AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
230 PM PDT TUE APR 15 2008
.SYNOPSIS...AN UPPER LEVEL TROUGH OF LOW PRESSURE CONTINUES TO
DEEPEN OVER THE WESTERN STATES. THIS WILL ALLOW THE COASTAL MARINE
LAYER TO DEEPEN THROUGH WEDNESDAY...BRINGING NIGHT AND MORNING
LOW CLOUDS AND SOME PATCHY MOUNTAIN FOG. COOLER DAYS ARE ALSO
EXPECTED THROUGH WEDNESDAY. WEAK OFFSHORE FLOW AND BETTER
CLEARING MOST AREAS IS EXPECTED THURSDAY AND FRIDAY AS A WARMING
TREND DEVELOPS...FOLLOWED BY ANOTHER TROUGH OF LOW PRESSURE OVER THE
WEEKEND FOR ANOTHER INCREASE IN LOW CLOUDS AND A COOLING TREND.
&&
.DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO...
ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES.
MUCH LOW CLOUDINESS TODAY AS 30 KNOT WINDS SCREAMING PAST SAN
NICOLAS ISLAND DRIVE A STRONG EDDY. THE CLOUDS DECK WAS FAIRLY THIN
AND THE INVERSION WAS ONLY MODERATELY STRONG SO IN SPITE OF THE GOOD
ONSHORE FLOW AND TREND THERE WAS STILL GOOD CLEARING MOST AREAS. WE
EXPECT THE LOW CLOUDS TO RETURN OVERNIGHT. A BASIC REPEAT OF TODAYS
WEATHER IS ON TAP FOR WEDNESDAY. SOME DRIZZLE IS POSSIBLE TONIGHT
AND WEDNESDAY MORNING...BUT LOOKS LIKE IT WOULD BE VERY ISOLATED.
STRONG WESTERLY FLOW SHOULD BRING WIND ADVISORY CONDITIONS TO SOME
MOUNTAIN AND DESERT AREAS INTO THE EVENING.
WEDNESDAY NIGHT AND THURSDAY A TRANSITION IN THE PATTERN IS EXPECTED
SINCE THERE IS A SWITCH BACK TO OFFSHORE FLOW. THIS SHOULD LOWER
AND POSSIBLE ELIMINATE THE COASTAL MARINE LAYER LOW CLOUDS...
RESULTING IN A WARMING TREND.
BY FRIDAY NIGHT ANOTHER TROUGH IS FORECAST TO DEEPEN OVER THE
WESTERN STATES WITH THE MARINE LAYER DEEPENING RAPIDLY FRIDAY NIGHT
THROUGH SATURDAY MORNING. THE TROUGH IS FORECAST TO CONTINUE WELL
INTO THE COMING WEEK WITH BREEZY TO WINDY CONDITIONS IN THE
MOUNTAINS AND DESERTS...COOLER DAYS...AND A DEEP MARINE LAYER.
SUNDAY REMAINS RATHER COOL WITH THE INFLUENCE OF THE TROUGH
REMAINING IN THE AREA. BY MONDAY THE FORECAST MODELS DEVIATE
SIGNIFICANTLY. THE GFS HAS A MONSTER OF A LOW OVER THE WESTERN
STATES...WHILE THE ECMWF SIMPLY HAS A BROAD TROUGH AND A MUCH WEAKER
INFLUENCE ON OUR AREA. WE WILL PROBABLY GET A MARINE LAYER SEVERAL
THOUSAND FEET DEEP OUT OF IT AND MAYBE SOME DRIZZLE. AS THE MODELS
CONVERGE ON ONE SOLUTION WE SHOULD BE ABLE TO GET A BETTER IDEA.
&&
.AVIATION...
151915Z...MDCRS SOUNDINGS SHOW THE MARINE LAYER DEPTH AROUND 3500
FEET THIS AFTERNOON. THE MARINE LAYER SHOULD DEEPEN TO AROUND 4000
FEET TONIGHT BEFORE LOWERING DURING THE DAY ON WEDNESDAY. SCATTERED
TO BROKEN STRATOCU OVER THE AREA WITH BASES AROUND 2500 TO 3000 FEET
SHOULD FILL IN DURING THE EVENING AND PUSH BACK INTO THE LOWER
COASTAL SLOPES OF THE MOUNTAINS TONIGHT. EXPECT THE STRATOCU TO
BREAKUP DURING THE AFTERNOON ON WEDNESDAY.
ABOVE THE MARINE LAYER INCLUDING THE MOUNTAINS AND DESERTS...A
MOSTLY CLEAR SKY WITH UNRESTRICTED VISIBILITIES WILL CONTINUE
THROUGH WEDNESDAY.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WIND ADVISORY...SAN BERNARDINO COUNTY MOUNTAINS...RIVERSIDE
COUNTY MOUNTAINS...APPLE AND LUCERNE VALLEYS UNTIL 8 PM PDT.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS IN EFFECT UNTIL 3 AM
PDT WEDNESDAY FOR WATERS FROM SAN MATEO POINT TO THE MEXICAN BORDER
EXTENDING 30 TO 60 NM OUT INCLUDING SAN CLEMENTE ISLAND.
&&
$$
PUBLIC.....SMALL
AVIATION...HORTON
AREA FORECAST DISCUSSION...CORRECTION
NWS CHICAGO/ROMEOVILLE IL
359 PM CDT TUE APR 15 2008
.DISCUSSION...
357 PM CDT
THE FORECAST TONIGHT WILL BE FOR A SOUTH WIND AND MOSTLY CLEAR SKY.
THERE IS A LARGE HIGH OVER THE LOWER MISSISSIPPI VALLEY AND
KENTUCKY AND A DEVELOPING LOW OVER THE GREAT PLAINS. THE PRESSURE
GRADIENT BETWEEN THE HIGH AND THE LOW WILL INCREASE WEDNESDAY
GIVING A SOUTH WIND OF UP TO 25 MPH AND GUSTS TO 35 TO 39 MPH. WE
WILL HOLD OFF ON A WIND ADVISORY TONIGHT. WE WILL EXAMINE THE
POSSIBILITY OF A WIND ADVISORY AFTER THE NEXT MODEL RUNS. THE
SOUTH WIND WILL BRING WARM AIR INTO OUR FORECAST AREA AND WE CAN
FORECAST TEMPERATURES AROUND 70 FOR WEDNESDAY. THE HUMIDITY IS JUST
A LITTLE JUST ABOVE THE 25 PERCENT AND THE WET FUELS INDEX WAS
AROUND 9. WE WILL NOT ISSUE A RED FLAG WARNING AT THIS TIME. WE WILL
MONITOR THE HUMIDITY FOR WEDNESDAY HOWEVER FOR FIRE WEATHER DANGER.
THE LOW IN THE GREAT PLAINS IS EXPECTED TO MOVE INTO ONTARIO AND
WEAKEN BY WEDNESDAY AFTERNOON. AS THE LOW MOVES INTO ONTARIO IT
WILL DRAG A COLD FRONT ACROSS NORTHERN ILLINOIS AND INTO LAKE
HURON BY THURSDAY EVENING. WITH A FRONT CLOSE BY TO PROVIDE LIFT
AND MOISTURE ADVECTION PRESENT WE WILL FORECAST THUNDERSTORMS
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. THIS FRONT WILL OSCILLATE
IN NORTHERN ILLINOIS AS A WARM FRONT ALONG THE WISCONSIN BORDER
THROUGH SATURDAY. A LOW WILL MOVE NORTH FROM MISSOURI TO SOUTHERN
LAKE MICHIGAN BY SATURDAY AFTERNOON. THERE WILL BE PERIODS OF
SHOWER AND THUNDERSTORMS FRIDAY THROUGH SATURDAY NIGHT. SOME OF
THE THUNDERSTORMS COULD PRODUCE RAIN FALL OF UP TO AROUND 1 INCH
OR MORE IN AN HOUR. THESE WOULD BE CLUSTER TYPE THUNDERSTORMS THAT
FORM AND REFORM ALONG A FRONTAL BOUNDARY. WE WILL HAVE TO DO LOCAL
ANALYSIS AND WATCH VERY CAREFULLY THE UPPER AIR WIND...TEMPERATURE
AND MOISTURE PATTERNS AFTER THURSDAY FOR LOCALLY HEAVY RAIN
FORECAST. THE FORECAST TEMPERATURE WILL BE LOWER FOR THURSDAY
THROUGH FRIDAY. SINCE THE FRONT WILL BE ALONG THE NORTHERN PART OF
OUR FORECAST AREA AND THE LOW WILL MOVE THROUGH ILLINOIS SOUTH OF
FOWLER INDIANA AND PONTIAC. AS AN EXAMPLE...WE WILL FORECAST THE
HIGHS IN THE LOWER 50S FOR ROCKFORD AND HIGHS IN THE MIDDLE 60S
FOR FOWLER INDIANA FOR FRIDAY
&&
.AVIATION...
1255 PM CDT
1800 UTC...MAIN AVIATION FORECAST ISSUE WILL CONTINUE TO BE WINDS.
SURFACE RIDGE AXIS CONTINUES TO MOVE OFF TO THE EAST ACROSS THE
OHIO RIVER VALLEY EARLY THIS AFTERNOON. SURFACE PRESSURE GRADIENT
WILL CONTINUE TO STRENGTHEN THROUGHOUT THE AFTERNOON AND ACARS
SOUNDINGS NEAR ORD INDICATE MIXED LAYER UP TO ABOUT 4500 FT WITH
WINDS OF 20 TO 25 KNOTS THROUGH THIS MIXED LAYER. WILL CONTINUE
WITH SOUTH WINDS OF 15 KNOTS GUSTING TO 25 KNOTS THROUGH THE EARLY
EVENING HOURS. AFTER 00Z...SHOULD BEGIN TO SEE SOME DIMINISHMENT
IN THE GUSTINESS AS MIXED LAYER ERODES BUT STRENGTH OF THE SURFACE
PRESSURE GRADIENT SHOULD ALLOW SOME GUSTS FROM 20 TO 25 KNOTS TO
CONTINUE THROUGH THE NIGHT. WINDIEST CONDITIONS OF THE PERIOD ARE
EXPECTED FROM MID MORNING WEDNESDAY ON AS STRONGEST SURFACE
PRESSURE GRADIENT AFFECTS THE NORTHERN ILLINOIS. MIXED LAYER
DEPTHS WILL BE A BIT MORE SHALLOW TOMORROW...BUT GIVEN STRENGTH OF
SURFACE PRESSURE GRADIENT AND STRONGER SFC PRESSURE FALLS ACROSS
WISCONSIN EXPECTING SOUTH GUSTS TO 30 TO 35 KNOTS WILL NOT BE HARD
TO ATTAIN BY LATE WEDNESDAY MORNING. OTHERWISE...IN TERMS OF SKY
COVER...JUST SOME INCREASING CIRRUS EXPECTED TONIGHT WITH VFR
CONDITIONS PERSISTING.
MARSILI
&&
.MARINE...
231 PM CDT
SURFACE LOW PRESSURE ACROSS THE DAKOTAS WILL TRACK INTO NORTHERN
ONTARIO THROUGH TOMORROW. AS THIS LOW TRACKS OFF TO THE
NORTHEAST...SOUTH WINDS WILL STRENGTHEN ACROSS LAKE MICHIGAN
TONIGHT. DESPITE SIGNIFICANT WARM ADVECTION AND LOW LEVEL
INVERSION...PRESSURE GRADIENT SHOULD BE FAVORABLE FOR SOUTHERLY
GALE GUSTS ACROSS THE NORTHERN TWO THIRDS OF LAKE MICHIGAN THROUGH
WEDNESDAY EVENING. ONLY CHANGE TO OPEN WATER GALE WARNING HEADLINE
WAS TO MOVE UP EXPIRATION SLIGHTLY TO 06Z WEDNESDAY NIGHT. ALSO
HAVE NOT MADE ANY CHANGES TO GOING NEARSHORE HEADLINES WITH A
SMALL CRAFT ADVISORY IN EFFECT THROUGH TONIGHT...TRANSITIONING TO A
GALE WARNING WEDNESDAY MORNING. SURFACE FRONT IS EXPECTED TO TRACK
ACROSS LAKE MICHIGAN LATE WEDNESDAY NIGHT WITH EAST/NORTHEAST FLOW
FOR THURSDAY.
MARSILI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 9 AM CDT WEDNESDAY FOR LMZ740-LMZ741-
LMZ742-LMZ743-LMZ744-LMZ745.
GALE WARNING FROM 9 AM TO 10 PM CDT WEDNESDAY FOR LMZ740-LMZ741-
LMZ742-LMZ743-LMZ744-LMZ745.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
244 PM CDT TUE APR 15 2008
.DISCUSSION...
300 AM CDT
SURFACE HIGH PRESSURE WILL CONTINUE TO SAG INTO THE OHIO
VALLEY...WHILE RIDGING ALOFT BUILDS OVER THE UPPER MISSISSIPPI
VALLEY TODAY AND MR SUNSHINE WILL MAKE A WELCOME APPEARANCE IN
FULL FORCE. AN INCREASING SOUTHERLY GRADIENT WILL SET UP AND WINDS
WILL BECOME QUITE BREEZY BY THIS AFTERNOON. HOWEVER...WITH SURFACE
TRAJECTORIES TAKING THE LANG PATH AROUND THE SURFACE HIGH...THE
SOURCE REGION FOR AIR PARCELS TODAY AND TOMORROW WILL COME FROM
THE SOUTH HIGH PLAINS. THROUGH THE SHORT TERM...BOTH THE NAM AND
GFS AGREE ON THIS SCENARIO...SO HAVE GONE WITH A DRY FORECAST
THROUGH WEDNESDAY...AND IN PARTICULAR...HAVE LOWERED
DEWPOINTS...AS THE GUIDANCE FROM BOTH MODELS INDICATE AN INCREASE
IN LOW LEVEL MOISTURE THAT DEFIES THE LOGIC OF THE SYNOPTIC SCALE
FLOW PATTERN. THE WARM...DRY...WINDY SCENARIO COULD POSSIBLY SET
UP A RED FLAG THREAT FOR FIRE WEATHER CONCERNS...BUT GIVEN THE
NEAR CONSTANT RAINFALL OF RECENT WEEKS...FUEL MOISTURE LEVELS WILL
LIKELY BE HIGH ENOUGH TO PRECLUDE THE NECESSITY OF ANY FIRE
WEATHER HEADLINES. THE MAIN FORECAST CHALLENGE FOR THE SHORT TERM
WILL BE TEMPERATURES FOR TODAY AND WEDNESDAY AND TIMING OF THE
NEXT FRONTAL PASSAGE...WHICH WILL BRING A QUICK AND DECISIVE END
TO THE BRIEF PERIOD OF PLEASANT WEATHER. HAVE ACTUALLY MADE LITTLE
CHANGE TO THE GOING FORECAST AS FAR AS TEMPERATURES ARE CONCERNED.
STILL SEE A GOOD LIKELIHOOD OF TEMPERATURES FINALLY REACHING INTO
THE LOW 70S BY WEDNESDAY. THEREFORE...THE MAIN ISSUE FOR THE
REMAINDER OF THE SHORT TERM FORECAST PERIOD WILL BE TIMING OF
THE FRONTAL PASSAGE. THE LATEST GUIDANCE SHOWS THAT THE NAM IS
TRENDING A BIT SLOWER AND STRONGER WITH THE SURFACE LOW ASSOCIATED
WITH THIS SYSTEM. PREFER THE NAM SOLUTION IN THIS CASE GIVEN THE
HIGH AMPLITUDE PATTERN SETTING UP...WHICH WOULD FAVOR A
STRONGER...BUT SLOWER PROGRESSION TO THE PATTERN. THIS WILL ALSO
ALLOW MORE TIME FOR AN INCREASE IN MOISTURE TRANSPORT. AS THE SFC
TROUGH TRACKS ACROSS THE UPPER MISSISSIPPI VALLEY WEDNESDAY AND A
SECONDARY LOW DEVELOPS OVER THE TEXAS PANHANDLE...THE GULF OF
MEXICO WILL FINALLY OPEN UP WEDNESDAY NIGHT AND THE MOISTURE WILL
BEGIN TO FLOW NORTHWARD INTO THE LOCAL AREA. BY THURSDAY...THE
COMBINATION OF THE APPROACHING COLD FRONT AND INCREASED MOISTURE
TRANSPORT WILL BRING A RENEWED CHANCE OF SHOWERS AND THUNDERSTORMS TO
THE REGION. ALSO..AS THE COLD FRONT ACCELERATES ACROSS THE UPPER
MIDWEST AND LAKE MICHIGAN...WINDS WILL BECOME MORE NELY ACROSS THE
NORTHERN PORTIONS OF THE CWA...BRINGING COOL LAKE MICHIGAN AIR AND
A SHARP DROP IN TEMPERATURES. BY THURSDAY AFTERNOON...EXPECT THAT
TEMPERATURES ACROSS THE NORTHERN TIER COUNTIES WILL CRASH BACK
INTO THE MIDDLE TO UPPER 50S. THE FRONTAL PROGRESSION WILL BE
SLOWER OVER THE SRN PORTIONS OF THE CWA...BEING HELD UP BY THE
DEVELOPMENT OF THE SOUTHERN STREAM SURFACE LOW. SO...THE
SOUTHEASTERN PORTIONS OF THE CWA COULD STILL SEE TEMPERATURES
REACHING NEAR 70F THURSDAY.
KREIN
&&
.AVIATION...
1255 PM CDT
1800 UTC...MAIN AVIATION FORECAST ISSUE WILL CONTINUE TO BE WINDS.
SURFACE RIDGE AXIS CONTINUES TO MOVE OFF TO THE EAST ACROSS THE
OHIO RIVER VALLEY EARLY THIS AFTERNOON. SURFACE PRESSURE GRADIENT
WILL CONTINUE TO STRENGTHEN THROUGHOUT THE AFTERNOON AND ACARS
SOUNDINGS NEAR ORD INDICATE MIXED LAYER UP TO ABOUT 4500 FT WITH
WINDS OF 20 TO 25 KNOTS THROUGH THIS MIXED LAYER. WILL CONTINUE
WITH SOUTH WINDS OF 15 KNOTS GUSTING TO 25 KNOTS THROUGH THE EARLY
EVENING HOURS. AFTER 00Z...SHOULD BEGIN TO SEE SOME DIMINISHMENT
IN THE GUSTINESS AS MIXED LAYER ERODES BUT STRENGTH OF THE SURFACE
PRESSURE GRADIENT SHOULD ALLOW SOME GUSTS FROM 20 TO 25 KNOTS TO
CONTINUE THROUGH THE NIGHT. WINDIEST CONDITIONS OF THE PERIOD ARE
EXPECTED FROM MID MORNING WEDNESDAY ON AS STRONGEST SURFACE
PRESSURE GRADIENT AFFECTS THE NORTHERN ILLINOIS. MIXED LAYER
DEPTHS WILL BE A BIT MORE SHALLOW TOMORROW...BUT GIVEN STRENGTH OF
SURFACE PRESSURE GRADIENT AND STRONGER SFC PRESSURE FALLS ACROSS
WISCONSIN EXPECTING SOUTH GUSTS TO 30 TO 35 KNOTS WILL NOT BE HARD
TO ATTAIN BY LATE WEDNESDAY MORNING. OTHERWISE...IN TERMS OF SKY
COVER...JUST SOME INCREASING CIRRUS EXPECTED TONIGHT WITH VFR
CONDITIONS PERSISTING.
MARSILI
&&
.MARINE...
231 PM CDT
SURFACE LOW PRESSURE ACROSS THE DAKOTAS WILL TRACK INTO NORTHERN
ONTARIO THROUGH TOMORROW. AS THIS LOW TRACKS OFF TO THE
NORTHEAST...SOUTH WINDS WILL STRENGTHEN ACROSS LAKE MICHIGAN
TONIGHT. DESPITE SIGNIFICANT WARM ADVECTION AND LOW LEVEL
INVERSION...PRESSURE GRADIENT SHOULD BE FAVORABLE FOR SOUTHERLY
GALE GUSTS ACROSS THE NORTHERN TWO THIRDS OF LAKE MICHIGAN THROUGH
WEDNESDAY EVENING. ONLY CHANGE TO OPEN WATER GALE WARNING HEADLINE
WAS TO MOVE UP EXPIRATION SLIGHTLY TO 06Z WEDNESDAY NIGHT. ALSO
HAVE NOT MADE ANY CHANGES TO GOING NEARSHORE HEADLINES WITH A
SMALL CRAFT ADVISORY IN EFFECT THROUGH TONIGHT...TRANSITIONING TO A
GALE WARNING WEDNESDAY MORNING. SURFACE FRONT IS EXPECTED TO TRACK
ACROSS LAKE MICHIGAN LATE WEDNESDAY NIGHT WITH EAST/NORTHEAST FLOW
FOR THURSDAY.
MARSILI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 9 AM CDT WEDNESDAY FOR LMZ740-LMZ741-
LMZ742-LMZ743-LMZ744-LMZ745.
GALE WARNING FROM 9 AM TO 10 PM CDT WEDNESDAY FOR LMZ740-LMZ741-
LMZ742-LMZ743-LMZ744-LMZ745.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
107 PM CDT TUE APR 15 2008
.DISCUSSION...
300 AM CDT
SURFACE HIGH PRESSURE WILL CONTINUE TO SAG INTO THE OHIO
VALLEY...WHILE RIDGING ALOFT BUILDS OVER THE UPPER MISSISSIPPI
VALLEY TODAY AND MR SUNSHINE WILL MAKE A WELCOME APPEARANCE IN
FULL FORCE. AN INCREASING SOUTHERLY GRADIENT WILL SET UP AND WINDS
WILL BECOME QUITE BREEZY BY THIS AFTERNOON. HOWEVER...WITH SURFACE
TRAJECTORIES TAKING THE LANG PATH AROUND THE SURFACE HIGH...THE
SOURCE REGION FOR AIR PARCELS TODAY AND TOMORROW WILL COME FROM
THE SOUTH HIGH PLAINS. THROUGH THE SHORT TERM...BOTH THE NAM AND
GFS AGREE ON THIS SCENARIO...SO HAVE GONE WITH A DRY FORECAST
THROUGH WEDNESDAY...AND IN PARTICULAR...HAVE LOWERED
DEWPOINTS...AS THE GUIDANCE FROM BOTH MODELS INDICATE AN INCREASE
IN LOW LEVEL MOISTURE THAT DEFIES THE LOGIC OF THE SYNOPTIC SCALE
FLOW PATTERN. THE WARM...DRY...WINDY SCENARIO COULD POSSIBLY SET
UP A RED FLAG THREAT FOR FIRE WEATHER CONCERNS...BUT GIVEN THE
NEAR CONSTANT RAINFALL OF RECENT WEEKS...FUEL MOISTURE LEVELS WILL
LIKELY BE HIGH ENOUGH TO PRECLUDE THE NECESSITY OF ANY FIRE
WEATHER HEADLINES. THE MAIN FORECAST CHALLENGE FOR THE SHORT TERM
WILL BE TEMPERATURES FOR TODAY AND WEDNESDAY AND TIMING OF THE
NEXT FRONTAL PASSAGE...WHICH WILL BRING A QUICK AND DECISIVE END
TO THE BRIEF PERIOD OF PLEASANT WEATHER. HAVE ACTUALLY MADE LITTLE
CHANGE TO THE GOING FORECAST AS FAR AS TEMPERATURES ARE CONCERNED.
STILL SEE A GOOD LIKELIHOOD OF TEMPERATURES FINALLY REACHING INTO
THE LOW 70S BY WEDNESDAY. THEREFORE...THE MAIN ISSUE FOR THE
REMAINDER OF THE SHORT TERM FORECAST PERIOD WILL BE TIMING OF
THE FRONTAL PASSAGE. THE LATEST GUIDANCE SHOWS THAT THE NAM IS
TRENDING A BIT SLOWER AND STRONGER WITH THE SURFACE LOW ASSOCIATED
WITH THIS SYSTEM. PREFER THE NAM SOLUTION IN THIS CASE GIVEN THE
HIGH AMPLITUDE PATTERN SETTING UP...WHICH WOULD FAVOR A
STRONGER...BUT SLOWER PROGRESSION TO THE PATTERN. THIS WILL ALSO
ALLOW MORE TIME FOR AN INCREASE IN MOISTURE TRANSPORT. AS THE SFC
TROUGH TRACKS ACROSS THE UPPER MISSISSIPPI VALLEY WEDNESDAY AND A
SECONDARY LOW DEVELOPS OVER THE TEXAS PANHANDLE...THE GULF OF
MEXICO WILL FINALLY OPEN UP WEDNESDAY NIGHT AND THE MOISTURE WILL
BEGIN TO FLOW NORTHWARD INTO THE LOCAL AREA. BY THURSDAY...THE
COMBINATION OF THE APPROACHING COLD FRONT AND INCREASED MOISTURE
TRANSPORT WILL BRING A RENEWED CHANCE OF SHOWERS AND THUNDERSTORMS TO
THE REGION. ALSO..AS THE COLD FRONT ACCELERATES ACROSS THE UPPER
MIDWEST AND LAKE MICHIGAN...WINDS WILL BECOME MORE NELY ACROSS THE
NORTHERN PORTIONS OF THE CWA...BRINGING COOL LAKE MICHIGAN AIR AND
A SHARP DROP IN TEMPERATURES. BY THURSDAY AFTERNOON...EXPECT THAT
TEMPERATURES ACROSS THE NORTHERN TIER COUNTIES WILL CRASH BACK
INTO THE MIDDLE TO UPPER 50S. THE FRONTAL PROGRESSION WILL BE
SLOWER OVER THE SRN PORTIONS OF THE CWA...BEING HELD UP BY THE
DEVELOPMENT OF THE SOUTHERN STREAM SURFACE LOW. SO...THE
SOUTHEASTERN PORTIONS OF THE CWA COULD STILL SEE TEMPERATURES
REACHING NEAR 70F THURSDAY.
KREIN
&&
&&
.AVIATION...
1255 PM CDT
1800 UTC...MAIN AVIATION FORECAST ISSUE WILL CONTINUE TO BE WINDS.
SURFACE RIDGE AXIS CONTINUES TO MOVE OFF TO THE EAST ACROSS THE
OHIO RIVER VALLEY EARLY THIS AFTERNOON. SURFACE PRESSURE GRADIENT
WILL CONTINUE TO STRENGTHEN THROUGHOUT THE AFTERNOON AND ACARS
SOUNDINGS NEAR ORD INDICATE MIXED LAYER UP TO ABOUT 4500 FT WITH
WINDS OF 20 TO 25 KNOTS THROUGH THIS MIXED LAYER. WILL CONTINUE
WITH SOUTH WINDS OF 15 KNOTS GUSTING TO 25 KNOTS THROUGH THE EARLY
EVENING HOURS. AFTER 00Z...SHOULD BEGIN TO SEE SOME DIMINISHMENT
IN THE GUSTINESS AS MIXED LAYER ERODES BUT STRENGTH OF THE SURFACE
PRESSURE GRADIENT SHOULD ALLOW SOME GUSTS FROM 20 TO 25 KNOTS TO
CONTINUE THROUGH THE NIGHT. WINDIEST CONDITIONS OF THE PERIOD ARE
EXPECTED FROM MID MORNING WEDNESDAY ON AS STRONGEST SURFACE
PRESSURE GRADIENT AFFECTS THE NORTHERN ILLINOIS. MIXED LAYER
DEPTHS WILL BE A BIT MORE SHALLOW TOMORROW...BUT GIVEN STRENGTH OF
SURFACE PRESSURE GRADIENT AND STRONGER SFC PRESSURE FALLS ACROSS
WISCONSIN EXPECTING SOUTH GUSTS TO 30 TO 35 KNOTS WILL NOT BE HARD
TO ATTAIN BY LATE WEDNESDAY MORNING. OTHERWISE...IN TERMS OF SKY
COVER...JUST SOME INCREASING CIRRUS EXPECTED TONIGHT WITH VFR
CONDITIONS PERSISTING.
MARSILI
&&
.MARINE...
145 AM CDT
HIGH PRESSURE SHIFTING TO THE EAST OF THE LAKES TODAY WILL OPEN
UP THE REGION TO A MUCH TIGHTER PRESSURE GRADIENT AS DEEPENING LOW
PRESSURE IN THE PLAINS INCREASES PRESSURE DIFFERENTIALS BETWEEN
THE TWO SYSTEMS. AS A RESULT...WINDS ARE LIKELY TO INCREASE TO
GALE FORCE OVER THE NORTHERN PORTIONS OF LAKE MICHIGAN WHILE
TAPPING JUST UNDER THAT CRITERIA ON THE SOUTHERN THIRD. THIS LOW
WEAKENS AS IT LIFTS NORTHEAST INTO ONTARIO LATE WEDNESDAY...JUST
CLIPPING LAKE SUPERIOR. THE HIGH WILL ANCHOR ALONG THE EAST COAST
THROUGH THAT TIME WITH THE LOW CONTINUING TO WEAKEN AS IT NEARS
JAMES BAY THURSDAY MORNING...TRAILING A COLD FRONT DOWN ACROSS
LAKE MICHIGAN DURING THE DAY. THIS FRONT WILL BECOME STATIONARY
JUST SOUTH OF THE LAKE EARLY FRIDAY...WITH WEAK HIGH PRESSURE
MOVING ACROSS THE NORTHERN LAKES.
RLB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 9 AM CDT WEDNESDAY FOR LMZ740-LMZ741-
LMZ742-LMZ743-LMZ744-LMZ745.
GALE WARNING FROM 9 AM TO 10 PM CDT WEDNESDAY FOR LMZ740-LMZ741-
LMZ742-LMZ743-LMZ744-LMZ745.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
1155 PM CDT SUN APR 13 2008
.DISCUSSION...
345 PM CDT
THE SATELLITE IMAGERY SHOWS THE CONVECTIVE NATURE OF THE CUMULUS
AND STRATOCUMULUS THIS AFTERNOON. THERE ARE A FEW SNOW SHOWERS
SCATTERED ABOUT. THE ACARS SOUNDING AT ORD AT 1916 UTC SHOWS NEAR
DRY ADIABATIC LAPSE RATE FROM THE 520 FEET TO 3590 FEET. THIS
LAYER IS FORECAST TO DECREASE TO 1200 FEET TONIGHT. WE EXPECT MOST
OF THE CLOUDS WILL DISSIPATE AFTER SUNSET. THERE MAY BE ENOUGH
MIXING TO PREVENT WIDESPREAD FOG AND DRIER AIR IS FORECAST AT THE
SURFACE. THE 500 MB TROUGH IS FORECAST T MOVE EAST DURING MONDAY.
THE COLD AIR ALOFT WILL MOVE EAST. WE EXPECT NO SHOWERS ON MONDAY
AS THE ATMOSPHERE WILL BECOME MORE STABLE BY MONDAY EVENING. THERE
WILL BE A NORTH FLOW ON MONDAY SO WE WILL FORECAST HIGHS IN THE
LOWER TO MIDDLE 50S.
WE USED THE GFS MODEL FOR OUR WIND FORECAST FOR THE BEGINNING OF
THE WEEK. THERE IS A SOUTHWEST WIND FORECAST FOR 850 MB STARTING
TUESDAY MORNING. WARM AIR ADVECTION WILL CONTINUE THROUGH
WEDNESDAY. THE THERMAL RIDGE WILL MOVE INTO NORTH CENTRAL ILLINOIS
WEDNESDAY AFTERNOON. WE WILL FORECAST THE HIGH TEMPERATURES INTO
TH LOWER 70S FOR WEDNESDAY. THE NEXT 500 MB TROUGH IS FORECAST TO
MOVE INTO THE GREAT PLAINS BY LATE THURSDAY. WE WILL FORECAST
SHOWERS AND THUNDERSTORMS FOR WEDNESDAY AND THURSDAY. THE WARM AIR
WILL BE IN PLACE AND WE EXPECT MORE INSTABILITY ESPECIALLY
THURSDAY AND FRIDAY.
&&
.AVIATION...
1155 PM CDT
RE 06Z TAFORS...BENIGN WX AS RIDGE SURFACE AND ALOFT CONTINUES TO
BUILD SE ACROSS THE UPPER MIDWEST OVERNIGHT AND MON. LOW LEVEL
FLOW IS PROVIDING A LONG FETCH DOWN LAKE MI INTO SE WI..NE IL AND
NW IN. THIS IS RESULTING IN DEW POINTS BEING MAINTAINED IN THE
UPPER 20S DOWNSTREAM WHILE THE SOURCE AIRMASS HAS DEW POINTS IN
THE UPPER TEENS AND LOWER 20S. DOES NOT APPEAR THESE ELEVATED DEW
POINTS WILL BE ENOUGH TO GENERATE LAKE EFFECT CLOUDS WITH H8 TEMPS
OF AROUND -5C.
DIFFERENTIAL HEATING DURING THE DAY MON WILL RESULT IN LAKE
BREEZE DEVELOPMENT VEERING THE NNW SYNOPTIC SCALE WINDS TO THE WNW
ACROSS FAR NE IL DURING THE AFTERNOON. WIND WILL BE LIGHT/NIL MON
EVE WITH SURFACE RIDGE OVERHEAD.
TRS
&&
.MARINE...
150 PM CDT
NORTH TO NORTHEASTERLY WINDS ACROSS THE LAKE HAVE BEEN SLOWLY
DIMINISHING THROUGHOUT THE DAY TODAY. THIS TREND WILL CONTINUE
OVERNIGHT AS A RIDGE OF HIGH PRESSURE MOVES INTO THE REGION. WINDS
WINDS WILL HAVE RECEDED IN THE NEARSHORE ZONES...DUE TO THE
EXTENDED PERIOD OF COLD NORTHERLIES...WAVE ACTION WILL STILL BE
RATHER HIGH. SO WILL BE KEEPING THE SMALL CRAFT ADVISORY
GOING...MAINLY FOR WAVES OVER 4 FEET...THROUGH MONDAY MORNING. AS
THE RIDGE AXIS MOVES THROUGH THE LAKE AND EVENTUALLY OFF TO THE
SOUTHEAST...WINDS WILL BEGIN PICKING UP OUT OF THE SOUTH AND WEST
THROUGH MID WEEK. SUSTAINED WINDS WILL LIKELY GET UP AROUND 30
KNOTS...ESPECIALLY ACROSS THE NORTH HALF...BUT WHETHER OR NOT ANY
GUSTS CAN MIX DOWN BELOW THE SHALLOW COLD MARINE LAYER AND TO THE
LAKE IS STILL UP FOR DEBATE. THIS...ALONG WITH THE FACT THAT THE
GALES LIKELY WILL NOT ARRIVE UNTIL BEYOND 48 HOURS...WILL HOLD OFF
ON ISSUING ANY GALE WATCH HEADLINES.
HALBACH
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 4 AM CDT MONDAY FOR LMZ740-LMZ741-
LMZ742-LMZ743-LMZ744-LMZ745.
&&
$$
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
720 PM EDT TUE APR 15 2008
.SYNOPSIS...
WV IMAGERY AND RUC ANALYSIS INDICATED A TROUGH OVER THE WRN CONUS
AND A RIDGE FROM THE SRN PLAINS TO THE WRN GREAT LAKES. AT THE
SFC...A TIGHT GRADIENT HAS DEVELOPED ACROSS THE UPR MS VALLEY INTO
THE NRN LAKES BTWN A 987 MB LOW OVER NORTH DAKOTA AND A RIDGE OVER
THE ERN GREAT LAKES. THE WAA PATTERN HAS BROUGHT A LARGE PATCHY OF
HIGH CLOUDS INTO UPPER MI WHICH HAS BEEN ENOUGH TO REDUCE INSOLATION
AND MIXING DEPTH. TAMDAR SOUNDINGS SHOWED MIXING HEIGHT TO 900-875
MB AT KRHI/KCMX/KSAW. WITH SLIGHTLY LESS MIXING TEMPS HAD NOT
CLIMBED BEYOND THE MID 50S AND WIND GUSTS HAVE GENERALLY REMAINED
AOB 40 MPH.
&&
.SHORT TERM...(TONIGHT AND WEDNESDAY)
EXPECT POTENTIAL FOR WIND GUSTS TO AROUND 40 MPH TO PERSIST LATE
THIS AFTERNOON AND EARLY EVENING AS THE 45 TO 55 KT 925-850 MB WIND
MAX OVER MN INTO NW WI SHIFTS EASTWARD THIS EVENING.
HOWEVER...DIURNAL COOLING SHOULD ALLOW WINDS TO DIMINISH AT MOST
LOCATIONS BY AROUND 00Z. DOWNSLOPE LOCATIONS THAT OFTEN DO NOT
DECOUPLE SUCH AS LOCATIONS ALONG LAKE SUPERIOR NEAR
IRONWOOD/ONTONAGON AND MARQUETTE COULD SEE CONTINUE STRONG GUSTS
INTO THE LATE EVENING. HOWEVER...GIVEN ONLY LCL EFFECTS THE ADVISORY
WILL ONLY CONTINUE TO 23Z. WINDS/MIXING WILL KEEP MIN TEMPS WELL
ABOVE NORMAL WITH READINGS TO AROUND 40 INLAND AND THE MID AND UPPER
40S IN DOWNSLOPE LOCATIONS NEAR LAKE SUPERIOR.
A TROUGH AND COLD FRONT SLOWLY APPROACHES UPPER MICHIGAN. SINCE THE
SIGNIFICANT 800-600 MB FGEN REMAINS WEST OF THE CWA THE FCST
CONTINUES ONLY SLIGHT CHANCE POPS INTO WRN LAKE SUPERIOR DURING THE
AFTERNOON. WITH THE BOUNDARY LAYER STARTING OUT WARMER ADDITIONAL
SUNSHINE AND BREEZY SSW WINDS IN THE 15 TO 25 MPH RANGE TEMPS SHOULD
CLIMB INTO THE LOWER TO MID 60S...EXCEPT DOWNWIND FROM LAKE MICHIGAN.
&&
.HYDROLOGY...AT THIS POINT IT APPEARS SOME RIVERS WILL REACH FLOOD
STAGE THOUGH ONLY MINOR FLOODING IS EXPECTED. DID COORDINATE WITH
THE RIVER FORECAST CENTER THIS MORNING...THEIR LATEST FORECAST
INDICATES THE TAHQUAMENON...PRESQUE ISLE AND MIDDLE BRANCH OF THE
ESCANABA RIVERS WILL GET CLOSE TO FLOOD STAGE THIS WEEKEND. OTHER
RIVERS TO WATCH ARE THE MICHIGAMME...FORD AND STURGEON RIVER NEAR
ALSTON. WITH NO SIGNIFICANT QPF IN THE FORECAST...THE SNOWMELT IS
NOT EXPECTED TO GET TOO OUT OF HAND. THOUGH TEMPERATURES ARE WARM
TODAY...SNOWMELT WILL NOT BE DRAMATIC DUE TO SNOWPACK
TEMPERATURES...ACROSS THE WEST HALF...REMAINING JUST BELOW 32
DEGREES. OVERNIGHT TEMPS REMAINING ABOVE FREEZING WILL ALLOW FOR
SIGNIFICANT SNOWMELT TO TAKE PLACE TOMORROW AS TEMPERATURES WILL BE
IN THE 60S...DEWPOINTS WILL BE ABOVE FREEZING AND WINDS WILL REMAIN
STRONG. AS A RESULT...SHOULD START SEEING SIGNIFICANT RIVER RISES
STARTING TOMORROW AND CONTINUING THROUGH NEXT WEEK.
&&
.LONG TERM (WEDNESDAY NIGHT THROUGH NEXT TUESDAY)...
MAIN CONCERN IS IF THERE WILL BE ANY PCPN.
SFC FRONT CLOSES IN ON FAR WESTERN UPR MI BY 00Z THU. DRY AIRMASS
AHEAD OF FRONT SHOULD PRECLUDE ANY PRE FRONTAL PCPN. FOR THE MOST
PART EXPECT PCPN ON WED EVENING TO STAY WELL TO THE NORTH OVR
ONTARIO WHERE MORE IMPRESSIVE HEIGHT FALLS/H85-H5 Q-VECTOR
CONVERGENCE/H3 DIVERGENCE ARE MAXIMIZED. AFTER FRONT PUSHES
THROUGH...BETTER DYNAMICS PUSH ACROSS CWA LATER WED NIGHT.
CONCENTRATED DEEPER MOISTURE IS LACKING SO NOT EXPECTING MUCH FOR
PCPN. COULD BE SOME SHOWERS JUST IN THE WAKE OF THE FRONT THOUGH.
ALTHOUGH SFC FRONT SHIFTS TO FAR EASTERN UPR MI BY 12Z THU...THREAT
OF SOME RAIN HANGS IN OVR EAST HALF OF CWA AS H85-H7 MOISTURE
STREAMS UP ALONG LINGERING H85 FRONT. SINCE TROUGH IS STILL
OVERHEAD...H3 JET LIFTS OUT OF CNTRL MISSISSIPPI RIVER VALLEY AND
HELPS ENHANCE LIFTING ALONG THE H85 FRONT. AT THIS POINT...MODELS
DIVERGE WITH HANDLING OF THE H85 FRONT AND RESULTANT STRIPE OF
MODERATE QPF. NAM/GFS KEEP THE PCPN OVR ERN CWA WHILE
ECMWF/UKMET/CANADIAN KEEP QPF OVR WI AND LWR MI THU NIGHT INTO FRI.
SINCE SIGNAL FOR PCPN IS PRESENT ON ALL MODELS ALTHOUGH PLACEMENT IS
DIFFERENT...KEPT A SMALL CHANCE OF PCPN IN OVR SE CWA THU NIGHT.
UPR LEVEL PATTERN REMAINS QUITE AMPLIFIED THROUGH THE PERIOD. MAIN
FEATURE IMPACTING UPR MI IS TROUGHING FM CNTRL CANADA INTO WESTERN
CONUS. OVERALL...DAYTIME TEMPS WILL BE ABOVE NORMAL INTO EARLY NEXT
WEEK...ESPECIALLY INLAND AWAY FM THE COOLING INFLUENCE OF LAKE
SUPERIOR AND LAKE MICHIGAN. NIGHTTIME LOWS MAY DIP BLO NORMAL AS
AIRMASS IS PRETTY DRY. BY FRI...PREVAILING WIND IS FM THE ESE AS
HIGH PRESSURE BUILDS FM HUDSON BAY INTO QUEBEC WHILE A SFC TROUGH
PERSISTS OVR THE PLAINS. EVENTUALLY...THE TROUGH OVR WESTERN CONUS
WILL EDGE EAST AND BRING A FRONT INTO UPR LAKES EARLY NEXT WEEK.
OUTSIDE OF THIS FRONT FOR EARLY NEXT WEEK...THE ONLY OTHER FEATURE
THAT COULD BRING CLOUDS AND SOME RAIN TO UPR LAKES IS A CUTOFF LOW
THAT FORMS OVR OHIO VALLEY ON FRI. LATEST GFS AND NAM NOW TRENDING
FARTHER NORTH WITH THE UPR LOW...AND NOW BOTH ARE BRINGING A SFC
TROUGH INTO UPR LAKES FOR SAT. LATEST ECMWF BUCKS ITS PREVIOUS RUNS
BY INDICATING QPF OVR MOST OF UPR MI FRI NIGHT INTO SAT. NOT QUITE
CONVINCED YET AS THIS REPRESENTS A SUDDEN CHANGE FM PREVIOUS ECWMF.
LET THE DRY FORECAST GO FOR NOW...BUT DID INCREASE CLOUDS FRI NIGHT
AND SAT.
&&
.AVIATION (FOR THE 00Z TAF ISSUANCE)...
VFR CONDITIONS WILL CONTINUE WITH MID/UPPER LEVEL RIDGE DOMINATING.
GUSTY SOUTH WINDS WILL CONTINUE TONIGHT WITH A TIGHT GRADIENT BTWN
LOW PRES OVER THE NRN PLAINS AND THE DEPARTING HIGH OVER THE
SOUTHERN GREAT LAKES. EXPECT WINDS TO DIE DOWN SOME THIS EVENING
WITH LOSS OF DIURNAL MIXING...BUT KSAW SHOULD STILL GUST TO AROUND
25 KT THROUGH THE PERIOD. INCLUDED LLWS AT KCMX AND KSAW WITH STRONG
WINDS OFF THE SURFACE TONIGHT.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
STIFF SOUTHERLY WINDS APPROACHING GALE STRENGTH WILL CONTINUE THIS
EVENING WITH A TIGHT PRES GRADIENT BTWN AN APPROACHING LOW PRES AND
HIGH PRES OVER THE EASTERN LAKES. HOWEVER...WARM AIR OVERRIDING COLD
LAKE TEMPS WILL CREATE A STABLE PROFILE AND PROHIBIT A WIDESPREAD
GALE EVENT. WILL KEEP MENTION OF GALE FORCE GUSTS. SUSTAINED 30 KNOT
WINDS WILL CONTINUE TONIGHT INTO WEDNESDAY. WITH STRONG DOWNSLOPING
SOUTHERLY WINDS 35-40 KT...GALE WARNING STILL LOOKS ON TRACK OVER
ERN LAKE SUPERIOR NEARSHORE AREAS THIS AFTERNOON AND EVENING.
AS THE LOW LIFTS INTO NORTHERN ONTARIO ON WED...IT WILL DRAG A FRONT
ACROSS LAKE SUPERIOR WEDNESDAY NIGHT INTO THU. WINDS WILL GENERALLY
DIMINISH TO 25 KNOTS OR LESS BY THIS TIME. EXPECT LIGHT WINDS
THURSDAY INTO SATURDAY AS HIGH PRESSURE MOVES ACROSS THE AREA IN THE
WAKE OF THE FRONT.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
WIND ADVISORY UNTIL 7 PM EDT THIS EVENING MIZ002-004-005-009.
LAKE SUPERIOR...
GALE WARNING UNTIL 7 PM EDT /6 PM CDT/ THIS EVENING LSZ240-241.
GALE WARNING UNTIL 11 PM EDT THIS EVENING LSZ250-251.
LAKE MICHIGAN...NONE.
&&
$$
SYNOPSIS/SHORT TERM...JLB
HYDROLOGY...DJP
LONG TERM...JLA
MARINE...JLB
AVIATION...GJM
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
420 PM EDT TUE APR 15 2008
.SYNOPSIS...
WV IMAGERY AND RUC ANALYSIS INDICATED A TROUGH OVER THE WRN CONUS
AND A RIDGE FROM THE SRN PLAINS TO THE WRN GREAT LAKES. AT THE
SFC...A TIGHT GRADIENT HAS DEVELOPED ACROSS THE UPR MS VALLEY INTO
THE NRN LAKES BTWN A 987 MB LOW OVER NORTH DAKOTA AND A RIDGE OVER
THE ERN GREAT LAKES. THE WAA PATTERN HAS BROUGHT A LARGE PATCHY OF
HIGH CLOUDS INTO UPPER MI WHICH HAS BEEN ENOUGH TO REDUCE INSOLATION
AND MIXING DEPTH. TAMDAR SOUNDINGS SHOWED MIXING HEIGHT TO 900-875
MB AT KRHI/KCMX/KSAW. WITH SLIGHTLY LESS MIXING TEMPS HAD NOT
CLIMBED BEYOND THE MID 50S AND WIND GUSTS HAVE GENERALLY REMAINED
AOB 40 MPH.
&&
.SHORT TERM...(TONIGHT AND WEDNESDAY)
EXPECT POTENTIAL FOR WIND GUSTS TO AROUND 40 MPH TO PERSIST LATE
THIS AFTERNOON AND EARLY EVENING AS THE 45 TO 55 KT 925-850 MB WIND
MAX OVER MN INTO NW WI SHIFTS EASTWARD THIS EVENING.
HOWEVER...DIURNAL COOLING SHOULD ALLOW WINDS TO DIMINISH AT MOST
LOCATIONS BY AROUND 00Z. DOWNSLOPE LOCATIONS THAT OFTEN DO NOT
DECOUPLE SUCH AS LOCATIONS ALONG LAKE SUPERIOR NEAR
IRONWOOD/ONTONAGON AND MARQUETTE COULD SEE CONTINUE STRONG GUSTS
INTO THE LATE EVENING. HOWEVER...GIVEN ONLY LCL EFFECTS THE ADVISORY
WILL ONLY CONTINUE TO 23Z. WINDS/MIXING WILL KEEP MIN TEMPS WELL
ABOVE NORMAL WITH READINGS TO AROUND 40 INLAND AND THE MID AND UPPER
40S IN DOWNSLOPE LOCATIONS NEAR LAKE SUPERIOR.
A TROUGH AND COLD FRONT SLOWLY APPROACHES UPPER MICHIGAN. SINCE THE
SIGNIFICANT 800-600 MB FGEN REMAINS WEST OF THE CWA THE FCST CONTINUES
ONLY SLIGHT CHANCE POPS INTO WRN LAKE SUPERIOR DURING THE AFTERNOON.
WITH THE BOUNDARY LAYER STARTING OUT WARMER ADDITIONAL SUNSHINE AND
BREEZY SSW WINDS IN THE 15 TO 25 MPH RANGE TEMPS SHOULD CLIMB INTO
THE LOWER TO MID 60S...EXCEPT DOWNWIND FROM LAKE MICHIGAN.
&&
.HYDROLOGY...AT THIS POINT IT APPEARS SOME RIVERS WILL REACH FLOOD
STAGE THOUGH ONLY MINOR FLOODING IS EXPECTED. DID COORDINATE WITH
THE RIVER FORECAST CENTER THIS MORNING...THEIR LATEST FORECAST
INDICATES THE TAHQUAMENON...PRESQUE ISLE AND MIDDLE BRANCH OF THE
ESCANABA RIVERS WILL GET CLOSE TO FLOOD STAGE THIS WEEKEND. OTHER
RIVERS TO WATCH ARE THE MICHIGAMME...FORD AND STURGEON RIVER NEAR
ALSTON. WITH NO SIGNIFICANT QPF IN THE FORECAST...THE SNOWMELT IS
NOT EXPECTED TO GET TOO OUT OF HAND. THOUGH TEMPERATURES ARE WARM
TODAY...SNOWMELT WILL NOT BE DRAMATIC DUE TO SNOWPACK
TEMPERATURES...ACROSS THE WEST HALF...REMAINING JUST BELOW 32
DEGREES. OVERNIGHT TEMPS REMAINING ABOVE FREEZING WILL ALLOW FOR
SIGNIFICANT SNOWMELT TO TAKE PLACE TOMORROW AS TEMPERATURES WILL BE
IN THE 60S...DEWPOINTS WILL BE ABOVE FREEZING AND WINDS WILL REMAIN
STRONG. AS A RESULT...SHOULD START SEEING SIGNIFICANT RIVER RISES
STARTING TOMORROW AND CONTINUING THROUGH NEXT WEEK.
&&
.LONG TERM (WEDNESDAY NIGHT THROUGH NEXT TUESDAY)...
MAIN CONCERN IS IF THERE WILL BE ANY PCPN.
SFC FRONT CLOSES IN ON FAR WESTERN UPR MI BY 00Z THU. DRY AIRMASS
AHEAD OF FRONT SHOULD PRECLUDE ANY PRE FRONTAL PCPN. FOR THE MOST
PART EXPECT PCPN ON WED EVENING TO STAY WELL TO THE NORTH OVR ONTARIO
WHERE MORE IMPRESSIVE HEIGHT FALLS/H85-H5 Q-VECTOR CONVERGENCE/H3
DIVERGENCE ARE MAXIMIZED. AFTER FRONT PUSHES THROUGH...BETTER
DYNAMICS PUSH ACROSS CWA LATER WED NIGHT. CONCENTRATED DEEPER
MOISTURE IS LACKING SO NOT EXPECTING MUCH FOR PCPN. COULD BE SOME
SHOWERS JUST IN THE WAKE OF THE FRONT THOUGH. ALTHOUGH SFC FRONT
SHIFTS TO FAR EASTERN UPR MI BY 12Z THU...THREAT OF SOME RAIN HANGS
IN OVR EAST HALF OF CWA AS H85-H7 MOISTURE STREAMS UP ALONG
LINGERING H85 FRONT. SINCE TROUGH IS STILL OVERHEAD...H3 JET LIFTS
OUT OF CNTRL MISSISSIPPI RIVER VALLEY AND HELPS ENHANCE LIFTING
ALONG THE H85 FRONT. AT THIS POINT...MODELS DIVERGE WITH HANDLING OF
THE H85 FRONT AND RESULTANT STRIPE OF MODERATE QPF. NAM/GFS KEEP THE
PCPN OVR ERN CWA WHILE ECMWF/UKMET/CANADIAN KEEP QPF OVR WI AND LWR
MI THU NIGHT INTO FRI. SINCE SIGNAL FOR PCPN IS PRESENT ON ALL
MODELS ALTHOUGH PLACEMENT IS DIFFERENT...KEPT A SMALL CHANCE OF PCPN
IN OVR SE CWA THU NIGHT.
UPR LEVEL PATTERN REMAINS QUITE AMPLIFIED THROUGH THE PERIOD. MAIN
FEATURE IMPACTING UPR MI IS TROUGHING FM CNTRL CANADA INTO WESTERN
CONUS. OVERALL...DAYTIME TEMPS WILL BE ABOVE NORMAL INTO EARLY NEXT
WEEK...ESPECIALLY INLAND AWAY FM THE COOLING INFLUENCE OF LAKE
SUPERIOR AND LAKE MICHIGAN. NIGHTTIME LOWS MAY DIP BLO NORMAL AS
AIRMASS IS PRETTY DRY. BY FRI...PREVAILING WIND IS FM THE ESE AS
HIGH PRESSURE BUILDS FM HUDSON BAY INTO QUEBEC WHILE A SFC TROUGH
PERSISTS OVR THE PLAINS. EVENTUALLY...THE TROUGH OVR WESTERN CONUS
WILL EDGE EAST AND BRING A FRONT INTO UPR LAKES EARLY NEXT WEEK.
OUTSIDE OF THIS FRONT FOR EARLY NEXT WEEK...THE ONLY OTHER FEATURE
THAT COULD BRING CLOUDS AND SOME RAIN TO UPR LAKES IS A CUTOFF LOW
THAT FORMS OVR OHIO VALLEY ON FRI. LATEST GFS AND NAM NOW TRENDING
FARTHER NORTH WITH THE UPR LOW...AND NOW BOTH ARE BRINGING A SFC
TROUGH INTO UPR LAKES FOR SAT. LATEST ECMWF BUCKS ITS PREVIOUS RUNS
BY INDICATING QPF OVR MOST OF UPR MI FRI NIGHT INTO SAT. NOT QUITE
CONVINCED YET AS THIS REPRESENTS A SUDDEN CHANGE FM PREVIOUS ECWMF.
LET THE DRY FORECAST GO FOR NOW...BUT DID INCREASE CLOUDS FRI NIGHT
AND SAT.
&&
.AVIATION (FOR THE 18Z TAF ISSUANCE)...
VFR CONDITIONS WILL CONTINUE WITH MID/UPPER LEVEL RIDGE DOMINATING.
GUSTY SOUTH WINDS WILL CONTINUE TONIGHT WITH A TIGHT GRADIENT BTWN
LOW PRES OVER THE NRN PLAINS AND THE DEPARTING HIGH OVER THE
SOUTHERN GREAT LAKES. EXPECT WINDS TO DIE DOWN SOME THIS EVENING
WITH LOSS OF DIURNAL MIXING...BUT KSAW SHOULD STILL GUST TO 25 KT.
INCLUDED LLWS AT KCMX WITH WINDS TO 40 KT AROUND 1KFT AS AXIS OF
LOW-LVL JET MOVES OVER THE AREA THIS EVENING.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
STIFF SOUTHERLY WINDS APPROACHING GALE STRENGTH WILL CONTINUE THIS
EVENING WITH A TIGHT PRES GRADIENT BTWN AN APPROACHING LOW PRES AND
HIGH PRES OVER THE EASTERN LAKES. HOWEVER...WARM AIR OVERRIDING COLD
LAKE TEMPS WILL CREATE A STABLE PROFILE AND PROHIBIT A WIDESPREAD
GALE EVENT. WILL KEEP MENTION OF GALE FORCE GUSTS. SUSTAINED 30 KNOT
WINDS WILL CONTINUE TONIGHT INTO WEDNESDAY. WITH STRONG DOWNSLOPING
SOUTHERLY WINDS 35-40 KT...GALE WARNING STILL LOOKS ON TRACK OVER
ERN LAKE SUPERIOR NEARSHORE AREAS THIS AFTERNOON AND EVENING.
AS THE LOW LIFTS INTO NORTHERN ONTARIO ON WED...IT WILL DRAG A FRONT
ACROSS LAKE SUPERIOR WEDNESDAY NIGHT INTO THU. WINDS WILL GENERALLY
DIMINISH TO 25 KNOTS OR LESS BY THIS TIME. EXPECT LIGHT WINDS
THURSDAY INTO SATURDAY AS HIGH PRESSURE MOVES ACROSS THE AREA IN THE
WAKE OF THE FRONT.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...
WIND ADVISORY UNTIL 7 PM EDT THIS EVENING MIZ002-004-005-009.
LAKE SUPERIOR...
GALE WARNING UNTIL 7 PM EDT /6 PM CDT/ THIS EVENING LSZ240-241.
GALE WARNING UNTIL 11 PM EDT THIS EVENING LSZ250-251.
LAKE MICHIGAN...NONE.
&&
$$
SYNOPSIS/SHORT TERM...JLB
HYDROLOGY...DJP
LONG TERM...JLA
AVIATION/MARINE...JLB
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
1012 PM EDT TUE APR 15 2008
.SYNOPSIS...
HIGH PRESSURE WILL BE CENTERED OVER THE REGION THROUGH FRIDAY.
AN UPPER LEVEL LOW AND ITS ASSOCIATED SURFACE FRONT WILL CROSS THE
REGION OVER THE WEEKEND.
&&
.NEAR TERM /UNTIL 9 AM WEDNESDAY MORNING/...
SATELLITE PICTURES SHOWING A CLEAR SKY THROUGHOUT THE REGION.
WINDS HAVE DECOUPLED AND TEMPERATURES HAVE DROPPED INTO THE UPPER
30S TO LOWER 50S. ONLY MINOR TWEAKS NEEDED TO FORECAST FOR
TONIGHT.
A FREEZE WARNING IS IN EFFECT FOR ALL OF OUR FOOTHILL AND
PIEDMONT COUNTIES WHERE THE GROWING SEASON HAS BEGUN. THERE WILL
ALSO BE A HARD FREEZE IN THE MTNS WHERE LOWS SHOULD DROP WELL INTO
THE 20S...BUT NO FREEZE WARNING HEADLINE...SINCE GROWING SEASON
HAS NOT OFFICIALLY BEGUN.
&&
.SHORT TERM /9 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
MODELS HAVE A 1027 MB SURFACE HIGH CENTERED DIRECTLY OVERHEAD ON
WEDNESDAY...WHICH THEN BECOMES STATIONARY AND DOMINATES OUR
WEATHER THROUGH THE SHORT TERM. MODEL SOUNDINGS SHOW A VERY DRY
AIRMASS...SO ANTICIPATE A LARGE NOCTURNAL/DIURNAL TEMPERATURE
RANGE...THE T-MAX WED AFTN ABOUT 40 DEGREES WARMER THAN THE T-MIN.
READINGS AREAWIDE SHOULD REACH THE 60S. WARM TEMPS AND LOW
DEWPOINTS SUPPORT A LOW RH...AFTN MINS OF 20-25 PERCENT.
GOOD RADIATIONAL CONDITIONS SET UP AGAIN WEDNESDAY NIGHT. PATCHY
FROST LIKELY...ESP VALLEYS WHERE TEMPS DROP BACK INTO THE LOWER TO
MID 30S.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
THURSDAY INTO FRIDAY THE AXIS OF THE UPPER RIDGE WILL START TO HEAD
EAST OF THE AREA IN RESPONSE TO AN UPPER LOW CLOSING OFF AND
DEEPENING ACROSS CENTRAL CONUS. DRY WEATHER AND MILD TEMPERATURES
SHOULD CONTINUE...BUT THERE WILL BE A GRADUAL TREND TOWARDS MORE
CLOUD COVER THROUGH THE PERIOD AS MOISTURE FROM THE SOUTH
INCREASES...AND BLOW OFF THIN CIRRUS FROM THE CENTRAL CONUS SYSTEM
STARTS TO ENTER THE AREA.
HEADING INTO THE WEEKEND...GUIDANCE VARIES AS TO THE TRACK AND
TIMING OF THE CENTRAL CONUS LOW. HPC HAS BEEN VIEWING THE GFS AS A
SOLUTION TOO FAR NORTH AS COMPARED TO THE PREFERRED ECMWF SOLUTION.
AS SUCH...WILL FAVOR THE HPC GRIDS IN THE DAY 4-7 TIME PERIOD FOR
THE FORECAST PACKAGE. THIS SOLUTION BRINGS BRINGS A NEARLY
VERTICALLY STACKED LOW ACROSS THE FORECAST AREA ON SUNDAY.
ASSOCIATED PRECIPITATION FROM THE SYSTEM WILL START TO IMPACT
WESTERN PARTS OF THE AREA ON FRIDAY NIGHT. WILL BE CARRYING
SCATTERED SHOWERS ACROSS MUCH OF THE AREA THROUGH SUNDAY
NIGHT...WITH THE SYSTEM SLOWLY EXITING THE AREA TO THE EAST ON
MONDAY...WITH AN ISOLATED CHANCE OF SHOWERS REMAINING INTO MONDAY
NIGHT. WE COULD SEE ENOUGH INSTABILITY NEAR THE CENTER OF THE
SURFACE LOW SATURDAY AFTERNOON AND EVENING FOR SOME ISOLATED
THUNDERSTORMS ACROSS THE NORTHERN MOUNTAINS OF NORTH CAROLINA AND
NEIGHBORING PARTS OF THE MOUNTAIN EMPIRE REGION OF SOUTHWEST
VIRGINIA.
AS WE HEAD INTO TUESDAY...ANOTHER SYSTEM HEADING THROUGH THE OHIO
VALLEY MAY BRING ISOLATED/SCATTERED SHOWERS TO MAINLY THE MOUNTAINS.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDITIONS WILL PREVAIL TONIGHT INTO FRIDAY. HIGH PRESSURE WILL
BE IN CONTROL OF OUR WEATHER. LIGHT WINDS EXPECTED 12 KNOTS OR LESS
AT THE SURFACE. SOME RIVER FOG IS POSSIBLE ALONG THE RIVERS AROUND
DAYBREAK EACH MORNING. TEMPERATURES WILL BE COLD ENOUGH FOR FROST TO
FORM ON GROUND BASED AIRCRAFT AT ALL AIRPORTS WEDNESDAY MORNING.
THE NEXT COLD FRONT TO INFLUENCE THE TERMINAL AREA WILL BE PASSING
THROUGH THE REGION THIS WEEKEND. MAY SEE SOME INCREASE IN CLOUD
COVER AHEAD OF THIS SYSTEM LATE FRIDAY...WITH CLOUDS AND SHOWERS
PRODUCING MVFR OR OCCASIONAL IFR CONDITIONS AT ALL AIRPORTS ON
SATURDAY.
&&
.FIRE WEATHER...
DRY THE NEXT 3 DAYS AS HIGH PRESSURE PASSES OVERHEAD. AFTERNOON RH
VALUES WILL SLIP INTO THE 20-30 PERCENT RANGE WEDNESDAY AND THURSDAY
AFTERNOONS. WINDS SHOULD BE LIGHT...AND WILL LIMIT VENTILATION
AND SMOKE TRANSPORT.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...FREEZE WARNING UNTIL 9 AM EDT WEDNESDAY FOR VAZ019-022>024-
032>035-043>047-058-059.
NC...FREEZE WARNING UNTIL 9 AM EDT WEDNESDAY FOR NCZ003>006-019-020.
WV...NONE.
&&
$$
SYNOPSIS...JJ/WP
NEAR TERM...AMS
SHORT TERM...PM
LONG TERM...DS
AVIATION...KK/PM
FIRE WEATHER...
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
732 PM EDT TUE APR 15 2008
.SYNOPSIS...
HIGH PRESSURE WILL BE CENTERED OVER THE REGION THROUGH FRIDAY.
AN UPPER LEVEL LOW AND ITS ASSOCIATED SURFACE FRONT WILL CROSS THE
REGION OVER THE WEEKEND.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
CLEAR SKIES NOTED ACROSS THE ENTIRE CWA AT 18 UTC. VISIBLE SAT
PIX INDICATES A FEW CU OVER THE MOUNTAINS...BUT AIRMASS IS SO
DRY...SFC DEWPOINTS NEAR 20...THAT CU HARD PRESSED TO FORM EVEN AT
THE TOP OF THE LCL WHICH IS AROUND 6KFT. WIND WAS A LITTLE
STRONGER THAN FCST...ESP EASTERN COUNTIES WHICH HAVE REMAINED
UNDER STRONGER NE FLOW FROM THE STORM SYSTEM JUST OFF THE COAST.
HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE AREA THIS EVENING
WITH WINDS DECOUPLING AFTER SUNSET. EXCELLENT RADIATION CONDS
ARE ANTICIPATED FOR THE OVERNIGHT...ESPECIALLY IN THE MTN
VALLEYS...WITH FROST/FREEZE CONCERNS AREAWIDE. SINCE THE LOWER
ELEVATION COUNTIES ARE THE ONLY ONES THAT HAVE ENTERED OUR GROWING
SEASON WINDOW...THESE WILL BE THE ONLY ONES WITH A HEADLINE.
HOWEVER...TEMPS OUTSIDE THIS AREA (IN THE MTNS) WILL BE JUST AS
COLD IF NOT COLDER...SOMETHING TO KEEP IN MIND EVEN THOUGH THE
HEADLINE MAPS DO NOT SHOW IT. LOW TEMPS ARE EXPECTED TO BE AT OR
BELOW FREEZING FOR ALL OR NEARLY ALL OF THE FORECAST AREA...T-MINS
DIPPING INTO THE LOWER 20S IN THE MTNS VALLEYS.
IN SUMMARY...A FREEZE WARNING IS IN EFFECT FOR ALL OF OUR
FOOTHILL AND PIEDMONT COUNTIES WHERE THE GROWING SEASON HAS BEGUN.
THERE WILL ALSO BE A HARD FREEZE IN THE MTNS WHERE LOWS SHOULD
DROP WELL INTO THE 20S...BUT NO FREEZE WARNING HEADLINE...SINCE
GROWING SEASON HAS NOT OFFICIALLY BEGUN.
MODELS CONTINUE TO HAVE IT
DIRECTLY OVER THE FCST AREA BY WED MORNING. MODEL SOUNDINGS SHOW A
VERY DRY AIRMASS...SO WILL SEE A LARGE NOCTURNAL/DIURNAL SPREAD OF
TEMPERATURES ALONG WITH LOW AFTERNOON RH MINIMA. I LOWERED THE
DEWPOINTS THIS AFTERNOON BASED ON UPSTREAM DEWPOINTS IN THE LOWER
20S. RH MINS THIS AFTN SHOULD DROP TO BETWEEN 20-25 PERCENT.
&&
.SHORT TERM /WEDNESDAY NIGHT/...
MODELS HAVE A 1027 MB SURFACE HIGH CENTERED DIRECTLY OVERHEAD ON
WEDNESDAY...WHICH THEN BECOMES STATIONARY AND DOMINATES OUR
WEATHER THROUGH THE SHORT TERM. MODEL SOUNDINGS SHOW A VERY DRY
AIRMASS...SO ANTICIPATE A LARGE NOCTURNAL/DIURNAL TEMPERATURE
RANGE...THE T-MAX WED AFTN ABOUT 40 DEGREES WARMER THAN THE T-MIN.
READINGS AREAWIDE SHOULD REACH THE 60S. WARM TEMPS AND LOW
DEWPOINTS SUPPORT A LOW RH...AFTN MINS OF 20-25 PERCENT.
GOOD RADIATIONAL CONDTIONS SET UP AGAIN WEDNESDAY NIGHT. PATCHY
FROST LIKELY...ESP VALLEYS WHERE TEMPS DROP BACK INTO THE LOWER TO
MID 30S.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
THURSDAY INTO FRIDAY THE AXIS OF THE UPPER RIDGE WILL START TO HEAD
EAST OF THE AREA IN RESPONSE TO AN UPPER LOW CLOSING OFF AND
DEEPENING ACROSS CENTRAL CONUS. DRY WEATHER AND MILD TEMPERATURES
SHOULD CONTINUE...BUT THERE WILL BE A GRADUAL TREND TOWARDS MORE
CLOUD COVER THROUGH THE PERIOD AS MOISTURE FROM THE SOUTH
INCREASES...AND BLOW OFF THIN CIRRUS FROM THE CENTRAL CONUS SYSTEM
STARTS TO ENTER THE AREA.
HEADING INTO THE WEEKEND...GUIDANCE VARIES AS TO THE TRACK AND
TIMING OF THE CENTRAL CONUS LOW. HPC HAS BEEN VIEWING THE GFS AS A
SOLUTION TOO FAR NORTH AS COMPARED TO THE PREFERRED ECMWF SOLUTION.
AS SUCH...WILL FAVOR THE HPC GRIDS IN THE DAY 4-7 TIME PERIOD FOR
THE FORECAST PACKAGE. THIS SOLUTION BRINGS BRINGS A NEARLY
VERTICALLY STACKED LOW ACROSS THE FORECAST AREA ON SUNDAY.
ASSOCIATED PRECIPITATION FROM THE SYSTEM WILL START TO IMPACT
WESTERN PARTS OF THE AREA ON FRIDAY NIGHT. WILL BE CARRYING
SCATTERED SHOWERS ACROSS MUCH OF THE AREA THROUGH SUNDAY
NIGHT...WITH THE SYSTEM SLOWLY EXITING THE AREA TO THE EAST ON
MONDAY...WITH AN ISOLATED CHANCE OF SHOWERS REMAINING INTO MONDAY
NIGHT. WE COULD SEE ENOUGH INSTABILITY NEAR THE CENTER OF THE
SURFACE LOW SATURDAY AFTERNOON AND EVENING FOR SOME ISOLATED
THUNDERSTORMS ACROSS THE NORTHERN MOUNTAINS OF NORTH CAROLINA AND
NEIGHBORING PARTS OF THE MOUNTAIN EMPIRE REGION OF SOUTHWEST
VIRGINIA.
AS WE HEAD INTO TUESDAY...ANOTHER SYSTEM HEADING THROUGH THE OHIO
VALLEY MAY BRING ISOLATED/SCATTERED SHOWERS TO MAINLY THE MOUNTAINS.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDITIONS WILL PREVAIL TONIGHT INTO FRIDAY. HIGH PRESSURE WILL
BE IN CONTROL OF OUR WEATHER. LIGHT WINDS EXPECTED 12 KNOTS OR LESS
AT THE SURFACE. SOME RIVER FOG IS POSSIBLE ALONG THE RIVERS AROUND
DAYBREAK EACH MORNING. TEMPERATURES WILL BE COLD ENOUGH FOR FROST TO
FORM ON GROUND BASED AIRCRAFT AT ALL AIRPORTS WEDNESDAY MORNING.
THE NEXT COLD FRONT TO INFLUENCE THE TERMINAL AREA WILL BE PASSING
THROUGH THE REGION THIS WEEKEND. MAY SEE SOME INCREASE IN CLOUD
COVER AHEAD OF THIS SYSTEM LATE FRIDAY...WITH CLOUDS AND SHOWERS
PRODUCING MVFR OR OCCASIONAL IFR CONDITIONS AT ALL AIRPORTS ON
SATURDAY.
&&
.FIRE WEATHER...
DRY THE NEXT 3 DAYS AS HIGH PRESSURE PASSES OVERHEAD. AFTERNOON RH
VALUES WILL SLIP INTO THE 20-30 PERCENT RANGE WEDNESDAY AND THURSDAY
AFTERNOONS. WINDS SHOULD BE LIGHT...AND WILL LIMIT VENTILATION
AND SMOKE TRANSPORT.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT WEDNESDAY FOR
VAZ019-022>024-032>035-043>047-058-059.
NC...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT WEDNESDAY FOR
NCZ003>006-019-020.
WV...NONE.
&&
$$
SYNOPSIS...JJ/WP
NEAR TERM...PM
SHORT TERM...PM
LONG TERM...DS
AVIATION...KK/PM
FIRE WEATHER...
AREA FORECAST DISCUSSION
NWS BLACKSBURG VA
300 PM EDT TUE APR 15 2008
.SYNOPSIS...
HIGH PRESSURE WILL BE CENTERED OVER THE REGION THROUGH FRIDAY.
AN UPPER LEVEL LOW AND ITS ASSOCIATED SURFACE FRONT WILL CROSS THE
REGION OVER THE WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
CLEAR SKIES NOTED ACROSS THE ENTIRE CWA AT 18 UTC. VISIBLE SAT
PIX INDICATES A FEW CU OVER THE MOUNTAINS...BUT AIRMASS IS SO
DRY...SFC DEWPOINTS NEAR 20...THAT CU HARD PRESSED TO FORM EVEN AT
THE TOP OF THE LCL WHICH IS AROUND 6KFT. WIND WAS A LITTLE
STRONGER THAN FCST...ESP EASTERN COUNTIES WHICH HAVE REMAINED
UNDER STRONGER NE FLOW FROM THE STORM SYSTEM JUST OFF THE COAST.
HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE AREA THIS EVENING
WITH WINDS DECOUPLING AFTER SUNSET. EXCELLENT RADIATION CONDS
ARE ANTICIPATED FOR THE OVERNIGHT...ESPECIALLY IN THE MTN
VALLEYS...WITH FROST/FREEZE CONCERNS AREAWIDE. SINCE THE LOWER
ELEVATION COUNTIES ARE THE ONLY ONES THAT HAVE ENTERED OUR GROWING
SEASON WINDOW...THESE WILL BE THE ONLY ONES WITH A HEADLINE.
HOWEVER...TEMPS OUTSIDE THIS AREA (IN THE MTNS) WILL BE JUST AS
COLD IF NOT COLDER...SOMETHING TO KEEP IN MIND EVEN THOUGH THE
HEADLINE MAPS DO NOT SHOW IT. LOW TEMPS ARE EXPECTED TO BE AT OR
BELOW FREEZING FOR ALL OR NEARLY ALL OF THE FORECAST AREA...T-MINS
DIPPING INTO THE LOWER 20S IN THE MTNS VALLEYS.
IN SUMMARY...A FREEZE WARNING IS IN EFFECT FOR ALL OF OUR
FOOTHILL AND PIEDMONT COUNTIES WHERE THE GROWING SEASON HAS BEGUN.
THERE WILL ALSO BE A HARD FREEZE IN THE MTNS WHERE LOWS SHOULD
DROP WELL INTO THE 20S...BUT NO FREEZE WARNING HEADLINE...SINCE
GROWING SEASON HAS NOT OFFICIALLY BEGUN.
MODELS CONTINUE TO HAVE IT
DIRECTLY OVER THE FCST AREA BY WED MORNING. MODEL SOUNDINGS SHOW A
VERY DRY AIRMASS...SO WILL SEE A LARGE NOCTURNAL/DIURNAL SPREAD OF
TEMPERATURES ALONG WITH LOW AFTERNOON RH MINIMA. I LOWERED THE
DEWPOINTS THIS AFTERNOON BASED ON UPSTREAM DEWPOINTS IN THE LOWER
20S. RH MINS THIS AFTN SHOULD DROP TO BETWEEN 20-25 PERCENT.
&&
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
MODELS HAVE A 1027 MB SURFACE HIGH CENTERED DIRECTLY OVERHEAD ON
WEDNESDAY...WHICH THEN BECOMES STATIONARY AND DOMINATES OUR
WEATHER THROUGH THE SHORT TERM. MODEL SOUNDINGS SHOW A VERY DRY
AIRMASS...SO ANTICIPATE A LARGE NOCTURNAL/DIURNAL TEMPERATURE
RANGE...THE T-MAX WED AFTN ABOUT 40 DEGREES WARMER THAN THE T-MIN.
READINGS AREAWIDE SHOULD REACH THE 60S. WARM TEMPS AND LOW
DEWPOINTS SUPPORT A LOW RH...AFTN MINS OF 20-25 PERCENT.
GOOD RADIATIONAL CONDTIONS SET UP AGAIN WEDNESDAY NIGHT. PATCHY
FROST LIKELY...ESP VALLEYS WHERE TEMPS DROP BACK INTO THE LOWER TO
MID 30S.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
THURSDAY INTO FRIDAY THE AXIS OF THE UPPER RIDGE WILL START TO HEAD
EAST OF THE AREA IN RESPONSE TO AN UPPER LOW CLOSING OFF AND
DEEPENING ACROSS CENTRAL CONUS. DRY WEATHER AND MILD TEMPERATURES
SHOULD CONTINUE...BUT THERE WILL BE A GRADUAL TREND TOWARDS MORE
CLOUD COVER THROUGH THE PERIOD AS MOISTURE FROM THE SOUTH
INCREASES...AND BLOW OFF THIN CIRRUS FROM THE CENTRAL CONUS SYSTEM
STARTS TO ENTER THE AREA.
HEADING INTO THE WEEKEND...GUIDANCE VARIES AS TO THE TRACK AND
TIMING OF THE CENTRAL CONUS LOW. HPC HAS BEEN VIEWING THE GFS AS A
SOLUTION TOO FAR NORTH AS COMPARED TO THE PREFERRED ECMWF SOLUTION.
AS SUCH...WILL FAVOR THE HPC GRIDS IN THE DAY 4-7 TIME PERIOD FOR
THE FORECAST PACKAGE. THIS SOLUTION BRINGS BRINGS A NEARLY
VERTICALLY STACKED LOW ACROSS THE FORECAST AREA ON SUNDAY.
ASSOCIATED PRECIPITATION FROM THE SYSTEM WILL START TO IMPACT
WESTERN PARTS OF THE AREA ON FRIDAY NIGHT. WILL BE CARRYING
SCATTERED SHOWERS ACROSS MUCH OF THE AREA THROUGH SUNDAY
NIGHT...WITH THE SYSTEM SLOWLY EXITING THE AREA TO THE EAST ON
MONDAY...WITH AN ISOLATED CHANCE OF SHOWERS REMAINING INTO MONDAY
NIGHT. WE COULD SEE ENOUGH INSTABILITY NEAR THE CENTER OF THE
SURFACE LOW SATURDAY AFTERNOON AND EVENING FOR SOME ISOLATED
THUNDERSTORMS ACROSS THE NORTHERN MOUNTAINS OF NORTH CAROLINA AND
NEIGHBORING PARTS OF THE MOUNTAIN EMPIRE REGION OF SOUTHWEST
VIRGINIA.
AS WE HEAD INTO TUESDAY...ANOTHER SYSTEM HEADING THROUGH THE OHIO
VALLEY MAY BRING ISOLATED/SCATTERED SHOWERS TO MAINLY THE MOUNTAINS.
&&
.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
ANTICIPATE MAINLY CLEAR SKIES FOR THE NEXT 3 DAYS...WEDNESDAY...
THURSDAY...AND MOST OF FRIDAY. HIGH PRESSURE WILL BE IN CONTROL
WITH WINDS 12 KNOTS OR LESS AT THE SURFACE. SOME RIVER FOG IS
POSSIBLE ALONG THE RIVERS AROUND DAYBREAK EACH MORNING...BUT ASIDE
FROM THE RIVER FOG...VFR CONDITIONS ARE EXPECTED TO PREVAIL. TEMPS
WILL BE COLD ENOUGH FOR FROST TO FORM ON GROUND BASED AIRCRAFT AT
ALL AIRPORTS WEDNESDAY MORNING.
THE NEXT COLD FRONT TO INFLUENCE THE TERMINAL AREA WILL BE PASSING
THROUGH THE REGION THIS WEEKEND. MAY SEE SOME INCREASE IN CLOUD
COVER AHEAD OF THIS SYSTEM LATE FRIDAY...WITH CLOUDS AND SHOWERS
PRODUCING MVFR OR OCCASIONAL IFR CONDITIONS AT ALL AIRPORTS ON
SATURDAY.
&&
.FIRE WEATHER...
DRY THE NEXT 3 DAYS AS HIGH PRESSURE PASSES OVERHEAD. AFTERNOON RH
VALUES WILL SLIP INTO THE 20-30 PERCENT RANGE WEDNESDAY AND THURSDAY
AFTERNOONS. WINDS SHOULD BE LIGHT...AND WILL LIMIT VENTILATION
AND SMOKE TRANSPORT.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT WEDNESDAY FOR
VAZ019-022>024-032>035-043>047-058-059.
NC...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT WEDNESDAY FOR
NCZ003>006-019-020.
WV...NONE.
&&
$$
SYNOPSIS...JJ/WP
NEAR TERM...PM
SHORT TERM...PM
LONG TERM...DS
AVIATION...PM
FIRE WEATHER...PM
AREA FORECAST DISCUSSION
NWS LA CROSSE WI
304 PM CDT TUE APR 15 2008
.SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT
FORECAST CONCERNS THIS PACKAGE...WINDS TONIGHT INTO WED...-SHRA/
TSRA CHANCES WED NIGHT THRU FRI NIGHT...TEMPERATURES THRU THE
PERIOD.
18Z DATA ANALYSIS HAD A 988MB LOW OVER WEST CENTRAL ND...WHILE BROAD
HIGH PRESSURE WAS CENTERED OVER THE OH VALLEY. 3HR PRESSURE FALLS
OF 3MB TO 4MB WERE COMMON ACROSS MN/IA/WI EARLY THIS AFTERNOON. THIS
ALONG WITH THE TIGHT PRESSURE GRADIENT BETWEEN THE LOW AND HIGH
WERE PRODUCING SOUTH WINDS OF 20 TO 35MPH GUSTS 35 TO 45MPH ACROSS
THE FLAT OPEN TERRAIN AREAS OF IA/MN. TAMDAR SOUNDINGS INDICATE
AIRMASS MIXED TO ABOUT 900MB WITH A RATHER STRONG INVERSION ABOVE
THIS LEVEL. WINDS JUST ABOVE THE INVERSION IN THE 40 TO 50+ KT
RANGE. VIS IMAGERY SHOWED ONLY CIRRUS ACROSS THE REGION. THE SOUTH
WINDS AND SUNSHINE WERE PUSHING TEMPS INTO THE MID 50S-LOW 60S
ACROSS MUCH OF MN/IA/WI.
15.12Z NAM/GFS LOOK TO HAVE INITIALIZED QUITE WELL AND OFFER
REASONABLY SIMILAR SOLUTION FOR TONIGHT INTO FRI NIGHT. PER RA-
OBS...GFS WITH A SLIGHT EDGE ON 700MB HGTS ACROSS MT AND A BIT
BETTER ON THE 500MB WIND SPEEDS ACROSS MT/WY. DPROG/DT OF 500MB HGTS
AT 15.12Z SHOWED NAM/GFS RUNS OF 13.12Z AND 14.12Z VERIFIED QUITE
WELL ACROSS NOAM WITH A SLIGHT EDGE AND BETTER CONSISTENCY TO GFS.
THRU 36HRS TREND IS TOWARD A FASTER PROGRESSION OF THE NORTHERN
STREAM PORTION OF THE WESTERN TROUGH INTO THE UPPER MIDWEST AND
SLOWER WITH THE SOUTHERN STREAM PORTION OVER THE SOUTHERN ROCKIES.
TREND FOR 36-60HRS IS FASTER WITH THE NORTHERN STREAM PORTION
LIFTING INTO EASTERN CAN AND A BIT SLOWER/FURTHER NORTH WITH THE
TROUGH/UPPER LOW INTO THE KS/OK AREA. THIS NORTHWARD TREND CONTINUES
IN THE 60-84HR TIME FRAME AS THE TROUGH/UPPER LOW LIFTS INTO THE MID
MS VALLEY. CHECK OF OBS VS. MODEL DATA AT 18Z SHOWED NAM/GFS
REASONABLE WITH THE SFC LOW DEPICTION OVER ND. A COMPROMISE OF
NAM/GFS LOOKED BEST WITH THE SHORTWAVE FEATURES OVER WESTERN NOAM...
THUS NO CLEAR MODEL FAVORITE BASED ON 18Z DATA. WITH GFS SHOWING A
BIT BETTER INITIALIZATION AND RUN-TO-RUN CONSISTENCY...WOULD TEND TO
FAVOR ITS SOLUTION. HOWEVER FAVORING NAM OR GFS LOOKS TO HAVE LITTLE
IMPACT ON THE SENSIBLE WEATHER THRU FRI NIGHT AND FAVORED A NAM/GFS
BLEND. SHORT-TERM FORECAST CONFIDENCE ON THE GOOD SIDE THIS CYCLE.
FOR THE SHORT TERM...PRESSURE GRADIENT REMAINS QUITE TIGHT OVER THE
AREA INTO THE EARLY EVENING HOURS. GRADIENT WINDS TO REMAIN QUITE
STRONG AS WELL AS THE LOW MOVES INTO THE EASTERN DAKOTAS/NORTHWEST
MN. WITH SOUNDING INDICATING 50KTS NEAR OR JUST ABOVE 900MB/
INVERSION AT 00Z AND BOUNDARY LAYER NOT DECOUPLING MUCH UNTIL AFTER
SUNSET WILL EXTEND WIND ADVISORY UNTIL 02Z. WINDS DO REMAIN BRISK
TONIGHT AHEAD OF THE LOW/FRONT...KEEPING BOUNDARY LAYER STIRRED AND
TEMPERATURES NOT LIKELY TO DROP OFF MUCH. TROUGH/FRONT APPROACHES/
MOVES INTO THE AREA WED WITH PRESSURE GRADIENT RELAXING DURING THE
DAY. GFS INSISTS ON GENERATING SOME LIGHT PRECIP ACROSS THE AREA WED
AFTERNOON...BUT THIS LOOKS OVERDONE. FORCING/CONVERGENCE/LIFT WITH
THE FRONT IS MODERATE AT BEST AND LIMITED TO THE SFC-850MB LAYER...
UNDER A RATHER STRONG INVERSION IN THE 850-700MB LAYER. MOISTURE
REMAINS LIMITED AS WELL...BUT ENOUGH MOISTURE EVENTUALLY DRAWN NORTH
AHEAD OF THE TROUGH FOR INCREASING STRATO-CU CLOUDS DURING THE
AFTERNOON. CARRIED DRY FORECAST THRU WED. INVERSION ERODES FOR WED
NIGHT WITH PASSAGE OF THE MID LEVEL TROUGH AXIS...BUT POST FRONTAL
FORCING/LIFT REMAIN WEAK. CONTINUED SMALL -SHRA CHANCE FOR WED
NIGHT WHICH BLENDS WELL WITH NEIGHBORS...BUT WITH WEAK FORCING AT
BEST AND NO INSTABILITY REMOVED ISOLATED -TSRA MENTION. FRONT IS
SOUTH OF THE AREA ON THU...AS A WAVE IN RESPONSE TO THE UPPER
TROUGH/SHORTWAVE ENERGY EJECTING INTO THE CENTRAL/SOUTHERN PLAINS
BEGINS TO EJECT NORTHEAST ALONG IT. X-SECTIONS SHOW RATHER STRONG
850-700MB FN CONVERGENCE/THETA-E CONVERGENCE SPREADING ACROSS THE
AREA NORTH OF THE FRONT FOR THU INTO THU NIGHT. NEAR NEUTRAL
STABILITY /-EPV/ ABOVE THE FORCING/LIFT LAYER AS WELL. RAISED -SHRA
CHANCES ACROSS MUCH OF THE AREA THU/THU NIGHT. GIVEN STRENGTH OF
LIFT AND NEAR NEUTRAL STABILITY ABOVE IT...CONTINUED ISOLATED -TSRA
MENTION ON THU. WITH THE FURTHER NORTH SOLUTION OF THE UPPER LOW/
TROUGH ON FRI...SUPPORTED BY ECMWF...APPEARS DEFORMATION BAND OF
PRECIP NORTH OF THE SFC-MID LEVEL LOW WILL CLIP AT LEAST THE
SOUTHEAST END OF THE FORECAST AREA FRI INTO FRI NIGHT. RAISED -SHRA
CHANCES ACROSS ROUGHLY THE SOUTHEAST HALF OF THE FORECAST AREA TO
ACCOUNT FOR THIS...WHICH BLEND QUITE WELL WITH NEIGHBORING GRIDS.
WITH THE WINDS TONIGHT...FAVORED WARMER OF GUIDANCE LOWS. WITH THE
WARMER START AND FRONT NOT TO PASS UNTIL MID/LATE AFTERNOON...
FAVORED WARMER OF GUIDANCE HIGHS WED. WITH CLOUDS EXPECTED WED
NIGHT...TRENDED TOWARD WARMER OF GUIDANCE LOWS. WITH CLOUDS/-SHRA ON
THU...LOWERED HIGHS SOME TOWARD A BLEND OF GUIDANCE VALUES. WITH
MORE CLOUDS THU NIGHT/FRI...TRENDED THU NIGHT LOWS A FEW DEGREES
ABOVE GUIDANCE LOWS AND FRI HIGHS TOWARD COOLER 15.12Z GFS MEX MOS
VALUES. USED A BLEND OF GFS MEX/ENSEMBLE MOS AND HPC GUIDANCE FOR
LOWS FRI NIGHT.
.LONG TERM...SATURDAY THROUGH TUESDAY
16.00Z MEDIUM RANGE MODELS...ECMWF/GFS/UKMET IN REASONABLE AGREEMENT
WITH EACH OTHER THRU 00Z MON. SOLUTIONS THEN DIVERGING WITH
EVOLUTION OF THE WESTERN CONUS UPPER LOW AND STRONGER SHORTWAVES
ROTATING AROUND IT. RUN-TO-RUN SIMILARITY TO 14.00Z RUNS REMAINS
GOOD TO 00Z WED /04/23/...ESPECIALLY ECMWF...WITH GFS SHOWING A
SHIFT TOWARD THE MORE PROGRESSIVE ECMWF WITH THE UPPER LOW/TROUGH
INTO CENTRAL NOAM. HOWEVER...GFS ENSEMBLE MEAN/UKMET SUPPORT THE
SLOWER OPERATIONAL GFS RUN. FORECAST CONFIDENCE GOOD FOR SAT/SUN
WITH MODEL SOLUTIONS QUITE SIMILAR. SOUTHERN STREAM WAVE PASSING
THRU THE MID MS VALLEY SAT PROVIDES POTENTIAL FOR LINGERING
DEFORMATION BAND OF -RA/ -SHRA TO CLIP THE SOUTHEAST END OF THE
FORECAST AREA...AND CONTINUED SMALL -SHRA CHANCE THERE. CONTINUED
DRY FORECAST FOR SAT NIGHT/SUN WITH SFC AND SHORTWAVE RIDGING ALOFT
TO SLIDE ACROSS THE AREA. CONFIDENCE DROPS OFF FOR MON/TUE WITH
GFS/ECMWF AT ODDS WITH TIMING OF FEATURES ACROSS THE REGION. MODEL
CONSENSUS VERY GOOD FOR A STRONG LOW OVER WY/WESTERN SD AT 12Z SUN.
THIS GOOD CONSENSUS BREAKS DOWN BY 12Z MON AS THE LOW PROGRESSES
INTO THE CENTRAL/NORTHERN PLAINS AND A STRONG COLD FRONT IS PUSHED
EAST. FRONT TO PUSH TOWARD THE AREA MON AS THE SFC LOW LIFTS TOWARD
THE CAN BORDER. MOISTURE/INSTABILITY INCREASE AHEAD OF THIS FRONT
FOR MON AS GULF OF MEX MOISTURE IS BROUGHT NORTHWARD. WITH THE
TIMING DIFFERENCES...CARRIED -SHRA CHANCE FOR SUN NIGHT THEN -TSRA
CHANCE MON/MON NIGHT. AS TIMING DETAILS BECOME CLEARER...LATER
FORECAST CYCLES WILL BE ABLE TO NARROW DOWN THE FRONTAL TIMING AND
PERIOD OF -TSRA CHANCE. STRONG COOLING BEHIND THIS FRONT...WITH
850MB TEMPS DROPPING TO NEAR OR BELOW 0C BY TUE...BUT AGAIN TIMING
DIFFERENCES AS TO WHEN THIS COOLING ARRIVES.
FAVORED A BLEND OF GFS MEX/ENSEMBLE MOS AND HPC GUIDANCE FOR
HIGHS/LOWS SAT THRU MON. FAVORED THE COOLER GFS ENSEMBLE MOS/HPC
GUIDANCE VALUES FOR MON NIGHT/TUE.
&&
.AVIATION...TONIGHT AND WEDNESDAY
WIND IS THE MAIN CONCERN FOR AVIATION INTERESTS WITH DRY AIRMASS IN
PLACE. PRESSURE FALLS OVER MOST OF THE CENTRAL U.S. CREATING WIDE-
SPREAD SOUTH WINDS IN 20 TO 30 KNOT RANGE WITH GUSTS UP TO 40 KTS AT
TIMES. WINDS ARE EXPECTED TO STAY UP OVERNIGHT BUT SHOULD SLACKEN
SOMEWHAT AROUND MID EVENING WITH LESS MIXING AND LAPSE RATES
DROPPING.
AS MID LEVEL TROUGH EDGES CLOSER ON WEDNESDAY...EXPECT MORE MID AND
HIGH LEVEL CLOUDS AS VFR CONDITIONS CONTINUE.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...WIND ADVISORY UNTIL 9 PM THIS EVENING FOR MNZ086-MNZ087-
MNZ094-MNZ095.
IA...WIND ADVISORY UNTIL 9 PM THIS EVENING FORIAZ008-IAZ009-
IAZ010-IAZ018-IAZ019-IAZ029.
&&
$$
SHORT/LONG TERM...RRS
AVIATION..........SHEA
|