FXUS62 KCAE 250532
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
1232 AM EST FRI DEC 25 2009
.SYNOPSIS...
AN APPROACHING WARM FRONT WILL LIFT NORTH OF THE FORECAST AREA
THIS CHRISTMAS MORNING. A COLD FRONT WILL MOVE THROUGH THE AREA
DURING THE AFTERNOON. HIGH PRESSURE BEHIND THE FRONT WILL BE
CENTERED NEAR THE REGION SATURDAY NIGHT.
&&
.NEAR TERM /THROUGH TODAY/...
RAIN WILL BECOME WIDESPREAD TONIGHT AS ISENTROPIC LIFT CONTINUES.
THE HEAVIEST RAIN SHOULD OCCUR TOWARD MORNING AS THE H85 JET MOVES
INTO THE REGION. SHEAR WILL BE VERY STRONG...BUT THE SEVERE
THUNDERSTORM RISK APPEARS LOW THROUGH TONIGHT BECAUSE OF A LACK OF
SURFACE-BASED INSTABILITY. THE NAM INDICATES SURFACE-BASED LI/S
REMAINING POSITIVE AND RANGING FROM 2 NEAR WAYNESBORO...10 AROUND
COLUMBIA...AND 20 NEAR LANCASTER 12Z FRIDAY.
EXPECT LITTLE CHANGE IN TEMPERATURE TONIGHT BECAUSE OF CLOUDINESS
AND WIND. THE TIGHTENING PRESSURE GRADIENT AHEAD OF THE COLD FRONT
SUPPORTS THE LAKE WIND ADVISORY FOR LATE TONIGHT.
&&
.SHORT TERM /TONIGHT THROUGH SUNDAY/...
CONTINUED STRONG SHEAR WITH H85 WINDS AROUND 50 KNOTS WILL OCCUR
FRIDAY. THE NAM INDICATES THE EXTREME EAST PART MAY GET INTO THE
WARM SECTOR FRIDAY. THE NAM SHOWS SURFACE-BASED LI/S -1 TO -2.
HOWEVER...DEEPER MOISTURE MAY BE LIFTING EAST OF THE REGION AT
THIS TIME AND THE MODEL INSTABILITY MAY BE OVERDONE BECAUSE OF
THUNDERSTORMS SOUTH AND EAST OF THE FORECAST AREA. THE RISK OF SEVERE
THUNDERSTORMS APPEARS LOW BUT CANNOT BE RULED OUT BECAUSE OF THE
STRONG SHEAR AND POSSIBLE INSTABILITY. THE STORM PREDICTION CENTER
HAS THE EAST PART OUTLOOKED IN A SLIGHT RISK OF SEVERE.
THE NAM AND GFS SHOW RAIN TOTALS OF ONE TO TWO INCHES. BASED ON
FLASH FLOOD GUIDANCE WE HAVE NOT ISSUED A FLOOD WATCH BUT THERE
MAY BE SOME FLOODING IN POOR-DRAINAGE AREAS AND ALONG SMALL
STREAMS.
DRYING SHOULD DOMINATE FRIDAY NIGHT AND SATURDAY AS HIGH PRESSURE
MOVES INTO THE AREA.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
LARGE MID-LEVEL VORTEX OVER THE GREAT LAKES REGION LIFTS
NORTHEAST AND OPENS UP EARLY NEXT WEEK. SURFACE HIGH PRESSURE
BUILDING IN FROM THE WEST SUNDAY THROUGH TUESDAY. WEST/NORTHWEST
H85 FLOW WILL KEEP THE GULF CLOSED. DRY AND COOL PERIOD THROUGH
WEDNESDAY.
NEXT MID-LEVEL DISTURBANCE ALONG THE CA COAST WILL MOVE THROUGH
THE SOUTHWEST TUESDAY...AND DEVELOP ANOTHER AREA OF LOW PRESSURE
IN THE WESTERN GULF OF MEXICO THURSDAY. LOW PRESSURE IS FORECAST TO
MOVE/REFORM OFF THE SOUTHEAST SEABOARD LATE THURSDAY OR FRIDAY.
UNCERTAINTY IS HIGH WITH THIS SYSTEM. ECMWF IS WARMER AND WETTER
THAN THE DRY AND COOL GFS. FOR NOW WILL INTRODUCE A CHANCE OF
LIQUID PRECIPITATION THURSDAY.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
CLOUDY SKIES ALONG WITH SOME AREAS OF LIGHT RAIN MOVING INTO THE CWA
TONIGHT. 88D REGIONAL COMPOSITE SHOWS HEAVIER SHRA ACRS ERN AL/WRN
GA AHEAD OF A COLD FRONT THAT WILL BE MOVING IN THE REGION BY
MORNING. CURRENTLY NO LIGHTNING SHOWING UP IN SHOWERS. MVFR CIGS
PREVAILING ACRS THE REGION TONIGHT AND EXPECT CIGS TO CONTINUE TO
LOWER TOWARD DAYBREAK AS HEAVIER PCPN APPROACHES. MAIN ISSUE
OVERNIGHT WILL BE WIND SHEAR. SURFACE WINDS REMAIN NE/ENE FROM 10
TO 15 KNOTS WITH GUSTS ARND 20 KTS. VWP SHOWS WINDS AT 2K FT 35 TO
40 KTS AND AT 3K FT FROM 40 TO 50 KTS. MODELS INDICATE STRONG LLJ
WILL MOVE INTO THE REGION TOWARD MORNING OF ARND 70 KTS AT 5-7K
FT. LOW LEVEL WINDS WILL BE INCREASING TOWARD MORNING. WILL
CONTINUE MENTION OF WIND SHEAR INTO THE EARLY AFTERNOON UNTIL
PASSAGE OF COLD FRONT. EXPECT PERIODS OF MVFR/IFR CIGS/VSBYS FROM
FRIDAY MORNING UNTIL EARLY FRIDAY AFTERNOON. HAVE DECIDED TO
MENTION TEMPO GROUP FOR TSRA AS AIRMASS AHEAD OF COLD FRONT FRI
MORNING/EARLY AFTERNOON BECOMES WEAK UNSTABLE. WOULD NOT BE
SURPRISED TO HEAR A RUMBLE OR TWO OF THUNDER. BY FRI
AFTERNOON...MODELS SHOW THAT COLD FRONT WILL MOVE ACRS THE CWA AND
CLEARING WILL BEGIN. MODEL TIME SECTIONS SHOW RAPID DROP OFF OF
MOISTURE ACRS THE REGION AND EXPECT SOME SUN DURING THE LATE
AFTERNOON. VFR CONDITIONS WILL RETURN FROM LATE AFTERNOON INTO THE
EVENING HOURS.
EXTENDED AVIATION OUTLOOK...HIGH PRESSURE WILL BUILD INTO THE REGION
FOR FRIDAY NIGHT THROUGH TUESDAY.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...LAKE WIND ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR SCZ015-
016-018-020>022-025>031-035>038-041.
GA...LAKE WIND ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR GAZ040-
063>065-077.
&&
$$
