FXUS62 KILM 221725 RRA
AFDILM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
1225 PM 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 9:00 AM TUESDAY...HAVE MADE SOME MINOR ADJUSTMENTS TO CURRENT
TEMPERATURES AND CLOUD COVER GRIDS TO MATCH ONGOING TRENDS
OTHERWISE...NO CHANGES TO FORECAST THIS MORNING.
&&
.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 /18Z TUESDAY THROUGH SATURDAY/...
AS OF 18Z...SURFACE RIDGE OF HIGH PRESSURE WILL DOMINATE THE
SENSIBLE WEATHER WITH LIGHT WINDS AND MOSTLY CLEAR SKY CONDITIONS.
HIGH CONFIDENCE IN VFR THROUGH THE PERIOD AT ALL TERMINALS. SKC AT
ALL TERMINALS THIS AFTN...BUT HAVE INTRODUCED A FEW CIRRUS AT 25K
FEET THIS EVENING TO ACCOUNT FOR INCREASING UPPER LEVEL MOISTURE
DEPICTED ON WV IMAGERY AND TIME HEIGHTS. MODELS HAVING A DIFFICULT
TIME DETERMINING A PREDOMINATE WIND DIRECTION DUE TO THE LIGHT
GRADIENT...BUT EXPECT PRIMARILY LIGHT NORTH WINDS AROUND 5 KT AS THE
HIGH SETTLES 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. TOMORROW WILL FEATURE
MORE OF THE SAME...WITH THE ONLY NOTICEABLE DIFFERENCE BEING AN
INCREASE IN CIRRUS COVERAGE WITH SCT TO POTENTIALLY BKN CIGS AT 25K
FEET.
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 9:00 AM TUESDAY...CURRENT FORECAST OF NORTHERLY WINDS OF 10-15
KNOTS WITH SEAS ON 2-3 FEET LOOKS GOOD AS THE GRADIENT IS EXPECTED
TO CHANGE LITTLE DURING THE DAY. NO CHANGES TO THE FORECAST THIS
MORNING.
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...SHK
SHORT TERM...III
LONG TERM...III
AVIATION...JDW
