605
FXUS62 KILM 091645
AFDILM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1145 AM EST TUE FEB 9 2010
SYNOPSIS
A DEVELOPING AREA OF LOW PRESSURE OFF THE CAROLINA COAST WILL
MOVE NORTHEAST OF THE AREA THIS EVENING BEFORE BEGINNING TO
RAPIDLY INTENSIFY LATE TONIGHT AND WEDNESDAY. THIS WILL CREATE A
VERY TIGHT PRESSURE GRADIENT ACROSS THE AREA WHICH WILL LINGER
INTO THURSDAY AS THE STORM DEEPENS FURTHER SOUTHEAST OF NEW
ENGLAND. THE NEXT IN THE PARADE OF LOW PRESSURE SYSTEMS WILL MOVE
BY TO OUR SOUTH FRIDAY NIGHT AND SATURDAY BRINGING A CHANCE OF
SNOW. HIGH PRESSURE WILL BUILD IN FOR THE LATTER HALF OF THE
WEEKEND.
NEAR TERM /THROUGH TONIGHT/
AS OF 11 AM TUESDAY...CHARACTER OF PRECIPITATION LOOKS MORE
SHOWERY THAN STRATIFORM PER RADAR REPRESENTATIONS.
THEREFORE...CHANGED RAIN TO SHOWERS AND GIVEN THE LIGHTNING
STRIKES TO OUR S AND WITH LOW PRESSURE CLOSING OFF TO OUR S...WILL
INCLUDE MENTION OF THUNDERSTORMS THROUGHOUT THE FORECAST AREA.
OTHER SIGNIFICANT CHANGES INCLUDED RAISING MAXIMUMS FOR TODAY
GIVEN THE INFLUX OF MILDER AIR THAT IS BEING ENTRAINED INTO THE
COASTAL LOW. ALSO...BASED ON RADAR TRENDS AND WITH SYSTEM
ORGANIZING QUICKER THAN PREVIOUSLY THOUGHT...RAISED QPF AMOUNTS TO
ONE-HALF TO ALMOST AN INCH. THE SIGNIFICANT QPF IS EXPECTED TO
OCCUR THIS AFTERNOON AND EVE AS LOW PRESSURE MOVES NORTHEAST
ALONG THE CAROLINA COAST. THERE MAY BE A PERIOD OF MUCH LIGHTER
RAIN WITH THE PASSAGE OF A COLD FRONT OVERNIGHT. SOUTH WINDS WILL
SHIFT TO WEST NORTHWEST WITH THE PASSAGE OF A COLD FRONT OVERNIGHT
WITH WINDS INCREASING SHARPLY AS STRONG MIXING ENSUES AND BRINGS
HIGHER MOMENTUM AIR ALOFT TO THE SURFACE. A WIND ADVISORY WILL LIKELY BE
ISSUED LATER TODAY FOR THE STRONG WINDS THAT ARE EXPECTED TO
DEVELOP BEGINNING VERY LATE TONIGHT. THE STRONGEST WINDS WILL LIKELY
OCCUR WED AFTERNOON AND EVE AS LOW PRESSURE BOMBS SOUTH OF NEW
ENGLAND. TEMPS WILL FALL SHARPLY WITH THE PASSAGE OF THE COLD
FRONT AFTER MIDNIGHT. TEMPS IN THE LOWER TO MID 30S AT SUNRISE WED
WILL COMBINE WITH THE STRONG WINDS TO MAKE IT FEEL AS IF IT WERE
WELL DOWN IN THE 20S.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
AS OF 3 AM TUESDAY...ARCTIC HIGH BUILDING IN BEHIND EXITING COLD
FRONT WILL ENSURE TEMPERATURES THROUGH THE PERIOD REMAIN WELL BELOW
CLIMO. DEEP MIXING WED...FORECAST SOUNDINGS ARE DRY ADIABATIC TO
OVER 7K FT...WILL ENSURE 40 TO 45 MPH WINDS AT 2K FT MIX DOWN AS
GUSTS. IN ADDITION TO THE GUSTS...TIGHT GRADIENT AND STRONG COLD
ADVECTION PRODUCE SUSTAINED WEST TO NORTHWEST WINDS OVER 20
MPH...FWIW MOS IS FORECASTING WIND SPEEDS WED AROUND 25 MPH. COLD
ADVECTION STARTS TO WANE WED NIGHT BUT CONDITIONS REMAIN BREEZY WITH
WINDS CLOSE TO 15 MPH. LOWS WILL BE IN THE MID TO UPPER 20S DESPITE
GOOD MIXING.
HIGH PRESSURE REMAINS IN CONTROL THU BUT GRADIENT STARTS TO RELAX.
LOW PRESSURE ACCELERATES AWAY FROM THE MID ATLANTIC COAST AND CENTER
OF HIGH MOVES CLOSER. THU WILL BE BREEZY...BUT WINDS WILL BE ALMOST
HALF OF WHAT WE EXPERIENCE WED. AIR MASS STARTS TO WARM UP THU WITH
FULL SUN AND NO COLD ADVECTION...BUT HIGH WILL STILL END UP ALMOST
10 DEGREES BELOW CLIMO. LIGHT WINDS AND DRY AIR THU NIGHT MAY END UP
MAKING THU NIGHT A FEW DEGREES COOLER THAN WED NIGHT...ESPECIALLY
FOR TYPICAL COLD SPOTS.
LONG TERM /FRIDAY THROUGH MONDAY/
AS OF 3 AM TUESDAY...MAIN CONCERN FOR THE PERIOD IS GULF LOW
CROSSING SOUTHERN FL FRI INTO SAT. LATEST GFS KEEPS THE LOW WELL
SOUTH OF THE AREA...MOVING ACROSS THE BAHAMAS. THE CANADIAN TURNS IT
NORTHEAST AFTER IT CROSSES FLORIDA AND PASSES THE LOW A COUPLE
HUNDRED MILES OFF THE SOUTHEAST COAST. LATEST ECMWF IS IN BETWEEN
THESE 2 SOLUTIONS AND OFFERS A NICE COMPROMISE...AND IS ALSO CLOSE
TO HPC. THIS SOLUTION WOULD RESULT IN A SOME PRECIP BRUSHING THE
AREA FRI NIGHT...AS SNOW OR A MIX OF RAIN AND SNOW. PREVIOUS
FORECAST WAS ALONG THESE LINES SO LARGE CHANGES NEEDED FOR THE
WEEKEND. HIGH PRESSURE BUILDS IN LATER SAT THROUGH SUN BEFORE
ANOTHER POTENTIAL SHOT AT WINTER WEATHER IMPACTS THE AREA LATE IN
THE FORECAST. STILL A LOT OF UNCERTAINTY FOR MON BUT THE
GFS/CANADIAN/ECMWF ALL AGREE ON STRONG SHORTWAVE CROSSING THE AREA.
FOR NOW WILL HOLD ONTO SILENT POPS FOR MON. SEMI-PERMANENT LARGE
AMPLITUDE 5H TROF OVER THE EASTERN US WILL KEEP TEMPERATURES BELOW
TO WELL BELOW CLIMO THROUGH THE PERIOD.
AVIATION /12Z TUESDAY THROUGH SATURDAY/
AS OF 12Z...WEDGE HOLDS FIRM INITIALLY AS DEVELOPING LOW IN
NORTHERN GULF OF MEXICO BEGINS ITS TREK ACROSS PANHANDLE OF
FLORIDA. WEDGE WILL WORK TO KEEP COLUMN FAIRLY DRY THROUGH THE
EARLY PORTION OF THE TAF. AS LOW DEVELOPS AN STARTS TO PUMP IN
MOISTURE FROM THE ATLANTIC...LIGHT RAIN BEGINS AFTER 16Z ALONG THE
COASTAL TERMINALS AND BY 17Z FOR THE INLAND TERMINALS. DURATION
WILL BE FAIRLY SHORT LIVED WITH THE LOW MOVING RAPIDLY UP THE
CAROLINA COASTS. LOOK FOR RAIN TO END BY MIDNIGHT/05Z.
WIND WILL VEER AROUND FROM EASTERLY AT 6 TO 12 KNOTS...TO SOUTH
SOUTHEASTERLY AT 8 TO 16 KNOTS BY 21Z...TO SOUTHWESTERLY 10 TO 20
KNOTS BY 05Z.
EXTENDED OUTLOOK...HIGH CONFIDENCE VFR WEDNESDAY THROUGH FRIDAY.
MEDIUM CONFIDENCE FOR MVFR SATURDAY AS UPPER LEVEL SHORT WAVE TROUGH
BRINGS SHOWERS.
MARINE
NEAR TERM /THROUGH TONIGHT/...
AS OF 11 AM TUESDAY...SMALL CRAFT ADVISORY CONDITIONS WILL DEVELOP
THIS AFTERNOON AND EVE WITH A GALE WARNING IN EFFECT LATE TONIGHT.
ON THE BACKSIDE OF DEPARTING LOW PRESSURE...WINDS WILL BEGIN TO
INCREASE AFTER MIDNIGHT...INCREASING FURTHER ON WED AS THE PRESSURE
GRADIENT SIGNIFICANTLY TIGHTENS AS LOW PRESSURE BOMBS SOUTH OF NEW
ENGLAND. SOUTHERLY WINDS TODAY WILL SHIFT TO THE WEST NORTHWEST
WITH THE PASSAGE OF A COLD FRONT AFTER MIDNIGHT. SEAS WILL BUILD
THROUGH THE DAY ON SOUTHERLY WINDS. MUCH STRONGER WINDS WILL
BEGIN TO DEVELOP TONIGHT...ESPECIALLY AFTER MIDNIGHT. SINCE THE
STRONGEST WINDS WILL OCCUR WHEN THE WIND DIRECTION IS WEST
NORTHWEST...SEAS WILL NEVER FULLY DEVELOP. THEREFORE...SEAS WILL
NOT REACH LEVELS THAT WIND SPEEDS ALONE WOULD INDICATE. STILL WE
DO EXPECT SEAS TO REACH ABOVE 6 FT WITHIN 20 NM...HIGHEST SEAS WILL
OCCUR OVERNIGHT AND WED.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 3 AM TUESDAY...STRONG OFFSHORE FLOW WED AND WED NIGHT WILL
REQUIRE CONTINUATION OF HEADLINES. RIGHT NOW LOOKS LIKE EVENT WILL
BE STRONG SCA...BUT CANNOT RULE OUT POSSIBILITY OF A PERIOD OF GALE
STRENGTH WINDS. WINDS REMAIN OFFSHORE THU...BUT SPEEDS START TO
DECREASE IN THE AFTERNOON AS GRADIENT RELAXES. NORTHWEST WINDS WILL
KEEP HIGHEST SEAS BEYOND 20 NM AND RESULT IN A LARGE GRADIENT
BETWEEN SEAS NEAR SHORE AND CLOSE TO 20 NM GENERALLY SEAS WILL BE
BELOW 6 FT...THOUGH AT THE TIME OF STRONGEST WINDS SEAS AROUND 20 NM
COULD BE AS HIGH AS 9 FT NEAR FRYING PAN SHOALS.
LONG TERM /FRIDAY THROUGH SATURDAY/...
AS OF 3 AM TUESDAY...OFFSHORE FLOW THROUGH THE PERIOD BUT SOME
UNCERTAINTY DOES EXIST. LOW PRESSURE CROSSING FL FRI WILL TURN
NORTHEAST AT SOME POINT. DIFFERENCES BETWEEN LATEST GFS/ECMWF AND
CANADIAN ALL HAVE RAMIFICATIONS FOR COASTAL WATERS FORECAST. ECMWF
SOLUTION IS CLOSE TO A COMPROMISE BETWEEN THE CANADIAN AND GFS AND
IS THE SOLUTION CURRENTLY BEING FAVORED. OFFSHORE FLOW 10 KT OR LESS
FRI WILL INCREASE INTO SAT ENDING UP NEAR 20 KT AS THE PASSES. SEAS
WITHIN 20 NM MILES SHOULD REMAIN BELOW HEADLINE CRITERIA.
ILM WATCHES/WARNINGS/ADVISORIES
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 3 AM EST
WEDNESDAY FOR AMZ254-256.
GALE WARNING FROM 3 AM TO 7 PM EST WEDNESDAY FOR AMZ250-252-
254-256.
SMALL CRAFT ADVISORY UNTIL 3 AM EST WEDNESDAY FOR AMZ250-252.
NEAR TERM...RJD
SHORT TERM...III
LONG TERM...III
AVIATION...MDC
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