FXUS62 KILM 231139
AFDILM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON NC
638 AM EST WED DEC 23 2009
.SYNOPSIS...
COOL AND DRY HIGH PRESSURE WILL RIDGE DOWN THROUGH THE SOUTHEAST
FROM CANADA UNTIL THURSDAY. PRECIPITATION CHANCES WILL INCREASE
INTO CHRISTMAS DAY...ALONG WITH A WARMING TREND...AS A FRONT
APPROACHES FROM THE SOUTHWEST. A DRIER AND COOLER AIR MASS WILL
BUILD IN BEHIND THIS FRONT THROUGH THE SECOND HALF OF THE WEEKEND
INTO EARLY NEXT WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 3 AM WEDNESDAY...S/W RIDGING ALOFT TO AMPLIFY THRU THE FCST
PERIOD...WITH THE RIDGE AXIS EITHER ACROSS OR JUST WEST OF THE ILM
CWA. THIS A RESULT OF THE EVOLUTION...AMPLIFICATION AND MOVEMENT OF
THE UPPER/SFC LOWS ACROSS THE CENTRAL U.S.. MOISTURE IN THE UPPER
LEVELS TO SPORADICALLY MOVE ACROSS THE UPPER RIDGE AXIS AND AT TIMES
ACROSS THE ILM CWA. FOR THE MAJORITY OF THE TIME THE CI WILL NOT BE
OPAQUE ENOUGH TO WORSEN FORECAST SKY CONDITIONS FROM MOSTLY SUNNY.
AT THE SFC...RIDGING WILL EXTEND ACROSS THE AREA ALL THE WAY FROM A
SUB-1040 HIGH CENTERED ACROSS CANADA JUST NORTH OF THE GREAT LAKES.
AM HOLDING OFF WITH THE LOW LEVEL PUSH OF CLOUDS ONSHORE BY THE NAM
FROM THE CAPE FEAR REGION NORTHWARD LATE TONIGHT...AND THERE4 PTLY
CLOUDY AT WORST FOR SKY CONDITIONS DUE TO CONTINUED AND MORE OPAQUE
CI/CS. MAX/MIN TEMPS THROUGH TONIGHT WILL FAVOR THE GFS MOS GUIDANCE
AS A RESULT OF ITS CUMULATIVE BETTER PERFORMANCE WITH THIS AIR MASS
OVER THE PAST SEVERAL DAYS.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 3 AM WEDNESDAY...HIGH PRESSURE WILL RIDGE DOWN THROUGH THE
SOUTHEAST CONUS FROM CANADA THROUGH THURS AS FRONTAL SYSTEM
APPROACHES FROM THE SOUTHWEST. NORTHERLY WINDS WILL INCREASE AS
THEY BEGIN TO VEER AROUND TO THE E-NE BY THURS EVNG AND THEN E-SE
THROUGH FRI MORNING WITH AN INCREASING ON SHORE PUSH. IN A TYPICAL
WEDGE-LIKE SCENARIO...EXPECT SW-S WINDS TO BEGIN TO OVERRUN SHALLOW
COOL AIR MASS IN PLACE. BY FRI MORNING H85 TO H7 SOUTHERLY FLOW WILL
INCREASE TO 45 TO 60 KTS AS SFC WINDS SLOWLY VEER AROUND FROM THE NE
TO E. LOOKS LIKE BEST ISENTROPIC LIFT WILL COME SHORTLY AFTER
MIDNIGHT ON THURS LASTING THROUGH CHRISTMAS EARLY AFTN. MOISTURE
PROFILES SHOW LOWER CLOUDS AND PCP POSSIBLE FRI EVENING ALONG THE
COAST AS WINDS BECOME ON SHORE AND MAY SEE SOME MOISTURE CONVERGENCE
ALONG THE COAST...BUT MOST OF THE RAIN WILL NOT COME UNTIL AFTER
MIDNIGHT OR SO. DEEPER LAYER MOISTURE WILL BE PRESENT THROUGH AT
LEAST EARLY FRI AFTN. LOOKS LIKE WAVE OF LOW PRESSURE DEVELOPS BY
FRI MORNING AND FRONT MAY BE SLOW TO MAKE IT OFF THE COAST AS MID TO
UPPER LEVEL FLOW REMAINS SW OR PARALLEL TO FRONT WITH MAIN H5 BROAD
TROUGH STILL BACK OVER THE PLAINS. PCP WATER INCREASES UP OVER 1.5
INCHES FRI...BUT DROPS DOWN BELOW A HALF INCH BY END OF PERIOD
INLAND. SHOULD BE A DECENT QPF EVENT THURS NIGHT THROUGH FRI AFTN.
OVERALL SHOULD SEE INCREASE IN CLOUDS THROUGH THURS AND PCP
SPREADING ACROSS AREA FROM THE SW LATER IN THE DAY AND THEN RAINY
AND MILD ON CHRISTMAS DAY.
AS FOR TEMPS...SHOULD REMAIN COOLER INITIALLY ON THURS WITH WEDGE
IN PLACE AND TEMPS HOLDING IN THE MID 50S MOST PLACES. BY THURS
NIGHT INTO FRI AS WINDS BECOME ON SHORE THE DEWPOINTS AND TEMPS
WILL INCREASE REACHING INTO THE UPPER 50S INLAND TO 60S ALONG THE
COAST IN INCREASING WARM AND MOIST FLOW.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 3 AM WEDNESDAY...BROAD H5 TROUGH STILL HANGING WAY BACK OVER
CENTRAL CONUS WITH SW FLOW BECOMING MORE WESTERLY AS BASE OF
TROUGH FLATTENS THROUGH THE WEEKEND. THEREFORE EXPECT A GRADUAL
DECREASE IN TEMPS THROUGH THE WEEKEND BUT MORE IN THE WAY OF
DRYING. WILL GET PUSH OF COLDER AIR LATE MON AS TROUGH AXIS
FINALLY CLEARS THE COAST AND DEEPER NW FLOW OF COLD AIR COMES
FUNNELING INTO THE CAROLINAS. THIS BLAST OF COLD AIR MAY BE BRIEF
AS H5 RIDGE PUSHES MID LEVEL HEIGHTS BACK UP BY MID WEEK. OVERALL
FRONT SHOULD PUSH OFF THE COAST WITH A CLEARING TREND THROUGH
EARLY SAT. THEN DRYING AND COOLING TREND THROUGH THE REMAINDER OF
THE WEEKEND INTO EARLY NEXT WEEK. TEMPS SHOULD START OUT ON THE
WARM SIDE BUT WILL COOL DOWN BACK AROUND NORMAL THROUGH THE
WEEKEND AND THEN BELOW NORMAL LATE MON INTO TUES. LOW LEVEL
THICKNESSES AND 850 TEMPS PEAK FRI EVENING AND THEN SEE A DECLINE
THROUGH THE REMAINDER OF THE WEEKEND IN A DRIER AND COOLER
WESTERLY FLOW.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
AS OF 12Z...SURFACE HIGH PRESSURE WILL WEDGE DOWN TO THE SOUTH TODAY
KEEPING VFR AT ALL THE TERMINALS THROUGH THE TAF PERIOD WITH
DEVELOPING CIRRUS CIGS. WINDS WILL INITIALLY BE LIGHT BUT INCREASE
LATE AS GRADIENT TIGHTENS. SOME LOW STRATUS COULD DEVELOP AT THE
COAST TONIGHT.
HIGH CONFIDENCE IN TODAYS AVIATION FORECAST AS MVFR FOG AT LBT/FLO
WILL BURN OFF AFTER SUNRISE...GIVING WAY TO VFR AT ALL TERMINALS AS
HIGH PRESSURE WEDGE STRENGTHENS AND SHIFTS SOUTHWARD TODAY. HAVE
INCREASED 25K FOOT CIRRUS COVERAGE TO BKN AT THE SOUTHERN TERMINALS
DUE TO CURRENT 11U-3.9U SATELLITE IMAGERY...BUT ILM/LBT WILL REMAIN
ONLY SCT UNTIL TONIGHT. WINDS WILL GENERALLY BE LIGHT AT 5 TO 10
KT...HIGHEST AT THE COAST. TONIGHT WINDS WILL VEER TO A MORE
EASTWARD DIRECTION AND INCREASE TO 10 KT OR MORE AT THE COAST AS THE
GRADIENT TIGHTENS. THIS DECREASES FORECAST CONFIDENCE SINCE SOME LOW
CIGS MAY DEVELOP AT ILM/CRE/MYR WITH A MORE ONSHORE FLOW ADVECTING
LOW LEVEL MOISTURE INLAND. NOTE THAT GFS IS ADVERTISING SOME IFR
STRATUS AT ILM OVERNIGHT...AND WITH SIGNIFICANT STRATUS OFFSHORE
THERE IS SOME POTENTIAL FOR THIS...BUT BELIEVE ITS PROBABLY
OVERDOING LOW LEVEL MOISTURE AND EXPECT 5K FOOT CIGS TO BE MORE
LIKELY. WILL HAVE TO MONITOR LATEST GUIDANCE THOUGH...AND UPDATE IN
LATER TAFS. INLAND TERMINALS WILL REMAIN VFR WITH ONLY HIGH LEVEL CI
THROUGH THE PERIOD.
EXTENDED OUTLOOK...MODERATE CONFIDENCE IN PERIODS OF IFR LATE
THURSDAY NIGHT THROUGH SATURDAY MORNING WITH RAIN AND LOW CEILINGS.
VFR SUNDAY.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
AS OF 3 AM WEDNESDAY...SFC RIDGING PROGGED TO CONTINUALLY STRENGTHEN
ACROSS THE WATERS FROM THE SUB 1040 HIGH HIGH CENTERED ACROSS CANADA
JUST NORTH OF THE GREAT LAKES. WILL SLOWLY HAVE N-NE INCREASING
WINDS THROUGH THE FCST PERIOD AS THE SFC PRESSURE GRADIENT TIGHTENS.
SEAS WILL ALSO RESPOND AS THE LATEST DECAYING SWELL IS REPLACED BY
THE WIND DRIVEN LOCALLY PRODUCED SHORT PERIOD WAVES. WILL LIKELY
OBSERVE 5 FOOTERS BY THE END OF THE NEAR TERM FORECAST PERIOD.
LATEST CLOUD FEATURES AND TRENDS ACROSS THE ADJACENT OFFSHORE WATERS
INDICATE AN INVERTED SFC TROF HAVING DEVELOPED. THIS IS PROGGED TO
STRENGTHEN WITH TIME BY THE MODELS. THE NAM IS MORE PROMINENT WITH
THIS FEATURE THAN THE GFS BY THU MORNING BUT BOTH KEEP IT OFFSHORE
BY THIS TIME.
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 3 AM WEDNESDAY...GRADIENT WILL BECOME PINCHED ON THURS AS
WEDGE HOLDS ON INLAND AND COASTAL TROUGH BECOMES MORE PRONOUNCED
THEN A CONTINUED INCREASE IN WINDS WILL COME AS FRONTAL SYSTEM
ADVANCES FROM THE SOUTHWEST THROUGH FRI. WINDS WILL VEER AROUND
THROUGH THURS NIGHT BECOMING INCREASINGLY ON SHORE. WINDS AND SEAS
SHOULD REACH SCA CRITERIA THURS NIGHT INTO FRI MORNING WITH
INCREASING ON SHORE FETCH. ONCE COASTAL TROUGH/WARM FRONT BLOWS
INLAND BY FRI AFTN SHOULD SEE A STRONG SOUTHEAST WIND WHICH MAY
PUSH SEAS UP NEAR 4 TO 5 FT NEAR SHORE AND UP TO 10 FT IN THE
OUTER WATERS BY FRI NIGHT. WNA SHOWS PEAK IN WINDS AND SEAS FRI
EVENING AHEAD OF FRONT WHICH SHOULD MOVE ACROSS THE WATERS BY
EARLY SAT.
LONG TERM /SATURDAY THROUGH SUNDAY/...
AS OF 3 AM WEDNESDAY...FRONT WILL MOVE FARTHER OFF SHORE THROUGH
SAT WITH OFF SHORE WEST TO NORTHWEST FLOW HELPING TO KNOCK SEAS
DOWN NEAR SHORE. SHOULD START OUT JUST ABOVE SCA WITH SEAS NEAR 6
FT IN OUTER WATERS BUT OFF SHORE FLOW SHOULD HAVE NEAR SHORE SEAS
DOWN TO 2 TO 4 FT BY SAT MORNING. NOT MUCH OF A COLD SURGE
EXPECTED BEHIND FRONT...BUT ENOUGH COOL AND DRY AIR TO KEEP SEAS
FROM DECREASING AND LEVELING OFF SEAS JUST BELOW SCA THROUGH THE
REMAINDER OF THE PERIOD. WINDS SHOULD BE IN THE 15 TO 20 KT RANGE
OUT OF THE WEST THROUGH MOST OF THE WEEKEND.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
NC...NONE.
MARINE...NONE.
&&
$$
NEAR TERM...DCH
SHORT TERM...RGZ
LONG TERM...RGZ
AVIATION...JDW
