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000
FXUS62 KGSP 191455
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1055 AM EDT SUN MAY 19 2013

.SYNOPSIS...
A WEAK UPPER LEVEL TROUGH WILL LINGER OVER THE REGION THROUGH
MONDAY...THEN WILL MOVE OFF TO THE EAST. THE FORECAST AREA WILL
REMAIN IN A MOIST AND RATHER UNSTABLE AIRMASS...BEFORE A COLD FRONT
CROSSES MOVES THROUGH LATE IN THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1040 AM...LARGE COMPLEX OF SHOWERS THAT DEVELOPED ALONG A
SPEED CONVERGENCE AXIS ASSOCIATED WITH W/SW LLJ CONTINUES TO
DISSIPATE OVER OUR SOUTHERN ZONES LATE THIS MORNING. MEANWHILE...THE
FOCUS FOR HEAVY RAINFALL IN THE NEAR TERM HAS SHIFTED WELL WEST OF
THE GSP CWFA...ACROSS NW/CTRL GEORGIA...AT THE LEADING EDGE OF THE
MORE ROBUST INSTABILITY. THE AFTERNOON CONVECTIVE PICTURE FOR OUR
CWFA IS NOMINALLY CLEARER THAN IT WAS YESTERDAY. WITH ONLY A FEW
PATCHY AREAS OF SHOWERS AROUND THIS MORNING...FAIRLY RAPID CLEARING
OF THE OVERCAST IS OCCURRING...ESP ACROSS THE NC MTNS. THIS SHOULD
ALLOW FOR MODERATE LEVELS OF INSTABILITY TO DEVELOP THIS
AFTERNOON...ALLOWING FOR GREATER COVERAGE OF SHOWERS AND STORMS
THAT WAS SEEN SATURDAY AFTERNOON. IT IS SOMEWHAT DIFFICULT TO
PINPOINT ANY PARTICULAR AREAS FOR HIGHER POPS...BUT SHORT TERM
MODELS DO INDICATE AN AREA OF LOW LEVEL CONVERGENCE/CONFLUENCE
SETTING UP OVER THE EASTERN ZONES THIS AFTERNOON...AND WE WILL FOCUS
80 POPS ACROSS THIS AREA. ONCE AGAIN...AN ISOLATED SEVERE STORM
CANNOT BE RULED OUT...BUT HEAVY/LOCALLY EXCESSIVE RAINFALL WILL
CONTINUE TO BE THE PRIMARY THREAT. CURRENT INDICATIONS ARE THE MOST
LIKELY AREA FOR HEAVY RAINFALL WILL BE ACROSS THE EASTERN ZONES...
WHERE LOW LEVEL CONFLUENCE COULD AID AND ABET TRAINING OF CELLS...
AND SLIGHTLY ENHANCED LOW LEVEL SHEAR COULD ALSO PROMOTE SOME DEGREE
OF MESOSCALE ORGANIZATION. HOWEVER...CONSIDERING THE UNCERTAINTY IN
THIS EVOLUTION...AS WELL AS THE FACT THAT FFG/S ARE VERY HIGH IN
THOSE AREAS...DON/T THINK I CAN JUSTIFY ISSUANCE OF A WATCH IN THIS
OR ANY OTHER AREA DURING THE AFTERNOON.

AS OF 655 AM...LARGE AREA OF CONVECTION OVER THE SAV RIVER VALLEY
WILL SLIDE SE THRU THE MORNING. ADDITIONAL CONVECTION MOVES INTO THE
MTNS DURING THE MORNING AS SHRA SLOWLY INCREASE THRU THE MORNING
ELSEWHERE. EXPECT WIDESPREAD SHRA BY AFTERNOON WITH INCREASING CHC
OF TSRA. STILL EXPECTING SOME AREAS OF HEAVY RAIN THRU THE MORNING.

SHORT WAVE ROTATING THRU THE OPEN WAVE OF AN UPPER LOW CROSSES THE
AREA TODAY. A SLY LOW LEVEL JET MOVES ACROSS AT LEAST THE SRN
PORTION OF THE CWFA AS WELL. THESE FEATURES WILL COMBINE WITH THE
MOIST UNSTABLE AIR MASS ALREADY IN PLACE TO PRODUCE WIDESPREAD
SHOWERS AND THUNDERSTORMS. STORMS WITH HEAVY RAINFALL ON THE NOSE OF
THE LOW LEVEL JET ARE MOVING TOWARD THE ARE ACROSS GA. HOWEVER...
THERE IS A DEFINITE SELY TRAJECTORY TO THE STORMS WITH THE HEAVIEST
RAINFALL. THAT SAID...STORMS WITH HEAVY RAINFALL COULD DEVELOP
ALMOST ANYWHERE OVER THE CWFA. THIS PRESENTS NO EASY WAY TO HANDLE
ANY WATCH ISSUANCE. TRYING TO PICK ONE AREA OVER ANOTHER MAY LEAD TO
LESS CONCERN OVER ANOTHER AREA WHERE FLOODING COULD DEVELOP. ISSUING
FOR THE ENTIRE CWFA WILL CERTAINLY BE TOO BROAD. THEREFORE...WILL
JUST CONTINUE THE MENTION IN THE HWO. MAY STILL SEE AN ISOLATED SVR
STORM THIS AFTERNOON GIVEN MODERATE DEEP INSTABILITY AND SOME SHEAR
WITH THE JET.

EXPECT CONVECTION TO DIMINISH OVERNIGHT AS THE FORCING MOVES EAST OF
THE AREA. HOWEVER...THE FLOOD AND SVR THREAT WILL INTO THE EVENING.
LOWS WILL BE 5 TO 10 DEGREES ABOVE NORMAL.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AT 300 AM EST SUNDAY...ON MONDAY THE UPPER TROUGH AXIS WILL MOVE
SLOWLY OVER THE INTERSTATE 77 CORRIDOR. THE GFS BRINGS THIS
WEAKENING UPPER FEATURE EAST OF OUR AREA ON MONDAY NIGHT AS AN UPPER
RIDGE ARRIVES...WHILE THE NAM LEAVES IT ALMOST STATIONARY. ON
TUESDAY THE GFS RIDGE AXIS REACHES THE SPINE OF THE APPALACHIANS.

ON MONDAY AS THE UPPER TROUGH AXIS MOVES EAST...DRIER AIR ALOFT WILL
MOVE IN FROM THE EAST...INSTABILITY AND SHEAR INCREASE...SUPPORTING
MORE OF A CONVECTIVE MODE...EVEN AS COVERAGE GRADUALLY DECREASES.
SHEAR WILL DECREASE ON MONDAY NIGHT. TUESDAY FEATURES LESS SHEAR...
BUT EVEN GREATER INSTABILITY...AND MORE DRY ARI ALOFT AND BENEATH
THE CLOUD LAYER...SUPPORTING EVAPORATIVE COOLING AND DOWNDRAFT
PRODUCTION. INSTABILITY IS SLOW TO WANE ON TUESDAY NIGHT.
TEMPERATURES WILL TREND UPWARD FROM MONDAY TO TUESDAY...REACHING
ABOVE NORMAL VALUES...AS HEIGHTS RISE ALOFT.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AT 300 AM EST SUNDAY...AN UPPER RIDGE AXIS WILL CROSS THE EASTERN
SEABOARD ON WEDNESDAY...WHILE AND UPPER TROUGH CROSSES THE MS RIVER
VALLEY. THE TROUGH CROSSES THE OH AND TN VALLEYS ON THURSDAY...AND
CROSSES THE CENTRAL AND SOUTHERN APPALACHIANS ON FRIDAY. ON SATURDAY
THE ECMWF MOVES ITS TROUGH AXIS SLOWLY OFF THE COAST...WHILE THE GFS
TROUGH AXIS REMAINS ALONG THE EAST COAST.

THE CAROLINAS AND GA REMAIN IN A WARM AND MOIST AIR MASS ON
WEDNESDAY AND THURSDAY. BOTH THE ECMWF AND GFS SHOW ATLANTIC
MOISTURE MOVING INTO THE SOUTHERN APPALACHIANS IN AN EASTERLY
UPSLOPE COMPONENT WEDNESDAY...AND MOISTURE ASSOCIATED WITH A FORMER
COLD FRONT CONVERGING WITH THE ATLANTIC MOISTURE ON WEDNESDAY NIGHT.
THE MODELS ALSO SHOW A WEAK SURFACE LOW MOVING UP THE FLORIDA
PENINSULA...FEEDING MORE ATLANTIC MOISTURE INTO THE GA AND CAROLINA
COASTS. THE MODELS DIFFER ON WHETHER THE REMAINS OF THE OLD FRONT
WILL SWEEP EAST OF OUR AREA ON THU. THE ECMWF SUPPORTS DOES SO...
MOVING MOISTURE OUT OF OUR AREA...WHILE THE GFS KEEPS MOISTURE OVER
OUR AREA UNTIL THE SURFACE LOW MOVES OFF TO THE NE ON FRI. A COLD
FRONT WILL APPROACH FROM THE NW ON THURSDAY NIGHT...CROSSING OUR
AREA ON FRIDAY. SATURDAY WILL FEATURE COOL AND DRY HIGH PRESSURE
BUILDING IN FROM THE NORTH. TEMPERATURES WILL COOL FROM SLIGHTLY
ABOVE NORMAL ON WEDNESDAY TO AROUND NORMAL LATER IN THE WEEK AS
HEIGHTS FALL ALOFT.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
AT KCLT AND ELSEWHERE...A WEAK UPPER WAVE WILL CROSS THE REGION.
WIDESPREAD SHRA WITH ISOLATED TSRA NEAR THE WRN SITES WILL MOVE EAST
TO THE ERN SITES BY LATE MORNING OR EARLY AFTERNOON. CIGS AND VSBY
ARE ALREADY LOW AND WILL SLOWLY INCREASE THRU THE DAY TO VFR.
RESTRICTIONS WILL BE LIMITED TO CONVECTION DURING THE AFTERNOON AND
EVENING. HOWEVER...IFR CIGS WILL RETURN AFTER MIDNIGHT. S TO SW
WINDS WILL CONTINUE THRU THE PERIOD.

OUTLOOK...SHOWERS AND THUNDERSTORMS...AND ASSOCIATED RESTRICTIONS...
WILL PERSIST THROUGH MONDAY. FAIR WEATHER MAY RETURN BY TUESDAY.

CONFIDENCE TABLE...

            15-21Z        21-03Z        03-09Z        09-15Z
KCLT       HIGH 100%     HIGH  95%     HIGH  93%     HIGH  96%
KGSP       HIGH  90%     HIGH  91%     HIGH  82%     MED   75%
KAVL       HIGH  91%     HIGH  96%     MED   74%     MED   75%
KHKY       HIGH  91%     HIGH  95%     HIGH  91%     MED   78%
KGMU       HIGH  93%     HIGH  93%     HIGH  83%     MED   75%
KAND       HIGH  95%     HIGH  96%     MED   78%     MED   75%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE
HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE
FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

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

&&

$$
SYNOPSIS...JAT
NEAR TERM...JDL/RWH
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...RWH