Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 210002
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
702 PM EST SAT DEC 20 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 SUNDAY MORNING/...
RAIN CLEARED THE FORECAST AREA (FA) EARLIER TODAY AS AN UPPER
SHORT WAVE DEPARTED TO OUR EAST...LEAVING BEHIND EXTENSIVE LOW
CLOUDINESS AND WEDGE LIKE CONDITIONS OVER THE REGION. THE NEXT
UPPER DISTURBANCE...CURRENTLY OVER TEXAS...WILL ROLL EAST
TONIGHT...AHEAD OF WHICH SOME WEAK ISENTROPIC LIFT WILL
RECOMMENCE NEAR THE SOUTHERN FA AND POINTS SOUTHWARD. LATEST
RADAR MOSAIC INDICATES LIGHT RAIN ACROSS PORTIONS OF S GA...WHICH
LATEST HIGH RESOLUTION MODELS BRING NORTH INTO OUR SOUTHERN FA
LATE TONIGHT. OTHERWISE...EXPECT CLOUDY AND SEASONABLY COOL
CONDITIONS OVERNIGHT WITH A LIGHT NE WIND. GUIDANCE INDICATING
MIXED SIGNALS WITH REGARD TO THE EXTENT OF FOG OVERNIGHT.
CONFIDENCE OF DENSE WORDING NOT SUFFICIENT TO PUT IN THE FORECAST
AT THIS TIME.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
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 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 /00Z SUNDAY THROUGH THURSDAY/...
MVFR AND IFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD.

SATELLITE IMAGERY AND SURFACE OBS CONTINUE TO SHOW WIDESPREAD MVFR
AND IFR CONDITIONS ACROSS THE REGION. MODELS CONTINUE TO AGREE ON
SIGNIFICANT MOISTURE REMAINING TRAPPED UNDER THE INVERSION WITH
FOG DEVELOPING DURING THE EARLY MORNING HOURS AS WELL AS CIGS
LOWERING OVERNIGHT. EXPECT LOWEST CONDITIONS AT AGS/DNL/OGB WHERE
EASTERLY FLOW WILL PUSH ADDITIONAL MOISTURE INTO THE LOW LEVELS.
CONDITIONS WILL IMPROVE TO MVFR AROUND 13Z WITH DETERIORATING
CONDITIONS BEGINNING AROUND 16Z AGS/DNL/OGB...20Z CAE/CUB...AS
SHOWERS BEGIN DEVELOPING ACROSS THE AREA.

EXTENDED AVIATION OUTLOOK...WIDESPREAD MVFR TO IFR CONDITIONS
EXPECTED SUNDAY EVENING 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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