FXUS62 KCAE 301951
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
251 PM EST MON NOV 30 2009
.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH THE FORECAST AREA BY THIS
EVENING BRINGING SOME RAIN SHOWERS AS IT PASSES. A STRONG LOW
PRESSURE SYSTEM WILL IMPACT THE AREA ON WEDNESDAY AND WEDNESDAY
NIGHT...BRINGING POTENTIALLY SIGNIFICANT RAINFALL. COLD HIGH
PRESSURE WILL SETTLE IN FOR THE END OF THE WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
COLD FRONT MOVING THROUGH THE TN VALLEY THIS AFTERNOON WITH MAINLY
LIGHT SHOWERS AHEAD OF IT. FRONT WILL CONTINUE TO ADVANCE EASTWARD
THROUGH THIS EVENING AND MOVE OFFSHORE. CHANCE POPS THROUGH THIS
EVENING. SKIES WILL BECOME MOSTLY CLEAR OVERNIGHT.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
A TRANSIENT SURFACE HIGH PRESSURE SYSTEM WILL MOVE OVER THE
FORECAST AREA ON TUESDAY INTO TUESDAY EVENING BEFORE SHIFTING OFF
THE COAST BY EARLY WEDNESDAY AS A VERY STRONG LOW PRESSURE SYSTEM
TRACKS ACROSS THE SOUTHERN UNITED STATES. A STRONG WARM ADVECTION
PATTERN DEVELOPS TUESDAY NIGHT ALONG THE GULF COAST STATES AND
SPREADS NORTHEASTWARD TOWARD THE FORECAST AREA BY WEDNESDAY
MORNING.
THERE IS SOME DIFFERENCES IN TIMING OF THIS LOW PRESSURE SYSTEM
WITH THE GFS ABOUT 12 HOURS OR SO FASTER THAT THE NAM AND ECMWF.
THIS IS A DIFFICULT FORECAST FOR A POTENTIALLY HIGH IMPACT RAIN
EVENT DUE TO SOME MODEL DIFFERENCES IN THE TIMING AND LOCATION OF
THE SURFACE LOW AS IT MOVES QUICKLY NORTHWARD FROM THE GULF ON
WEDNESDAY AND WEDNESDAY NIGHT. MODEL CONSENSUS IS TO TAKE THE
SURFACE LOW WEST OF THE FORECAST AREA RESULTING IN STRONG
SOUTHERLY LOW LEVEL WINDS OF 50 TO 65 KNOTS OUT OF THE SOUTH TO
SOUTHEAST. THIS RESULTS IN STRONG ISENTROPIC LIFTING AND MOISTURE
FLUX OVER THE AREA...AND WILL BE COINCIDING WITH STRONG JET
DYNAMICS AS THE RIGHT ENTRANCE REGION OF THE JET BECOMES SITUATED
OVER THE SOUTHEAST. EXPECT WIDESPREAD MODERATE...AND POSSIBLY AT
TIMES...HEAVY RAIN TO OCCUR ACROSS PORTIONS OF THE FORECAST AREA
WEDNESDAY WITH THE HIGHEST QPF AMOUNTS BEING FOCUSED IN THE
WESTERN MIDLANDS AND IN THE UPSTATE OF SOUTH CAROLINA. WILL
CONTINUE CATEGORICAL POPS BY WEDNESDAY MORNING BUT WILL LEAVE OUT
MENTION OF THUNDER SINCE ATMOSPHERE REMAINS STABLE WITH WEAK WEDGE
DEVELOPING. TEMPERATURES WILL SUFFER DUE TO THE CLOUDS AND
DEVELOPING EASTERLY FLOW AND MODERATE PRECIPITATION...HOLDING
HIGHS IN THE 50S ACROSS MOST OF THE AREA.
AS THE SURFACE LOW LIFTS NORTHWARD WEDNESDAY EVENING THE FORECAST
AREA WILL LIKELY MOVE INTO THE WARM SECTOR AND BECOME SOMEWHAT
UNSTABLE AS LIFTED INDEX VALUES DROP TO AROUND -2C...SO WILL
INCLUDE THUNDER IN THE WEDNESDAY AFTERNOON AND EVENING PERIOD.
TEMPERATURES WILL BE QUITE TRICKY AS WELL...AS THEY COULD REMAIN
STEADY OR SLOWLY RISE THROUGH THE NIGHT AND THEN POSSIBLY FALL
AGAIN DEPENDING ON HOW FAST THE COLD FRONT PUSHES THROUGH EARLY
THURSDAY MORNING. EXPECTING UPWARDS OF 1-2 INCHES ACROSS MUCH OF
THE FORECAST AREA THROUGH THIS EVENT WITH SOME LOCATIONS POSSIBLY
EXCEEDING 2 INCHES.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
SKIES WILL BE CLEARING WITH BREEZY WESTERLY WINDS IN THE WAKE OF
THE STRONG STORM SYSTEM MOVING INTO THE NORTHEASTERN STATES ON
THURSDAY. STRONG HIGH PRESSURE WILL BUILD INTO THE AREA THROUGH
SATURDAY AND REMAIN OVER THE SOUTHEAST INTO SUNDAY. THE AIRMASS
WILL BE QUITE CHILLY AND WE SHOULD SEE TEMPERATURES WELL BELOW
NORMAL FRIDAY THROUGH SUNDAY WITH MUCH OF THE EAST COAST UNDER THE
INFLUENCE OF AN UPPER TROUGH. GFS SHOWS A DEVELOPING LOW PRESSURE
SYSTEM IN THE GULF OF MEXICO WHICH MAY BEGIN TO AFFECT OUR AREA BY
LATE MONDAY...BUT WILL LEAVE MONDAY DRY FOR NOW.
&&
.AVIATION /19Z MONDAY THROUGH SATURDAY/...
AS A COLD FRONT APPROACHES THE AREA..MID LEVEL...AROUND 10K FT...CIGS
HAVE MOVED OVER ALL TAF SITES EXCEPT OGB WITH A SCT LAYER 3 TO
3.5K FT BELOW IT. EXPECT THE LOWER SCT LAYER TO THICKEN AND BECOME
A CIG BY 19Z TO 21Z. THERE WILL BE SCATTERED AREAS OF LIGHT RAIN
THIS AFTERNOON AND EVENING WHICH FOR NOW I HAVE INDICATED AS VCSH
IN THE TAFS. AFTER AROUND 04Z TO 05Z...WINDS WILL SHIFT TO THE
NORTHWEST AND SKIES WILL BEGIN TO CLEAR. HIGH PRESSURE WILL BUILD
OVER THE AREA TONIGHT AND TUESDAY. THE WIND SHOULD BECOME LIGHT
AND VARIABLE BY EARLY AFTERNOON TUESDAY WITH THE HIGH OVER HEAD
AND MOSTLY CLEAR SKIES.
EXTENDED AVIATION OUTLOOK...MVFR TO IFR CONDITIONS EXPECTED
WEDNESDAY INTO THURSDAY MORNING AS A LOW PRESSURE SYSTEM CROSSES
THE THE AREA.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&
$$
