987
FXUS62 KILM 100241
AFDILM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
941 PM EST MON NOV 9 2009
SYNOPSIS
HIGH PRESSURE WILL REMAIN WELL EAST OF THE MID-ATLANTIC COAST
THROUGH WEDNESDAY AS TROPICAL STORM IDA WEAKENS ALONG THE EASTERN
GULF COAST. MOISTURE FROM IDA IN COMBINATION WITH MOISTURE FROM THE
ATLANTIC COULD BRING A SOAKING RAIN TO THE CAROLINAS TUESDAY THROUGH
WEDNESDAY. A COLD FRONT WILL MOVE OFF THE COAST ON THURSDAY...WITH
COOL AND BREEZY CONDITIONS EXPECTED THE LATTER HALF OF THE WEEK AS
HIGH PRESSURE BUILDS IN FROM THE NORTH.
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
AS OF 9 PM MONDAY...HIGH PRESSURE NOW WELL EAST OF THE NORTH
CAROLINA COAST WILL MOVE FARTHER OFFSHORE OVERNIGHT. WEAKENING
TROPICAL STORM IDA IS APPROACHING A LANDFALL NEAR MOBILE BAY.
NORTHEAST WINDS OVER THE EASTERN CAROLINAS ARE DUE TO THE LARGE
OUTER ENVELOPE OF CYCLONIC FLOW AROUND IDA. ALTHOUGH SATELLITE SHOWS
THICKENING OVERCAST OVER THE ENTIRE SOUTHEAST...RADAR COMPOSITES
SHOW ONLY SCATTERED SHOWERS OVER THE COASTAL WATERS. ECHOES OBSERVED
ON RADAR OVER THE WESTERN 2/3 OF THE CAROLINAS APPEAR TO BE VIRGA
FROM MID-LEVEL CLOUDS.
WEAK BUT INCREASING ISENTROPIC LIFT COULD ALLOW SOME OF THE ATLANTIC
SHOWERS TO MAKE IT ONSHORE BY MIDNIGHT WITH A FEW HUNDREDTHS OF AN
INCH IN SPOTS. FOR MOST AREAS RAINFALL AMOUNTS WILL REMAIN IN THE
TRACE RANGE. THE BEST CHANCE FOR MEASURABLE RAINFALL WILL BE NEAR
SOUTHPORT/BALD HEAD ISLAND OVER THE NEXT FEW HOURS...THEN SHIFTING
TO THE GEORGETOWN VICINITY AFTER MIDNIGHT AS ADDITIONAL SHOWERS
DEVELOP OFFSHORE.
WE HAVE ADJUSTED LOW TEMPERATURES DOWN JUST SLIGHTLY ALONG THE COAST
BUT AGREE WITH EARLIER FORECASTS THAT ARE WELL ABOVE BOTH NAM AND
GFS MOS GUIDANCE. LOWS SHOULD ONLY REACH THE UPPER 50S INLAND AND
LOWER 60S AT THE COAST.
SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/
AS OF 3 PM MONDAY...STILL A LOW-CONFIDENCE FORECAST AS THE NAM AND
GFS CANNOT SEEM TO AGREE ON JUST HOW MUCH RAINFALL WE CAN EXPECT.
PER NHC FORECAST IDA WILL DECAY JUST INLAND FROM THE GULF COAST
TUESDAY INTO TUESDAY NIGHT...WHILE THE STRONG HIGH REMAINS PARKED
OFF THE VIRGINIA CAPES. THE STRONG EASTERLY FLOW IN BETWEEN WILL
FEED MOISTURE IN OFF THE ATLANTIC...BUT THEN WE SEE THE MODEL
DIFFERENCES. NAM SUGGESTS WE WILL BE HARD PRESSED TO SEE AN INCH
OF RAIN...AND INLAND LOCATIONS WOULD SEE A LOT LESS. GFS IS
POINTING TO SEVERAL INCHES AS IT PHASES THE NORTHERN AND SOUTHERN
STREAM AND DEVELOPS A NOR'EASTER OFF THE CAROLINA COAST.
WILL GO WITH A WEAKER VERSION OF THE GFS SOLUTION...AND RAINFALL
TOTALS IN THE 2-3 INCH BALLPARK. GIVEN LOW CONFIDENCE AND THAT THE
RAIN SHOULD FALL OVER A ROUGHLY 36 HR TIME PERIOD...WILL NOT POST
ANY FLOOD WATCHES AT THIS TIME.
LONG TERM /THURSDAY THROUGH MONDAY/
AS OF 3 PM MONDAY...IT APPEARS THE ACTION WILL BE WINDING DOWN AS
THE LONG TERM PERIOD BEGINS. FOLLOWING HPC GUIDANCE...STILL
EXPECT SOME LIGHT RAIN AND OR DRIZZLE TO OCCUR MAINLY ALONG THE
COAST THURSDAY VIA ISENTROPIC LIFT AS LOW PRESSURE IS SOMEWHERE
OFF THE SOUTHEAST COAST AND HIGH PRESSURE IS ANCHORED OVER THE
NORTHEAST. INCREASED THE POPS AND CLOUD COVER FOR THIS TIME. MODEL
SOUNDINGS DRY OUT DRAMATICALLY LATE THURSDAY AND FRIDAY HOWEVER
MOISTURE IN THE FORM OF LOW LEVEL STRATUS MAY CONTINUE TO PLAGUE
THE AREA THROUGH FRIDAY AND MAYBE INTO THE DAY SATURDAY. CONTINUED
TO TREND DOWN SKY COVER FOR SATURDAY BUT CONFIDENCE IS LOW. SUNDAY
AND MONDAY SHOULD SEE A DRIER SOUTHWEST FLOW DEVELOP AHEAD OF THE
NEXT SYSTEM WHICH GIVES A BETTER SHOT AT MORE SUNSHINE. TRIMMED
BACK HIGHS THURSDAY THROUGH SATURDAY AND INCREASED MINS SLIGHTLY
CONSIDERING ALL THE MOISTURE.
AVIATION /00Z TUESDAY THROUGH SATURDAY/
THE MAIN FEATURES AFFECTING THE TAF SITES ARE HIGH PRESSURE ABOUT
300 NM EAST OF NORFOLK VIRGINIA AND TROPICAL STORM IDA ABOUT 120 NM
SOUTH OF MOBILE BAY ALABAMA IN THE GULF OF MEXICO. IN BETWEEN AN
EASTERLY GRADIENT IS IN PLACE.
HIGH OVERCAST TO START THE PERIOD FOR ALL TERMINALS...VFR. LOW LEVEL
EASTERLY FLOW WILL BE RESPONSIBLE FOR STRATOCUMULUS MOVING INTO THE
TERMINAL AREA LATER THIS EVENING. VFR OVERNIGHT FOR ALL
TERMINALS...INLAND SITES WILL EXPERIENCE MVFR IN FOG IN THE EARLY
HOURS BEFORE SUNRISE.
AS IDA BOUNCES ALONG THE GULF COAST STATES CU AND STRATOCU CIGS FORM
ACROSS ALL TERMINALS FIRST AT INLAND TERMINALS BY 13Z...BY 17Z AT
COASTAL SITES. SCATTERED SHOWERS ACCOMPANY THESE CEILINGS. WIND TO
REMAIN EASTERLY AROUND 8 TO 10 KNOTS FOR THE PERIOD.
EXTENDED OUTLOOK...CHANCE OF IFR LATE TUESDAY AND WEDNESDAY WITH
RAIN AND FOG.
MARINE
NEAR TERM /THROUGH TONIGHT/...
AS OF 9 PM MONDAY...AFTER THE COASTAL TROUGH APPARENTLY MOVED INLAND
EARLIER TODAY...WIND DIRECTIONS HAVE BACKED AROUND TO THE NE OVER
THE COASTAL WATERS IMPLYING THE TROUGH HAS REDEVELOPED OFFSHORE.
EVEN AT FRYING PAN SHOALS WINDS ARE NE CURRENTLY. WAVES OF MAINLY
LIGHT SHOWERS ARE DEVELOPING OVER THE WATERS 40-60 MILES FROM SHORE
AND MOVING WEST AT 10-15 MPH. THESE WILL LIKELY CONTINUE THROUGH THE
NIGHT.
HIGH PRESSURE IS CENTERED ~600 MILES EAST OF THE OUTER BANKS AND IS
CONTINUING TO MOVE AWAY. TROPICAL STORM IDA IS WEAKENING IN THE
NORTHERN GULF AS IT APPROACHES A LANDFALL NEAR MOBILE BAY. THE
PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS IS PRODUCING 10-15 KT
WINDS AND LITTLE CHANGE IS EXPECTED OVERNIGHT. THE ONSHORE FETCH IS
LEADING TO SLOWLY BUILDING SEAS: THE FRYING PAN SHOALS BUOY REPORTED
4.6 FT SEAS AT 9 PM. SEAS OVER THE COASTAL WATERS WITHIN 20 MILES
SHOULD BUILD FROM THE CURRENT 3 FT TO 4 FT BY DAYBREAK...WITH
FURTHER LARGE INCREASES EXPECTED OVER THE NEXT 24-48 HOURS.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 3 PM MONDAY...HAVE GENERALLY SLOWED DOWN THE TIMING FROM THE
PREVIOUS FORECAST...AS WE ARE NOT JUMPING ON THE BULLISH GFS
SOLUTION. STILL THE PERSISTENT EASTERLY FETCH SHOULD GIVE US
MARGINAL SCA SEAS BY THE END OF THE DAY ON TUESDAY. BASED ON SCA
ALREADY FLYING AND WANTING TO HAVE A SLIGHT BUFFER...WILL TWEAK
THE START TIME TO TUESDAY AFTERNOON AND CARRY THE ADVISORY OUT TO
THE END OF 4TH PERIOD...00Z THURSDAY. CONDITIONS WILL STILL BE
QUITE FRISKY...SO THIS WILL LIKELY BE EXTENDED.
WIND FORECAST REMAINS WELL SHORT OF THE GALES ADVERTISED BY
GFS...BASICALLY A SOLID 25 KT WITH 8 FOOTERS MAKING IT WITHIN 20NM
BY WEDNESDAY EVENING.
LONG TERM /THURSDAY THROUGH SATURDAY/...
AS OF 3 PM MONDAY...GRADIENT WILL REMAIN IN PLACE THROUGH FRIDAY AS
LOW PRESSURE WILL BE TRUDGING OFF TO THE EAST OFF THE SOUTHEAST
COAST AND HIGH PRESSURE REMAINS ENTRENCHED ACROSS THE NORTHEAST.
FLAG CONDITIONS WILL CERTAINLY CONTINUE THROUGH THIS TIME. GRADIENT
FINALLY BREAKS DOWN ENOUGH LATE FRIDAY INTO SATURDAY TO ALLOW THE NE
WINDS TO DIP BELOW 25 KNOTS AND WIND DRIVEN SEAS TO DROP BELOW SIX
FEET OTHER THAT THE OUTER MOST WATERS.
ILM WATCHES/WARNINGS/ADVISORIES
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 1 PM TUESDAY TO 7 PM EST
WEDNESDAY FOR AMZ250-252-254-256.
NEAR TERM...TRA
SHORT TERM...RAS
LONG TERM...SHK
AVIATION...MDC
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