FXUS62 KCAE 250139
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
839 PM EST THU DEC 24 2009
.SYNOPSIS...
AN APPROACHING WARM FRONT WILL LIFT NORTH OF THE FORECAST AREA
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 FRIDAY/...
MERRY CHRISTMAS FROM THE WEATHER SERVICE OFFICE IN COLUMBIA.
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 /FRIDAY NIGHT 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 /02Z FRIDAY THROUGH TUESDAY/...
VFR CONDITIONS QUICKLY GIVING WAY TO MVFR AND IFR. HIGH PRESSURE
WILL SLIDE FURTHER AWAY FROM THE AREA AS LOW PRESSURE AND AN
ASSOCIATED COLD FRONT MARCH INTO THE REGION. SATELLITE IMAGERY
SHOWS LOW LEVEL CLOUDS DEVELOPING AROUND THE TAF SITES AS EASTERLY
WINDS PUSH INCREASING MOISTURE INLAND. THIS TREND WILL BE AIDED BY
SOUTHERLY LOW LEVEL JET THIS EVENING PUSHING GULF MOISTURE
NORTHWARD. BY 25/06Z EXPECT RAIN TO BEGIN AT THE TAF SITES WITH
THE COLD FRONT NOT ARRIVING UNTIL VERY LATE IN THE TAF PERIOD.
HEAVIEST RAIN WILL ARRIVE AROUND 25/14Z WITH CIGS AND VSBYS
EXPECTED IN THE IFR RANGE. WINDS WILL INCREASE THROUGH THE PERIOD
WITH AROUND 15 KNOTS BY 25/06Z WITH GUSTS TO AROUND 22 KNOTS.
EXTENDED AVIATION OUTLOOK...IFR/MVFR CONDITIONS POSSIBLE FRIDAY AS A
COLD FRONT MOVES THROUGH THE REGION. HIGH PRESSURE WILL BUILD INTO
THE REGION FOR FRIDAY NIGHT THROUGH TUESDAY.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...LAKE WIND ADVISORY FROM MIDNIGHT TONIGHT TO 5 PM EST FRIDAY
FOR SCZ015-016-018-020>022-025>031-035>038-041.
GA...LAKE WIND ADVISORY FROM MIDNIGHT TONIGHT TO 5 PM EST FRIDAY
FOR GAZ040-063>065-077.
&&
$$
SYNOPSIS...JL
NEAR TERM...JL
SHORT TERM...JL
LONG TERM...99
AVIATION...LCV
