAT FEB 16 2008
AVIATION...
TAF SITES EXPECTED TO EXPERIENCE SEVERAL HOURS OF FREEZING RAIN
VERY LATE TONIGHT AND SUNDAY MORNING.
00Z MODEL DATA REVEALING NO WHOLESALE CHANGE TO EARLIER FORECAST
INDICATIONS. RAPID INFLUX OF MOISTURE AND WARMER TEMPERATURES
FROM THE SOUTH ON TAP FOR LATE TONIGHT AND ESPECIALLY THROUGHOUT
THE DAY SUNDAY. 06Z TAFS WILL REFLECT CEILINGS LOWERING STEADILY
OVERNIGHT TO AROUND 25 HUNDRED FEET BY 10Z TO 11Z...FURTHER
LOWERING TO IFR DURING THE MORNING AND TO LIFR DURING THE
AFTERNOON. VISIBILITIES MVFR IN FREEZING RAIN POSSIBLY MIXED WITH
SLEET AFTER ABOUT 10Z...TRANSITIONING TO RAIN FROM SOUTH TO NORTH
14Z TO 17Z AS WARMER TEMPERATURES SURGE NORTHWARD. SURFACE DEW
POINTS CLIMBING WELL INTO THE 30S SUNDAY AFTERNOON...ATOP SNOW
COVER...EXPECTED TO LOWER PREVAILING VISIBILITIES TO AROUND A MILE
IN FOG/MIST. ONLY SLIGHT IMPROVEMENT INTO LOW MVFR CONDITIONS BY
LATE SUNDAY EVENING AS WINDS VEER TO SOUTHWEST AS COLD FRONT NEARS.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...FREEZING RAIN ADVISORY...MIZ068-MIZ069-MIZ070-MIZ075-MIZ076-MIZ082-
MIZ083...UNTIL 10 AM SUNDAY.
FREEZING RAIN ADVISORY...MIZ047-MIZ048-MIZ049-MIZ053-MIZ054-MIZ055-
MIZ060-MIZ061-MIZ062-MIZ063...UNTIL 1 PM SUNDAY.
LAKE HURON...
GALE WARNING...LHZ362-LHZ363-LHZ462-LHZ463-LHZ464...FROM 1 PM
SUNDAY TO 4 PM MONDAY.
BRISK WIND ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
HURON INCLUDING OUTER SAGINAW BAY...FROM NOON SUNDAY TO
MIDNIGHT MONDAY.
LAKE ST CLAIR...
BRISK WIND ADVISORY...FROM NOON SUNDAY TO MIDNIGHT MONDAY.
MI WATERS OF LAKE ERIE...
BRISK WIND ADVISORY...FROM NOON SUNDAY TO MIDNIGHT MONDAY.
&&
$$
SHORT TERM...MR
LONG TERM....CB
MARINE.......MR
AVIATION.....DWD
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
1155 PM EST SAT FEB 16 2008
LATEST UPDATE...AVIATION...
.SYNOPSIS...(340 PM EST SAT FEB 16 2008)
A DEVELOPING AREA OF LOW PRESSURE WILL LIFT NORTH OUT OF THE LOWER
MISSISSIPPI VALLEY TONIGHT...RIDING ACROSS LAKE MICHIGAN ON SUNDAY
MOVING INTO ONTARIO SUNDAY NIGHT. SOUTHWEST LOWER MICHIGAN WILL BE
ON THE WARMER SIDE OF THE SYSTEM...THEREFORE FREEZING RAIN IS
EXPECTED TO DEVELOP TONIGHT...CHANGING OVER TO RAIN SUNDAY. TRAVEL
MAY BECOME HAZARDOUS SUNDAY MORNING AS A LIGHT COATING OF ICE
APPEARS LIKELY. ONE TO TWO TENTHS OF AN INCH OF ICE IS EXPECTED.
COLD AIR WILL WRAP INTO THE AREA FROM THE WEST SUNDAY NIGHT AS THE
LOW LIFTS NORTHEAST AWAY FROM THE AREA. LAKE EFFECT SNOW IS EXPECTED
FROM SUNDAY NIGHT PERSISTING INTO MONDAY NIGHT. SEVERAL INCHES OF
SNOW IS POSSIBLE ALONG AND WEST OF HIGHWAY 131 DURING THIS TIME
FRAME.
&&
.SHORT TERM...(1032 PM EST SAT FEB 16 2008)
(TONIGHT THROUGH MONDAY NIGHT)
FORECAST APPEARS TO BE ON TRACK. PCPN WAS SPREADING NORTH INTO
NORTHERN IL THIS EVENING AND WILL ARRIVE IN SW MI AFTER MIDNIGHT.
WARM CORE ALOFT WAS ALREADY NOTED OVERHEAD ON TAMDAR SOUNDINGS WITH
+1C AT 4K FT. THIS LAYER WILL CONTINUE TO WARM ADVECT AND EXPAND AS
THE SURFACE TEMPS REMAIN BELOW FREEZING. FREEZING RAIN STILL
APPEARS TO BE THE PREDOMINATE PCPN TYPE...ALTHOUGH SOME SLEET MAY
MIX IN ACROSS THE NORTHERN CWA. HEADLINES LOOK FINE...HOWEVER WILL
TALK UP THE ICE ACCUMULATION A BIT MORE ACROSS THE NORTH. EXPECT WE
WILL SEE BETWEEN A QUARTER AND HALF INCH OF ICE NORTH OF HIGHWAY
46. STILL COULD ENVISION OVER A HALF INCH OF ICE POSSIBLE IN THE
FAR NORTH... NORTH OF HIGHWAY 10. THIS WHICH WOULD BE WARNING
CRITERIA...AS THIS AREA WILL BE THE SLOWEST TO WARM AS THE SURGE OF
PCPN HEADS NORTH. WILL MONITOR THE 00Z MODELS AND IRON THIS OUT ON
THE MIDNIGHT SHIFT.
PREVIOUS DISCUSSION...
MAIN FOCUS OF THE SHORT TERM IS THE BURST OF WARM AIR ADVECTION
PRECIPITATION TONIGHT INTO SUNDAY. INITIALLY COLD AIR WILL BE IN
PLACE IN THE LOWEST COUPLE THOUSAND FEET OF THE ATMOSPHERE...SO
EXPECTING FREEZING RAIN TO BE THE PREDOMINANT PRECIPITATION TYPE
OVERNIGHT AND SUNDAY MORNING. SOME SLEET WILL MIX IN AT TIMES AS
WELL. HAVE OPTED TO ISSUE A FREEZING RAIN ADVISORY FOR THE ENTIRE
CWA FROM THE OVERNIGHT HOURS INTO MIDDAY ON SUNDAY. ACCUMULATIONS OF
A TENTH OR TWO WILL BE QUITE POSSIBLE...WITH THE HIGHEST AMOUNTS
ACROSS CENTRAL LOWER MICHIGAN...WHERE THE COLD AIR WILL HANG IN THE
LONGEST.
FOG WILL ALSO BE AN ISSUE SUNDAY...AS WARM MOIST AIR IS ADVECTED
OVER A SNOWPACK. NOT EXPECTING WIDESPREAD DENSE FOG AT THIS POINT
BASED ON THE STRENGTH OF THE WIND AND GUIDANCE VALUES...BUT IT IS
CERTAINLY POSSIBLE. WE WILL BE MONITORING THIS CLOSELY.
THE PRECIPITATION SHOULD SWITCH OVER TO ALL RAIN FROM SOUTH TO NORTH
DURING THE DAY ON SUNDAY...BETWEEN 13Z AND 19Z. THE RAIN WILL BE
MODERATE TO HEAVY AT TIMES GIVEN THE STRENGTH OF THE WARM AIR
ADVECTION.
THE RAIN WILL MIX WITH AND CHANGE OVER TO SNOW FROM WEST TO EAST
BETWEEN 00Z AND 06Z TOMORROW EVENING. LAKE EFFECT SNOW WILL THEN
BECOME THE FOCUS LATE SUNDAY NIGHT INTO MONDAY NIGHT. SEVERAL INCHES
OF ACCUMULATION ARE EXPECTED IN THIS TIME FRAME...BUT IS SHOULD BE A
FAIRLY DRAWN OUT LAKE EFFECT EVENT...WITH TOTALS BELOW ADVISORY
CRITERIA EXPECTED AT THIS POINT.
&&
.LONG TERM...(254 PM EST SAT FEB 16 2008)
(TUESDAY THROUGH SATURDAY)
UPPER CYCLONIC FLOW WILL BE IN PLACE OVER MOST OF THE ERN PORTION OF
THE COUNTRY AT THE BEGINNING OF THE LONG TERM TUE MORNING. ONE WAVE
WILL MOVE OUT ON TUE...HOWEVER ONE MORE STRONG PIECE OF ENERGY WILL
DIVE DOWN FROM HUDSON BAY LATE TUE AND EARLY WED AND SLIDE NORTHEAST
OF THE STATE. COLD AIR WILL REMAIN IN PLACE...AND LAKE EFFECT WILL
REMAIN POSSIBLE THROUGH WED MORNING.
PATTERN THEN LOOKS TO SHIFT FOR THE REMAINDER OF THE PERIOD. UPPER
CYCLONIC FLOW WILL RETREAT INTO CANADA AS THE TUE NIGHT/WED ENERGY
ROUNDS THE TROUGH AND HEADS NE. PREVIOUS MODEL RUNS WERE A BIT
UNCERTAIN WITH THE EVOLUTION OF THE PATTERN...BUT IT NOW APPEARS
THAT WITH A MORE AMPLIFIED FLOW...LOWER MICHIGAN WILL BE BETWEEN
UPPER RIDGE TO THE WEST AND UPPER TROUGH TO EAST. THIS WOULD PLACE
STRONG RIDGING AT THE SFC OVERHEAD THROUGH THE END OF THE PERIOD
WITH SLOWLY MODIFYING TEMPS. PREVIOUS FORECAST HAD POTENTIAL OF PCPN
WITH A HUNG UP FRONT JUST TO THE SOUTH AND WITH ENERGY EJECTING FROM
THE SW. THE HIGH NOW SUPPRESSES THE FRONT SOUTH AND THE SW ENERGY IS
DELAYED AS EXPECTED. WE HAVE MAINTAINED A LOW CHC OF PCPN THU NIGHT
THROUGH SAT MAINLY DUE TO BEING SURROUNDED BY PCPN FROM SURROUNDING
OFFICES AND THIS BEING THE FIRST SET OF RUNS WITH GOOD MODEL
CONSENSUS. WE FEEL THAT IF MODELS CONTINUE TO SHOW THIS TREND OF
MUCH DRIER CONDITIONS FOR ANOTHER SET OF RUNS...ALMOST ALL OF THE
PCPN THU NIGHT THROUGH SAT WILL BE ABLE TO BE PULLED OUT.
&&
.AVIATION...(1155 PM EST SAT FEB 16 2008)
CLEAR SKIES INITIALLY HAVE ALLOWED FOR COLDER
TEMPERATURES. WHAT THIS MEANS TO TAFS SITES...IS A LONGER PERIOD OF
FREEZING RAIN SUN AM. SOME SLEET COULD MIX IN AT THE ONSET FROM
KMKG TO KGRR TO KLAN. LOW LEVEL WIND SHEAR COULD BECOME AN ISSUE
PRIOR TO THE WARM FRONTAL PASSAGE 16Z TO 18Z SUN. WARMER AIR WILL
EVENTUALLY OVERSPREAD ALL TAF SITES BY 15Z. AT THAT TIME...FOG AND
LOW CLOUDS SHOULD BE WIDESPREAD WITH LIFR CONDITIONS EXPECTED. NO
IMPROVEMENT IN THE CLOUD HEIGHTS OR VSBYS THROUGH 06Z MON...EXCEPT
FOR KMKG DUE TO THE COLD FRONTS ARRIVAL.
&&
.MARINE...(340 PM EST SAT FEB 16 2008)
HAVE ISSUED A SMALL CRAFT ADVISORY FROM HOLLAND NORTH TONIGHT INTO
TOMORROW MORNING. SOUTH FLOW SHOULD BUILD WAVES HEIGHTS TO SMALL
CRAFT CRITERIA IN ABOUT THE NORTHERN HALF OF THE NEARSHORE AREA.
NEXT ISSUE WILL BE THE WINDS BEHIND THE COLD FRONT SUNDAY NIGHT.
WINDS WILL LIKELY APPROACH GALE FORCE...WITH WAVES BUILDING TO
AROUND 10 FEET. LATER FORECASTS WILL ADDRESS THIS THREAT.
&&
.HYDROLOGY...(340 PM EST SAT FEB 16 2008)
HYDROLOGY MAY BECOME A CONCERN OVER THE NEXT FEW DAYS...AS A WARM UP
ON SUNDAY COMBINED WITH A DECENT DOSE OF RAIN WILL ACT TO BRING
RISES TO AREA RIVERS. AT THIS POINT LOOKS LIKE A HALF INCH TO INCH
OF RAIN WILL BE LIKELY AS THE WARM AIR SURGES THROUGH THE REGION.
THE WARM UP WILL BE RATHER BRIEF AND THE COLD SNAP TOMORROW NIGHT
WILL TEND TO HOLD THINGS IN CHECK. WILL BE MONITOR THE POTENTIAL FOR
LOCALIZED FLOODING WITH THE MODERATE RAIN ON SUNDAY. RESIDUAL
AFFECTS WILL THEN BE FELT AS THE WATER WORKS ITS WAY INTO AREA
RIVERS AND STREAMS. LATER FORECASTS BOTH TONIGHT AND TOMORROW WILL
BEGIN TO INCORPORATE MORE OF THE QPF. THIS WILL DETERMINE THE EXTENT
OF THE POTENTIAL FLOODING.
ICE JAMS WILL CONTINUE TO BE A PROBLEM THROUGH THIS COMING WEEK AS
MORE POLAR AIR EARLY IN THE WEEK WILL ONLY COMPLICATE HYDRO ISSUES.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...FREEZING RAIN ADVISORY FOR ALL OF SW MI OVERNIGHT INTO SUNDAY.
LM...SMALL CRAFT ADVISORY TONIGHT THROUGH SUNDAY MORNING.
&&
$$
SYNOPSIS: DUKE
SHORT TERM: DUKE/JK
LONG TERM: NJJ
AVIATION: MJS
MARINE: DUKE
HYDROLOGY: DUKE
AREA FORECAST DISCUSSION...UPDATED
NWS DULUTH MN
1130 PM CST SAT FEB 16 2008
.UPDATE...
UPDATED ZFP TO CANX WINT WEA ADVY AND TO REMOVE ZR AND IP FROM
FCST. ALL REPORTS NOW SHOWING -SN.
&&
.PREV DISCUSSION... /ISSUED 1005 PM CST SAT FEB 16 2008/
UPDATE...
STILL GETTING REPORTS OF UNKN PRECIP FROM PINE RIVER AUTOMATED
OBSV SITE...AND CASS CO SHERIFF REPORTED SOME LIGHT -FZRA EARLIER
THIS EVE...BUT WARM LYR ALOFT HAS ERODED RAPIDLY WITH EVAP
COOLING. 00Z MODEL SOUNDINGS SHOWING ONLY A VERY SHALLOW WARM LYR
ATTM...WHICH DISAPPEARS ALTOGETHER BY 06Z. WILL LIKELY CANX WINT
WEA ADVY BY MIDNIGHT AND REMOVE -FZRA FROM THE OVNGT FCST...BUT
WOULD LIKE TO WAIT ANOTHER HR OR SO TO SEE IF THERE ARE ANY MORE
INDICATIONS OF FZG OR MIXED PRECIP.
PREV DISCUSSION... /ISSUED 355 PM CST SAT FEB 16 2008/
DISCUSSION...NORTHERN STREAM IMPULSE CONTINUES TO AMPLIFY THIS
AFTERNOON WHILE DIGGING SEWD FROM SASKATCHEWAN. RATHER STRONG
DYNAMIC FORCING FOR ASCENT EXISTS CURRENTLY FROM ERN ND NEWD INTO
SW ONTARIO WHERE A 50-80 MILE WIDE BAND OF MIXED PRECIPITATION HAS
DEVELOPED. WE EXPECT THIS LOBE OF FORCING AND PRECIP TO TRANSLATE
STEADILY EASTWARD OVERNIGHT WITH THE UPPER LEVEL IMPULSE..WHICH
SHUD SPREAD PRECIP INTO THE WRN DLH CWA BETWEEN 6-9 PM..AND
REACHING THE MN ARROWHEAD SOMETIME AFTER MIDNIGHT. SFC TEMPS ARE
CURRENTLY ABOVE FREEZING IN MANY AREAS..BUT EXPECT THAT THEY WILL
FALL BACK BELOW FREEZING IN THE NEXT COUPLE HOURS WITH A SHORT
WINDOW OF RADIATIONAL COOLING BEFORE CLOUDS THICKEN UP AGAIN AS
THE FRONT APPROACHES. EXAMINATION OF RECENT TAMDAR SOUNDINGS
INDICATES A THAT THE MODELS CONTINUE TO UNDERESTIMATE THE
MAGNITUDE OF THE WARM LAYER ALOFT..SO EXPECT THE PRECIP TO BEGIN
AS FREEZING RAIN OR A MIXTURE OF FZRA/PL/SN AND THEN TRANSITION TO
SNOW FROM WEST TO EAST AS THE NIGHT PROGRESSES. GROUND/ROAD TEMPS
ARE LIKELY TO BE WELL BELOW FREEZING BY THE TIME THE PRECIP
ONSETS..SO WE HAVE OPTED TO HOIST A WINTER WX ADVISORY FOR ALL OF
OUR MINNESOTA COUNTIES WITH THE EXCEPTION OF PINE FOR TONIGHT AND
EARLY SUNDAY MORNING.
NORTHERN STREAM WAVE BEGINS TO WEAKEN TOMORROW AS SOUTHERN STREAM
WAVE AND ASSOCIATED PHASING/DEEP SURFACE LOW DEVELOPMENT MOVES
FROM THE SRN PLAINS INTO THE GREAT LAKES REGION. RIGHT NOW..IT
APPEARS THAT THE HEAVY SNOWS ON THE NW PERIPHERY OF THIS SYSTEM
WILL REMAIN JUST TO THE EAST OF THE DULUTH CWA..BUT SOME MINOR
ACCUMS PERHAPS UP TO 4 INCHES MAY AFFECT PARTS OF PRICE/IRON
COUNTIES. THE BIGGER STORY WILL BE THE LAKE EFFECT MACHINE
CRANKING UP AGAIN SUNDAY NIGHT AND MONDAY AS ANOTHER SHOT OF VERY
COLD AIR PLUNGES SOUTHWARD. WE HAVE ISSUED A WINTER STORM WATCH
FOR LK EFFECT SNOWS FOR ASHLAND/IRON COUNTIES FROM MIDNIGHT SUNDAY
NIGHT THROUGH MIDNIGHT MONDAY NIGHT IN EXPECTATION OF HEAVY SNOW
SHOWERS DEVELOPING.
FAST NW FLOW IS PROGGED TO REMAIN IN PLACE ACROSS THE REGION THRU
MUCH OF NEXT WEEK..ALONG WITH COLD TEMPS AND PERHAPS A COUPLE OF
WINDOWS FOR SOME LIGHT SNOW WITH LOW AMPLITUDE FAST-MOVING
IMPULSES. WARMER TEMPS LOOK TO BE ON TAP FOR LATE NEXT WEEK AS
LARGER SCALE FLOW DEAMPLIFIES AND A MODIFIED PACIFIC AIRMASS IS
FINALLY ABLE TO ADVECT NEWD FROM THE LEE OF THE ROCKIES.
AVIATION...VFR CONDITIONS WILL START THE NIGHT ACROSS THE CWA...
WITH SCT-BKN MID CLOUDS. HOWEVER...AS THE NIGHT WEARS ON...MVFR
CIGS WILL BECOME RATHER WIDESPREAD. A TROUGH OF LOW PRESSURE
MOVING IN FROM THE NORTHWEST...AND A POWERFUL STORM SYSTEM
SPREADING INTO WISCONSIN... WILL RESULT IN A PROLIFERATION OF LOW
CLOUDS AS THE NIGHT WEARS ON. OF PARTICULAR CONCERN FOR TONIGHT
WILL BE THE POTENTIAL FOR FZRA THAT COULD RESULT IN SIGNIFICANT
ICING. LOCAL IFR CIGS/VSBYS WILL ALSO BE POSSIBLE OVERNIGHT.
&&
POINT TEMPS/POPS...
DLH 22 24 -1 10 / 50 30 40 30
INL 15 17 -6 5 / 80 30 40 30
BRD 22 25 -1 10 / 50 30 20 10
HYR 22 30 0 10 / 30 50 40 30
ASX 22 31 5 13 / 30 50 60 60
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...WINTER STORM WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY EVENING
FOR ASHLAND-IRON.
$$
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