Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 021011
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
611 AM EDT THU APR 2 2015

.SYNOPSIS...
A WEAK WARM FRONT EXTENDING THROUGH GEORGIA TODAY WILL DISSIPATE
TONIGHT. A COLD FRONT APPROACHING FROM THE NORTHWEST WILL MOVE
THROUGH THE FORECAST AREA SATURDAY MORNING. DRY HIGH PRESSURE
BEHIND THIS FRONT WILL DOMINATE SUNDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
EVIDENT BY LOW CLOUDINESS THAT HAS DEVELOPED IN THE SOUTH PART OF
THE FORECAST AREA EARLY THIS MORNING...HIGH PRESSURE OFF THE
VIRGINIA AND NORTH CAROLINA COAST IS CIRCULATING INCREASED LOW-
LEVEL MOISTURE INTO THE FORECAST AREA. THE NAM AND GFS DISPLAY A
WEAK WARM FRONT IN GEORGIA WITH ISENTROPIC UPGLIDE IN THE
FORECAST AREA. THE MODELS SHOW THE GREATER LIFT IN THE WEST PART
OF THE FORECAST AREA. THERE WILL ALSO BE AN INCREASE IN MOISTURE
AND INSTABILITY ASSOCIATED WITH THE MID-LEVEL SHORTWAVE TROUGH
SHOWN BY THE WATER VAPOR IMAGERY IN THE LOWER MISSISSIPPI RIVER
VALLEY EARLY THIS MORNING WHICH SHOULD AFFECT THE FORECAST AREA
THIS AFTERNOON INTO THE EVENING. THIS SUPPORT PLUS HEATING SHOULD
LEAD TO SHOWERS AND THUNDERSTORMS. THE MODELS SHOW MOISTURE
REMAINING SOMEWHAT SHALLOW WHICH SHOULD LIMIT COVERAGE. WE KEPT
POPS IN THE CHANCE CATEGORY WITH THE GREATEST CHANCE IN THE WEST
PART. THE SPC WRF AND ARW DISPLAY THE GREATEST SHOWER OR
THUNDERSTORM COVERAGE IN THE WEST PART OF THE FORECAST AREA DURING
THE 500 PM TO 900 PM TIME FRAME. THE LATEST ANALYSIS SHOWED H5
TEMPERATURES -15 TO -16. THE MODELS INDICATED MODERATE TO STRONG
INSTABILITY THIS AFTERNOON. THE NAM HAD A TOTAL TOTALS AROUND 52
AND SURFACE-BASED LI -2 TO -5 WITH THE GREATEST INSTABILITY IN THE
SOUTH PART. THE MODEL INDICATED A WET BULB ZERO HEIGHT OF 8000 TO
9000 FEET. SHEAR WAS MARGINAL WITH H85 WINDS AROUND 25 KNOTS.
BASED MAINLY ON THE INSTABILITY...SEVERE THUNDERSTORMS MAY
OCCUR...BUT THE THREAT APPEARS LIMITED BY SHALLOW MOISTURE AND THE
MODEL FORECAST SOUNDINGS INDICATE SKINNY CAPE. THE SHOWER AND
THUNDERSTORM CHANCE SHOULD DIMINISH OVERNIGHT WITH THE LOSS OF
HEATING AND UPPER-LEVEL LIFT SHIFTING EAST OF THE AREA. WE USED
THE GUIDANCE CONSENSUS FOR THE TEMPERATURE FORECAST TODAY AND
TONIGHT.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
THE NAM AND GFS INDICATE LESS ISENTROPIC LIFT FRIDAY WITH THE WEAK
WARM FRONT DISSIPATED. MOISTURE APPEARS MORE SHALLOW IN THE WAKE
OF A MID-LEVEL SHORTWAVE TROUGH. FORCING ASSOCIATED WITH THE
APPROACHING COLD FRONT SHOULD REMAIN NORTHWEST OF THE AREA. THE
NAM...GFS...AND ECMWF MOS HAVE POPS LESS THAN 20 PERCENT. WE KEPT
THE FORECAST DRY. IT WILL BE WARM JUST AHEAD OF THE COLD FRONT AND
THE WARMER TEMPERATURE GUIDANCE IS USUALLY BEST WITH THIS PATTERN.

CONVERGENCE AHEAD OF THE COLD FRONT SUPPORTS A CHANCE OF SHOWERS
AND THUNDERSTORMS FRIDAY NIGHT. THE MODELS HAVE BEEN CONSISTENT
HOLDING BACK THE DEEPER MOISTURE ASSOCIATED WITH THE FRONT UNTIL
TOWARD MORNING. SHEAR WILL BE STRONG. THE MODELS SHOW H85 WINDS 40
TO 50 KNOTS. HOWEVER...A LACK OF SIGNIFICANT INSTABILITY SHOULD
LIMIT THE SEVERE THUNDERSTORM THREAT. THE NAM KEEPS SURFACE-BASED
LI/S ABOVE ZERO AND THIS APPEARS REASONABLE BASED ON JUST WEAK
UPPER-LEVEL LIFT AND NOCTURNAL COOLING. USED THE WARMER TEMPERATURE
GUIDANCE FRIDAY NIGHT BECAUSE OF MIXING AHEAD OF THE FRONT.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
CONVERGENCE ASSOCIATED WITH THE COLD FRONT SUPPORTS A CONTINUED
SHOWER OR THUNDERSTORM CHANCE SATURDAY MORNING. DRYING BEHIND THE
FRONT SHOULD DOMINATE DURING THE AFTERNOON. USED THE WARMER
TEMPERATURE GUIDANCE SATURDAY BECAUSE OF A RELATIVELY WARM START
AND DOWNSLOPE FLOW DURING THE AFTERNOON.

THE HIGH PRESSURE CENTER BEHIND THE FRONT SHOULD BE NEAR THE
FORECAST AREA BY LATE SATURDAY NIGHT. EXPECT MOSTLY CLEAR SKIES
AND LIGHT WINDS WITH STRONG NOCTURNAL COOLING. THE GFS AND ECMWF
MOS HAVE LOWS IN THE UPPER 30S TO AROUND 40. THE DRY AIR MASS
SHOULD REMAIN IN PLACE THROUGH SUNDAY AND THE MOS HAS HIGHS NEAR
70.

THE HIGH WILL BE OFF THE COAST MONDAY THROUGH WEDNESDAY. THE MODELS
INDICATE AN ASSOCIATED ONSHORE FLOW PLUS ISENTROPIC LIFT IN THE
FORECAST AREA. THE GFS HAS TRENDED WITH MORE MOISTURE MONDAY WITH
LESS ISENTROPIC LIFT TUESDAY AND WEDNESDAY. AN AVERAGE OF THE GFS
AND ECMWF MOS POPS PLUS GFS ENSEMBLE MEAN SUPPORT POPS OF 20 TO
30 PERCENT MONDAY THROUGH WEDNESDAY.

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS EXPECTED EARLY THIS MORNING. MVFR CEILINGS ACROSS THE
CSRA UNTIL AROUND 14Z.

THE FRONTAL BOUNDARY REMAINS JUST SOUTH OF THE CENTRAL SAVANNAH
RIVER AREA EARLY THIS MORNING. LATEST 11U-3.9U SATELLITE LOOP SHOWING
RETURN MOISTURE ALONG THE CSRA. MVFR CIGS AT AGS/DNL UNTIL AROUND
14Z THIS MORNING. BY 14Z...VFR ACROSS THE AREA UNTIL LATE AFTERNOON.
WARM FRONT WILL APPROACH FROM THE SW LATER TODAY WITH SHOWERS
POSSIBLE LATE AFTERNOON INTO THE EARLY EVENING WITH SOME MVFR CIGS.
SHOWERS SHOULD END BY LATE EVENING BUT EXPECT MVFR/POSSIBLE IFR CIGS
TO PERSIST DURING THE PRE-DAWN HOURS FRIDAY.  LIGHT EASTERLY WINDS EARLY
WINDS EARLY THIS MORNING WILL VEER TO SOUTHERLY BY LATE AFTERNOON.

EXTENDED AVIATION OUTLOOK...RESTRICTIONS POSSIBLE FRIDAY THROUGH
FRIDAY NIGHT AS FRONTAL BOUNDARIES MOVE THROUGH THE REGION DURING
THE PERIOD.

&&

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

$$





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