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[Printable]
569
FXUS62 KCAE 210735
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
235 AM EST SUN DEC 21 2014

.SYNOPSIS...
A FRONTAL ZONE WILL REMAIN NEAR THE SOUTHEAST COAST
THROUGH TUESDAY. A SERIES OF LOW PRESSURE SYSTEMS WILL MOVE
NORTHEASTWARD ALONG THE FRONT. A STRONG COLD FRONT APPROACHING
FROM THE WEST WILL MOVE THROUGH THE FORECAST AREA WEDNESDAY.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
LOW CLOUDINESS AND WEDGE LIKE CONDITIONS COVERING MUCH OF THE
REGION CURRENTLY. AN UPPER DISTURBANCE...CURRENTLY MOVING EAST
ACROSS THE LOWER MISS VLLY...WILL MOVE EAST OVERNIGHT...AHEAD OF
WHICH SOME WEAK ISENTROPIC LIFT WILL RECOMMENCE NEAR THE SOUTHERN
FA AND POINTS SOUTHWARD. LATEST RADAR MOSAIC INDICATES LIGHT RAIN
ACROSS MUCH OF S GA...WHICH LATEST HIGH RESOLUTION MODELS BRING
NORTH INTO OUR SOUTHERN FA LATE TONIGHT. OTHERWISE...EXPECT CLOUDY
TO MOSTLY CLOUDY SKIES AND SEASONABLY COOL CONDITIONS OVERNIGHT
WITH A LIGHT NE WIND.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
THE MID/UPPER FLOW WILL BECOME INCREASINGLY SOUTHWEST DURING THE
DAY ON SUNDAY INTO SUNDAY NIGHT AS A S/W TROUGH MOVES INTO  THE MS
VALLEY. MODEL TIME SECTIONS SHOW INCREASING LOW LEVEL MOISTURE AND
ISENTROPIC LIFT THROUGH THE PERIOD AS WEAK LOW PRESSURE DEVELOPS
IN THE GULF AND MOVES NORTHEAST ACROSS FLORIDA AND OFF THE
SOUTHEAST COAST. DURING THE PERIOD...PRECIPITATION AMOUNTS LOOK TO
BE LESS THAN ONE QUARTER INCH AS THE LIGHT RAIN/DRIZZLE IS
EXPECTED. WILL CONTINUE WITH SOME PATCHY FOG SUNDAY MORNING WITH
POPS AROUND 10 PERCENT OR LESS. HOWEVER...THROUGH THE AFTERNOON
WITH INCREASING ISENTROPIC LIFT FROM S TO N EXPECT A GRADUAL
INCREASE IN POPS. POPS GO FROM SLIGHT CHANCE SUNDAY TO CATEGORICAL
BY LATER SUNDAY NIGHT. AS FOR TEMPERATURES...EXPECT LITTLE DIURNAL
RANGE GIVEN CLOUD COVER AND PRECIPITATION POTENTIAL. HAVE TRENDED
TOWARD JUST BELOW CONSENSUS FOR HIGHS AND JUST ABOVE FOR LOWS.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
A MORE VIGOROUS S/W WILL DIG A DEEP TROUGH ACROSS THE EASTERN HALF
OF THE COUNTRY BY MID WEEK AS MID LEVEL LOW CLOSES OFF ACROSS THE
UPPER PLAINS/UPPER MIDWEST. MOISTURE ACROSS THE REGION WILL REMAIN
RATHER HIGH THROUGH MIDWEEK WITH PW VALUES INCREASING TO OVER 1.5
INCHES BY LATE TUESDAY NIGHT/INTO WEDNESDAY. AHEAD OF THIS SYSTEM
A WEDGE WILL DEVELOP ACROSS THE AREA ON MONDAY AND MODELS INDICATE
THIS FEATURE HOLDING INTO TUESDAY. HAVE TRENDED WITH LOWER
TEMPERATURES THROUGH THE PERIOD AS ECMWF/GFS/NAM INDICATE NE LOW
LEVEL FLOW AND VERY STABLE AIRMASS IN PLACES OVER THE REGION.
HOWEVER...BY LATE TUESDAY AFTERNOON/TUESDAY NIGHT BOTH ECMWF AND
GFS LIFT THE WARM FRONT NORTHWARD ACROSS THE AREA. TEMPERATURES
WILL LIKELY RISE SLOWLY TUESDAY NIGHT AS LOW LEVEL FLOW SHIFTS
FROM NE AND E TO A MORE SOUTHERLY DIRECTION. THE GFS AND ECMWF
MODELS HAVE CONTINUED WITH THE TREND OF THE SLOWER COLD FRONTAL
PASSAGE ON WEDNESDAY. THE AREA WILL REMAIN UNDER ISENTROPIC LIFT
THROUGH MUCH OF THE PERIOD FROM MONDAY INTO EARLY WEDNESDAY WITH
AN INCREASING WIND FIELD TUESDAY NIGHT INTO WEDNESDAY. THE GFS
SHOWS A 50 TO 60 KT H8 JET ASSOCIATED WITH THE SYSTEM EARLY
WEDNESDAY. WITH THE DELAY OF THE FRONTAL PASSAGE AND AREA BECOMING
INCREASINGLY UNSTABLE BY WEDNESDAY HAVE CONTINUED THE MENTION OF
THUNDERSTORMS IN THE FORECAST. ALSO EXPECT INCREASING SURFACE
WINDS WITH TIGHT PRESSURE GRADIENT AND STRONG LOW LEVEL WINDS ON
WEDNESDAY.

THE INCREASING SHEAR AND POTENTIAL FOR SUFFICIENT INSTABILITY
INDICATES A POSSIBILITY OF STRONG/SEVERE THUNDERSTORMS.

EXPECT A DIMINISHED SHOWER CHANCE WEDNESDAY NIGHT BEHIND THE
FRONT WITH BREEZY CONDITIONS. THE MODELS HAVE BEEN CONSISTENT
SHOWING A DRY WEST FLOW BETWEEN HIGH PRESSURE NEAR THE GULF COAST
AND LOW PRESSURE LIFTING NORTH OF THE GREAT LAKE REGION FOR
CHRISTMAS DAY. BREEZY CONDITIONS MAY CONTINUE DURING THE DAY...BUT
THE MODEL TREND HAS BEEN TO SHOW THE RIDGE FARTHER NORTHWARD WITH
LESS OF A PRESSURE GRADIENT IN THE FORECAST AREA.

MOISTURE MAY INCREASE AHEAD OF ANOTHER COLD FRONT APPROACHING
FRIDAY NIGHT INTO SATURDAY. HAVE CONTINUED THE MENTION OF A SMALL
POP FRIDAY NIGHT AND SATURDAY. EXPECT TEMPERATURES TO BE COOLER
THAN NORMAL MONDAY AND TUESDAY...ABOVE NORMAL WEDNESDAY AND THEN
RETURNING TO MORE NORMAL TEMPERATURES FOR THE REMAINDER OF THE
PERIOD.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
WEAK HIGH PRESSURE REMAINS TO OUR NORTH WITH A SLOWLY DEVELOPING
AREA OF LOW PRESSURE OFF THE SOUTHEAST COAST. GENERALLY MVFR CIGS
ACROSS THE AREA EARLY THIS MORNING...BUT THERE IS A TENDENCY TO
FLUCTUATE BETWEEN PERIODS OF VFR OR IFR CIGS. SOME OF THE MODEL
GUIDANCE DOES NOT SEEM TO HAVE A GOOD HANDLE ON THE SHORT-TERM
SITUATION SO CONFIDENCE IS SOMEWHAT LOW. FOR NOW...WILL CONTINUE
WITH MAINLY MVFR CIGS FOR THE EARLY MORNING HOURS...CONTINUING
INTO THE AFTERNOON. LATEST MET/MAV GUIDANCE SHOWING POSSIBLE IFR
CIGS AT AGS/DNL/OGB LATER THIS AFTERNOON...SO WILL NEED TO
CONTINUE MONITORING. THERE WILL BE A BETTER CHANCE FOR SHOWERS
ACROSS THE AREA LATER THIS AFTERNOON AS SHORT WAVE ENERGY BEGINS
TO LIFT OUT OF THE GULF OF MEXICO.

EXTENDED AVIATION OUTLOOK...WIDESPREAD MVFR TO IFR CONDITIONS
EXPECTED TONIGHT THROUGH WEDNESDAY EVENING AS A SERIES OF SYSTEMS
CROSS THE REGION. BREEZY CONDITIONS POSSIBLE WEDNESDAY AFTERNOON
INTO THURSDAY MORNING.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&

$$







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