Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 232108
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
508 PM EDT WED JUL 23 2014

.SYNOPSIS...
WEAK HIGH PRESSURE ATOP THE REGION WILL GIVE WAY TO A SURFACE FRONT
APPROACHING FROM THE NORTHWEST TONIGHT. THE FRONT IS EXPECTED TO
MOVE ACROSS THE CAROLINAS AND NORTH GEORGIA THURSDAY AFTERNOON AND
EVENING. HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT FOR FRIDAY AND
THE WEEKEND. ANOTHER FRONT IS EXPECTED TO PASS ON MONDAY.

&&

.NEAR TERM /THROUGH THURSDAY/...
AT 450 PM EDT...COVERAGE HAS EXPANDED EAST OF THE BLUE RIDGE TO
WARRANT BRIEF CATEGORICAL POP VALUES ACROSS THE NC FOOTHILLS BACK TO
THE IMMEDIATE ESCARPMENT AREAS. OUTFLOWS MAY DRIVE ADDITIONAL
CONVECTION FARTHER S INTO THE SRN FOOTHILLS AND PIEDMONT...SO CHC
POPS HAVE BEEN RAMPED UP THERE AS WELL THROUGH 7 PM. STILL
ANTICIPATE THAT THE STRONGEST STORMS WILL BE MAINLY MARGINAL FOR
SEVERE WIND AND HAIL AS DCAPE VALUES ARE NOT VERY HIGH IN THE BEST
COVERAGE AREAS AND THE PROFILES ARE QUITE WARM WITH FREEZING LEVELS
ABOVE 15 KFT. THE CONVECTION SHOULD WANE QUICKLY WITH THE LOSS OF
HEATING THIS EVENING...SO WILL LOWER POPS QUICKLY IN THE 23Z TO 02Z
TIMEFRAME.

AN UPPER TROUGH IS STILL FORECAST TO BECOME ESTABLISHED ACROSS THE
EASTERN U.S. ON THU AS A STRONG SHORT MOVES THROUGH THE GREAT LAKES.
THE ASSOCIATED SURFACE COLD FRONT CURRENTLY OVER OHIO VALLEY WILL
PUSH SOUTHEAST TO JUST NW OF THE NC MOUNTAINS BY 12Z THU....AND THEN
MOVE ACROSS THE REGION ON THU. WILL CONTINUE WITH THE IDEA THAT SOME
SHOWERS/THUNDERSTORMS COULD REACH THE MOUNTAINS BY SUNRISE.
GUIDANCE IS IN AGREEMENT THAT THE FRONT SHOULD BE ACCOMPANIED BY
NUMEROUS SHOWERS AND THUNDERSTORMS...EVEN OUTSIDE THE MOUNTAINS
WHERE WINDS THROUGH THE VERTICAL PROFILE ARE WESTERLY/DOWNSLOPE IN
NATURE. WILL BUY INTO THE HIGH POPS BEING ADVERTISED AS THE
SURFACE CONVERGENCE ALONG THE FRONT COMBINED WITH THE DIGGING UPPER
TROUGH/FALLING HEIGHTS WILL TAP INTO CAPES POOLING TO BETWEEN 1000-2000J
DURING THE AFTERNOON. SPC IS STILL JUST HIGHLIGHTING THE I-77
CORRIDOR EASTWARD WITH A 5% SEVERE THREAT ON THURSDAY. WITH
IMPROVING SHEAR...WOULD NOT BE SURPRISED TO SEE A FEW SEVERE STORMS
THURSDAY AFTERNOON. MAX TEMPS ON THU WILL BE TEMPERED BY CLOUDS AND
CONVECTION SO THEY SHOULD BE A COUPLE DEGREES LOWER THAN TODAY.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 200 PM WED...COLD FRONT WILL CONTINUE TO PUSH THRU THE PIEDMONT
THURSDAY EVENING...WITH AXIS OF DEEP UPPER TROUGH MOVING THRU EARLY
FRI. POPS WILL DECLINE EAST OF THE MTNS FOLLOWING THE END OF
HEATING...WITH LLVL CONVERGENCE UNLIKELY TO OVERCOME THE INHIBITION
RESULTING FROM POOR LAPSE RATES ABOVE THE PBL. PROFILES FROM THE
HIGHER TERRAIN HOWEVER DO SHOW THE EFFECTS OF MIDLEVEL CAA FOLLOWING
THE FRONT...THUS A SCHC POP IS KEPT INTO EARLY FRI MRNG. GOING
FORWARD HOWEVER...HIGH PRESSURE EXPANDS OUT OF THE MIDWEST WHICH
SHOULD PROVIDE AT LEAST A WEAK SUBSIDENCE INVERSION TO CAP OFF MOST
DEEP CONVECTION FRI AND SAT. THE NAM AND A PORTION OF THE SREF
MEMBERS DO NOT SHOW THE INVERSION BEING STRONG ENOUGH TO KEEP THE
ENTIRE CWFA DRY DURING THIS TIME. WILL ADVERTISE SCHC POPS OVER THE
BLUE RIDGE FRI AS WELL AS IN THE LOWER PIEDMONT...WELL SE OF
I-85...WHERE THE HIGH WILL HAVE THE LEAST INFLUENCE. THERE IS BETTER
CONSENSUS FOR A DRY FCST SATURDAY...THOUGH BY THAT TIME THE HIGH HAS
BECOME INDISTINCT DUE TO THE UPPER FLOW BECOMING NEARLY ZONAL. POPS
THUS COULD BE EASILY REINTRODUCED FOR SAT IN SUBSEQUENT FCST
PACKAGES. TEMPS DURING THE SHORT RANGE WILL RETURN TO NEAR NORMAL AS
THICKNESS VALUES INCREASE.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 1215 PM WEDNESDAY...DURING THE LATTER HALF OF THE UPCOMING
WEEKEND...DIURNALLY ENHANCED TSTM ACTIVITY HAS THE OPPORTUNITY TO
BECOME CONSIDERABLE ON SUNDAY WITHIN DEVELOPING LLVL RETURN FLOW
REGIME UNDERNEATH PROGRESSIVELY LOWERING UPPER HEIGHTS. L/WV TROUGH
AXIS IS PROGGED TO CONTINUE TO DIG INTO THE SE CONUS THROUGH
MONDAY...EVENTUALLY FORCING A COLD FRONT ACRS THE REGION BY MONDAY
NIGHT. WITH PRONOUNCED UPPER LEVEL TROUGH ACRS THE ERN CONUS AND
A CONTINENTAL AIRMASS OVERSPREADING THE REGION...A NOTABLY DRY AND
COOLER FCST IS ON TAP FOR TUESDAY AND WEDNESDAY.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...ALL CONVECTION THIS AFTN HAS THUS FAR REMAINED WELL NW OR
S OF THE AIRFIELD...AND THE LATEST HRRR RUN STILL DOES NOT SHOW MUCH
CONVECTIVE DEVELOPMENT IN IMMEDIATE AREA LATE THIS AFTERNOON. ..SO
WILL CONTINUE THE VCSH MENTION FOR NOW UNLESS ANY TS GETS CLOSER
THROUGH 00Z. OTHERWISE...THE NIGHT AND EARLY MORNING SHOULD BE QUIET
AND VFR. THE APPROACH OF A COLD FRONT ON THU WARRANTS A PROB30 FOR
TSRA AT THE END OF THE TAF PERIOD.

ELSEWHERE...FAIRLY SOLID COVERAGE HAS DEVELOPED FROM KAVL TO
KHKY...AND ALSO NEARING KGMU TO KGSP ON A SWD MOVING OUTFLOW.  THESE
SITES WILL GET TEMPO TSRA THROUGH LATE AFTN...WITH JUST VCTS
MENTIONED AT KAND. OTHERWISE...THE NIGHT SHOULD BE QUIET AND VFR.
THE EXCEPTION IS AT KAVL WHERE LIFR FOG WILL BE IN THE FORECAST
AGAIN FOR EARLY THU. AN APPROACH OF A COLD FRONT ON THU WARRANTS
PROB30 TSRA FOR THE END OF THE TAF PERIOD AT ALL SITES.

OUTLOOK... SHOWERS AND THUNDERSTORMS WILL END THURSDAY EVENING AS A
COLD FRONT MOVES SOUTHEAST OF THE AREA. FRIDAY AND SAT SHOULD BE
QUIET AND VFR...THE EXCEPTION WILL BE THE MOUNTAIN VALLEYS WHERE
EARLY MORNING FOG MAY OCCUR. THUNDERSTORMS WILL RETURN TO THE
FORECAST FOR SUNDAY AFTERNOON THROUGH MONDAY AS ANOTHER COLD FRONT
APPROACHES AND THEN MOVES THROUGH THE AREA ON MONDAY.

CONFIDENCE TABLE...

            21-03Z        03-09Z        09-15Z        15-21Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%
KAVL       HIGH  98%     HIGH  94%     MED   75%     HIGH  85%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  93%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%

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...CSH
NEAR TERM...HG/LG
SHORT TERM...WIMBERLEY
LONG TERM...CSH
AVIATION...HG/LG





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