Area Forecast Discussion
Issued by NWS Columbia, SC

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000
FXUS62 KCAE 200846
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
346 AM 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 /THROUGH TONIGHT/...
THE SURFACE TROUGH WILL REMAIN JUST OFF THE COAST THROUGH TONIGHT.
THE MODELS AND WATER VAPOR IMAGERY TRENDS INDICATE DEEPER
MOISTURE AHEAD OF A MID-LEVEL SHORTWAVE TROUGH WILL SHIFT EAST OF
THE FORECAST AREA AROUND THE MIDDLE OF TODAY. WE FORECASTED THE
HIGHEST POPS EARLY AND IN THE SOUTHEAST SECTION CLOSER TO THE
STRONGER ISENTROPIC LIFT. SHALLOW MOISTURE BEHIND THE SHORTWAVE
TROUGH SUPPORTS A DIMINISHED RAIN CHANCE LATE TODAY AND TONIGHT.
HIGH LOW-LEVEL MOISTURE WILL CONTINUE THROUGH TONIGHT. THERE MAY
BE AREAS OF FOG AS INDICATED BY THE GFS MOS. LITTLE TEMPERATURE
RECOVERY SHOULD OCCUR TODAY BECAUSE OF CLOUDINESS. THE HIGH
TEMPERATURE GUIDANCE IS LIKELY TOO WARM. LEANED TOWARD THE MORE
CONSISTENT GFS MOS FOR THE TEMPERATURE TONIGHT.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
WEAK ISENTROPIC LIFT SUPPORTS A RAIN CHANCE SUNDAY MAINLY LATE AS
MOISTURE BECOMES DEEPER AHEAD OF ANOTHER MID-LEVEL SHORTWAVE
TROUGH. THE GUIDANCE CONSENSUS SUPPORTS POPS OF 20 TO 30 PERCENT
FOR MAINLY LATE IN THE DAY. THE MODELS ARE CONSISTENT DISPLAYING
SIGNIFICANT MOISTURE AND ISENTROPIC LIFT SUNDAY NIGHT INTO MONDAY
ESPECIALLY IN THE SOUTHEAST PART OF THE FORECAST AREA. THE MODELS
INDICATE MOISTURE BECOMING SHALLOW LATE MONDAY BEHIND THE
ASSOCIATED MID-LEVEL SHORTWAVE TROUGH. USED THE GUIDANCE CONSENSUS
FOR THE POP FORECAST. THE GUIDANCE HIGH TEMPERATURES ARE LIKELY
TOO WARM BECAUSE OF CLOUDINESS AND A LOW-LEVEL NORTHEAST FLOW. THE
GUIDANCE LOW TEMPERATURE WERE CLOSE. THE MODELS HAVE BEEN
CONSISTENT INDICATING ALL-LIQUID PRECIPITATION.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
HIGH MOISTURE SHOULD CONTINUE MONDAY NIGHT THROUGH TUESDAY AHEAD
OF A WARM FRONT AND DEEPENING UPPER-LEVEL TROUGH. THE GFS AND
ECMWF MODELS HAVE TRENDED SLOWER WITH THE PASSAGE OF A STRONG
COLD FRONT AND NOW DISPLAY FRONTAL PASSAGE WEDNESDAY. THE WARM
FRONT MAY LIFT NORTHWARD AHEAD OF THE COLD FRONT.

IF THE FORECAST AREA GETS INTO THE WARM SECTOR THERE MAY BE
ENOUGH INSTABILITY FOR THUNDERSTORMS AHEAD OF THE COLD FRONT TUESDAY
NIGHT OR WEDNESDAY. THE GFS AND ECMWF DISPLAY H85 WINDS OF 40 TO
60 KNOTS. THE SHEAR AND POTENTIAL FOR SUFFICIENT INSTABILITY
INDICATES A POSSIBILITY OF 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. THE GFS SHOWS LESS MOISTURE COMPARED TO THE ECMWF. THE
ECMWF KEEPS MUCH OF THE FORCING ASSOCIATED WITH THE FRONT WEST OF
THE FORECAST AREA THROUGH FRIDAY. THE GFS...ECMWF...AND EKD MOS
POPS ARE JUST 10 TO 20 PERCENT.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
VFR CONDITIONS EXPECTED THROUGH THE EARLY MORNING HOURS THEN MVFR
CIGS EXPECTED TO DEVELOP AFTER 12Z.

HIGH PRESSURE OVER THE AREA WILL GIVE WAY TO A WEAK LOW PRESSURE
SYSTEM LIFTING NORTH ALONG THE SOUTHEAST COAST. INCREASING
MOISTURE WILL RESULT IN THICKENING CLOUDS WHICH WILL LOWER THROUGH
THE NIGHT AS ISENTROPIC LIFTING BECOMES STRONGER. LATEST RADAR
COMPOSITE AND SURFACE OBS INDICATING LIGHT RAIN AFFECTING ALL TAF
SITES EARLY THIS MORNING. MVFR CIGS EXPECTED AFTER 12Z AS WEDGE
STRENGTHENS WITH SOUTHWESTERLY FLOW ALOFT AND NORTHEASTERLY SURFACE
WINDS. RAIN WILL TAPER OFF TOWARD THE END OF THE TAF PERIOD WHILE
MVFR CEILING RESTRICTIONS HOLD STEADY.

EXTENDED AVIATION OUTLOOK...WIDESPREAD LOW CLOUDS AND
PRECIPITATION EXPECTED SUNDAY NIGHT INTO MONDAY WITH ANOTHER GULF
COAST SYSTEM CROSSING THE REGION. YET ANOTHER SYSTEM WILL AFFECT
THE AREA TUESDAY NIGHT BRINGING POSSIBLE RESTRICTIONS WITH WINDY
CONDITIONS EXPECTED WEDNESDAY.

&&

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

$$






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