Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 261432
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1032 AM EDT TUE APR 26 2016

.SYNOPSIS...
OFFSHORE ATLANTIC HIGH PRESSURE WILL PERSIST OVER THE SOUTHEAST
THROUGH MIDWEEK. THEN...A WEAK COLD FRONT WILL ARRIVE FROM THE
NORTHWEST ON THURSDAY. WEAK HIGH PRESSURE WILL RETURN BRIEFLY ON
FRIDAY...AS A LOW PRESSURE SYSTEM APPROACHES FROM THE WEST OVER THE
WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1025 AM...CLOUD COVER HAS INCREASED SIGNIFICANTLY ACROSS THE
MOUNTAINS THIS MORNING BUT REMAINS MORE SCATTERED OR EVEN
NON-EXISTENT ELSEWHERE. STILL EXPECT A GOOD CU FIELD TO DEVELOP FOR
THE AFTERNOON. PREVIOUS GUIDANCE SUGGESTED MODERATE INSTABILITY
WOULD DEVELOP ACROSS THE MOUNTAINS AND I-40 CORRIDOR TODAY WITH MUCH
LOWER NUMBERS TO THE SOUTH WITH A CAP IN PLACE. 12Z RAOBS FROM
KGSO...KFFC AND FROM THE UNCA CAMPUS SUGGEST INSTABILITY MAY BE
LOWER THAN FORECAST WITH WARMER MID LEVEL TEMPS AND A LOW LEVEL
INVERSION EVEN ACROSS THE NORTHERN PORTIONS OF THE CWFA. THE HOURLY
UPDATING CAM GUIDANCE IS SHOWING A TREND FAVORING THE SOUTHERN CWFA
OR JUST THE SOUTHWESTERN MOUNTAINS...WHILE THE LATEST SYNOPTIC SCALE
GUIDANCE CONTINUES TO FAVOR THE NORTHERN SECTIONS. GIVEN THE
DISCREPANCIES...WILL KEEP FORECAST COVERAGE AND PLACEMENT AS IS FOR
NOW. MAXES WILL REACH 5 TO 10 DEGREES ABOVE CLIMO THROUGHOUT.

THE MESOSCALE MODELS DEVELOP QUITE A BIT OF CONVECTION ALONG THE
BACK DOOR FRONT APPROACHING THROUGH THE VIRGINIAS LATE TODAY THROUGH
TONIGHT...BUT GENERALLY HAVE COVERAGE DIMINISHING AS ANY ATTENDANT
CONVECTION APPROACHES THE NORTHERN TIER OF THE FORECAST AREA
TONIGHT. WILL KEEP ANY LINGERING ISOLATED TO SCATTERED CONVECTION
CONFINED TO THE NORTHERN TIER AND THE MOUNTAINS TONIGHT.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 245 AM TUESDAY...A FLAT UPPER RIDGE WILL HOLD SWAY ACROSS THE
SOUTHEAST STATES DURING THE SHORT TERM...WITH SOME INCREASE IN FLOW
AND VORT ENERGY STREAMING THRU ON THURSDAY. AT THE SFC...HIGH
PRESSURE OFF THE EAST COAST WILL CONTINUE TO SUPPLY LLVL MOISTURE
INTO THE REGION. SO MODELS SHOW INCREASING INSTBY WEDNESDAY
AFTN...WITH THURSDAY LOOKING LIKE THE MOST UNSTABLE DAY. EXPECT BEST
COVERAGE ACRS THE MTNS ON WEDNESDAY...WHERE UPSLOPE AND DIFFERENTIAL
HEATING WILL SUPPLY SOME CONVERGENCE. ON THURSDAY...A WEAK COLD
FRONT IS PROGGED TO ENTER THE AREA IN THE AFTN. SO BETTER COVERAGE
EVEN EAST OF THE MTNS IS EXPECTED. SHEAR WILL BE MARGINAL FOR
ORGANIZING SOME UPDRAFTS THURSDAY...ON THE ORDER OF 30 KTS UP TO 6
KM. SO A SEVERE TSTM OR TWO WILL BE POSSIBLE. TEMPS WILL BE WELL
ABOVE NORMAL ACRS THE ENTIRE AREA...WITH HIGHS IN THE 80S AND LOWS
IN THE 60S ACRS THE PIEDMONT.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 315 AM TUESDAY...DRY NWLY LLVL FLOW AND WEAK CAA WILL DEVELOP
ATOP THE CWFA BEYOND THE FRONT BY DAYBREAK FRIDAY...MAKING FOR A DRY
DAY. TEMPS WILL ACTUALLY BE SLIGHTLY WARMER IN THE LOWER ELEVATIONS
THANKS TO DOWNSLOPE NEGATING THE CAA. HIGHS IN THE MID TO UPR 80S IS
EXPECTED ACRS THE PIEDMONT...AND IN THE UPR 70S TO AROUND 80 IN THE
MTN VALLEYS.

THE DRY WEATHER WILL BE SHORTLIVED...AS MODELS AGREE THAT THE UPPER
RIDGE WILL AMPLIFY AND SHIFT EAST...BRINGING INCREASING DEEP-LAYER
SWLY FLOW ACRS THE REGION. AT THE SFC...DRY HIGH PRES WILL WEDGE SWD
EAST OF THE APPALACHIANS BY SATURDAY MORNING...WITH MODELS STILL IN
DISAGREEMENT ON HOW FAST MOISTURE RETURNS ATOP THE WEDGE. THE GFS
HAS CLOUDS AND QPF INCREASING BY SATURDAY EVENING...WHILE THE ECMWF
DOES NOT HAVE MUCH POP UNTIL SUNDAY EVENING. SO WILL CONTINUE TO
ADVERTISE A COOLING TREND WITH GRADUAL INCREASE IN CLOUDS AND
POPS...WITH HIGHEST POPS ON SUNDAY. MOIST UPGLIDE WILL CONTINUE
THRU MONDAY AS LLVL FLOW TURNS OUT OF THE SW. SO WILL CONTINUE WITH
SOLID CHANCE POPS WITH NEAR NORMAL HIGH TEMPS AND ABOVE NORMAL LOWS.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
AT KCLT...SAT PIX SHOW LITTLE IN THE WAY OF LOW CLOUDS NEAR THE
AIRFIELD...BUT THERE IS SOME DEVELOPMENT UPSTREAM. WILL GO WITH FEW
LOW VFR BECOMING SCT HIGH BASED VFR IN RESPONSE. SOME LOW END S TO
SW GUSTS ARE EXPECTED DURING THE PERIOD OF BEST MIXING THIS
AFTERNOON. ANY CONVECTION WITH THE BACK DOOR COLD FRONT THROUGH THE
VIRGINIAS TONIGHT SHOULD STAY WELL NORTH OF THE AIRFIELD.

ELSEWHERE...STRATOCUMULUS BECOMING BKN ACROSS THE MOUNTAINS WITH
MAINLY VFR...BUT SOME SPOTTY MVFR LEVEL CLOUDS DEVELOPING ACROSS THE
FAR SOUTHERN CWFA. EXPECT THESE CLOUDS TO LIFT WITH MAINLY SCATTERED
VFR CUMULUS THROUGH THE AFTERNOON. ANY THUNDER CHANCES LOOK BEST AT
KAVL LATE IN THE DAY...WITH VCSH NEAR KHKY AS THE BACK DOOR FRONT
APPROACHES TONIGHT. EXPECT MAINLY S TO SW SURFACE WINDS...EXCEPT
TOGGLING NW AT KAVL IN THE FRENCH BROAD VALLEY FOR A PERIOD EARLY
TODAY.

OUTLOOK...INSTABILITY WILL INCREASE ACROSS THE REGION THROUGH
WEDNESDAY AS A BACK DOOR FRONT STALLS TO THE NORTH. PRECIPITATION
CHANCES AND ASSOCIATED RESTRICTIONS SHOULD INCREASE INTO THURSDAY
AHEAD OF A COLD FRONT APPROACHING FROM THE NORTHWEST. SOME DRYING IS
EXPECTED ON FRIDAY BEFORE UNSETTLED WEATHER RETURNS FROM THE WEST
OVER THE WEEKEND.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  91%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  81%     HIGH 100%     HIGH 100%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...ARK
NEAR TERM...HG/RWH
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...HG/RWH



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