Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 031842
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
242 PM EDT THU SEP 3 2015

.SYNOPSIS...
A BACK DOOR COLD FRONT IS EXPECTED TO PUSH ACROSS THE REGION ON
FRIDAY FOLLOWED BY A COOL AND MOIST AREA OF HIGH PRESSURE WHICH
WILL PERSIST THROUGH THROUGH THE HOLIDAY WEEKEND...BRINGING CLOUDS
AND INCREASED CHANCES OF PRECIPITATION. A GRADUAL WARMING TREND
AND MORE SUMMERLIKE CONDITIONS WILL RETURN TUESDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 230 PM...SEEING CONVECTION BLOSSOMING OVER N GEORGIA AT THE
BACK EDGE OF THE THICKER CLOUD COVER CENTERED OVER THE SAVANNAH
RIVER VALLEY AND E CENTRAL GA. MAIN CONCERN FOR THE AFTERNOON
CONTINUES TO BE LOW LEVEL MOISTURE POOLED NEAR THE CSRA THAT EXTENDS
UP INTO THE LAKELANDS. WHILE IT IS SUSPECTED THAT BAD DEWPTS (IN THE
MID 70S) ARE INFLATING BUOYANCY ESTIMATES IN THAT REGION...EVEN IF
WE THROW AWAY THE SUSPICIOUS OBS AND GO ONLY WITH KAHN AND KGRD...WE
STILL HAVE AROUND 3000 J/KG OF CAPE TO GO WITH 1000 J/KG OF DCAPE.
THAT SORT OF ENVIRONMENT IN THE SUMMER USUALLY WOULD SUPPORT
THUNDERSTORMS...WITH SOME STRONG TO SEVERE. YET...THE CONVECTION
ALLOWING MODELS STILL ARE NOT ON BOARD WITH DEVELOPING MUCH IN THAT
AREA. IT IS NOT KNOWN IF THE MODELS INITIALIZED PROPERLY WITH THE
MOISTURE POOL BEING BETTER THAN EXPECTED. THE LATEST RUNS OF THE WRF-
ARW AND 4KM WRF FOR SPC SHOW A BIT MORE DEVELOPMENT...SO PERHAPS THE
TREND IS IN THAT DIRECTION. WITH THAT IN MIND...WILL RAISE THE
PRECIP PROBABILITY INTO THE CHANCE RANGE IN ALL NE GEORGIA AND THE
LAKELANDS. BEST TO KEEP AN EYE OUT FOR A FEW STRONG/SEVERE STORMS AS
WELL...JUST IN CASE. THE REST OF THE FCST AREA LOOKS OK. NO CHANGES
TO MAX TEMPS. STILL EXPECT ANY SHOWER/TSTM ACTIVITY TO WANE AROUND
SUNSET WITH LOSS OF HEATING.

THE NEXT 24 HOURS FEATURE A STRANGE AND CONVOLUTED PATTERN ALOFT
WHICH BASICALLY RESULTS IN A WEAK NW FLOW...WITH A WEAK SHORT WAVE
DROPPING DOWN ACROSS THE REGION ON FRIDAY THAT LACKS DPVA. EXPECT A
GENERAL LACK OF MID/UPPER FORCING...WHICH MEANS THAT ANY THREAT FOR
PRECIP WILL BE ALMOST ENTIRELY DRIVEN BY DIURNAL HEATING. IN SPITE
OF A WEAK NE FLOW NEAR THE SURFACE COURTESY OF WEAK LOW PRESSURE
ALONG THE COAST AND HIGH PRESSURE WELL TO THE NE...THE MODEL
GUIDANCE DEVELOPS SUFFICIENT INSTABILITY TO ALLOW FOR SCATTERED DEEP
CONVECTION ACROSS THE WHOLE FCST AREA FRIDAY AFTERNOON. SO...LITTLE
CHANGE WAS MADE TO THE PREVIOUS FCST WHICH HAD A CHANCE POP
EVERYWHERE BY MID/LATE AFTERNOON. WENT ON THE HIGH SIDE OF GUIDANCE
AGAIN FOR TEMPS BASED ON RECENT VERIFICATION.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 230 PM THURSDAY...OUR AREA REMAINS CAUGHT IN BETWEEN THE
WESTERLY FLOW ALOFT... WHICH IS LOCATED WELL TO THE NORTH...AND AN
UPPER TROUGH MEANDERING ACROSS THE SOUTHEAST QUARTER OF THE CONUS.
MEANWHILE HIGH PRESSURE EDGING FROM THE NEW ENGLAND STATES DOWN TO
THE MID ATLANTIC...WILL HELP PUSH A "BACKDOOR COLD FRONT" INTO THE
REGION FRIDAY NIGHT AND INTO THE UPCOMING WEEKEND.

WE WOULD EXPECT DIURAL SHOWERS AND THUNDERSTORMS TO INITIALLY WANE
FRIDAY EVENING...THEN AN UPTICK IN OUR EASTERN FORECAST AREA (FA)
FRIDAY NIGHT. THE EASTERLY FLOW SHOULD CONTINUE TO DRAW ATLANTIC
MOISTURE INTO THE REGION SATURDAY WITH POPS STEADILY INCREASING IN
OUR WESTERN FA. WE HAVE BROUGHT HIGHEST POPS SATURDAY AND SATURDAY
NIGHT ALONG THE EAST FACING SLOPES WITH GOOD UPGLIDE EXPECTED. ALSO
DURING THIS PERIOD THE MODELS ARE SUGGESTING WEAK UPPER LEVEL
IMPULSES WILL BE PASSING THROUGH THE REGION...HELPING THE OVERALL
FORCING FOR PRECIPITATION POTENTIAL.

ALTHOUGH THE OVERALL SET-UP REMAINS STAGED SATURDAY NIGHT AND
SUNDAY... FORCING SHOULD DIMINISH ALONG WITH DEEPEST MOISTURE. WE
HAVE KEPT POPS GOING OVER THE WESTERN HALF OF THE AREA WITH CLOUDS
ELSEWHERE.

BECAUSE OF THE CLOUDS...PRECIPITATION POTENTIAL AND A FALLING
THERMAL PATTERN...MAXIMUM TEMPERATURES WILL CONTINUE TO FOLLOW THE
PREVIOUS FORECAST WITH VALUES NEAR OR SLIGHT UNDER GUIDE. THIS WILL
ALSO LEND ITSELF TO SMALLER DIURNAL TRENDS...AS OVERNIGHT LOW
TEMPERATURES BEING HELD IN CHECK BY CLOUDINESS. THE LATEST MODEL
GUIDE CONTINUES TO DISPLAY THIS TREND.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 130 PM THU...EARLY NEXT WEEK THE EASTERLY FLOW REGIME OVER
THE CAROLINAS WILL GRADUALLY BREAK DOWN AS HEIGHTS FALL OVER THE
NERN CONUS AND RIDGE BUILDS OVER THE WRN ATLANTIC. A DEVELOPING LOW
OFFSHORE SUNDAY NIGHT WILL ENHANCE MOISTURE TRANSPORT INTO THE CWFA
FROM THE EAST. SOUTHWEST LOW LEVEL FLOW DOES NOT REALLY RE-ESTABLISH
ITSELF UNTIL LATE TUESDAY OR POSSIBLY EVEN WEDNESDAY. MEANWHILE
AN INITIALLY STRONG LOW DEVELOPING IN THE LEE OF THE NRN ROCKIES
WILL MOVE TOWARD HUDSON BAY...WITH HEIGHTS FALLING OVER THE NORTH
CENTRAL CONUS IN RESPONSE. A COLD FRONT ASSOC WITH THE SYSTEM WILL
PUSH SEWD...AND WHILE GFS/EC DIFFER ON ITS DEPICTED STRENGTH THEY
AGREE IT WILL REACH THE TENN VALLEY AND SRN APPALACHIANS BY THU
NIGHT. IN SUMMARY...FOR THE FORECAST PERIOD THE CWFA WILL BE UNDER
A SOMEWHAT NEBULOUS WEAK RIDGE FOLLOWED BY A WEAK TROUGH IN ADVANCE
OF THE FROPA. EXCEPT FOR THE LINGERING POSSIBILITY OF OVERNIGHT
SPRINKLES OR LIGHT SHOWERS SUNDAY NIGHT...POPS WILL REMAIN STRONGLY
DIURNAL. TUE APPEARS TO BE THE DAY UNDER THE LEAST INFLUENCE OF
EITHER THE EASTERLY FLOW OR THE APPROACHING TROUGH...AND THEREFORE
BEARS THE LOWEST POPS OVERALL. MAX TEMPS WILL START OUT AT ABOUT
NORMAL MONDAY WITH THE WEDGELIKE AIRMASS STILL PRESENT...BUT AS
THIS RETREATS THEY WILL BEGIN TO WARM...ENDING UP SEVERAL DEGREES
ABOVE NORMAL BY THU WITH CONTINUED MODIFICATION. MINS WILL BE A
COUPLE DEGREES ABOVE NORMAL.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
AT KCLT AND ELSEWHERE...GENERALLY VFR THRU THE PERIOD...EXCEPT FOR
KAVL AROUND DAYBREAK. SCT HIGH BASED STRATOCU WILL DEVELOP THRU THE
AFTERNOON...WITH CLOUD BASES GENERALLY IN THE 060 TO 080 RANGE. THE
BEST PRECIPITATION CHANCES THIS AFTERNOON STILL LOOK TO BE THE BEST
ACROSS THE SRN TIER OF THE TERMINAL FORECAST AREA...MAINLY SOUTH OF
KAND...AND WITH SCATTERED RIDGE TOP DEVELOPMENT OVER THE HIGHER
TERRAIN. WILL INCLUDE A VCSH OR VCTS AT KAVL AND KAND. THE
CONVECTION SHOULD DIE OFF BY SUNSET. THERE COULD BE SOME FOG IN THE
MTN VALLEYS OVERNIGHT...WHICH MAY RESULT IN A VSBY RESTRICTION AT
KAVL THAT WOULD END BY MID MORNING. EXPECT THE REST OF THE MORNING
TO BE BENIGN. IN GENERAL...WIND WILL REMAIN N TO NE AND LIGHT THRU
THE PERIOD.

OUTLOOK...OVER THE WEEKEND...A MOIST EASTERLY FLOW SHOULD DEVELOP...
BRINGING BETTER CHANCES FOR SHOWERS AND RESTRICTIONS...IN PARTICULAR
ON SATURDAY. LOW CLOUDS AND FOG WILL BE POSSIBLE EACH NIGHT IN THE
MOUNTAIN VALLEYS.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
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 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  97%

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

&&

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

&&

$$
SYNOPSIS...WIMBERLEY
NEAR TERM...PM
SHORT TERM...TS
LONG TERM...WIMBERLEY
AVIATION...PM



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