Area Forecast Discussion
Issued by NWS Columbia, SC

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000
FXUS62 KCAE 260753
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
353 AM EDT SUN APR 26 2015

.SYNOPSIS...A BACK DOOR COLD FRONT WILL MOVE THROUGH THE REGION
TODAY. DRY COOL HIGH PRESSURE WILL BUILD SOUTH INTO THE REGION
BEHIND THE FRONT FOR SUNDAY NIGHT THROUGH TUESDAY. MOISTURE RETURN
EXPECTED LATE TUESDAY AND WEDNESDAY.

&&

.NEAR TERM /TODAY/...
A GENERAL W TO WNW UPPER FLOW WILL CONTINUE OVER OUR REGION
TODAY. AT THE SURFACE...WEAK IN SITU WEDGE IN PLACE MAINLY TO OUR
NE OVER VA/NC AND INTO OUR EXTREME NE FORECAST AREA (FA). AREAS OF
DENSE FOG WILL BE POSSIBLE OVER OUR NE FA...MAINLY LANCASTER AND
CHESTERFIELD CO...THROUGH THE OVERNIGHT INTO MID SUNDAY MORNING.
WILL HAVE TO MONITOR FOR POSSIBLE DENSE FOG ADVISORY. COLD FRONT
OVER TENN WITH AREA OF LOW PRESSURE ALONG IT. CONVECTIVE ACTIVITY
SHIFTING SE INTO W NC...BUT TREND IS TOWARDS WEAKENING...BUT WILL
MAINTAIN SMALL POP NE FA LATE TONIGHT INTO SUN MORN. AS UPPER
ENERGY MOVES EAST FROM THE OHIO VALLEY INTO THE MID ATLANTIC
TODAY...THE FRONT...AND SURFACE WAVE RIDING ALONG IT...WILL SLOWLY
BACK DOOR TO THE SOUTH ACROSS OUR FA TODAY INTO THIS EVENING. THE
FRONT WILL PROVIDE A FOCUSING MECHANISM FOR AFTERNOON CONVECTION.
CHANCE POPS NEAR THE FRONT...DIURNALLY FAVORED...APPEARS
REASONABLE. SATELLITE WATER VAPOR IMAGERY INDICATES A LARGE
EXPANSE OF DRY AIR ALOFT MOVING INTO THE REGION. MOISTURE IS A
LIMITING FACTOR BUT PWAT VALUES SURGE TO NEAR 1.5 INCHES WITHIN
THE FRONTAL ZONE THIS AFTERNOON. MODELS INDICATING SUFFICIENT
INSTABILITY TODAY ALONG WITH CONSIDERABLE SHEAR. STRONG LOW LEVEL
WIND FIELDS WITH SUFFICIENT SHEAR TO SUPPORT SVR CONVECTION IF
STORMS INITIATE. COLD AIR ALOFT SHOULD LEAD TO STEEP LAPSE RATES
AND MODERATE INSTABILITY. STORM MOTION AROUND 310/30 KNOTS MAY
SUPPORT TRAINING OF STORMS IF THEY DEVELOP. DRY AIR ALOFT WOULD
INCREASE THE POTENTIAL FOR DOWNBURST WINDS AND HAIL WITH ANY
THUNDERSTORMS THAT DO FORM. ISOLATED TORNADO WITH STORMS NEAR THE
FRONTAL ZONE AND ENHANCED HELICITY CANNOT BE RULED OUT. SPC HAS
AREA IN MARGINAL RISK BUT THINK THIS COULD BE UNDERDONE.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/...
FRONT WILL PUSH TO OUR SOUTH TONIGHT. ANY ASSOCIATED CONVECTION
EXPECTED TO WEAKEN AND/OR PUSH TO OUR SOUTH EARLY TONIGHT. COOL AND
GENERALLY DRY AIR WILL FILTER INTO THE REGION BEHIND THE
FRONT...APPEARING TO PRECLUDE POPS LATE TONIGHT INTO MONDAY.
INCREASING HIGH LEVEL CLOUDINESS AHEAD OF THE NEXT SYSTEM POSSIBLE
BY LATE MON OR MON NT.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
LATEST GFS AND ECMWF IN GOOD AGREEMENT THAT CLOSED UPPER LOW TO
OUR WEST WILL OPEN AND SHIFT EASTWARD...LEADING TO SURFACE LOW
DEVELOPING AND RIDING EAST ALONG THE GULF COAST SPREADING MOISTURE
INTO OUR REGION LATE TUE OR TUE NT THROUGH WED/WED NT. BOTH MODELS
ALSO INDICATE NORTHERN STREAM UPPER LOW DIGGING INTO THE E CONUS
THURSDAY WILL GENERALLY STAY TO OUR NE. HOWEVER...SOME
UNCERTAINTIES EXIST REGARDING TIMING AND POSITION OF THESE
SYSTEMS. WILL MAINTAIN THE SMALL POP THURSDAY. BEHIND THESE
SYSTEMS...A NW UPPER FLOW WILL DIRECT A DRY HIGH PRESSURE CENTER
SE INTO OUR REGION LATE WEEK INTO NEXT WEEKEND.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
EVENING CONVECTION HAS SHIFTED EAST OF THE AREA AND DRIER AIR
ALOFT IS MOVING IN. SURFACE LOW PRESSURE IS MOVING EASTWARD ACROSS
THE NC/VA MOUNTAINS AND WILL CONTINUE TO SHIFT EAST ACROSS NC
THROUGH THE DAY. CURRENT SATELLITE IMAGERY SHOWS WIDESPREAD LIFR
STRATUS/FOG ON THE NORTHSIDE OF A NEARLY STATIONARY FRONT ACROSS
THE NORTHERN MIDLANDS. THIS FRONT AND RESTRICTIONS ARE EXPECTED TO
REMAIN NORTH OF THE TERMINALS OVERNIGHT BUT THERE HAVE BEEN SIGNS
OF POCKETS OF LOW CLOUDS DEVELOPING DUE TO NOCTURNAL COOLING AND
MOS GUIDANCE IS SUGGESTING A PERIOD OF MVFR/IFR CIGS IMPACTING THE
TERMINALS. CONFIDENCE IS LOW IN THE IFR CIGS DEVELOPING BUT WILL
CARRY A PERIOD OF MVFR CIGS 08Z-12Z. STRONG LOW LEVEL JET AROUND
35 KNOTS SHOULD PREVENT/LIMIT FOG DEVELOPMENT ALTHOUGH IT CANNOT
BE RULED OUT.

INCREASING PRESSURE GRADIENT AND STRONG LOW LEVEL WIND FIELD WILL
ALLOW STRONG MIXING TO OCCUR DURING THE DAY TODAY AND EXPECT
BREEZY WESTERLY WINDS AROUND 15 KNOTS WITH GUSTS AROUND 25 KNOTS.
STRONG INSTABILITY THIS AFTERNOON BUT LIMITED MOISTURE PRECLUDES
ANY MENTION OF TSRA IN THIS FORECAST THOUGH THERE IS REASON TO
BELIEVE ISOLATED TO SCATTERED STORMS MAY DEVELOP WITH DIURNAL
HEATING.


EXTENDED AVIATION OUTLOOK...NO SIGNIFICANT IMPACTS EXPECTED
MONDAY AND TUESDAY. AN APPROACHING WARM FRONT MAY RESULT IN
WIDESPREAD RESTRICTIONS WEDNESDAY.

&&

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

$$





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