Area Forecast Discussion
Issued by NWS Columbia, SC

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000
FXUS62 KCAE 020707
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
307 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/...
HIGH PRESSURE OFF THE COAST WILL CIRCULATE 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 A MID-LEVEL SHORTWAVE TROUGH SHOWN BY THE WATER VAPOR IMAGERY
IN THE LOWER MISSISSIPPI RIVER VALLEY 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. MOISTURE
APPEARS 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 /06Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS EXPECTED EARLY THIS MORNING. POSSIBLE MVFR CEILINGS
ACROSS THE AREA TOWARDS SUNRISE.

THE FRONTAL BOUNDARY REMAINS JUST SOUTH OF THE CENTRAL SAVANNAH
RIVER AREA EARLY THIS MORNING. MODELS BEGIN TO INDICATE RETURN
MOISTURE ALONG THE CSRA TOWARDS SUNRISE...WITH SCTD/PSBL BKN CLOUDS
AROUND 2000-3000 FT BY SUNRISE. 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. MVFR
CIGS POSSIBLE. SHOWERS SHOULD END BY LATE EVENING. LIGHT EASTERLY WINDS
EARLY WINDS EARLY THIS MORNING WILL VEER TO SOUTHERLY BY LATE
AFTERNOON.

EXTENDED AVIATION OUTLOOK...RESTRICTIONS POSSIBLE THURSDAY NIGHT
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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