Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 091704
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
104 PM EDT WED JUL 9 2014

.SYNOPSIS...
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP TODAY IN
THE MOIST AIR MASS AHEAD OF A COLD FRONT ENTERING THE REGION. THAT
FRONT WILL STALL OVER THE AREA TONIGHT AND ENHANCE PRECIPITATION
CHANCES THURSDAY BEFORE WEAKENING FRIDAY. WEAK HIGH PRESSURE WILL
RETURN THROUGH THE WEEKEND BEFORE ANOTHER COLD FRONT APPROACHES THE
AREA EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AT 1215PM...RADAR RETURNS INCREASING TO THE SOUTH AND WEST AND
EXPECT THAT AS A WEAK S/W TRAVERSES THE AREA THAT COVERAGE OF
SHOWERS/STORMS WILL CONTINUE TO INCREASE. SBCAPES HAVE INCREASED TO
OVER 2000J/KG OVER A LARGE PORTION OF THE UPSTATE AND CLT METRO
AREA. SCATTERED THUNDERSTORMS HAVE DEVELOPED OVER THE SOUTHERN
UPSTATE APPARENTLY IN AN AREA OF DIFFERENTIAL HEATING CAUSED BY
CLOUDS TO THE N. HAVE UPDTATED POPS TO REFLECT THIS ACTIVITY.

AS OF 1015 AM...NOT MANY ECHOES ON RADAR AT MID MORNING.
HOWEVER...CAMS, 12Z NAM AND RAP ALL INDCIATE THAT COVERAGE WILL
INCREASE THIS AFTERNOON AS ATMOSPHERE DESTABLIZES WITH AFTERNOON
HEATING. RAP INDICATES A WEAK SHORT WAVE OVER EASTERN TN WHICH MOVES
THROUGH THE WESTERN CAROLINAS AND NE GA BY 00Z. THIS SHOULD
PROVIDE JUST ENOUGH UPPER FORCING TO PRODUCE SCT TO EVEN NUMEROUS
SHOWERS/THUNDERSTORMS. OUR LOCAL CAMPOP GUIDANCE SHOWS THE BEST
COVERAGE NORTH OF I-85 THIS AFTERNOON WITH THE ACTUAL HIGHEST POPS
OVER THE NC FOOTHILLS/NC PIEDMONT. HAVE ADJUSTED THE POP GRIDS TO
DEPICT THAT GENERAL SCENARIO BY BLENDING CAMPOP/CONSSHORT. CAN`T
RULE OUT A FEW STORMS THAT WILL PRODUCE SOME GUSTY WINDS/HAIL...BUT
THE OVERALL SEVERE THREAT IS ON THE LOW SIDE AS SHEAR IS
UNIMPRESSIVE. BLENDED IN THE LATEST CONSHORT DATA TO ADJUST
TEMPS/DEWPOINTS WINDS. THIS GENERALLY LOWERED MAX TEMPS BY A DEGREE
OR TWO DUE TO A BIT MORE CLOUDINESS.

PREVIOUS DISCUSSION:
THERE IS VERY LITTLE ONGOING CONVECTIVE ACTIVITY IN OR IMMEDIATELY
UPSTREAM OF THE CWA...NOT SURPRISING CONSIDERING THAT THE AREA IS
WITHIN AN INSTABILITY MINIMUM. NEVERTHELESS...THERE IS STILL SOME
WEAK BUOYANCY UPSTREAM OVER THE TENN VALLEY...AND LATEST KGSP VAD
WIND PROFILE IS CONFIRMING A STOUT 25 TO 35 KTS OF WESTERLY FLOW
ABOVE ABOUT 2 KFT. IN ADDITION...SCATTERED SHOWERS WERE DEVELOPING
AT 07Z ALONG THE WINDWARD SIDE OF THE CUMBERLAND PLATEAU...WHICH
WOULD PROBABLY ARRIVE IN THE FAR WESTERN NC MTNS BY THE START OF THE
PERIOD. WE WILL CONTINUE TO RAMP POPS UP TO HIGH CHANCE ACROSS THE
TENN BORDER COUNTIES BY SUNRISE.

OTHERWISE...THE CONVECTIVE SETUP FOR LATER TODAY LEAVES MUCH TO BE
DESIRED. THE FRONTAL ZONE...SUCH AS IT IS...IS STILL DRAPED FROM THE
OHIO VALLEY W/SW TOWARD THE ARKLATEX. IN OTHER WORDS...IT HAS A LONG
WAY TO GO TO BE A PLAYER IN CONVECTIVE CHANCES ACROSS OUR AREA THIS
AFTERNOON. IN FACT...IT MAY TURN OUT THAT THE MAIN FOCUS (OTHER THAN
THE USUAL TERRAIN/DIFFERENTIAL HEATING EFFECTS) MAY BE A LEE SIDE
TROUGH...BUT EVEN THAT MAY BE MORE OF A CONCERN FOR AREAS JUST TO
OUR EAST. ADDITIONALLY...THERE IS A FAIRLY STRONG SIGNAL IN THE
LATEST MODEL GUIDANCE...AND IN OBSERVATIONAL TRENDS...THAT PESKY
MID/HIGH LEVEL CLOUDS WILL HINDER DIURNAL DESTABILIZATION. IN
FACT...FOR THIS VERY REASON THE MAX TEMP FORECAST IS 2-4 DEGREES
LOWER THAN WHAT WE HAVE SEEN THE PAST COUPLE OF DAYS. FINALLY...
WHILE PROFILES WILL BE MOISTENING CONSIDERABLY...FORECAST PWATS ARE
ONLY 1-2 STANDARD DEVIATIONS ABOVE CLIMO. ALL THINGS CONSIDERED...
HAVE ESSENTIALLY OPTED FOR A SHOTGUNNED 40-50 POPS ACROSS THE CWA...
WITH A SMALL AREA OF LIKELY ACROSS THE SOUTHWEST MTNS...WHICH WILL
HAVE THE BENEFIT OF A CONTINUED (ALBEIT WEAKENING) W/SW UPSLOPE
FLOW. IN TERMS OF THE SEVERE THREAT...MODEST INSTABILITY/MOIST
PROFILES AND WEAKENING SHEAR SHOULD LIMIT THE POTENTIAL
CONSIDERABLY. HOWEVER...THE PIEDMONT WILL HAVE TO BE WATCHED
CLOSELY...ESPECIALLY IF INSOLATION/HEATING IS MORE SIGNIFICANT THAN
EXPECTED.

THE FRONTAL ZONE WILL FINALLY SETTLE INTO THE AREA TONIGHT...BUT BY
THAT TIME...WITH WIND PROFILES WEAKENING AND MODEST AT BEST
NOCTURNAL INSTABILITY...SUSPECT IT WILL BE DIFFICULT TO GET MUCH
MORE THAN SCATTERED CONVECTION FOR TOO LONG PAST MID-EVENING OR SO.
MIN TEMPS WILL REMAIN ABOVE CLIMO UNDER CONSIDERABLE CLOUD
COVER.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 100 PM WEDNESDAY...THE SHORT TERM PERIOD INITIALIZES THURSDAY
EVENING WITH A QUASI STATIONARY FRONTAL BOUNDARY POSITIONED JUST
SOUTH OF INTERSTATE 85 INTO THE MIDLANDS OF SC...NORTHEASTWARD INTO
CENTRAL NC.  SCATTERED CONVECTION WILL LIKELY BE ONGOING AS HEATING
WILL HAVE STEEPENED LAPSE RATES IN PROXIMITY TO THE SURFACE
BOUNDARY...WHICH WILL PROVIDE A FOCUS FOR SAID CONVECTION.
MEANWHILE...POSITIVELY TILTED UPPER TROF WILL BE LIFTING TO THE
NORTHEAST ALLOWING HEIGHTS TO RISE WITH POPS TAPERING DOWN INTO
FRIDAY MORNING.  LATEST GUIDANCE INDICATES WEAK MESOLOW DEVELOPMENT
ALONG THE FL PANHANDLE ON FRIDAY MORNING ALLOWING FOR ENHANCED
SOUTHEASTERLY FLOW INTO THE CAROLINAS.  THIS COMBINED WITH FLOW
AROUND THE WESTERN ATLANTIC SURFACE RIDGE WILL ALLOW THE STALLED
FRONTAL BOUNDARY TO GRADUALLY LIFT NORTHWARD TOWARDS THE SOUTHERN
APPS INTO THE LATE AFTERNOON HOURS.  MOISTURE CONVERGENCE ALONG THIS
BOUNDARY WILL PROVIDE A FOCUS FOR CONVECTION ACROSS THE NC/SC
PIEDMONT ON FRIDAY AFTERNOON WHERE STEEPENING LAPSE RATES AND
INCREASED MOISTURE YIELD SBCAPE VALUES IN EXCESS OF 1500J/KG.  THUS
WILL FAVOR LOW END CHANCE LEVEL POPS ACROSS THE PIEDMONT...AND ALSO
ALONG THE HIGH TERRAIN WHERE EAST SOUTHEAST UPSLOPE FLOW AIDS
CONVECTION.  SLIGHT CHANCE POPS WILL OVERSPREAD THE REMAINDER OF THE
FORECAST AREA.

SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD ACROSS THE NORTHEAST
INTO THE WEEKEND...AND WILL EXTEND SOUTHWARD INTO THE
SOUTHERN/CENTRAL APPS.   THIS COMBINED WITH RISING HEIGHTS ALOFT
WILL LIMIT CONVECTION EARLY ON SATURDAY BEFORE WEAK CIN IS OVERCOME
BY HEATING.  EXPECTING INITIATION TO OCCUR ACROSS THE HIGH TERRAIN
ON SATURDAY AFTERNOON BEFORE WEAK NW FLOW ALOFT PROPAGATES SHOWERS
AND THUNDERSTORMS SOUTHEAST INTO THE FOOTHILLS/PIEDMONT REGIONS OF
NC/SC.  DIURNALLY FAVORED LOW/MID LEVEL CHANCE POPS WILL HIGHLIGHT
THE FORECAST FOR SATURDAY.  TEMPERATURES THROUGH THE SHORT TERM
PERIOD WILL BE AT OR JUST SLIGHTLY BELOW CLIMO.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 300 AM TUE...WHILE SOME VESTIGE OF A FRONTAL BOUNDARY MAY
REMAIN OVER THE COASTAL PLAIN THIS WEEKEND...THE PATTERN ACRS THE
REGION WILL BE DOMINATED BY BERMUDA HIGH AT THE SFC. THAT WILL
MAINTAIN LIGHT SOUTHERLY FLOW INTO THE FA...BUT INSTEAD OF KEEPING
US CAPPED THRU SUBSIDENCE...BROADLY CYCLONIC UPPER FLOW ABOVE IT
WILL KEEP CONDITIONS MODESTLY FAVORABLE FOR DIURNAL CONVECTION. THIS
IS THE PREVAILING SIGNAL FOR POPS DURING THE PERIOD. TEMPS WILL
TREND FROM SLIGHTLY BELOW NORMAL SATURDAY TO SLIGHTLY ABOVE NORMAL
BY TUESDAY.

A FRONT WILL DIVE THRU THE NRN PLAINS OVER THE WEEKEND AS TROUGH DIGS
ACRS ERN CANADA. A WEAK LEADING FRONT WILL PUSH THRU THE OH/TN
VALLEYS AND INTO THE AREA MONDAY...ENHANCING PRECIP COVERAGE. THE
TROUGH AMPLIFIES FURTHER IN THE MIDDLE OF THE WEEK WHICH BRINGS THE
STRONGER FRONT SWD TOWARD US.  CURRENT GUIDANCE PUTS THIS ON WED
BEYOND THE END OF THE FCST.

&&

.AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT AND ELSEWHERE (EXCEPT KAVL)...CANNOT RULE OUT A FEW SHOWERS
POPPING UP OR MOVING OUT OF THE MTNS AT JUST ABOUT ANYTIME THIS
MORNING...BUT COVERAGE SHOULD BE VERY SPARSE UNTIL AFTERNOON.
OTHERWISE...PREVAILING VFR CONDITIONS ARE EXPECTED (OUTSIDE OF
SHOWERS/TSTORMS) THROUGH THE PERIOD. COVERAGE OF CONVECTION IS
EXPECTED TO INCREASE THIS AFTERNOON...BUT THERE IS STILL SOME
UNCERTAINTY AS TO THE DEGREE OR COVERAGE. OUR BEST EDUCATED GUESS
CONTINUES TO INDICATE COVERAGE SHOULD REMAIN SCATTERED...AND ALL
TAFS SEE A PROB30 DURING THE AFTERNOON THROUGH MID EVENING OR SO.

AT KAVL...OTHER THAN PERHAPS A STRAY SHOWER OR TWO DEVELOPING NEAR
THE TENN BORDER AND PASSING NEAR THE TERMINAL THIS MORNING...THE
BULK OF CONVECTIVE ACTIVITY SHOULD HOLD OFF UNTIL AFTERNOON...WHEN A
TEMPO IS BEING CARRIED BETWEEN 18Z AND 22Z...ALTHOUGH CONVECTIVE
CHANCES WILL CONTINUE INTO THE EVENING. WE ARE STILL WAITING FOR A
FOGGY NIGHT TO OCCUR AT KAVL...AND WHILE IT IS UNCLEAR THAT TONIGHT
WILL BE THE NIGHT...BASED UPON A CONSENSUS OF GUIDANCE...MVFR VISBY
HAS BEEN INTRODUCED TOWARD DAYBREAK.

OUTLOOK...SCATTERED MAINLY AFTN THUNDERSTORMS WILL CONTINUE THROUGH
LATE WEEK INTO THE WEEKEND AS HIGH PRESSURE SLOWLY SETTLES OVER THE
AREA. ANY RESTRICTIONS WOULD BE CONFINED TO DIURNAL TSTMS AND
MORNING VALLEY FOG EACH DAY.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-17Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  95%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     MED   71%     HIGH  83%
KHKY       HIGH 100%     HIGH 100%     HIGH  91%     HIGH  90%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  90%

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...WIMBERLEY
NEAR TERM...LG
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...JDL





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