FXUS62 KILM 221142
AFDILM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
642 AM EST TUE DEC 22 2009

.SYNOPSIS...
FAIR AND COOL WEATHER WILL CONTINUE INTO THURSDAY AS HIGH
PRESSURE AND A DRY AIR MASS HOLD OVER THE REGION. PRECIPITATION 
CHANCES WILL INCREASE THURSDAY NIGHT INTO FRIDAY NIGHT...ALONG WITH 
A GRADUAL WARMING TREND...AS A FRONTAL SYSTEM APPROACHES FROM THE 
SOUTHWEST. A CLEARING...COOLING AND DRYING TREND IS EXPECTED IN THE 
WAKE OF THIS SYSTEM HEADING INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 AM TUESDAY...THE SUBTROPICAL CIRRUS SHIELD HAS BEEN 
FINALLY SHUNTED SOUTH AND EAST OF THE AREA AS FLOW ALOFT HAS BECOME 
SOMEWHAT FLATTER. NO LONGER HAVE TO INCLUDE CLOUDS FROM THIS FEATURE 
IN THE FORECAST. MID-LEVEL IMPULSE TO PASS JUST NORTH OF THE AREA 
TODAY. VARIOUS MODEL TIME HEIGHT SECTIONS FROM VARIOUS LOCATIONS 
ACROSS THE CWA INDICATE THAT SCATTERED AC MAY BE POSSIBLE BUT AT 
THIS POINT MOISTURE SEEMS MINUSCULE ESPECIALLY WITH THE SCOURING 
EFFECT GOING ON WITH THE WNW DOWNSLOPE TRAJECTORY ALOFT. WILL GO 
WITH SUNNY/MOSTLY SUNNY. CHANNELED VORT STAYS JUST NORTH OF THE AREA 
LATER TODAY AND TONIGHT WHICH SHOULD KEEP THE MAJORITY OF THE 
CLOUDINESS THERE ALSO. THIS IN RESPONSE TO THE MAJOR LOW THAT WILL 
BEGINS TO EVOLVE ACROSS THE SW U.S. AND THE NE STATES CLOSED LOW 
EVOLUTION. THIS WILL PRODUCE RIDGING ALOFT AND SFC RIDGING FROM THE 
NORTH ACROSS THE ILM CWA BY LATE TONIGHT. NAM MODEL MOS GUIDANCE FOR 
MAXES AND MINS PREFERRED. HAVE INPUTTED SOME RAD COOLING TONIGHT BUT 
SFC PRESSURE PATTERN LOOKS TO BE CONDUCIVE FOR WINDS TO SLIGHTLY 
PICK UP AFTER MIDNIGHT AS THE STRENGTH OF THE HIGH FROM THE NORTH 
INCREASES. AM BANKING ON THE SFC BASED INVERSION BEING STRONG ENOUGH 
TO COUNTER IN KEEPING WINDS DECOUPLED FOR FORECAST MINS TO BE 
REACHED PRIOR TO THIS OCCURRING.   

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 3 AM TUESDAY...EVOLUTION OF STORM SYSTEM AFFECTING THE CENTRAL 
US MID WEEK CONTINUES TO SLOW DOWN...DELAYING ARRIVAL OF PRECIP IN 
THE ILM AREA. WEDGE IN PLACE WED INTO THU ENSURES DRY FORECAST FOR 
AT LEAST THE FIRST HALF OF THE PERIOD. MINIMAL RISE IN HEIGHTS AND 
THICKNESS DURING THE PERIOD MAY TRANSLATE INTO A 1 OR 2 DEGREE 
INCREASE IN DAYTIME HIGHS BETWEEN WED AND THU AS AIR MASS MODERATES. 
HOWEVER...INCREASING IN HIGH CLOUDS THU MIGHT OFFSET ANY WARMING
IF TIMING OF THE EVENT REMAINS UNCHANGED. HIGHS WILL FALL A FEW 
DEGREES SHORT OF CLIMO. TIGHTENING GRADIENT WED NIGHT WILL KEEP 
BOUNDARY LAYER WELL MIXED AND LIMIT STRENGTH OF RADIATIONAL 
COOLING...THOUGH LOW LEVEL COLD AIR POOL WILL STILL BE ABLE TO 
GENERATE LOWS BELOW CLIMO.

24 HOURS AGO IT APPEARED PRECIP WOULD BE OVER ALL OF THE FORECAST 
AREA THU NIGHT. NOW ITS STARTING TO LOOK LIKE MEASURABLE RAIN MAY 
ONLY IMPACT THE FARTHEST SOUTH/WEST SC COUNTIES WITHIN THE ILM AREA 
BEFORE THE END OF THE PERIOD. IN ADDITION TO THE SLOWER EVOLUTION OF 
THE SYSTEM...THE PRECIP SHIELD WILL BE BATTLING VERY DRY LOW LEVEL 
AIR. FORECAST SOUNDINGS DO SHOW A LARGE INCREASE IN LOW LEVEL 
MOISTURE FROM 06Z TO 12Z FRI...BUT GUIDANCE MAY BE UNDERESTIMATING 
THE STRENGTH OF THE RIDGE. LATER SHIFTS MAY NEED TO PUSH POPS BACK 
FURTHER IF THE SLOWING TREND SEEN THE LAST DAY OR SO CONTINUES. 
ANOTHER POSSIBLE FLY IN THE OINTMENT IS WEAK COASTAL TROF DEVELOPING 
THU NIGHT. THIS FEATURE COULD MOVE ONSHORE AND HASTEN BREAK DOWN OF 
WEDGE OR STRENGTHEN AND REMAIN OFFSHORE...INCREASING THE STRENGTH OF 
THE WEDGE. 

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 3 AM TUESDAY...MOST OF THE PERIOD WILL BE MARKED BY DRY 
WEATHER WITH SOUTHWESTERLY FLOW OVER THE WEEKEND BECOMING MORE 
WESTERLY ON MON AS SOUTHERN BRANCH OF THE JET STREAM BECOMES FLAT 
AND SURFACE HIGH BUILDS INTO THE AREA FROM THE SOUTHWEST. 

MAIN CONCERN FOR THE PERIOD WILL BE THE IMPACT OF THE LARGE STORM 
SYSTEM OVER THE CENTRAL US AND ITS IMPACTS ON THE CAROLINAS FRI AND 
FRI NIGHT. EXTENDED GUIDANCE CONTINUES THE TREND OF SLOWING THE 
FEATURE DOWN...THOUGH THE 00Z ECMWF/CANADIAN ARE NOT AS SLOW AS THE 
00Z GFS. FOR NOW WILL HOLD ONTO LIKELY POPS FRI WITH A TREND FROM 
SLIGHT CHANCE SW TO LIKELY NE FOR FRI NIGHT. 

WARM FRONT MOVES ACROSS THE AREA FRI AS COASTAL TROF IS MOVING 
ONSHORE. BOTH OF THESE FEATURES WILL PROVIDE SOME WEAK LIFT AND A 
BRIEF PERIOD OF INSTABILITY IN THE WARM SECTOR. EXPECTING SOME 
CONVECTION ON FRI WHICH MAY INITIALLY BE ELEVATED...AND MAY REMAIN 
ELEVATED INLAND. GFS CONTINUES TO DEVELOP A TRIPLE POINT LOW OVER 
SOUTHERN GA/SC WHICH TRACKS NORTH. THE 00Z ECMWF/CANADIAN ARE NOW 
SHOWING THIS LOW...PASSING IT WEST OF THE AREA FRI NIGHT. ENHANCED 
LIFT AHEAD OF THE LOW AND 40 TO 50 KT LOW LEVEL JET MAY RESULT IN 
SOME STRONG STORMS IN THE AFTERNOON AND EVENING. BEST CHANCE WOULD 
BE ALONG THE COAST AND OVER THE WATERS. SURFACE LAYER MAY REMAIN 
MORE STABLE OVER INLAND AREAS...KEEPING STRONGER WINDS ALOFT. DRY 
AIR WRAPPED AROUND THE MIDWEST STORM WILL SPREAD OVER THE AREA 
BEHIND THE LOW...ENDING PRECIP BY SAT MORNING. 

FORECAST AREA IN THE WARM SECTOR ON FRI SHOULD SEE TEMPS ABOVE CLIMO 
FRI THROUGH SAT...IF WEDGE HOLDS STRONG INLAND TEMPS SPREAD ACROSS 
THE REGION COULD BE 10 DEGREES OR MORE FRI. DRY COLD FRONT PASSES ON 
SAT WITH TEMPERATURES NEAR TO SLIGHTLY CLIMO SAT NIGHT THOUGH THE 
END OF THE PERIOD.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
AS OF 12Z...SURFACE RIDGE OF HIGH PRESSURE WILL DOMINATE TODAYS 
SENSIBLE WEATHER WITH LIGHT WINDS AND MOSTLY CLEAR SKY CONDITIONS.

HIGH CONFIDENCE IN VFR THROUGH THE PERIOD AT ALL TERMINALS. HIGH 
LEVEL CIRRUS HAS MOVED OFFSHORE THIS MORNING AS EVIDENCED ON 
11U-3.9U SATELLITE...BUT HAVE KEPT FEW AT 25K FEET TO ACCOUNT FOR 
INCREASING UPPER LEVEL MOISTURE AS EVIDENCED ON WV IMAGERY AND TIME 
HEIGHTS. MODELS HAVING A DIFFICULT TIME DETERMINING A PREDOMINATE 
WIND DIRECTION TODAY DUE TO THE LIGHT GRADIENT...BUT EXPECT 
PRIMARILY LIGHT NORTH WINDS AROUND 5 KT IN ADVANCE OF THE HIGH 
SETTLING TO THE SOUTH. WINDS WILL DECOUPLE TONIGHT WITH THE 
DEVELOPMENT OF THE NOCTURNAL INVERSION BUT NO FOG IS EXPECTED SINCE 
LOW LEVELS OF THE ATMOSPHERE WILL REMAIN DRY.

EXTENDED OUTLOOK...HIGH CONFIDENCE IN VFR WEDNESDAY. INCREASING 
CONFIDENCE IN PERIODS OF IFR LATE THURSDAY AND FRIDAY WITH RAIN AND 
LOW CEILINGS. VFR SATURDAY.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 300 AM TUESDAY...CENTER IN CANADA...JUST NORTH OF THE GREAT 
LAKES...TO BECOME THE DOMINANT HIGH TO RIDGE ACROSS THE WATERS 
BEGINNING LATER TODAY AND LASTING INTO THE SHORT TERM TO EARLY LONG 
TERM. THIS IN RESPONSE TO THE STORM SYSTEM THAT WILL EVENTUALLY 
EVOLVE ACROSS THE CENTRAL U.S.. IN THE MEAN-TIME...THE PROGGED SFC 
PRESSURE PATTERN TO PLACE WINDS FROM THE N TO NE ACROSS THE WATERS 
THROUGH TONIGHT. SPEEDS GENERALLY 10 TO 15 KT. RESIDUAL 2 FOOT SWELL 
WILL CONTINUE TO AFFECT THE AREA WATERS BUT OVERALL THE SWELL HAD 
PEAKED LATE MONDAY AND IS ON THE DECLINE. THEREFORE...LOOK FOR 2 TO 
OCCASIONALLY 3 FOOT SEAS TO RULE THE AREA WATERS.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 3 AM TUESDAY...NORTHEAST FLOW AROUND 10 KT WED WILL START TO 
INCREASE WED NIGHT AS PRESSURE GRADIENT OVER THE WATERS BECOMES 
PINCHED. SHOULD SEE SOLID 15 TO 20 KT BY THU AND MAY SEE CLOSER TO 
20 KT...ESPECIALLY ACROSS SC WATERS THU MORNING. LATEST GUIDANCE 
CONTINUES TO WEAKEN THE SURFACE RIDGE OVER THE CAROLINAS LATE THU 
ALLOWING WINDS TO BECOME MORE EASTERLY AS COASTAL TROF STARTS TO 
DEVELOP. FEEL THIS MAY BE A LITTLE EARLY...SO HELD ONTO NORTHEAST 
FLOW A LITTLE LONGER. COASTAL TROF MOVES ACROSS THE WATERS LATE THU 
NIGHT WITH WINDS BEHIND IT BECOMING EAST TO SOUTHEAST WITH A SLIGHT 
INCREASE IN SPEEDS. SEAS 2 TO 3 FT ON WED WILL GRADUALLY BUILD TO 5 
TO 7 BY THE END OF THE PERIOD...LIKELY REQUIRING HEADLINES FOR THU 
NIGHT.

LONG TERM /FRIDAY THROUGH SATURDAY/...
AS OF 3 AM TUESDAY...STRONG EAST TO SOUTHEAST FLOW OVER THE WATERS 
ATE THE START OF THE PERIOD WILL QUICKLY TRANSITION TO SOUTHERLY AS 
SURFACE LOW PASSES WEST OF THE WATERS. TIGHT GRADIENT OVER THE 
WATERS FRI INTO FRI NIGHT MAY RESULT IN GALE CONDITIONS...A LOT 
DEPENDS ON THE LOCATION AND THE STRENGTH OF THE LOW AND THE STRENGTH 
OF THE SURFACE HIGH TO THE NORTH. EVEN IF GALE CONDITIONS ARE NOT 
MET...WIND SPEEDS WILL BE CLOSE TO 30 KT WITH SEAS APPROACHING 
DOUBLE DIGITS. ONSHORE COMPONENT WILL ENSURE HIGHER SEAS ALL THE WAY 
TO THE COAST. AS QUICKLY AS SEAS RAMP UP FRI INTO FRI NIGHT THEY 
WILL BE KNOCKED DOWN SAT. COLD FRONT PUSHES ACROSS THE WATERS DURING 
THE DAY WITH OFFSHORE WINDS 15 TO 20 KT HELPING KNOCK SEAS DOWN. 
HEADLINES WILL LIKELY BE REQUIRED THROUGH THE PERIOD. 

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.

&&

$$

SYNOPSIS...III
NEAR TERM...DCH
SHORT TERM...III
LONG TERM...III
AVIATION...JDW