FXUS62 KILM 241449
AFDILM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
948 AM EST THU DEC 24 2009
.SYNOPSIS...
HIGH PRESSURE WILL BE LOSING ITS GRIP OVER THE SOUTHEAST THROUGH
FRIDAY. WARM AIR WILL STREAM ACROSS THE REGION ON FRIDAY AHEAD OF
A STRONG COLD FRONT. COLD AIR WILL BEGIN TO RETURN SATURDAY NIGHT
AND REMAIN WELL INTO NEXT WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 9:40 AM THURSDAY...SURFACE PRESSURES RISING THIS
MORNING AS HIGH PRESSURE CONTINUES TO BUILD DOWN INTO THE AREA FROM
THE NORTH. THERE IS AN AREA OF LOW CLOUDINESS EXTENDING FROM NEAR
CONWAY SOUTHWEST TO KINGSTREE. THIS SEEMS TO BE AN EXTENSION OF THE
MOISTURE OFFSHORE WITH THE STRUGGLING COASTAL TROUGH. DESPITE THIS
AREA...HAVE TRIMMED BACK CLOUD COVER FORECAST FOR THE REMAINDER OF
THE DAY AS THE LATEST NAM KEEPS THE MOISTURE OFF TO THE SOUTH. MORE
INSOLATION COULD BE TROUBLESOME FOR MAX TEMPERATURES...ALTHOUGH WITH
THIS SCENARIO WE ARE OFFICIALLY IN COLD AIR ADVECTION. LAV NUMBERS
KEEP NUMBERS IN THE CURRENT FORECAST RANGE. WILL CONTINUE TO MONITOR
CLOSELY.
&&
.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 3 AM THURSDAY...STRONG ISENTROPIC UPGLIDE SPREADS OVER THE
REGION IN THE 12Z TO 18Z TIMEFRAME. THERE ARE STILL SOME DIFFERENCES
IN GUIDANCE REGARDING WHEN MEASURABLE RAINFALL BREAKS OUT ACROSS THE
REGION AND THE RIBBON OF DEEP MOISTURE WILL BE QUITE NARROW. TIMING
ISSUES ASIDE...RAINFALL CHANCES JUST ABOUT 100 PERCENT AT SOME POINT
FRIDAY. MODELS HAVE COME INTO BETTER AGREEMENT IN THE WEDGE EROSION
AND NOW SHOW A SOUTHERLY COMPONENT TO WINDS AREA-WIDE BY 18Z. SEVERE
WEATHER THREAT APPEARS QUITE LOW BUT NONZERO DUE TO TYPICAL COLD
SEASON HIGH SHEAR-LOW CAPE SETUP. DRY MID LEVEL AIR SWEEPS IN FROM
THE SOUTHWEST BY 06Z AS SURFACE FRONT MOVES INTO WESTERN COUNTIES.
JUST OFF THE SURFACE HOWEVER DEEPLY ALIGNED SOUTHWESTERLY FLOW WILL
HOLD BACK LOW LEVEL COLD ADVECTION SATURDAY AND ANOTHER MILD
AFTERNOON EXPECTED. WINDS VEER JUST ENOUGH SATURDAY NIGHT TO ALLOW
COLD AIR ADVECTION TO KICK IN.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 3 AM THURSDAY...DEEP MID LEVEL VORTEX SPINS SLOWLY ACROSS THE
GREAT LAKES SUNDAY INTO MONDAY. THIS WILL BRING DRY AND COLD
ADVECTION LOCALLY WITH AFTERNOON HIGHS STRUGGLING INTO THE LOW 50S
IN A WELL MIXED ENVIRONMENT. TROUGH AXIS SWINGS THROUGH LATER MONDAY
FORTIFYING THE CAA TUESDAY AND WEDNESDAY. HIGH BOTH DAYS MAY
STRUGGLE TO REACH 50 ALL BUT SOUTHERNMOST ZONES WHERE LOW 50S
EXPECTED. CLOUD COVER GENERALLY AT A MINIMUM SAVE FOR MID OR HIGH
LEVEL MOISTURE ON WEDNESDAY WELL AHEAD OF DEVELOPING GULF OF MEXICO
SYSTEM.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
AS OF 12Z...HIGH PRESSURE WEDGE WILL SLOWLY GIVE WAY TO ADVANCING
WARM FRONT THROUGH THE PERIOD. WEAK TROUGH OFFSHORE MAY AFFECT THE
COASTAL TERMINALS WITH LOW CLOUDS THIS AFTN AS WINDS TURN MORE
EASTERLY AND INCREASE IN SPEED. RAIN WILL BEGIN TO AFFECT THE AREA
BY LATE IN THE TAF PERIOD.
LOW CONFIDENCE FORECAST AT THE COASTAL TERMINALS TODAY WITH MODERATE
CONFIDENCE INLAND. CURRENT SATELLITE IMAGERY DEPICTING MOSTLY CLEAR
SKY CONDITIONS...NOT EVEN ANY CIRRUS...BUT SOME LOW STRATUS
AFFECTING MYR/CRE ASSOCIATED WITH THE COASTAL TROUGH. BELIEVE THIS
HAS POTENTIAL TO CONTINUE AND SPREAD TO FLO THROUGH THE
MORNING...BUT IS HIGHLY DEPENDENT ON WESTWARD ADVANCE OF COASTAL
TROUGH. FOR NOW HAVE SCT AT 4K FEET MYR/CRE WITH FEW AT FLO BUT
COULD SEE SOME TEMPO BKN CIGS DEVELOP. ILM/LBT ARE MUCH LESS LIKELY
TO SEE ANY OF THIS LOW STRATUS TODAY AND HAVE NOT INCLUDED MENTION
OF ANY IN THE TAFS. SURFACE PRESSURE GRADIENT IS CONTINUING TO
STRENGTHEN...AND ONCE THE INVERSION BREAKS AFTER SUNRISE WINDS WILL
QUICKLY BEGIN TO GUST TO AROUND 20 KT AT ALL TERMINALS. WARM FRONT
AND OVERRUNNING PRECIP WILL APPROACH FIRST AT FLO AFTER 06Z AND
SPREAD NE ACROSS THE AREA. THESE HIGH PRESSURE WEDGES ARE NORMALLY
UNDERDONE BY GUIDANCE...SO HAVE SLOWED ONSET OF PRECIP FROM PROGS
AND ILM/LBT MAY NOT SEE ANY RAIN UNTIL AFTER THIS VALID TAF PERIOD.
WILL UPDATE RAIN CHANCES MORE SPECIFICALLY AT NEXT TAF ISSUANCE.
HIGH CONFIDENCE IN LOWERING CIGS TO MVFR AS WARM FRONT
ADVANCES...BUT LOW CONFIDENCE IN EXACT TIMING OF RAIN AND EVENTUAL
DEVELOPMENT OF IFR CIGS.
EXTENDED OUTLOOK...MODERATE CONFIDENCE IN PERIODS OF IFR THROUGH
SATURDAY MORNING WITH RAIN AND LOW CEILINGS. SOME FOG ALSO POSSIBLE
SATURDAY MORNING. VFR SUNDAY AND MONDAY.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 9:40 AM THURSDAY...WINDS FINALLY STARTING TO RESPOND TO THE
SURFACE PRESSURE PATTERN DEVELOPING ACROSS THE WATERS AS THE MOST
RECENT OBSERVATION FROM 41013 IS 19 KNOTS. WILL CONTINUE TO SEE
WINDS INCREASE INTO THE 20-25 KNOT RANGE THROUGH THE LATE
MORNING/AFTERNOON HOURS AS THE GRADIENT CONTINUES TO INTENSIFY. SEAS
ARE SHOWING SIGNS OF LIFE AS WELL WITH 4.6 FEET AT 41013 AND 41110.
NO CHANGES TO FORECAST.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 3 AM THURSDAY...SMALL CRAFT ADVISORY EXPECTED ON FRIDAY IN
STRONG PREFRONTAL REGIME. GALE FORCE GUSTS APPEAR POSSIBLE. IF
ONSHORE FLOW PERSISTS LONG ENOUGH TO SLOSH WARMER SSTS BACK INTO THE
FORECAST AREA THEN MIXING MAY BE STRONGER THAN CURRENTLY FORECASTED
AND SHORT FUSED GALE WARNING MAY BE NEEDED. SHARP VEER TO WEST WITH
FROPA FRIDAY NIGHT ACCOMPANIED BY DECREASE IN SPEEDS. NEAR SHORE
SEAS WILL BE BEATEN DOWN FIRST BY THE SHIFT TO OFFSHORE DIRECTION
AND CONDITIONS AWAY FROM SHORE WILL IMPROVE THEREAFTER. SATURDAY
AFTERNOON/EVENING APPEARS TO BE THE TIMEFRAME DURING WHICH SMALL
CRAFT ADVISORY CAN BE LOWERED.
LONG TERM /SUNDAY THROUGH MONDAY/...
AS OF 3 AM THURSDAY...LONG TERM PERIOD FEATURES COLD HIGH PRESSURE
BUILDING IN FROM THE NORTHWEST. THIS WILL BRING NORTHWESTERLY TO
WESTERLY WINDS THAT COULD BE QUITE GUSTY ON ACCOUNT OF GOOD
DIRECTIONAL ALIGNMENT IN THE LOW LAYERS JUST ABOVE THE SURFACE. THE
OFFSHORE WINDS WILL KEEP THE SHORT PERIOD WAVES FROM BUILDING
SIGNIFICANTLY WITHIN 20NM BUT SOME PERIODS OF SCEC WINDS NOT OUT OF
THE QUESTION.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 6 AM EST SATURDAY
FOR AMZ250-252-254-256.
&&
$$
SYNOPSIS...MBB
NEAR TERM...SHK
SHORT TERM...MBB
LONG TERM...MBB
AVIATION...JDW
