AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
114 PM PST SAT FEB 24 2007
.SYNOPSIS...
HIGH PRESSURE OVER THE AREA TODAY WILL GIVE WAY TO DEVELOPING LOW
PRESSURE ON SUNDAY. INCREASING ONSHORE FLOW WILL BRING COOLING...
GUSTY WINDS IN THE MOUNTAINS AND DESERTS...AND AN INCREASE IN
CLOUDINESS ALONG AND WEST OF THE MOUNTAINS. THERE IS ALSO A CHANCE
FOR SOME LIGHT PRECIPITATION TO BREAK OUT AT TIMES ON THE COASTAL
SLOPES BEGINNING SUNDAY NIGHT AND CONTINUING THROUGH TUESDAY. SOME
PATCHY DRIZZLE WILL BE POSSIBLE AT TIMES WEST OF THE MOUNTAINS AS
WELL...WITH THE BEST CHANCE FOR MEASURABLE LIGHT RAIN COMING ON
TUESDAY AS A TROUGH OF LOW PRESSURE SWINGS THROUGH THE REGION. THEN
BREEZY AT TIMES AND AND CONTINUED COOL THROUGH FRIDAY.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
SUNSHINE AND LIGHT WINDS MADE FOR A PLEASANT DAY ACROSS THE
SOUTHLAND...EVEN THOUGH MAX TEMPERATURES WERE STILL RUNNING A BIT
BELOW AVERAGE. SURFACE PRESSURE GRADIENTS WERE WEAK AND THE AIR
FAIRLY DRY WITH DEWPOINTS IN THE 20S AND 30S IN MOST AREAS WEST OF
THE MOUNTAINS. SUNDAY SHOULD STILL BE A DECENT DAY...BUT THE WEATHER
WILL DETERIORATE GRADUALLY AS THE WEST WINDS INCREASE AND THE
MARINE LAYER RETURNS.
SURFACE HIGH PRESSURE OVER THE AREA TODAY WILL WEAKEN OVERNIGHT AND
SUN AS WEAK HIGH PRESSURE ALOFT GIVES WAY TO INCREASING NW FLOW
ALOFT. DEVELOPING LOW PRESSURE OVER THE GREAT BASIN WILL BRING A
RETURN OF BRISK ONSHORE FLOW TO SOUTHWEST CALIFORNIA AND A DEEP
MARINE LAYER BEGINNING ON SUN AFTERNOON. THE MOIST WESTERLY FLOW
WILL BRING FOG...AND POSSIBLY LIGHT PRECIPITATION TO THE COASTAL
SLOPES...WITH PATCHY DRIZZLE POSSIBLE WEST OF THE MOUNTAINS AS WELL
BEGINNING SUNDAY NIGHT. THE WIND WILL BE STRONG AND GUSTY IN THE
MOUNTAINS AND DESERTS...AND COULD INCREASE TO NEAR ADVISORY STRENGTH
ON SUNDAY. THE ONSHORE FLOW AND ADDITIONAL MARINE CLOUDS WILL KEEP
DAYTIME TEMPERATURES SEVERAL DEGREES BELOW AVERAGE.
A LONG-WAVE TROUGH IS FORECAST TO SWING THROUGH THE REGION ON TUE.
ALL THE MAJOR MODELS ARE SIMILAR WITH THE INTENSITY AND TIMING...SO
IT LOOKS LIKE OUR BEST CHANCE FOR SOME MORE WIDESPREAD MEASURABLE
PRECIPITATION WOULD BE ON TUE. SOME SNOW WILL BE POSSIBLE IN THE
MOUNTAINS AS THE FREEZING LEVEL FALLS BELOW 5K FT TUE NIGHT AND WED.
IF THE PRECIP MATERIALIZES...EARLY INDICATIONS ARE MOST AREAS WOULD
RECEIVE LESS THAN ONE-HALF INCH...EXCEPT THE COASTAL SLOPES WHICH
WOULD GET ENHANCEMENT FROM THE STRONG UPSLOPE FLOW.
SOME LIGHT RAIN AND SNOW COULD LINGER INTO WED...DEPENDING ON THE
SPEED OF THE TROUGH. COOL AND BREEZY CONDITIONS ARE LIKELY TO LINGER
INTO THU...FOLLOWED BY WEAK OFFSHORE FLOW...CLEAR SKIES...AND SOME
MINOR WARMING FOR FRI AND SAT.
&&
.AVIATION...
241930Z...WEAK OFFSHORE FLOW CONTINUES BUT IS TRENDING ONSHORE AND
IS EXPECTED TO BECOME ONSHORE THIS AFTERNOON. LATE MORNING ACARS
SOUNDINGS INDICATE THE MARINE LAYER REMAINS DISRUPTED. EXPECT SOME
RECOVERY TO BEGIN THIS EVENING AS THE ONSHORE FLOW RETURNS. MORE
SIGNIFICANT DEEPENING OF THE MARINE LAYER IS EXPECTED SUNDAY
AFTERNOON WITH THE DEPTH TO 4000 FEET OR DEEPER EXPECTED SUNDAY
NIGHT.
A MOSTLY CLEAR SKY IS EXPECTED ALL AREAS THROUGH THIS EVENING. SOME
STRATUS/FOG COULD FORM ALONG THE COAST AFTER MIDNIGHT AND SOME
RADIATIONAL FOG IS POSSIBLE AROUND KCNO BEFORE SUNRISE ON SUNDAY.
KSAN...KCRQ AND KSNA...NO SIGNIFICANT WEATHER ISSUES THROUGH THIS
EVENING. STRATUS COULD MOVE OVER THE AIRPORTS AFTER MIDNIGHT. BASES
SHOULD BE AROUND 800 TO 1000 FEET MSL WITH TOPS TO 1200 FEET MSL.
KONT...NO SIGNIFICANT WEATHER ISSUES THROUGH THIS EVENING. PATCHY
FOG IS POSSIBLE VICINITY OF THE AIRPORT BEFORE SUNRISE ON SUNDAY
WHICH COULD MOVE OVER THE AIRPORT FROM TIME TO TIME. ANY FOG SHOULD
DISSIPATE WITHIN AN HOUR OR TWO AFTER SUNRISE.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
$$
PUBLIC...JAD
AVIATION/MARINE...HORTON
NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION
NWS MIAMI FL
816 AM EST SAT FEB 24 2007
.UPDATE...A SCATTEROMETER PASS ACROSS THE AREA THIS MORNING SHOWS
WINDS PREVAILING ACROSS THE ATLANTIC WATERS AT AROUND 15 KT AND 10
TO 15 KT ACROSS THE GULF WATERS. FOWEY ROCKS IS SHOWING INCREASING
WINDS JUST OVER 15 KNOTS. THE MIAMI SOUNDING THIS MORNING AND ACARS
DATA SHOW WINDS IN THE 15-17 KT RANGE BETWEEN 1-2K FT. SO WITH AN
INCREASING PRESSURE GRADIENT TODAY...EXPECTING WINDS ACROSS THE
COASTAL WATERS TO INCREASE TO 15 TO 20 KNOTS. THUS...UPDATED
GRIDS/ALL PRODUCTS TO ACCOUNT FOR THIS. THIS WIND WILL RESULT IN A
HIGH RISK OF RIP CURRENTS AT THE ATLANTIC BEACHES...AND A MARINE
WX STMT WAS SENT TO HIGHLIGHT THIS. OTHERWISE...ANOTHER NICE DAY
IS IN STORE FOR THE AREA...AS HIGH PRESSURE REMAINS IN CONTROL OF
OUR WEATHER. NO OTHER SIGNIFICANT CHANGES TO THE FCST ARE
ANTICIPATED THIS MORNING. /GREGORIA
&&
.PREV DISCUSSION... /ISSUED 255 AM EST SAT FEB 24 2007/
DISCUSSION...HIGH PRESSURE RIDGE ORIENTED N-S FROM THE GREAT
LAKES REGION TO THE ATLANTIC JUST E OF FLA ALONG WITH NEAR ZONAL
UPPER FLOW CONTINUES TO DOMINATE OUR WEATHER. LARGE CUT OFF LOW
DEVELOPING OVER THE CENTRAL PLAINS STATES WILL GRADUALLY MOVE NE
DRAGGING A SFC FRONT INTO N FLA ON SUNDAY. THIS WILL SHOVE THE
RIDGE TO THE EAST AND DOING SO WINDS WILL VEER TO THE E AND SE
HELPING TO INCREASE LOW LEVEL MOISTURE. ALTHOUGH IT WILL TAKE
AWHILE TO RECOVER FROM SUCH LOW DEW POINTS AS SEEN YESTERDAY AND
HAVE THUS LOWERED SUNDAY POPS ACCORDINGLY. GFS HAS ALSO BACKED OFF
ON THESE POPS. MOISTURE LEVELS WILL CONTINUE TO INCREASE THROUGH
EARLY NEXT WEEK AND POPS WILL THEN BE ON THE INCREASE. ENOUGH
INSTABILITY WILL EXIST BY TUESDAY KEPT THE WORDING OF SLIGHT
CHANCE OF THUNDER IN THE ZONES. ALL OF THIS MATERIALIZES WITH THE
SLOW SOUTHWARD MOVEMENT OF THE FRONT AND THE GFS CONTINUES TO
STRUGGLE WITH JUST HOW FAR SOUTH THE FRONT WILL ACTUALLY GET. IT
NOW BRINGS THE FRONT THROUGH S FLA ON WEDNESDAY WITH SOME SLIGHT
DRYING AND A COUPLE OF DEGREES OF COOLING. SO WE SHALL SEE.
AVIATION...VFR CONDITIONS WILL CONTINUE THROUGH THE PERIOD. THERE IS A
POSSIBILITY OF OCNL MVFR VSBY CONDITIONS IN FOG AT TMB. LIGHT
WIND FLOW AND SUFFICIENT TEMP/DEWPOINT SPREAD WILL HINDER FOG
DEVELOPMENT. OTHERWISE, A SCATTERED FAIR WEATHER CUMULUS DAY WITH
EAST WINDS UP TO 15 KNOTS.
MARINE...WINDS WILL CONTINUE TO VEER TO THE SE THROUGH THE
WEEKEND AND INCREASE IN SPEED AS THE GRADIENT TIGHTENS. SEAS WILL
BEGIN AT LESS THAN 5 FEET AND THEN BUILD TO 6 FEET BY SUNDAY
BEFORE SUBSIDING AGAIN NEXT WEEK WITH THE APPROACH OF THE FRONT.
FIRE WEATHER...DEW POINTS HAVE SLOWLY RECOVERED FROM 24 HOURS AGO
AND SHOULD CONTINUE TO DO SO. RH VALUES WILL DROP BELOW 40 PERCENT
THIS AFTERNOON OVER GLADES AND HENDRY COUNTIES BUT THINKING IS
THAT THEY WILL STAY ABOVE THE 35 PERCENT THRESHOLD. DEW POINTS
WILL CONTINUE TO CLIMB INTO EARLY NEXT WEEK.
&&
.PRELIMINARY POINT TEMPS/POPS...
WEST PALM BEACH 76 66 81 69 / 0 - 10 20
FORT LAUDERDALE 77 68 81 69 / 0 - 10 20
MIAMI 76 64 82 69 / 0 - 10 20
NAPLES 80 63 81 68 / 0 - 10 20
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
AM...NONE.
GM...NONE.
&&
$$
LONG TERM...30/KOB
SHORT TERM/AVIATION...18/GR
AREA FORECAST DISCUSSION...COR FOR HEADLINES
NWS CHICAGO/ROMEOVILLE IL
230 PM CST SAT FEB 24 2007
.DISCUSSION AFTERNOON FORECAST
STRONG RAPIDLY OCCLUDING LOW OVER CENTRAL KANSAS DESTINED TO MOVE
TOWARD NRN ILL LATER SUN AND MON BUT BE FILLING OVER TIME. INITIAL
CONCERN HOWEVER IS APPROACHING BAND OF RAIN THROUGH CENTRAL ILL. SFC
TEMPS ACROSS FCST AREA HAVE INCHED TOWARD 30-32F TODAY BUT HAVE
STRONG CONCERNS ABOUT CONTINUING FEED OF DRY AIR FROM EAST. ONCE
PRECIP FALLS INTO THIS ZONE THE WET BULB TEMP WILL BE REACHED WHICH
IS WELL BELOW 32F. THUS ANY PROGRESS IN WARMING TODAY WILL BE OFFSET
BY EVAP COOLING MUCH LESS DARKNESS.
FOCUS OF APPROACHING PRECIP AREA APPEARS TO BE SINKING TOWARD THE
OHIO VALLEY BUT MODELS SUGGEST VERY STRONG WARMING ALOFT WITH MARKED
VEERING SIGNATURE IN MODEL AND ACARS WIND FIELDS. THIS SHOULD FORCE
A PERIOD OF STEADY POTENTIALLY MODERATE RAIN FOR A FEW HOURS THIS
EVENING BEFORE AREA IS OVER RUN BY A DEVELOPING DRY SLOT /ALOFT/
FROM SW. TIMIMG STILL ON TRACK FOR MAIN EVENT BETWEEN 00Z AND 06Z
THIS EVENING. SOME MIX OF PRECIP IS LKLY MAINLY SLEET OVER SRN AND
CENTRAL FCST AREA WITH SNOW AND SLEET FURTHER N ALONG THE WISCONSIN
BORDER. ANY SNOW AMOUNTS WILL BE HELD DOWN BY PRECIP MIX.
WITH LOW TRACKING OVERHEAD LATER SUN AND MON AIRMASS WITH COOL AND
LINGERING PRECIP WILL BE TURNED TO SNOW. CANT RULE OUT AREAS OF
LIGHT SNOW ACCUMULATION MAINLY SUNDAY NIGHT AND MONDAY AS UNDERMINED
IMPULSES PIVOT AROUND DECAYING SYSTEM. IT WILL BE MID WEEK BEFORE
SUSTAINED CLEARING OCCURS. UPPER AIR PATTERN SHOWS THE APPROACHING
LOW RUNNING HEAD LONG INTO A TEMPORARY BLOCKING PATTERN WHICH
ACCOUNTS FOR THE SLUGGISH RETREAT. HOWEVER THIS SITUATION WONT LAST
LONG AND ANOTHER SIMILAR HIGH AMPLITUDE TROUGH FCST TO SWING THROUGH
THE AREA ABOUT THUR-FRI. THIS TIME NO ICE.
NEXT 12HRS WILL BE CRITICAL FOR FORECAST AREA. GIVEN EXPECTATION OF
SUBFREEZING SFC TEMPS THROUGH AT LEAST THE FIST PART OF THE NIGHT
AND POTENTIAL INTENSITY OF RAIN THE COURSE OF LEAST REGRET DICTATES
AN ICE STORM WARNING FOR THE CENTRAL 2/3 OF FCST AREA WITH A WINTER
STORM WARNING ALONG THE WISC BORDER...MAINLY FOR SNOW AND SLEET SOME
FRZG RAIN. SOUTHERN THIRD OF AREA WILL CONTINUE A FREEZING RAIN
ADVISORY. ALL ARE 6PM THIS EVENING TO 6AM SUNDAY. EXPECT MOST
INTENSE PRECIPITATION DURING FIRST 6HRS THIS EVENING. DRYING ALOFT
LATER IN THE NIGHT MAY REDUCE PRECIP TO DRIZZLE.
THRESHOLD FOR ICE STORM IS QUARTER INCH OF ICE AND WITH EXPECTED
INTENSITY OF RAIN THIS LEVEL MAY BE REACHED IN MANY SPOTS. TEMPS
COULD STRUGGLE ABOVE FREEZING LATER TONIGHT IN WARNING AREA...AND
LIKELY BE IN LOW TO MID 30S ON BY SUNDAY AFTERNOON. THIS IS ONE OF
THE MORE CHALLENGING FCST SITUATIONS OF RECENT MEMORY. KML
&&
.AVIATION...
650 AM CST
MAJOR STORM SYSTEM CENTERED OVER THE CENTRAL PLAINS ALREADY MAKING
IT PRESENCE KNOWN FAR AND WIDE. BIGGEST CONCERN FOR LOCAL AREA IN
SHORTER TERM IS WINDS. EAST WINDS ALREADY GUSTING TO 30KTS IN
CENTRAL AND NORTHWEST IL EARLY THIS MORNING AND CONTINUE TO INCREASE
IN STRENGTH TODAY EVEN THOUGH LOW LEVEL INVERSION REMAINS IN PLACE.
DEEPENING LOW PRESSURE IN KS AND STRONG HIGH PRESSURE RIDGE
EXTENDING FROM HUDSON BAY SOUTHWARD TO THE SE U.S. WILL MAINTAIN
TICHT PRESSURE GRADIENT ACROSS THE REGION. AS LOW APPROACHES THE
LOWER MO VALLEY BY LATE AFTERNOON EXPECT GUSTS TO AROUND 35 KTS
LOCALLY. AS THE VERY DYNAMIC SYSTEM MOVES INTO THE MID MS VALLEY
TONIGHT THE BIG QUESTION FOR THE TERMINALS IS PRECIP TYPE AS SEVERAL
FACTORS INVOLVED. THERE IS THE CONTINUED FEED OF VERY DRY LOW LEVEL
AIR TO MAINTAIN EVAPORATIVE COOLING EVEN AFTER PRECIP BREAKS OUT
LATE THIS AFTERNOON...THERE IS THE MASSIVE WARM AIR ADVECTION WITH
MODELS SHOWING 60 TO 75 KT SE WINDS AT 850 MB BY 00Z SUN...THERE IS
THE ADIABATIC COOLING RESULTING FROM THE STRONG ASCENT...AND THE
RELEASE OF LATENT HEAT AS WATER VAPOR CONDENSES. FINE BALACE OF
THESE FACTORS RESULTS IN WHERE SURFACE WILL REMAIN COLD ENOUGH AND
WAA STRONG ENOUGH TO OVERCOME DYNAMIC COOLING TO KEEP FZRA AND PL
GOING AND WHERE/WHEN COLUMN WILL BE COLD ENOUGH TO SUPPORT ONLY SN.
HAVE BASICALLY FOLLOWED 00Z ENSEMBLE MEAN FORCAST AS GOOD COMPROMISE
AT THIS POINT. THIS LEADS TO INITIAL OUTBREAK OF PCPN TO BE AS FZRA
AND PL...CHANGING TO MAINLY RA THIS EVE FOR GYY AND MDW AS WAA
PUNCHES NORTHWARD...BUT TURNING TO SN FOR RFD AND ORD AS MAX OF UVV
EXPECTED TO BE ENOUGH TO COOL COLUMN.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...WINTER STORM WARNING 6PM SAT TO 6AM SUN FOR WISC BORDER
COUNTIES
ICE STORM WARNING 6PM TO 6AM OGLE TO COOK COUNTY SOUTH TO
LASALLE TO KANKAKEE COUNTY
FREEZING RAIN ADVISORY 00 UTC TO 12 UTC SUNDAY LIVINGSTON
IROQUOIS AND FORD COUNTIES IN ILLINOIS.
.IN...ICE STORM WARNING LAKE PORTER NEWTON AND JASPER CO 00Z TO 12Z.
FREEZING RAIN ADVISORY BENTON COUNTY FROM 00 UTC TO 12 UTC
SUNDAY.
.LM...GALE WRNG ALL LM AND NR SHORES TODAY THROUGH SUNDAY NIGHT.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
650 AM CST SAT FEB 24 2007
.UPDATE...
635 AM CST
WE SAW THE OUTPUT FROM THE THE 06 UTC LOCALLY RUN WRF ARW MODEL WITH
SOME ADVANCED PRECIPITATION PHYSICS. WE DECIDED TO UPDATE THE SNOW
AMOUNTS AND TOTAL STORM ACCUMULATION FOR TONIGHT AND SUNDAY.
&&
.DISCUSSION...
345 AM CST
THIS IS A VERY DYNAMIC AND BAROCLINIC SURFACE CYCLONE DEVELOPING
IN KANSAS. THERE IS STRONG WARM AIR ADVECTION EAST OF THE LOW WHICH
IS IN WESTERN KANSAS. THUNDERSTORMS FROM OKLAHOMA TO WESTERN IOWA
SHOW THE LARGE INSTABILITY. THE PROFILER WIND AT 300 MB AT 09 UTC
SHOWS A 120 KNOT JET STREAK IN WEST CENTRAL TEXAS. WATER VAPOR LOOPS
SHOW THE INTENSE CIRCULATION OVER SOUTHEAST COLORADO. WE EXPECT THIS
SURFACE CYCLONE TO DEEPEN AND MOVE INTO SOUTHEAST IOWA BY 12 UTC
SUNDAY. THE ACARS SOUNDING AT ORD SHOWS AN INVERSION AND THE STRONG
WIND ABOVE 1400 FT FROM THE EAST. TAMDAR SOUNDING AT PIA AT 336 UTC
SHOWS A DRY LAYER AROUND 900 MB. THIS DRY LAYER WAS UP TO 800 MB.
AS THE LOW DEEPENS THE WIND WILL INCREASE DUE TO THE INCREASE IN THE
PRESSURE GRADIENT. WE MAY HAVE WIND GUSTS TO 40 MPH IN NORTH CENTRAL
ILLINOIS. UPPER AIR SUPPORT WITH THIS STORM AND A STRONG COLD
CONVEYOR BELT WILL INCREASE MID LEVEL BAROCLINICITY AND INCREASE
UPWARD VERTICAL MOTION OVER NORTHERN ILLINOIS AND NORTHWEST INDIANA.
THIS CAN BE SEEN ON THE ISENTROPIC FORECASTS FOR 290 AND 300 K
SURFACES. THE WARM AIR WHICH WILL WRAP AROUND THE EAST SIDE OF THE
LOW WILL KEEP THE SNOW TO A MINIMUM OVER THE SOUTHERN PARTS OF THE
FORECAST AREA OF NORTHERN ILLINOIS AND NORTHWEST INDIANA. WE WILL
FORECAST THE HEAVIEST SNOW ALONG THE WISCONSIN BORDER. THE STRONG
WIND AND SNOW IS EXPECTED TO CAUSE BLOWING SNOW. SO A BLIZZARD
WARNING WAS ISSUED FOR EXTREME NORTHERN ILLINOIS. THE CENTER PART OF
THE FORECAST AREA CAN EXPECT FREEZING RAIN...SLEET AND SNOW. THERE
WILL BF FREEZING RAIN AND RAIN WILL IN THE SOUTH THIRD OF THE
FORECAST AREA.
WE WILL ISSUE A WINTER STORM ADVISORY FOR MOST OF NORTHEAST
ILLINOIS. THIS WILL BE FOR FREEZING RAIN AND ICE PELLETS. A DRY SLOT
MAY MOVE INTO EASTERN ILLINOIS AND NORTHWEST INDIANA BY SUNDAY
MORNING. THE FORECAST SOUNDINGS SHOW FREEZING RAIN IN THE SOUTHERN
PORTIONS OF THE CWA AND IN INDIANA. WE WILL FORECAST FREEZING RAIN
FOR THOSE COUNTIES. ON SUNDAY NIGHT THE SURFACE LOW MOVES INTO
NORTHERN ILLINOIS. WE EXPECT THE WIND TO DIMINISH LATE SUNDAY
AFTERNOON. THEN COLD AIR IS EXPECTED TO MOVE IN AND THE
PRECIPITATION WILL BECOME SNOW. ALONG THE WISCONSIN BORDER THIS
STORM MAY PRODUCE UP TO EIGHT INCHES OF SNOW FOR A TOTAL SNOWFALL BY
MONDAY MORNING.
BY TUESDAY THE 500 MB CLOSED LOW WILL BE OVER MICHIGAN. THE
PRECIPITATION WILL MOVE EAST BY THURSDAY THE HIGH TEMPERATURES
WILL BE IN THE 40S. BY FRIDAY ANOTHER 500 MB TROUGH WAVE IS EXPECTED
TO BE OVER MINNESOTA AND IOWA GIVING A CHANCE OF RAIN AND SNOW
WEDNESDAY NIGHT AND THURSDAY.
&&
.AVIATION...
650 AM CST
MAJOR STORM SYSTEM CENTERED OVER THE CENTRAL PLAINS ALREADY MAKING
IT PRESENCE KNOWN FAR AND WIDE. BIGGEST CONCERN FOR LOCAL AREA IN
SHORTER TERM IS WINDS. EAST WINDS ALREADY GUSTING TO 30KTS IN
CENTRAL AND NORTHWEST IL EARLY THIS MORNING AND CONTINUE TO INCREASE
IN STRENGTH TODAY EVEN THOUGH LOW LEVEL INVERSION REMAINS IN PLACE.
DEEPENING LOW PRESSURE IN KS AND STRONG HIGH PRESSURE RIDGE
EXTENDING FROM HUDSON BAY SOUTHWARD TO THE SE U.S. WILL MAINTAIN
TICHT PRESSURE GRADIENT ACROSS THE REGION. AS LOW APPROACHES THE
LOWER MO VALLEY BY LATE AFTERNOON EXPECT GUSTS TO AROUND 35 KTS
LOCALLY. AS THE VERY DYNAMIC SYSTEM MOVES INTO THE MID MS VALLEY
TONIGHT THE BIG QUESTION FOR THE TERMINALS IS PRECIP TYPE AS SEVERAL
FACTORS INVOLVED. THERE IS THE CONTINUED FEED OF VERY DRY LOW LEVEL
AIR TO MAINTAIN EVAPORATIVE COOLING EVEN AFTER PRECIP BREAKS OUT
LATE THIS AFTERNOON...THERE IS THE MASSIVE WARM AIR ADVECTION WITH
MODELS SHOWING 60 TO 75 KT SE WINDS AT 850 MB BY 00Z SUN...THERE IS
THE ADIABATIC COOLING RESULTING FROM THE STRONG ASCENT...AND THE
RELEASE OF LATENT HEAT AS WATER VAPOR CONDENSES. FINE BALACE OF
THESE FACTORS RESULTS IN WHERE SURFACE WILL REMAIN COLD ENOUGH AND
WAA STRONG ENOUGH TO OVERCOME DYNAMIC COOLING TO KEEP FZRA AND PL
GOING AND WHERE/WHEN COLUMN WILL BE COLD ENOUGH TO SUPPORT ONLY SN.
HAVE BASICALLY FOLLOWED 00Z ENSEMBLE MEAN FORCAST AS GOOD COMPROMISE
AT THIS POINT. THIS LEADS TO INITIAL OUTBREAK OF PCPN TO BE AS FZRA
AND PL...CHANGING TO MAINLY RA THIS EVE FOR GYY AND MDW AS WAA
PUNCHES NORTHWARD...BUT TURNING TO SN FOR RFD AND ORD AS MAX OF UVV
EXPECTED TO BE ENOUGH TO COOL COLUMN.
TRS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...BLIZZARD WARNING 22 UTC TO 18 UTC SUNDAY WINNEBAGO...BOONE
MCHENRY AND OGLE COUNTIES IN ILLIOIS
WINTER STORM WARNING FROM LEE COUNTY TO COOK COUNTY AND FROM
LAKE COUNTY IN ILLINOIS TO KANKAKEE COUNTY FROM 00 UTC TO 18
UTC SUNDAY.
FREEZING RAIN ADVISORY 00 UTC TO 12 UTC SUNDAY LIVINGSTON
IROQUOIS AND FORD COUNTIES IN ILLINOIS.
.IN...FREEZING RAIN ADVISORY FOR LAKE PORTER JASPER NEWTON AND BENTON
COUNTIES IN INDIANA FROM 00 UTC TO 18 UTC SUNDAY.
.LM...GALE WRNG ALL LM AND NR SHORES TODAY THROUGH SUNDAY NIGHT.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
635 AM CST SAT FEB 24 2007
.UPDATE...
635 AM CST
WE SAW THE OUTPUT FROM THE THE 06 UTC LOCALLY RUN WRF ARW MODEL WITH
SOME ADVANCED PRECIPITATION PHYSICS. WE DECIDED TO UPDATE THE SNOW
AMOUNTS AND TOTAL STORM ACCUMULATION FOR TONIGHT AND SUNDAY.
&&
.DISCUSSION...
345 AM CST
THIS IS A VERY DYNAMIC AND BAROCLINIC SURFACE CYCLONE DEVELOPING
IN KANSAS. THERE IS STRONG WARM AIR ADVECTION EAST OF THE LOW WHICH
IS IN WESTERN KANSAS. THUNDERSTORMS FROM OKLAHOMA TO WESTERN IOWA
SHOW THE LARGE INSTABILITY. THE PROFILER WIND AT 300 MB AT 09 UTC
SHOWS A 120 KNOT JET STREAK IN WEST CENTRAL TEXAS. WATER VAPOR LOOPS
SHOW THE INTENSE CIRCULATION OVER SOUTHEAST COLORADO. WE EXPECT THIS
SURFACE CYCLONE TO DEEPEN AND MOVE INTO SOUTHEAST IOWA BY 12 UTC
SUNDAY. THE ACARS SOUNDING AT ORD SHOWS AN INVERSION AND THE STRONG
WIND ABOVE 1400 FT FROM THE EAST. TAMDAR SOUNDING AT PIA AT 336 UTC
SHOWS A DRY LAYER AROUND 900 MB. THIS DRY LAYER WAS UP TO 800 MB.
AS THE LOW DEEPENS THE WIND WILL INCREASE DUE TO THE INCREASE IN THE
PRESSURE GRADIENT. WE MAY HAVE WIND GUSTS TO 40 MPH IN NORTH CENTRAL
ILLINOIS. UPPER AIR SUPPORT WITH THIS STORM AND A STRONG COLD
CONVEYOR BELT WILL INCREASE MID LEVEL BAROCLINICITY AND INCREASE
UPWARD VERTICAL MOTION OVER NORTHERN ILLINOIS AND NORTHWEST INDIANA.
THIS CAN BE SEEN ON THE ISENTROPIC FORECASTS FOR 290 AND 300 K
SURFACES. THE WARM AIR WHICH WILL WRAP AROUND THE EAST SIDE OF THE
LOW WILL KEEP THE SNOW TO A MINIMUM OVER THE SOUTHERN PARTS OF THE
FORECAST AREA OF NORTHERN ILLINOIS AND NORTHWEST INDIANA. WE WILL
FORECAST THE HEAVIEST SNOW ALONG THE WISCONSIN BORDER. THE STRONG
WIND AND SNOW IS EXPECTED TO CAUSE BLOWING SNOW. SO A BLIZZARD
WARNING WAS ISSUED FOR EXTREME NORTHERN ILLINOIS. THE CENTER PART OF
THE FORECAST AREA CAN EXPECT FREEZING RAIN...SLEET AND SNOW. THERE
WILL BF FREEZING RAIN AND RAIN WILL IN THE SOUTH THIRD OF THE
FORECAST AREA.
WE WILL ISSUE A WINTER STORM ADVISORY FOR MOST OF NORTHEAST
ILLINOIS. THIS WILL BE FOR FREEZING RAIN AND ICE PELLETS. A DRY SLOT
MAY MOVE INTO EASTERN ILLINOIS AND NORTHWEST INDIANA BY SUNDAY
MORNING. THE FORECAST SOUNDINGS SHOW FREEZING RAIN IN THE SOUTHERN
PORTIONS OF THE CWA AND IN INDIANA. WE WILL FORECAST FREEZING RAIN
FOR THOSE COUNTIES. ON SUNDAY NIGHT THE SURFACE LOW MOVES INTO
NORTHERN ILLINOIS. WE EXPECT THE WIND TO DIMINISH LATE SUNDAY
AFTERNOON. THEN COLD AIR IS EXPECTED TO MOVE IN AND THE
PRECIPITATION WILL BECOME SNOW. ALONG THE WISCONSIN BORDER THIS
STORM MAY PRODUCE UP TO EIGHT INCHES OF SNOW FOR A TOTAL SNOWFALL BY
MONDAY MORNING.
BY TUESDAY THE 500 MB CLOSED LOW WILL BE OVER MICHIGAN. THE
PRECIPITATION WILL MOVE EAST BY THURSDAY THE HIGH TEMPERATURES
WILL BE IN THE 40S. BY FRIDAY ANOTHER 500 MB TROUGH WAVE IS EXPECTED
TO BE OVER MINNESOTA AND IOWA GIVING A CHANCE OF RAIN AND SNOW
WEDNESDAY NIGHT AND THURSDAY.
&&
.AVIATION...
1100 PM CST
06Z TAFS...BAND OF -SN PASSING JUST NORTH OF ORD ATTM...WITH NO
RADAR ECHOES UPSTREAM ACROSS CENTRAL IL AND MO. WINDS HAVE TURNED A
BIT MORE EASTERLY IN THE LAST FEW HRS...SO EXPECT MVFR CIGS COMING
OFF LAKE MICHIGAN TO HOLD NORTH OF ORD THROUGH THE REST OF THE
NIGHT.
WINDS INCREASE SHARPLY TOMORROW OUT OF THE EAST AS LOW PRESSURE
RAPIDLY DEEPENS OVR KS AND SFC HIGH REMAINS OVR ONTARIO. WARM AND
VERY MOIST AIR ADVECTING NWD OVR THE COOL AND DRIER SFC LAYER LATE
SAT AFTN SHOULD ALLOW SOME -FZDZ TO DEVELOP LATE SAT AFTN. FCST
SOUNDINGS ARE INDICATING TEMPS RIGHT NEAR THE 0 DEG C ISOTHERM
THROUGH SAT EVENING. THERE IS SOME QUESTION AS TO WHETHER THE
STRENGTH OF LOW LEVEL WARM AIR SURGING NORTHWARD IN 75KT H8 JET WILL
PUSH TEMP PROFILES ABV FREEZING. THUS...KEPT P-TYPE FZRA FOR THE
CHICAGO AREA TERMINALS FROM 23Z THROUGH 06Z AND INDICATED A MIX OF
FZRASNPL FOR RFD FOR THE SAME TIME FRAME. STRONGLY FORCED BAND
INDICATED BY THE MODELS SHOULD CROSS THE AIRPORTS BTWN 03-06Z. THE
DEEPER CONVECTION ASSOCIATED WITH THIS BAND SHOULD ALLOW MORE PL FOR
A PERIOD AND PERHAPS MDT SN/PL AT RFD WHERE TEMPS WILL BE A FEW
DEGREES COOLER.
HANDEL
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...BLIZZARD WARNING 22 UTC TO 18 UTC SUNDAY WINNEBAGO...BOONE
MCHENRY AND OGLE COUNTIES IN ILLIOIS
WINTER STORM WARNING FROM LEE COUNTY TO COOK COUNTY AND FROM
LAKE COUNTY IN ILLINOIS TO KANKAKEE COUNTY FROM 00 UTC TO 18
UTC SUNDAY.
FREEZING RAIN ADVISORY 00 UTC TO 12 UTC SUNDAY LIVINGSTON
IROQUOIS AND FORD COUNTIES IN ILLINOIS.
.IN...FREEZING RAIN ADVISORY FOR LAKE PORTER JASPER NEWTON AND BENTON
COUNTIES IN INDIANA FROM 00 UTC TO 18 UTC SUNDAY.
.LM...GALE WRNG ALL LM AND NR SHORES TODAY THROUGH SUNDAY NIGHT.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
345 AM CST SAT FEB 24 2007
.DISCUSSION...
345 AM CST
THIS IS A VERY DYNAMIC AND BAROCLINIC SURFACE CYCLONE DEVELOPING
IN KANSAS. THERE IS STRONG WARM AIR ADVECTION EAST OF THE LOW WHICH
IS IN WESTERN KANSAS. THUNDERSTORMS FROM OKLAHOMA TO WESTERN IOWA
SHOW THE LARGE INSTABILITY. THE PROFILER WIND AT 300 MB AT 09 UTC
SHOWS A 120 KNOT JET STREAK IN WEST CENTRAL TEXAS. WATER VAPOR LOOPS
SHOW THE INTENSE CIRCULATION OVER SOUTHEAST COLORADO. WE EXPECT THIS
SURFACE CYCLONE TO DEEPEN AND MOVE INTO SOUTHEAST IOWA BY 12 UTC
SUNDAY. THE ACARS SOUNDING AT ORD SHOWS AN INVERSION AND THE STRONG
WIND ABOVE 1400 FT FROM THE EAST. TAMDAR SOUNDING AT PIA AT 336 UTC
SHOWS A DRY LAYER AROUND 900 MB. THIS DRY LAYER WAS UP TO 800 MB.
AS THE LOW DEEPENS THE WIND WILL INCREASE DUE TO THE INCREASE IN THE
PRESSURE GRADIENT. WE MAY HAVE WIND GUSTS TO 40 MPH IN NORTH CENTRAL
ILLINOIS. UPPER AIR SUPPORT WITH THIS STORM AND A STRONG COLD
CONVEYOR BELT WILL INCREASE MID LEVEL BAROCLINICITY AND INCREASE
UPWARD VERTICAL MOTION OVER NORTHERN ILLINOIS AND NORTHWEST INDIANA.
THIS CAN BE SEEN ON THE ISENTROPIC FORECASTS FOR 290 AND 300 K
SURFACES. THE WARM AIR WHICH WILL WRAP AROUND THE EAST SIDE OF THE
LOW WILL KEEP THE SNOW TO A MINIMUM OVER THE SOUTHERN PARTS OF THE
FORECAST AREA OF NORTHERN ILLINOIS AND NORTHWEST INDIANA. WE WILL
FORECAST THE HEAVIEST SNOW ALONG THE WISCONSIN BORDER. THE STRONG
WIND AND SNOW IS EXPECTED TO CAUSE BLOWING SNOW. SO A BLIZZARD
WARNING WAS ISSUED FOR EXTREME NORTHERN ILLINOIS. THE CENTER PART OF
THE FORECAST AREA CAN EXPECT FREEZING RAIN...SLEET AND SNOW. THERE
WILL BF FREEZING RAIN AND RAIN WILL IN THE SOUTH THIRD OF THE
FORECAST AREA.
WE WILL ISSUE A WINTER STORM ADVISORY FOR MOST OF NORTHEAST
ILLINOIS. THIS WILL BE FOR FREEZING RAIN AND ICE PELLETS. A DRY SLOT
MAY MOVE INTO EASTERN ILLINOIS AND NORTHWEST INDIANA BY SUNDAY
MORNING. THE FORECAST SOUNDINGS SHOW FREEZING RAIN IN THE SOUTHERN
PORTIONS OF THE CWA AND IN INDIANA. WE WILL FORECAST FREEZING RAIN
FOR THOSE COUNTIES. ON SUNDAY NIGHT THE SURFACE LOW MOVES INTO
NORTHERN ILLINOIS. WE EXPECT THE WIND TO DIMINISH LATE SUNDAY
AFTERNOON. THEN COLD AIR IS EXPECTED TO MOVE IN AND THE
PRECIPITATION WILL BECOME SNOW. ALONG THE WISCONSIN BORDER THIS
STORM MAY PRODUCE UP TO EIGHT INCHES OF SNOW FOR A TOTAL SNOWFALL BY
MONDAY MORNING.
BY TUESDAY THE 500 MB CLOSED LOW WILL BE OVER MICHIGAN. THE
PRECIPITATION WILL MOVE EAST BY THURSDAY THE HIGH TEMPERATURES
WILL BE IN THE 40S. BY FRIDAY ANOTHER 500 MB TROUGH WAVE IS EXPECTED
TO BE OVER MINNESOTA AND IOWA GIVING A CHANCE OF RAIN AND SNOW
WEDNESDAY NIGHT AND THURSDAY.
&&
.AVIATION...
1100 PM CST
06Z TAFS...BAND OF -SN PASSING JUST NORTH OF ORD ATTM...WITH NO
RADAR ECHOES UPSTREAM ACROSS CENTRAL IL AND MO. WINDS HAVE TURNED A
BIT MORE EASTERLY IN THE LAST FEW HRS...SO EXPECT MVFR CIGS COMING
OFF LAKE MICHIGAN TO HOLD NORTH OF ORD THROUGH THE REST OF THE
NIGHT.
WINDS INCREASE SHARPLY TOMORROW OUT OF THE EAST AS LOW PRESSURE
RAPIDLY DEEPENS OVR KS AND SFC HIGH REMAINS OVR ONTARIO. WARM AND
VERY MOIST AIR ADVECTING NWD OVR THE COOL AND DRIER SFC LAYER LATE
SAT AFTN SHOULD ALLOW SOME -FZDZ TO DEVELOP LATE SAT AFTN. FCST
SOUNDINGS ARE INDICATING TEMPS RIGHT NEAR THE 0 DEG C ISOTHERM
THROUGH SAT EVENING. THERE IS SOME QUESTION AS TO WHETHER THE
STRENGTH OF LOW LEVEL WARM AIR SURGING NORTHWARD IN 75KT H8 JET WILL
PUSH TEMP PROFILES ABV FREEZING. THUS...KEPT P-TYPE FZRA FOR THE
CHICAGO AREA TERMINALS FROM 23Z THROUGH 06Z AND INDICATED A MIX OF
FZRASNPL FOR RFD FOR THE SAME TIME FRAME. STRONGLY FORCED BAND
INDICATED BY THE MODELS SHOULD CROSS THE AIRPORTS BTWN 03-06Z. THE
DEEPER CONVECTION ASSOCIATED WITH THIS BAND SHOULD ALLOW MORE PL FOR
A PERIOD AND PERHAPS MDT SN/PL AT RFD WHERE TEMPS WILL BE A FEW
DEGREES COOLER.
HANDEL
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...BLIZZARD WARNING 22 UTC TO 18 UTC SUNDAY WINNEBAGO...BOONE
MCHENRY AND OGLE COUNTIES IN ILLIOIS
WINTER STORM WARNING FROM LEE COUNTY TO COOK COUNTY AND FROM
LAKE COUNTY IN ILLINOIS TO KANKAKEE COUNTY FROM 00 UTC TO 18
UTC SUNDAY.
FREEZING RAIN ADVISORY 00 UTC TO 12 UTC SUNDAY LIVINGSTON
IROQUOIS AND FORD COUNTIES IN ILLINOIS.
.IN...FREEZING RAIN ADVISORY FOR LAKE PORTER JASPER NEWTON AND BENTON
COUNTIES IN INDIANA FROM 00 UTC TO 18 UTC SUNDAY.
.LM...GALE WRNG ALL LM AND NR SHORES TODAY THROUGH SUNDAY NIGHT.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1100 PM CST FRI FEB 23 2007
.UPDATE...
600 PM CST
SENT QUICK UPDATE TO THE ZONES AND GRIDS. REFER TO THE AVIATION
DISCUSSION BELOW FOR DETAILS.
&&
.DISCUSSION...AFTERNOON FORECAST...
230 PM CST
INITIAL ROUND OF MID LEVEL WARM ADVECTION SENDING A PLUME OF CLOUDS
ACROSS FCST ARE THIS AFTERNOON. ASIDE FROM PUTTING A LID ON
TEMPERATURE RISE LOW LEVEL DRYNESS HAS PRECLUDED ANY SFC PRECIP.
UPPER TROUGH AND SURFACE FRONT MOVING INTO WRN COLO THIS AFTERNOON
AND WARM INCRESINGLY MOIST AIRMASS ADVECTING N INTO CENTRAL PLAINS.
SFC LO EXPECTED TO FORM OVER THE WESTERN HIGH PLAINS OF COLO-KANSAS
TONIGHT AND TRACK NE TOWARD MID MISS VALLEY SAT INTO EARLY SUNDAY.
MODELS SUGGEST THIS SYSTEM WILL RAPIDLY OCCLUDE AND ACTURALLY BEGIN
DECAY/FILLING PROCESS AS IT REACHS LOWER WESTERN LAKES SUNDAY.
LOW LEVELS AS SAMPLED BY TAMDAR FLIGHTS IN CENTRAL IL ARE VERY DRY
AND SE WINDS CONTINUE TO ADVECT TEENS DEW PTS INTO REGION THIS
AFTERNOON. NEW GFS HAS COME INTO PHASE WITH NAM AND OTHER MODELS IN
SLOWING ONSET OF APPROAHING LOW AND PRECI UNTIL LATER SAT. THE
UPSHOT OF ALL THIS IS AN EXPECTED BEGINNING OF PRECIP SAT AFTN OVER
NWRN IL SPREADING INTO NW IN AFTER SUNSET. LOW DEW POINT AIR AND DRY
LOWER LEVELS INDICATE AN INITIAL LOW WET BULB /BELOW FREEZING/
CONDITION TO BEGIN ANY PRECIP AS SNOW.
WIND FIELD AROUND APPROACHING LOW WILL INCR RAPIDLY LATER SAT AND
SAT NIGHT WITH VERY WELL DEVELOPED WARM ADVECTION SIGNAL SEEN IN
MODEL SOUNDINGS AFTER 00Z SUN /6PM SAT/. THIS SIGNAL IS IN VICINITY
OF THE TROWAL FEATURE OF THE OCCLUSION AND PRONE TO THE MOST INTENSE
PRECIP. MODEL SOUNDINGS ALSO REVEAL THE TEMPERATURE PROFILE TO HOVER
AROUND 0 DEG C BELOW 850MB OVER AT LEAST THE NRN HALF OF THE FCST
AREA INTO SUNDAY MORNING WHICH SUPPORTS A MIXED PRECIP WITH THE
POTENTIAL FOR SIGNIFICANT FRZG RAIN OR SLEET. SNOW MAY DOMINATE
TOWARD THE WISC BORDER WITH GRID TOTAL OF 5-7 INCH STORM TOTAL
REFLECTING THE INITIAL GUESS. ELSEWHERE ACCUMULATIONS OF SLEET AND
SOME FREEZING RAIN WILL REDUCE TOTALS. RAIN WILL LIKELY DOMINATE
SOUTH OF THE KANKAKEE RIVER TOWARD PONTIAC.
MOST CONCENTRATED PRECIP PERIOD APPEARS TO BE BETWEEN 6PM SAT AND
6AM SUN WITH RESIDUAL SNOW CONTINUING SUNDAY. AS UPPER TROUGH
WEAKENS OVERHEAD AND SLOWLY RECEDES TO THE EAST PERIODS OF LIGHT
SNOW ARE EXPECTED TO PERSIST INTO MON AND TUE. ANOTHER HIGH
AMPLITUDE UPPER TROUGH MOVING ONTO THE WEST COAST AT MIDWEEK WILL
KICK OFF ANOTHER PLAINS CYCLONE ABOUT THURS WITH A MODEST WARM UP
TOWARD THE END OF THE WEEK.
TEMPS TONIGHT WILL BE MODIFIED BY CLOUDS ALTHOUGH IF CLOUDS THIN
LATER IN THE NIGHT DRY AIR MAY ALLOW BRIEF DIP..BUT WILL GO ABOVE
GUIDANCE PLAYING FOR CLOUDS.
THIS SYSTEM HAS THE POTENTIAL TO BE A SIGNIFICANT PRECIPITATION
PRODUCER GIVEN THE SLOWING NATURE OF MOVEMENT AS IT APPROACHES.
PRECIP TYPE UNCERTAINTY IS A CONCERN ALTHOUGH THAT MAY BE OFFSET
SOME BY THE SE TRAJECTORY OF THE INCOMING AIRMASS..AS OPPOSED TO A
NE COMPONENT. SNOW TOTALS GOING NORTH TOWARD THE WISC BORDER WILL
INCREASE RAPIDLY ESPECIALLY NORTH OF THE BORDER. WHILE THE OVERALL
SCENARIO HAS BECOME MORE CLEAR THE DETAILS OF PRECIP TYPE IS A
LINGERING CONCERN KML
&&
.AVIATION...
1100 PM CST
06Z TAFS...BAND OF -SN PASSING JUST NORTH OF ORD ATTM...WITH NO
RADAR ECHOES UPSTREAM ACROSS CENTRAL IL AND MO. WINDS HAVE TURNED A
BIT MORE EASTERLY IN THE LAST FEW HRS...SO EXPECT MVFR CIGS COMING
OFF LAKE MICHIGAN TO HOLD NORTH OF ORD THROUGH THE REST OF THE
NIGHT.
WINDS INCREASE SHARPLY TOMORROW OUT OF THE EAST AS LOW PRESSURE
RAPIDLY DEEPENS OVR KS AND SFC HIGH REMAINS OVR ONTARIO. WARM AND
VERY MOIST AIR ADVECTING NWD OVR THE COOL AND DRIER SFC LAYER LATE
SAT AFTN SHOULD ALLOW SOME -FZDZ TO DEVELOP LATE SAT AFTN. FCST
SOUNDINGS ARE INDICATING TEMPS RIGHT NEAR THE 0 DEG C ISOTHERM
THROUGH SAT EVENING. THERE IS SOME QUESTION AS TO WHETHER THE
STRENGTH OF LOW LEVEL WARM AIR SURGING NORTHWARD IN 75KT H8 JET WILL
PUSH TEMP PROFILES ABV FREEZING. THUS...KEPT P-TYPE FZRA FOR THE
CHICAGO AREA TERMINALS FROM 23Z THROUGH 06Z AND INDICATED A MIX OF
FZRASNPL FOR RFD FOR THE SAME TIME FRAME. STRONGLY FORCED BAND
INDICATED BY THE MODELS SHOULD CROSS THE AIRPORTS BTWN 03-06Z. THE
DEEPER CONVECTION ASSOCIATED WITH THIS BAND SHOULD ALLOW MORE PL FOR
A PERIOD AND PERHAPS MDT SN/PL AT RFD WHERE TEMPS WILL BE A FEW
DEGREES COOLER.
HANDEL
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
.IL...WINTER STORM WATCH 18Z SATURDAY TO 00Z MONDAY WINNEBAGO BOONE
MCHENRY LAKE COOK DUPAGE KANE DEKALB OGLE LEE LASALLE KENDALL
GRUNDY WILL.
.IN...WINTER STORM WATCH 18Z SATURDAY TO 00Z MONDAY LAKE PORTER.
.LM...GALE WRNG ALL LM AND NR SHORES 21Z SAT TO 21Z SUN..
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
357 PM EST SAT FEB 24 2007
.DISCUSSION...
TAKING A LOOK AT CURRENT CONDITIONS...HIGH PRESSURE RULES...AT LEAST
THE NORTHEASTERN TWO THIRDS OF THE REGION. THE CENTER OF HIGH
PRESSURE IS WELL TO OUR NORTHEAST...WITH ITS CORE OVER HUDSON BAY.
THIS HIGH WILL NOT BUDGE MUCH OVER THE NEXT SEVERAL DAYS...HELPING
TO KEEP THE EXTREME EASTERN PORTIONS OF THE CWA CLOUD FREE...AND
DRYING UP THE LOWER LEVELS OF THE ATMOSPHERE...SLOWING DOWN THE
ONSET OF SNOW FROM THE SOUTHWEST. LOOKING TO OUR SOUTHWEST...A
SLOWLY WEAKENING LOW OVER EASTERN KANSAS IS POISED TO HEAD INTO THE
GREAT LAKES REGION...BRINGING ITS MIXED BAG OF PRECIPITATION TOWARDS
THE AREA. FREEZING RAIN WAS BEING REPORTED AS FAR NORTH AS
SOUTHEASTERN MINNESOTA AND WEST CENTRAL WISCONSIN...AS TEMPERATURES
HOVER RIGHT AROUND THE FREEZING MARK. WITH PLENTY OF GULF MOISTURE
TO WORK WITH...THUNDERSTORMS WERE COMMON FROM LOUISIANA UP THROUGH
EASTERN MISSOURI...AND THEN BACK INTO KANSAS AROUND THE SURFACE
LOW...OUT AHEAD OF THE 115KT 250MB JET ACROSS NORTHERN TEXAS AND
WESTERN ARKANSAS.
MAIN FCST CONCERNS ARE HANDLING OF POTENT SHRTWV SET TO LIFT NE FM
THE SRN PLAINS AND SN TIMING/AMTS/HEADLINES. PER NCEP PREFERENCE...
GENERALLY FOLLOWED THE GFS THRU F36...THEN A BLEND OF GFS/NAM AFT
F36 FOR EVOLVING LO PRES SYS.
FOR TNGT...125KT H3 JET MAX ROUNDING UPR LO OVER THE SRN ROCKIES
FCST TO LIFT NEWD AND DRAG OCCLUDING LO TO THE MO/IA BORDER BY 12Z
SUN...FARTHER N THAN FCST BY PREVIOUS GUIDANCE BUT NOT UNRSNBL
CONSIDERING THE HEFTY DYNAMICS THAT CAUSED 00Z-12Z H3 HGT FALLS UP
TO 200M AT AMA LAST NGT. NAM IS EVEN FARTHER N WITH THE CENTER OF
LOWEST HGTS/PRES (INTO CNTRL IA)...BUT WL FOLLOW MORE CONSISTENT GFS
FOR NOW. THE AREA OF UPR DVGC TO THE N OF THE UPR JET ROUNDING THE E
SIDE OF THE LO FCST TO LIFT N INTO THE FA AFT MIDNGT. QUESTION
REMAINS HOW QUICKLY/EFFECTIVELY ACCOMPANYING UVV CAN SATURATE THE
BONE DRY LO-MID LVLS SHOWN ON THE 12Z APX RAOB/ 15Z TAMDAR SDNG FM
TVC THAT IS REPRESENTATIVE OF AIRMASS OVER THE FA. GIVEN THE SHARP
GRADIENT OF MSTR BTWN GRB/APX AT 12Z...EXPECT A VERY SHARP GRADIENT
BTWN MODERATE SN AND LTL IF ANY SN. LLVL FLOW FCST TO REMAIN E
TNGT...MAXIMIZING DRY ADVCTN. EXPECT A MAINLY DRY EVNG...BUT WL THEN
INCRS POPS OVERNGT NEAR THE WI BORDER WITH ARRIVAL OF UPR DVGC.
ADJUSTED FOR SLOWLY FALLING TO STEADY TEMPERATURES...MAINLY ACROSS
THE WESTERN HALF OF THE CWA THROUGH MIDNIGHT TONIGHT...GIVEN GOOD
MIXING IN THE LOWER LEVELS AND CLOUD COVER. AS FOR SUNDAY
NIGHT...WENT SLIGHTLY COOLER WEST AND WARMER EAST FOR HIGH
TEMPERATURES GIVEN THE FACT THAT CLOUDS WILL STILL HAVE A TOUGH TIME
GETTING INTO THE EASTERN MOST COUNTIES OF THE CWA.
NAM/GFS IN GOOD AGREEMENT SHOWING QPF BULLSEYE ARND 0.50 INCH S OF
IMT-ESC TO MNM BTWN 12Z-18Z SUN UNDER AREA OF SHARPER H4-2 DVGC IN
LEFT EXIT OF UPR JET LIFTING INTO THE LWR GRT LKS INTERACTS WITH
SHARPER ISENTROPIC LIFT ON THE 280-300K SFC (H85-6)/ESE H85 WINDS TO
50KT/AXIS OF HIER SPECIFIC HUMIDITY (ABOUT 3 G/KG AT H7-75)/SHARPER
H85-7 FGEN AND WHERE E LLVL FLOW OFFERS POTENTIAL FOR LK ENHANCEMENT
OFF NRN LK MI. 280-290KISENTROPIC LIFT/MSTR TO THE NE IS QUITE A BIT
WEAKER/ LESS...SO EXPECT A SHARP TRANSITION TO JUST THICKENING MID
CLD ASSOCIATED WITH THE BETTER LIFT PRESENT THERE ON THE 300K SFC.
THE BETTER ISENTROPIC LIFT/UPR DVGC/FGEN IS FCST TO DRIFT TO THE NE
IN THE AFTN INTO THE DRIER AIR...SO THE HVY SN IN THE MRNG OVER THE
SCNTRL MAY DIMINISH A BIT IN THE AFTN. TENDED TO SHARPEN THE NRN
EDGE OF THE HIER QPF VS WHAT WAS FCST BY GUIDANCE TO ACCOUNT FOR
TENACIOUS DRY AIR ASSOCIATED WITH SLOWLY BACKING LLVL FLOW AND MODEL
TENDENCY TO SMOOTH QPF TOO FAR INTO THE DRIER AIR.
ON SUN NGT/MON...GFS/NAM INDICATE OCCLUDED LO DRIFTING SLOWLY E...
WITH FA IN GENERAL UPR DVGC TO THE N OF CLOSED LO CENTER. BEST H85-5
QVECTOR CNVGC REMAINS OVER THE SCNTRL ZNS. ALTHOUGH THERE IS A SLOW
BACKING TREND TO THE LLVL WINDS...FLOW REMAINS FVRBL FOR A CONTINUED
LONG FETCH ACRS NRN LK MI AND PERSISTENT WEAK LK ENHANCEMENT...
MAINLY S OF HIGHWAY 2. BUT CONSIDERING THE LACK OF SHARP PERSISTENT
FGEN AND APPRECIABLE JET DYNAMICS/SHARPER UPR DVGC...AND TENDENCY
FOR SLOWLY BACKING LLVL FLOW TO ADVECT LLVL DRY AIR INTO THE FA AND
WEAKEN THE OCCLUSION TO THE S...THINK SN INTENSITY WL BE LESS THAN
EARLY ON SUN. BEST CHC FOR ADDITIONAL HEAVIER SN WL BE OVER THE FAR
SCNTRL WHERE THERE IS POTENTIAL FOR LK ENHANCEMENT/UPSLOPING. SLOWED
THE EXIT OF WEATHER DOWN SLIGHTLY...ADDING FLURRIES BEHIND THE
DEPARTING SYSTEM...FOR TUESDAY...WITH THE EXITING 500MB LOW STILL
STUCK NEAR CHICAGO AND NORTHERN INDIANA.
UPGRADED GOING WATCH TO WRNG FOR DELTA/DICKINSON/MNM COUNTIES FOR
SUN THRU MON EVEN THOUGH SN INTENSITY AT MOST PLACES WL TEND TO
DIMINISH SUN NGT/MON. SINCE BEST DYNAMICS ON SUN WL MISS IRON COUNTY
TO THE E AND THERE IS LESS CHC FOR APPRECIABLE LK ENHANCEMENT
THERE...OPTED TO ISSUE ONLY ADVY FOR THAT COUNTY.
IN THE MEDIUM/EXTENDED RANGE...EXPECT HI PRES RDG TO BRING
RELATIVELY TRANQUIL WX TUE NGT THRU WED BEFORE LO PRES E OF
DEEPENING TROF IN THE ROCKIES EJECTS TO THE NE. OPERATIONAL GUIDANCE
HAS COME INTO BETTER AGREEMENT SHOWING LO TRACKING TO THE W OF THE
CWA INTO MN BY LATE THU AND THEN INTO ONTARIO ON FRI WHILE DRAGGING
AN OCCLUSION ACRS THE FA AS ANOTHER LO DVLPS IN THE OHIO VALLEY.
EXPANDED AREA OF MIXED PCPN TO INCLUDE RA OVER THE SCNTRL ON THU/THU
NGT CONSIDERING THE STRENGTH OF SLY FLOW AHEAD OF DEEP LO TRACKING
TO THE W AND ECMWF FCST H85 TEMPS AOA 0C AT 00Z FRI. THEN COLDER
FRI-SAT WITH CYC WNW FLOW TO THE S OF LO IN ONTARIO BRINGING LES
CHCS.
COORDINATED WITH GRB.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING 08Z SUN-00Z TUE MIZ012.
WINTER STORM WARNING 12Z SUN-00Z TUE MIZ011-013.
SNOW ADVY 12Z SUN-00Z TUE MIZ010.
GALE WARNING ALL OF LAKE SUPERIOR.
GALE WARNING LAKE MICHIGAN NEAR SHORE AREAS.
&&
$$
KC/KF
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
741 AM EST SAT FEB 24 2007
.UPDATE...
SENT AN UPDATE TO THE ZONES TO MENTION LIGHT SNOW LIKELY FROM
MUSKEGON SOUTH DOWN THE LAKE SHORE TO SOUTH HAVEN AND EXTENDING
INLAND TO PLAINWELL AND KALAMAZOO. REPORTS FROM BLOOMINGDALE AND
KALAMAZOO THIS MORNING INDICATE THAT AROUND AN INCH OF SNOW HAS
FALLEN. THE LIGHT SNOW IS ASSOCIATED WITH ISENTROPIC LIFT...WHICH
WILL BE FADING THROUGH THE COURSE OF THE MORNING. NOT EXPECTING MUCH
MORE IN THE WAY OF ACCUMULATION...BUT ANOTHER HALF INCH TO AN INCH
IS POSSIBLE BEFORE IT TAPERS OFF BY MIDDAY.
.PREV DISCUSSION...ISSUED AT 312 AM
SHORT TERM...
SKIES ARE MO CLOUDY ATTM. REGIONAL RADARS SHOWS A LARGE ARC OF SNOW
STRETCHING ACROSS SOUTHERN WISCONSIN. THIS SNOW IS CONVECTIVE IN
NATURE AS LIGHTNING HAS BEEN EMBEDDED WITH IT MUCH OF THE NIGHT.
KGRR-88D SHOWS SNOW ALOFT TRYING TO MOVE INTO THE SOUTHWEST CWA.
TAMDAR SOUNDINGS FROM A CHI-MKG LINE SHOW VERY DRY AIR IN PLACE AND
THIS PCPN WILL HAVE DIFFICULTY MAKING INTO THE CWA.
NONETHELESS...BEH JUST DROPPED TO 5SM -SN.
SFC ANALYSIS SHOWS LOW PRESSURE IN COLORADO. CONVECTION STRETCHES
FROM THE RED RIVER TO THE RED RIVER OF THE NORTH. THIS CONTINUES TO
BE A DYNAMIC SYSTEM AND IS THE FOCUS OF THE SHORT TERM.
GFS/NAM CONTINUE TO SHOW THE LOW MOVING ENE THROUGH KANSAS BEFORE
TURNING NORTHEAST AND MOVING TOWARD THE SOUTHERN CWA LATE SUNDAY.
THE GULF IS WIDE OPEN IN FRONT OF IT AND WILL SUPPLY AN AMPLE SOURCE
OF MOISTURE. THERE IS A LARGE AREA OF PCPN ATTM STRETCHING FROM
WISCONSIN SOUTHEAST TO SOUTHERN LAKE MICHIGAN. THIS PCPN IS BEING
GENERATED BY STRONG ISENTROPIC LIFT. CONDENSATION PRESSURE DEFICITS
FALL TO NEAR 0MB THIS MORNING OVER THE WESTERN CWA. WILL ADD A CHC
OF SNOW TO THE SOUTHWEST CWA THIS MORNING.
THE GFS ENSEMBLES ARE IN CLOSE AGREEMENT ON THE TRACK OF THE LOW AND
LINE UP WITH THE NAM TOO. THOSE SOLUTIONS TAKE THE LOW ACROSS SBN TO
DTW. THAT WOULD PLACE THE HEAVIEST SNOW ACROSS THE NORTHERN CWA.
FCST SOUNDINGS SHOW THE POTENTIAL FOR SOME IP TO DEVELOP OVER THE
SOUTHERN CWA AS THE NOSE OF WARM AIR NEAR 800 MB TOUCHES THE 0C
MARK. LATEST 20KM WRF AND GLBL GEM ARE SIMILAR TO THE GFS IN
BRINGING PCPN INTO THE SOUTHWEST CWA THIS EVENING AND COVERING MUCH
OF THE CWA BY 06Z. WITH THAT IN MIND WILL BUMP UP THE START TIME OF
THE WINTER STORM WATCH OVER THE NORTHERN 2/3 OF THE CWA TO MATCH THE
SOUTHERN CWA...06Z.
THE NAM SEEMS A BIT WET GIVEN THE WEAKENING NATURE OF THE SYSTEM.
BUT THERE ARE SOME STRONG DYNAMICS IN THE FORM OF 850-500 MB FGEN
FORCING TO KEEP THE SYSTEM GOING. ONE THING THAT STILL IS TROUBLING
IS THAT THE TIP OF THE DRY SLOT IS STILL PROGD TO MOVE THROUGH THE
CWA LATE SUNDAY MORNING AND EARLY AFTERNOON WITH DEEPER MOISTURE
MOVING BACK IN LATE SUNDAY AND SUNDAY NIGHT. THUS...THERE LOOKS TO
BE TWO PERIODS OF PCPN WITH A LULL IN BETWEEN. GFS SNOW AMOUNTS LOOK
GOOD WITH TOTALS FROM THIS EVENING THROUGH SUNDAY EVENING 6-8
INCHES...AND THEN ANOTHER 2 TO 4 SUNDAY NIGHT. THE UPPER LOW REMAINS
OVER LOWER MICHIGAN THROUGH MONDAY. SO THIS COULD BE A PROLONGED
SNOW EVENT. WINDS WILL STILL BE A FACTOR. BUFKIT WIND PROFILE SHOWS
40 KT WINDS AROUND 1K FEET AT 12Z SUNDAY. I DON/T THINK WE/LL BE
ABLE TO TAP ALL OF THAT AT THAT TIME OF DAY BUT GUSTY WINDS WILL
CREATE A HAZARD. WOULDN/T BE SURPRISED TO SEE VISIBILITIES DROP TO A
HALF MILE AT TIMES.
WITH THE UPPER LOW IN PLACE...MORE SNOW IS EXPECTED MONDAY. QPF
AROUND A TENTH OF AN INCH WOULD SUGGEST ANOTHER 1-3 INCHES.
.LONG TERM...
NO CHANGES MADE IN THE EXTENDED PORTION OF THE FORECAST (FROM MONDAY
NIGHT THROUGH THE END OF THE WORK WEEK). STACKED LOW WILL STILL BE
SITUATED OVER THE AREA MONDAY NIGHT...BUT IT WILL HAVE WEAKENED
SUBSTANTIALLY BY THIS POINT. USED THE GFS FOR GUIDANCE. GIVEN ITS
SOLUTION...THE SURFACE LOW WILL HAVE RISEN TO 1003MB/S BY MONDAY
EVENING. IT CONTINUES TO WEAKEN AND SLIDE EAST WITH TIME INTO
TUESDAY. MAINTAINED THE CHANCES FOR LIGHT SNOW BOTH MONDAY NIGHT AND
TUESDAY AS THERE SHOULD BE SOME LINGERING LIGHT SNOW...JUST NOT
EXPECTING A WHOLE LOT OF ACCUMULATION IN THIS TIME FRAME. TUESDAY
NIGHT SHOULD BE A COLD NIGHT GIVEN SURFACE RIDGING IN PLACE AND A
FRESH SNOWPACK.
THE MIDDLE OF THE WEEK WILL SEE A SHORT RESPITE TO THE WX...BEFORE
OUR NEXT SYSTEM APPROACHES FROM THE WEST WEDNESDAY NIGHT. WE MAY
NEED TO ADD PRECIPITATION TO THE FORECAST WEDNESDAY NIGHT WITH
STRONG WARM AIR ADVECTION ONGOING. THURSDAY AND THURSDAY NIGHT MAY
BE TRENDING MORE TOWARD RAIN AS WELL...AS 850MB TEMPS RISE TO AROUND
+6 C. COLDER AIR SWEEPS IN BEHIND A FRONTAL PASSAGE ON FRIDAY.
$$
&&
.GRR WATCHES/WARNINGS/ADVISORIES...WINTER STORM WATCH FOR THE
ENTIRE CWA FROM 1 AM SUNDAY THROUGH 7 AM MONDAY.
&&
$$
93 DUKE
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
312 AM EST SAT FEB 24 2007
.SHORT TERM...
SKIES ARE MO CLOUDY ATTM. REGIONAL RADARS SHOWS A LARGE ARC OF SNOW
STRETCHING ACROSS SOUTHERN WISCONSIN. THIS SNOW IS CONVECTIVE IN
NATURE AS LIGHTNING HAS BEEN EMBEDDED WITH IT MUCH OF THE NIGHT.
KGRR-88D SHOWS SNOW ALOFT TRYING TO MOVE INTO THE SOUTHWEST CWA.
TAMDAR SOUNDINGS FROM A CHI-MKG LINE SHOW VERY DRY AIR IN PLACE AND
THIS PCPN WILL HAVE DIFFICULTY MAKING INTO THE CWA. NONTHELESS...BEH
JUST DROPPED TO 5SM -SN.
SFC ANALYSIS SHOWS LOW PRESSURE IN COLORADAO. CONVECTION STRETCHES
FROM THE RED RIVER TO THE RED RIVER OF THE NORTH. THIS CONTINUES TO
BE A DYNAMIC SYSTEM AND IS THE FOCUS OF THE SHORT TERM.
GFS/NAM CONTINUE TO SHOW THE LOW MOVING ENE THROUGH KANSAS BEFORE
TURNING NORTHEAST AND MOVING TOWARD THE SOUTHERN CWA LATE SUNDAY.
THE
GULF IS WIDE OPEN IN FRONT OF IT AND WILL SUPPLY AN AMPLE SOURCE OF
MOISTURE. THERE IS A LARGE AREA OF PCPN ATTM STRETCHING FROM
WISCONSIN SOUTHEAST TO SOUTHERN LAKE MICHIGAN. THIS PCPN IS BEING
GENERATED BY STRONG ISENTROPIC LIFT. CONDENSATION PRESSURE DEFICITS
FALL TO NEAR 0MB THIS MORNING OVER THE WESTERN CWA. WILL ADD A CHC
OF SNOW TO THE SOUTHWEST CWA THIS MORNING.
THE GFS ENSEMBLES ARE IN CLOSE AGREEMENT ON THE TRACK OF THE LOW AND
LINE UP WITH THE NAM TOO. THOSE SOLUTIONS TAKE THE LOW ACROSS SBN TO
DTW. THAT WOULD PLACE THE HEAVIEST SNOW ACROSS THE NORTHERN CWA.
FCST SOUNDINGS SHOW THE POTENTIAL FOR SOME IP TO DEVELOP OVER THE
SOUTHERN CWA AS THE NOSE OF WARM AIR NEAR 800 MB TOUCHES THE 0C
MARK. LATEST 20KM WRF AND GLBL GEM ARE SIMILAR TO THE GFS IN
BRINGING PCPN INTO THE SOUTHWEST CWA THIS EVENING AND COVERING MUCH
OF THE CWA BY 06Z. WITH THAT IN MIND WILL BUMP UP THE START TIME OF
THE WINTER STORM WATCH OVER THE NORTHERN 2/3 OF THE CWA TO MATCH THE
SOUTHERN CWA...06Z.
THE NAM SEEMS A BIT WET GIVEN THE WEAKENING NATURE OF THE SYSTEM.
BUT THERE ARE SOME STRONG DYNAMICS IN THE FORM OF 850-500 MB FGEN
FORCING TO KEEP THE SYSTEM GOING. ONE THING THAT STILL IS TROUBLING
IS THAT THE TIP OF THE DRY SLOT IS STILL PROGD TO MOVE THROUGH THE
CWA LATE SUNDAY MORNING AND EARLY AFTERNOON WITH DEEPER MOISTURE
MOVING BACK IN LATE SUNDAY AND SUNDAY NIGHT. THUS...THERE LOOKS TO
BE TWO PERIODS OF PCPN WITH A LULL IN BETWEEN. GFS SNOW AMOUNTS LOOK
GOOD WITH TOTALS FROM THIS EVENING THROUGH SUNDAY EVENING 6-8
INCHES...AND THEN ANOTHER 2 TO 4 SUNDAY NIGHT. THE UPPER LOW REMAINS
OVER LOWER MICHIGAN THROUGH MONDAY. SO THIS COULD BE A PROLONGED
SNOW EVENT. WINDS WILL STILL BE A FACTOR. BUFKIT WIND PROFILE SHOWS
40 KT WINDS AROUND 1K FEET AT 12Z SUNDAY. I DON/T THINK WE/LL BE
ABLE TO TAP ALL OF THAT AT THAT TIME OF DAY BUT GUSTY WINDS WILL
CREATE A HAZARD. WOULDN/T BE SURPRISED TO SEE VISIBILITIES DROP TO A
HALF MILE AT TIMES.
WITH THE UPPER LOW IN PLACE...MORE SNOW IS EXPECTED MONDAY. QPF
AROUND A TENTH OF AN INCH WOULD SUGGEST ANOTHER 1-3 INCHES.
.LONG TERM...
NO CHANGES MADE IN THE EXTENDED PORTION OF THE FORECAST (FROM MONDAY
NIGHT THROUGH THE END OF THE WORK WEEK). STACKED LOW WILL STILL BE
SITUATED OVER THE AREA MONDAY NIGHT...BUT IT WILL HAVE WEAKENED
SUBSTANTIALLY BY THIS POINT. USED THE GFS FOR GUIDANCE. GIVEN ITS
SOLUTION...THE SURFACE LOW WILL HAVE RISEN TO 1003MB/S BY MONDAY
EVENING. IT CONTINUES TO WEAKEN AND SLIDE EAST WITH TIME INTO
TUESDAY. MAINTAINED THE CHANCES FOR LIGHT SNOW BOTH MONDAY NIGHT AND
TUESDAY AS THERE SHOULD BE SOME LINGERING LIGHT SNOW...JUST NOT
EXPECTING A WHOLE LOT OF ACCUMULATION IN THIS TIME FRAME. TUESDAY
NIGHT SHOULD BE A COLD NIGHT GIVEN SURFACE RIDGING IN PLACE AND A
FRESH SNOWPACK.
THE MIDDLE OF THE WEEK WILL SEE A SHORT RESPITE TO THE WX...BEFORE
OUR NEXT SYSTEM APPROACHES FROM THE WEST WEDNESDAY NIGHT. WE MAY
NEED TO ADD PRECIPITATION TO THE FORECAST WEDNESDAY NIGHT WITH
STRONG WARM AIR ADVECTION ONGOING. THURSDAY AND THURSDAY NIGHT MAY
BE TRENDING MORE TOWARD RAIN AS WELL...AS 850MB TEMPS RISE TO AROUND
+6 C. COLDER AIR SWEEPS IN BEHIND A FRONTAL PASSAGE ON FRIDAY.
$$
&&
.GRR WATCHES/WARNINGS/ADVISORIES...WINTER STORM WATCH FOR THE
ENTIRE CWA FROM 1 AM SUNDAY THROUGH 7 AM MONDAY.
&&
$$
93 DUKE
AREA FORECAST DISCUSSION...UPDATED
NWS TWIN CITIES/CHANHASSEN MN
1153 PM CST FRI FEB 23 2007
.UPDATE...
SNOW FALLING GENERALLY NEAR THE -2 850 MB ISOTHERM AND
1540-1544 850-700 MB THICKNESS..WHICH ARCS FROM SW WI/SE MN TO
NEAR THE MSP AREA AND THEN INTO WEST CENTRAL MN. MAIN ISEN LIFT ON
295 SURFACE WILL STILL BE FOCUSING OVER SE MN AND WEST CENTRAL WI
OVERNIGHT...BUT SOME REGENERATION A LITTLE FARTHER WEST LATER
TONIGHT. THIS WILL CUT BACK ON SNOW AMOUNTS OVER MN PART OF
CWA...BUT POSSIBLY A LITTLE MORE THAN EARLIER THOUGHT INTO CENTRAL
MN NORTHEAST OF KSTC. LOW LEVEL JET WEAKENING SLIGHTLY TOWARD
MORNING AS UPPER HEIGHT FALLS FORCE LOW LEVEL CIRC FARTHER SOUTH.
WILL EMPHASIZE MORE FREEZING PRECIP IN SOUTH CENTRAL AND SOUTH
WEST MN OVERNIGHT AND A LITTLE FATHER NORTH AS WELL. LATER PERIODS
SOMEWHAT OF A QUESTION...BUT LESS SNOW TONIGHT WILL CUT BACK ON
GRAND TOTALS. A QUICK LOOK AT 200 MB TEMP PATTERN SUGGESTS HEAVY
SNOW POTENTIAL STILL THERE WITH STRONG WARM ADVECTION INTO
SOUTHERN MN ON SATURDAY INTO SATURDAY NIGHT...ALTHOUGH 850 MB LOW
TRACK OFF 00Z WRF-NAM A TOUCH TOO FAR SE FOR MAX SNOWS IN EAST
CENTRAL MN.
PREV DISCUSSION... /ISSUED 353 PM CST FRI FEB 23 2007/
DISCUSSION...
LONG DURATION WINTER EVENT TO BEGIN THIS EVENING AND PERSIST INTO
SUNDAY EVENING. PUT MORE WEIGHT ON THE GFS TODAY WHICH WOULD FAVOR
12 TO 15 INCHES OVER THE TWIN CITIES AS WELL AS TO THE SOUTH AND
EAST. EVEN THE FAR WESTERN AND NORTHERN AREAS OF THE CWA SHOULD SEE
8 TO 12 INCHES BY THE TIME THE EVENT ENDS. MUCH OF THIS SNOW IS
EXPECTED SATURDAY NIGHT AND SUNDAY MORNING. IN THE MEAN TIME...THE
REAL CHALLENGE IS GETTING THROUGH TONIGHT AND SATURDAY. SOME
THUNDERSTORMS HAVE DEVELOPED JUST SOUTHWEST OF FAIRMONT AT MID
AFTERNOON. WILL INCLUDE A CHANCE OVER SOUTH CENTRAL THIS EVENING
IN ZONE OF STRONG THETA-E ADVECTION. AT THE SAME TIME...
TEMPERATURES AT THE SURFACE ARE AT OR BELOW FREEZING. COBB BUFKIT
DATA FROM THE GFS SHOWS FREEZING RAIN DEVELOPING ALONG AND SOUTH
OF THE MINNESOTA RIVER THIS EVENING AND PERSISTING OVER FAR SOUTH
CENTRAL AREAS EARLY SATURDAY MORNING. SOME SLEET EXPECTED TO OCCUR
WITH THE SNOW FROM THE TWIN CITIES ON WEST TONIGHT. INCREASED POPS
FROM CHANCE TO CATEGORICAL AS THE NIGHT PROGRESSES. ICE AMOUNTS OF
A QUARTER TO A HALF INCH POSSIBLE FAR SOUTH. A LULL IN THE ACTION
EARLY ON SATURDAY AS THE FIRST ROUND OF THETA-E ADVECTION MOVES
EAST OF THE CWA AND A SECOND ROUND DEVELOPS OVER IA ASSOCIATED
WITH THE CLOSED LOW DEVELOPING TO OUR SOUTH. LATE SATURDAY AND
SATURDAY NIGHT THE DIFFERENTIAL DIVERGENCE INCREASES DRAMATICALLY
OVER US AND TO THE SOUTHEAST. THIS IS ALSO ALONG THE AXIS OF BEST
MOISTURE FLUX IN THE 850-700MB LAYER. HENCE...THIS PERIOD LOOKS
THE BEST FOR MODERATE TO HEAVY SNOW. THE SNOW WILL DIMINISH OVER
WESTERN MN SUNDAY MORNING BUT WEST CENTRAL WI STILL LOOKS GOOD FOR
MORE ACCUMULATING SNOW BEFORE IT TAPERS OFF IN THE AFTERNOON.
BLOCKING THAT DEVELOPS TO THE NORTHEAST OF THE LOW PRESSURE SYSTEM
WILL KEEP US IN CLOUDS AND LIGHT SNOW INTO MONDAY. LONGER
TERM...GFS/ECMWF SHOW ANOTHER STORM SYSTEM FOR LATE NEXT WEEK.
&&
AVIATION...
PRECIP WILL CONTINUE AND INCREASE IN INTENSITY DURING THE EARLY
MORNING HOURS ACROSS TAF SITES. HEAVIEST SNOW IS EXPECTED OVER EAU
GIVEN RADAR TRENDS WHICH REFLECT A BANDED NATURE TO THE HIGHEST
ECHOES IN SW AND WRN WI. FOR MSP AND SATELLITE AIRPORTS UP TOWARDS
STC AND AXN...A MIX IS MORE THAN LIKELY ESPECIALLY BEFORE
SATURATED COOLING OCCURS. LATE EVE TAMDAR SOUNDINGS FROM BOTH MSP
AND STC INDICATE A SUB FREEZING LAYER OF 3-4KFT AT THE SFC WITH
HARDLY ANY ICE IN THE CLOUDS. TOP DOWN METHOD WOULD FAVOR ICE
PELLETS MORE SO THAN FZRA...BUT FZRA HAS BEEN REPORTED IN SEVERAL
OBS SO WILL LEAVE MENTION EARLY IN THE TAF. RWF BEING FURTHER
SOUTH AND WEST WILL SEE ONLY IP AND FZRA THROUGH LATE SAT MORNING.
ROUND TWO BEGINS SAT AFTN AT RWF AND AXN...AND SAT EVE OVER REST
OF TAF SITES. DEFORMATION ZONE FROM PRIMARY SYSTEM ALONG WITH A
TIGHTENING MID LEVEL BAROCLINIC ZONE WILL OFFER LIKELY POTENTIAL
FOR MODERATE TO HEAVY SNOW. THIS IS SUPPORTED BY ENSEMBLE
PROBABILISTIC FORECASTS FOR SAT NIGHT. IFR CONDITIONS WILL BE ON
THE WAY WITH LIFR LIKELY AT TIMES AT RWF...MSP...AND EAU. AIRPORT
WEATHER WARNING FOR MSP SEEMS LIKELY FOR SOMETIME DURING SAT EVE.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER STORM WARNING UNTIL 6 PM CST SUNDAY FOR BLUE EARTH-BROWN-
CARVER-CHIPPEWA-DAKOTA-FARIBAULT-FREEBORN-GOODHUE-KANDIYOHI-
LAC QUI PARLE-LE SUEUR-MARTIN-MCLEOD-MEEKER-NICOLLET-
REDWOOD-RENVILLE-RICE-SCOTT-SIBLEY-STEELE-SWIFT-WASECA-
WATONWAN-YELLOW MEDICINE COUNTY(IES).
WINTER STORM WARNING UNTIL 6 PM CST SUNDAY FOR ANOKA-BENTON-
CHISAGO-DOUGLAS-HENNEPIN-ISANTI-KANABEC-MILLE LACS-MORRISON-
POPE-RAMSEY-SHERBURNE-STEARNS-STEVENS-TODD-WASHINGTON-
WRIGHT COUNTY(IES).
WI...WINTER STORM WARNING UNTIL 6 PM CST SUNDAY FOR BARRON-CHIPPEWA-
DUNN-EAU CLAIRE-PEPIN-PIERCE-POLK-RUSK-ST. CROIX
COUNTY(IES).
&&
$$
JPR/RAH/MTF
AREA FORECAST DISCUSSION...UPDATED
NWS BINGHAMTON NY
957 PM EST SUN FEB 25 2007
.UPDATE...
UPDATE TO ACCOUNT FOR CURRENT RADAR/OBSERVATION TRENDS WHICH SHOW
STEADIEST SNOW MOVING NORTH AND EAST OF KBGM ATTM WITH MORE
SHOWERY SNOW IN ITS WAKE. HAVE REMOVED MUCH OF THE MENTION OF
SLEET...WITH NONE EXPECTED TO MAKE IT NORTH OF OUR NORTHERN PA
BORDER COUNTIES. THIS IS IN GOOD AGREEMENT WITH CURRENT ACARS
SOUNDINGS AS WELL AS NAM/RUC BUFKIT PROFILES. IN ADDITION...HAVE
ADDED MENTION OF FZDZ...AS IN BETWEEN SHSN LATER TONIGHT...THE
SATURATED LAYER SINKS SOMEWHAT TO LIE COMPLETELY WITHIN THE 0 -
-10C ZONE...SUGGESTING FZDZ MAY PROVIDE A VERY LIGHT ICE COATING
OVERNIGHT.
SNOWFALL AMOUNTS SO FAR HAVE BEEN AROUND 1 INCH. IMPRESSIVE
BANDING OVER THE PAST FEW HOURS YIELDED RIMED SNOW CRYSTALS HERE
AT KBGM...SUGGESTING THAT MUCH OF THE LIFT IS BELOW THE BEST
DENDRITIC GROWTH ZONE. THUS..EVEN WITH THE MODELS GIVING US PRETTY
DECENT QPF OVERNIGHT...BELIEVE SNOW PRODUCTION WILL NOT BE
PARTICULARLY EFFICIENT AND THEREFORE ACCUMS WILL SUFFER AS A
RESULT. A GENERAL 1-3 LOOKS ON TRACK...WITH A SLIGHT CHANCE OF
SOME 4 INCH AMOUNTS...ESPECIALLY OVER SOUTHEASTERN PORTIONS OF
SULLIVAN/PIKE COUNTIES. HAVE DECIDED TO LEAVE THE ADVISORY AS
IS...AS THE AREA IT COVERS HAS THE BEST SHOT OF SEEING SOME
MIX...AND WILL ALSO BE THE CLOSEST TO THE DEVELOPING SFC LOW THAT
WILL BE MOVING OFF THE EAST COAST OVERNIGHT. IF THAT LOW FAILS TO
SEND APPRECIABLE MOISTURE TOWARDS THE SOUTHEASTERN PORTION OF THE
CWA...ADVISORIES MAY NEED TO BE DROPPED.
UPDATED CURRENT TEMPS/DEWPOINTS BASED ON LATEST TRENDS AS WELL. -JMA
&&
.PREV DISCUSSION...
/ISSUED 747 PM EST SUN FEB 25 2007/
UPDATE...
UPDATE TO ACCOUNT FOR DECENT BAND OF LGT/MOD SNOW MOVING NORTHEAST
THROUGH THE CWA ATTM. WILL UP POPS OVER THE NORTHEASTERN ZONES TO
CATEGORICAL WITH ABOUT AN INCH OF SNOW OVERNIGHT. HAVE ALSO
ELIMINATED THE CHC FOR IP OVER WESTERN ZONES THROUGH THE NIGHT AS
ACARS SOUNDINGS ALONG WITH RUC SHORT TERM GUIDANCE SUGGESTS NO
ABOVE FREEZING AIR IN THE COLUMN. AM THINKING THAT IP/ZR CHANCES
OVER THE SOUTHEAST MAY BE A BIT OVERDONE AS WELL...BUT THE BEST
CHC FOR A MIX REMAINS OVER THIS AREA. ALSO...AS THE PCP BECOMES
MORE SHOWERY LATER...FZDZ IS POSSIBLE IN BETWEEN SHOWERS OF
SN/IP...BUT NO MORE THAN A VERY LIGHT GLAZE IS EXPECTED. -JMA
PREV DISCUSSION...
/ISSUED 700 PM EST SUN FEB 25 2007/
AVIATION /260000Z - 270000Z/...
FOR KSYR AND KRME...VFR WILL PERSIST THROUGH AT LEAST THE FIRST HALF
OF TONIGHT. WE EXPECT LIGHT SNOW TO MOVE IN LATE TONIGHT...GENERALLY
AFTER 04Z AT KSYR...AND POSSIBLY NOT UNTIL TOWARDS DAYBREAK AT KRME.
ONCE SNOW STARTS...IT WILL CONTINUE MOST OF THE TIME...RIGHT THROUGH
THE DAY MONDAY...WITH PREVALENT MVFR TO IFR CONDITIONS.
ELSEWHERE IN CENTRAL NY/NORTHEAST PA (KELM...KITH...KBGM...AND
KAVP)...IT WILL SNOW MUCH OF THE TIME...RIGHT THROUGH MONDAY
EVENING. THE MOST PERSISTENT AND HEAVIEST SNOWS WILL OCCUR
TONIGHT...WITH OCCASIONAL IFR/LIFR EXPECTED (UNDER 1 MILE
VISIBILITY). THE SNOW SHOULD BE SOMEWHAT LIGHTER AND MORE SPORADIC
DURING THE DAY MONDAY...BUT CEILINGS/VISIBILITIES WILL STILL LIKELY
BE LOW ENOUGH FOR PERIODIC IFR. -MJ
PREV DISCUSSION...
/ISSUED 214 PM EST SUN FEB 25 2007/
SHORT TERM /TONIGHT THROUGH TUESDAY/...
SLOW MOVG UPR LOW OVER THE GTLAKES WILL GRADUALLY SHEAR OUT OVER
THE NXT 46-60 HRS. 2NDRY LOW DVLPS OVR THE MID ATLC CST TNGT, WITH
A SURGE OF PCPN XPCTD TO WORK NWD INTO NE PA, WITH HEAVIEST PCPN
SCRAPING OUR FAR SE ZONES. MDLS SUGGEST A WEAK SFC WAVE
TRANSLATING EWD ACRS CNTRL NY ON MONDAY. LEADING EDGE OF PCPN HAS
HAD A HARD TIME MOVG NEWD DUE TO LOW LVL DRY AIR, WITH A "SPLIT"
IN THE MAIN PCPN AREA OVER WRN PA. HOWEVER, XPCT THIS AREA TO FILL
IN LATER THIS AFTN AND EVNG.
FAIRLY COMPLEX WX SCENARIO UNFOLDING FOR TNGT WITH MAIN CONCERNS
PCPN TYPE AND AMTS ACRS THE CNTRL SRN TIER AND NE PA, AND ALSO THE
NWD PROGRESSION OF THE PCPN. GFS CLEARLY SHOWS THE BEST POTNL FOR
FZRA OVER THE CNTRL SRN TIER AND NE PA. LOCAL WRF MDL PROFILES MORE
CLOSELY RESEMBLE THE NAM PROFILES, WHICH SUGGEST SNOW AND SOME
SLEET...MAYBE SOME -FZRA ACRS PORTIONS OF NE PA. WE ARE LEANING TWDS
THE COLDER SOLUTION, BUT EVNG CREW WILL HAVE TO MONITOR, AS FZRA
WOULD REQUIRE THE ISSUANCE OF AN ADVISORY FOR THE CNTRL SRN TIER.
SNOW ACCUMS ARE NOT XPCTD TO REACH ADVISORY LVLS ACRS THIS AREA.
LATEST TRENDS ALSO INDICATE THE ADVISORY FOR NE PA MAY NOT PAN OUT
WITH MAIN PCPN SHIELD ASSCD WITH MID ATLC 2NDRY LOW REMAINING TO
OUR SE. FOR NOW WILL STICK WITH ADVISORY FOR 2-5 INCHES (BEST
ACCUMS ACRS SRN SXNS OF THESE COUNTIES) AND MIX WITH SLEET, AND
ADD SULLIVAN COUNTY TO THE ADVISORY. BEST POTNL FOR ADVISORY SNOW
ACCUMS STILL APPEARS TO BE SOUTH OF A MSV-AVP LINE. FAR SRN
LUZERNE AND PIKE COUNTIES MIGHT SEE A SLIGHTLY BETTER CHC FOR SOME
-FZRA LATE TNGT. WE ALSO RAISED POPS FOR NRN ZONES (ONEIDA COUNTY)
AS MDLS NOW IN AGREEMENT THAT NRN EDGE OF PCPN SHIELD WILL REACH
THIS AREA.
WE WENT WITH CAT POPS FOR MOST OF THE AREA TMRW, GIVEN THE
SHEARED-OUT VORT LOBE AND WEAK SFC WAVE/TROF. PCPN TYPE LOOKS TO BE
SNOW, BUT SOME PROFILES FOR NE PA INDICATES POTNL FOR -FZDZ IN THE
MRNG. CONTINUED UNSETTLED CONDITIONS INTO TUES WITH PDS OF LGT
SNOW OR SNOW SHOWERS, WITH ACCUMS OF 1-2 INCHES PSBL IN ANY 12-HR
PD, PRIMARILY ACRS UPSTATE NY. ACTIVITY NOT XPCTD TO BE AS WDSPRD
ON TUES.
LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
NW FLOW BEHIND SYSTEM ON TUESDAY NIGHT COULD SPARK SOME LE SNOW
SHOWERS OVER PARTS OF THE AREA. HOWEVER MOISTURE DEPTH WILL BE
LACKING AND NOT LOOKING FOR MUCH IN THE WAY OF COVERAGE/INTENSITY.
HIGHLY AMPLIFIED PATTERN WILL BE IN PLACE THROUGH THE REMAINDER OF
THE WEEK INTO THE WEEKEND. UPPER LOW DIVES INTO MIDWEST ON
THURSDAY...BRINGING H5 RIDGE AND DRYING CONDS TO CWA THRU THE DAY.
YET ANOTHER SFC SYSTEM DEVELOPS WITH SFC WARM FRONT AND WAA GIVING
QUICK SHOT OF PCPN LATE IN THE WEEK. ECMWF ADVERTISES THIS SYSTEM
GOING WELL TO OUR WEST AS WAS THE CASE FOR THE PREVIOUS SYSTEM. GFS
ALSO SHOWS THIS SOLN WITH SECONDARY LOW DEVELOPMENT ALONG THE
COAST. HAVE FOLLOWED ECMWF/HPC GUIDANCE THIS PERIOD...ALTHOUGH HAVE
LOWERED TEMPS A TAD EACH DAY GIVEN PRIOR HISTORY TO THESE SYSTEMS TO
HAVE A TOUCH COLDER AIR THAN EXPECTED. HAVE OPTED FOR A SLOWER/MORE
AMPLIFIED SCENARIO IN EXTENDED PERIOD...WITH UL LOW REMAINING OVER
CENTER OF NATION UNTIL NEXT KICKER DROPS DOWN INTO PACIFIC
NORTHWEST.
AVIATION /18Z-18Z/...
HIGH OVC DECK ARND 20KFT WILL GAVE WAY TO LOWERING CIGS THIS
AFTERNOON AND EVENING AS STORM SYSTEM APPROACHES FROM THE WEST.
FOUR SRN TERMINALS TO SEE MVFR CIGS MOVING IN BTWN 21Z-23Z WITH
CEILINGS EXPECTED TO BE 2500FT. BY 00Z KELM/KAVP/KBGM WILL SEE 2SM
VSBYS IN LIGHT SNOW...SPREADING TO KITH BY 02Z. VISIBILITIES WILL
OCNLY BE REDUCED TO BLO 1SM DURING THE OVERNIGHT PERIOD.
AT KELM...COULD SEE SNOW MIXING WITH -FZRA BTWN 04Z-08Z AND WITH
SLEET AT KAVP BTWN 07Z-11Z.
FURTHER NORTH AT KSYR/KRME...SNOW EXPECTED TO MOVE IN AFTER
MIDNIGHT. LEAST LIKELY SITE WILL BE KRME WITH VSBYS RESTRICTED TO
4SM ENTIRE TAF PERIOD. ALL SITES WITH EXCEPTION OF KRME WILL SEE
CIGS DROP BLO 1KFT AS LOW PRESSURE CTR APPROACHES.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
NY...WINTER WEATHER ADVISORY UNTIL 1 PM EST MONDAY FOR NYZ062.
PA...WINTER WEATHER ADVISORY UNTIL 1 PM EST MONDAY FOR PAZ044-047-
048-072.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
NWS BINGHAMTON NY
747 PM EST SUN FEB 25 2007
.UPDATE...
UPDATE TO ACCOUNT FOR DECENT BAND OF LGT/MOD SNOW MOVING NORTHEAST
THROUGH THE CWA ATTM. WILL UP POPS OVER THE NORTHEASTERN ZONES TO
CATEGORICAL WITH ABOUT AN INCH OF SNOW OVERNIGHT. HAVE ALSO
ELIMINATED THE CHC FOR IP OVER WESTERN ZONES THROUGH THE NIGHT AS
ACARS SOUNDINGS ALONG WITH RUC SHORT TERM GUIDANCE SUGGESTS NO
ABOVE FREEZING AIR IN THE COLUMN. AM THINKING THAT IP/ZR CHANCES
OVER THE SOUTHEAST MAY BE A BIT OVERDONE AS WELL...BUT THE BEST
CHC FOR A MIX REMAINS OVER THIS AREA. ALSO...AS THE PCP BECOMES
MORE SHOWERY LATER...FZDZ IS POSSIBLE IN BETWEEN SHOWERS OF
SN/IP...BUT NO MORE THAN A VERY LIGHT GLAZE IS EXPECTED. -JMA
&&
.PREV DISCUSSION...
/ISSUED 700 PM EST SUN FEB 25 2007/
AVIATION /260000Z - 270000Z/...
FOR KSYR AND KRME...VFR WILL PERSIST THROUGH AT LEAST THE FIRST HALF
OF TONIGHT. WE EXPECT LIGHT SNOW TO MOVE IN LATE TONIGHT...GENERALLY
AFTER 04Z AT KSYR...AND POSSIBLY NOT UNTIL TOWARDS DAYBREAK AT KRME.
ONCE SNOW STARTS...IT WILL CONTINUE MOST OF THE TIME...RIGHT THROUGH
THE DAY MONDAY...WITH PREVALENT MVFR TO IFR CONDITIONS.
ELSEWHERE IN CENTRAL NY/NORTHEAST PA (KELM...KITH...KBGM...AND
KAVP)...IT WILL SNOW MUCH OF THE TIME...RIGHT THROUGH MONDAY
EVENING. THE MOST PERSISTENT AND HEAVIEST SNOWS WILL OCCUR
TONIGHT...WITH OCCASIONAL IFR/LIFR EXPECTED (UNDER 1 MILE
VISIBILITY). THE SNOW SHOULD BE SOMEWHAT LIGHTER AND MORE SPORADIC
DURING THE DAY MONDAY...BUT CEILINGS/VISIBILITIES WILL STILL LIKELY
BE LOW ENOUGH FOR PERIODIC IFR. -MJ
PREV DISCUSSION...
/ISSUED 214 PM EST SUN FEB 25 2007/
SHORT TERM /TONIGHT THROUGH TUESDAY/...
SLOW MOVG UPR LOW OVER THE GTLAKES WILL GRADUALLY SHEAR OUT OVER
THE NXT 46-60 HRS. 2NDRY LOW DVLPS OVR THE MID ATLC CST TNGT, WITH
A SURGE OF PCPN XPCTD TO WORK NWD INTO NE PA, WITH HEAVIEST PCPN
SCRAPING OUR FAR SE ZONES. MDLS SUGGEST A WEAK SFC WAVE
TRANSLATING EWD ACRS CNTRL NY ON MONDAY. LEADING EDGE OF PCPN HAS
HAD A HARD TIME MOVG NEWD DUE TO LOW LVL DRY AIR, WITH A "SPLIT"
IN THE MAIN PCPN AREA OVER WRN PA. HOWEVER, XPCT THIS AREA TO FILL
IN LATER THIS AFTN AND EVNG.
FAIRLY COMPLEX WX SCENARIO UNFOLDING FOR TNGT WITH MAIN CONCERNS
PCPN TYPE AND AMTS ACRS THE CNTRL SRN TIER AND NE PA, AND ALSO THE
NWD PROGRESSION OF THE PCPN. GFS CLEARLY SHOWS THE BEST POTNL FOR
FZRA OVER THE CNTRL SRN TIER AND NE PA. LOCAL WRF MDL PROFILES MORE
CLOSELY RESEMBLE THE NAM PROFILES, WHICH SUGGEST SNOW AND SOME
SLEET...MAYBE SOME -FZRA ACRS PORTIONS OF NE PA. WE ARE LEANING TWDS
THE COLDER SOLUTION, BUT EVNG CREW WILL HAVE TO MONITOR, AS FZRA
WOULD REQUIRE THE ISSUANCE OF AN ADVISORY FOR THE CNTRL SRN TIER.
SNOW ACCUMS ARE NOT XPCTD TO REACH ADVISORY LVLS ACRS THIS AREA.
LATEST TRENDS ALSO INDICATE THE ADVISORY FOR NE PA MAY NOT PAN OUT
WITH MAIN PCPN SHIELD ASSCD WITH MID ATLC 2NDRY LOW REMAINING TO
OUR SE. FOR NOW WILL STICK WITH ADVISORY FOR 2-5 INCHES (BEST
ACCUMS ACRS SRN SXNS OF THESE COUNTIES) AND MIX WITH SLEET, AND
ADD SULLIVAN COUNTY TO THE ADVISORY. BEST POTNL FOR ADVISORY SNOW
ACCUMS STILL APPEARS TO BE SOUTH OF A MSV-AVP LINE. FAR SRN
LUZERNE AND PIKE COUNTIES MIGHT SEE A SLIGHTLY BETTER CHC FOR SOME
-FZRA LATE TNGT. WE ALSO RAISED POPS FOR NRN ZONES (ONEIDA COUNTY)
AS MDLS NOW IN AGREEMENT THAT NRN EDGE OF PCPN SHIELD WILL REACH
THIS AREA.
WE WENT WITH CAT POPS FOR MOST OF THE AREA TMRW, GIVEN THE
SHEARED-OUT VORT LOBE AND WEAK SFC WAVE/TROF. PCPN TYPE LOOKS TO BE
SNOW, BUT SOME PROFILES FOR NE PA INDICATES POTNL FOR -FZDZ IN THE
MRNG. CONTINUED UNSETTLED CONDITIONS INTO TUES WITH PDS OF LGT
SNOW OR SNOW SHOWERS, WITH ACCUMS OF 1-2 INCHES PSBL IN ANY 12-HR
PD, PRIMARILY ACRS UPSTATE NY. ACTIVITY NOT XPCTD TO BE AS WDSPRD
ON TUES.
LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
NW FLOW BEHIND SYSTEM ON TUESDAY NIGHT COULD SPARK SOME LE SNOW
SHOWERS OVER PARTS OF THE AREA. HOWEVER MOISTURE DEPTH WILL BE
LACKING AND NOT LOOKING FOR MUCH IN THE WAY OF COVERAGE/INTENSITY.
HIGHLY AMPLIFIED PATTERN WILL BE IN PLACE THROUGH THE REMAINDER OF
THE WEEK INTO THE WEEKEND. UPPER LOW DIVES INTO MIDWEST ON
THURSDAY...BRINGING H5 RIDGE AND DRYING CONDS TO CWA THRU THE DAY.
YET ANOTHER SFC SYSTEM DEVELOPS WITH SFC WARM FRONT AND WAA GIVING
QUICK SHOT OF PCPN LATE IN THE WEEK. ECMWF ADVERTISES THIS SYSTEM
GOING WELL TO OUR WEST AS WAS THE CASE FOR THE PREVIOUS SYSTEM. GFS
ALSO SHOWS THIS SOLN WITH SECONDARY LOW DEVELOPMENT ALONG THE
COAST. HAVE FOLLOWED ECMWF/HPC GUIDANCE THIS PERIOD...ALTHOUGH HAVE
LOWERED TEMPS A TAD EACH DAY GIVEN PRIOR HISTORY TO THESE SYSTEMS TO
HAVE A TOUCH COLDER AIR THAN EXPECTED. HAVE OPTED FOR A SLOWER/MORE
AMPLIFIED SCENARIO IN EXTENDED PERIOD...WITH UL LOW REMAINING OVER
CENTER OF NATION UNTIL NEXT KICKER DROPS DOWN INTO PACIFIC
NORTHWEST.
AVIATION /18Z-18Z/...
HIGH OVC DECK ARND 20KFT WILL GAVE WAY TO LOWERING CIGS THIS
AFTERNOON AND EVENING AS STORM SYSTEM APPROACHES FROM THE WEST.
FOUR SRN TERMINALS TO SEE MVFR CIGS MOVING IN BTWN 21Z-23Z WITH
CEILINGS EXPECTED TO BE 2500FT. BY 00Z KELM/KAVP/KBGM WILL SEE 2SM
VSBYS IN LIGHT SNOW...SPREADING TO KITH BY 02Z. VISIBILITIES WILL
OCNLY BE REDUCED TO BLO 1SM DURING THE OVERNIGHT PERIOD.
AT KELM...COULD SEE SNOW MIXING WITH -FZRA BTWN 04Z-08Z AND WITH
SLEET AT KAVP BTWN 07Z-11Z.
FURTHER NORTH AT KSYR/KRME...SNOW EXPECTED TO MOVE IN AFTER
MIDNIGHT. LEAST LIKELY SITE WILL BE KRME WITH VSBYS RESTRICTED TO
4SM ENTIRE TAF PERIOD. ALL SITES WITH EXCEPTION OF KRME WILL SEE
CIGS DROP BLO 1KFT AS LOW PRESSURE CTR APPROACHES.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
NY...WINTER WEATHER ADVISORY UNTIL 1 PM EST MONDAY FOR NYZ062.
PA...WINTER WEATHER ADVISORY UNTIL 1 PM EST MONDAY FOR PAZ044-047-
048-072.
&&
$$
AREA FORECAST DISCUSSION...UPDATED AVIATION DISCUSSION
NWS SEATTLE WA
830 PM PST FRI FEB 23 2007
.SYNOPSIS...A VIGOROUS FRONTAL SYSTEM WILL SWEEP THROUGH WESTERN
WASHINGTON LATER TONIGHT THROUGH SATURDAY MORNING. A COLD UPPER
LEVEL TROUGH WILL REMAIN IN THE NORTHEAST PACIFIC INTO THE FIRST
PART OF NEXT WEEK...FOR COOL SHOWERY AND AT TIMES BLUSTERY WEATHER.
&&
.SHORT TERM...VIGOROUS FRONT THRU WESTERN WA OVERNIGHT THROUGH
SATURDAY MORNING. ANOTHER BATCH OF COLD AIR ALOFT WILL DIG INTO THE
NORTHEAST PACIFIC OVER THE WEEKEND...AN UPPER RIDGE BUILDS OUT
AROUND 170W AND A BROAD TROF SETTLES IN THE NE PAC. WASHINGTON WILL
BE ON THE COOL SIDE OF THE POLAR JET FOR AT LEAST THE NEXT SEVERAL
DAYS. IT WILL BE WINDY WITH THE FRONT LATE TONIGHT AND SATURDAY
MORNING IN MANY AREAS...ESPECIALLY OVER THE MARINE ZONES...AND
BLUSTERY AT TIMES RIGHT THROUGH MONDAY AS SEVERAL SURFACE TROFS COME
IN.
LATE TONIGHT...THE HILLS AROUND HOODSPORT AND LAKE CUSHMAN MAY SEE
SNOW FOR A FEW HOURS...BUT A QUICK CHANGE TO RAIN AT DAYBREAK IS A
GOOD BET AND THE MM5 SNOW ACCUM FCST THERE LOOKS OVERDONE. H850
TEMPS WILL RISE TO AROUND 0C ON SATURDAY OVER THE OLYMPICS AND BY
AFTERNOON OUR FCST SNOW LEVEL IS ACTUALLY TOO LOW. FOR NOW...THE
SNOW LEVEL FCST TONIGHT IS 1000FT AND THAT LOOKS GOOD TIL FROPA SAT
MORNING...THE CURRENT ACARS FREEZING LEVEL OVER PUGET SOUND IS
2200FT.
&&
.AVIATION...AN INCOMING WARM FRONT WILL FIRST CAUSE MID-HIGH CLOUDS
TO CONTINUE THICKENING THE REST OF THIS EVENING OVER SEA-TAC. RAIN
WILL BEGIN OVERNIGHT...MOISTENING THE LOW LEVELS SUFFICIENTLY FOR
IFR CONDITIONS BY SUNRISE AND LOWER VSBYS IN MODERATE RAIN DURING
THE MORNING. WINDS ALOFT MAY BE AN ISSUE FOR AIRCRAFT ON APPROACH
WITH WINDS AROUND 040 OF 50 KTS EXPECTED FROM 14Z-18Z. HANER
.AVALANCHE...ABUNDANT LOW DENSITY SNOW RECEIVED DURING PAST FEW DAYS
WITH SEVERAL BURIED WEAK LAYERS. WHILE MUCH OF THIS RECENT SNOW HAS
BEGUN TO STABILIZE, DECENT INCOMING STORM ON SATURDAY SHOULD BE
ACCOMPANIED BY MODERATE TO STRONG WINDS, SLIGHT WARMING AND MODERATE
TO LOCALLY HEAVY SNOWFALL ESPECIALLY NEAR THE VOLCANOES. THIS SHOULD
LOAD AND STRESS EXISTING SNOWPACK WITH HIGHER DENSITY WIND SLABS.
ISSUED AVALANCHE WATCH THIS MORNING TO HIGHLIGHT UPCOMING
SIGNIFICANT DANGER INCREASE TO RELATIVELY LOW ELEVATIONS ON
SATURDAY, AND WILL PROBABLY ISSUE WARNING EARLY SATURDAY. WITH MORE
SNOWFALL AND ANOTHER, THOUGH WEAKER, SYSTEM EXPECTED SUNDAY, EXPECT
ONLY MINOR DANGER DECREASE THROUGH THE WEEKEND AND HOPE THAT BACK
COUNTRY FOLKS WILL HEED THE WARNING AND TRAVEL ON MORE GENTLE
TERRAIN FOR AWHILE. FOR DETAILS SEE WWW.NWAC.US. MOORE
THIS SECTION IS PROVIDED IN PARTNERSHIP WITH THE USDA FOREST SERVICE
NW WEATHER AND AVALANCHE CENTER. THIS IS THE DEBUT OF THIS SECTION
AND WILL BE PROVIDED ON AN EVENT DRIVEN BASIS.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
...GALE WARNING FOR THE COAST...WEST ENTRANCE...EAST ENTRANCE...
ADMIRALTY INLET...AND THE NORTHERN INLAND WATERS...
...SMALL CRAFT ADVISORY CENTRAL STRAIT...PUGET SOUND AND HOOD
CANAL
...SMALL CRAFT ADVISORY FOR ROUGH BAR CONDITIONS GRAYS
HARBOR BAR...
$$
WEATHER.GOV/SEATTLE
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