Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 081807
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
206 PM EDT TUE JUL 8 2014

.SYNOPSIS...
A COLD FRONT WILL APPROACH THE AREA FROM THE NORTHWEST AND SHOULD
CROSS THE REGION WEDNESDAY NIGHT THROUGH THURSDAY. THIS SHOULD YIELD
HEIGHTENED PRECIP CHANCES UNTIL AFTER THE FRONT PASSES. WEAK HIGH
PRESSURE WILL RETURN THROUGH THE WEEKEND BEFORE ANOTHER COLD FRONT
APPROACHES THE AREA BY EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 140 PM EDT...EARLY RADAR RETURNS FROM THE WESTERN UPSTATE AND
NE GA THIS AFTN DEPICT CONVECTION FIRING RIGHT ALONG A DIFFERENTIAL
HEATING LINE CREATED BY HIGHER DEBRIS CLOUDS TO THE WEST...AND ALSO
AHEAD OF A WEAK UPPER VORTICITY MAXIMUM CROSSING THE SRN HALF OF THE
FORECAST AREA THIS AFTN. SBCAPE VALUES HAVE POOLED TO 2000 TO 2500
J/KG IN THIS AREA...BUT THE ACTIVITY WILL HAVE TO FIGHT IT/S WAY
EAST INTO LOWER 60S DEWPOINT AIR AND A SLIGHTLY MORE CAPPED
ENVIRONMENT. BETWEEN OUTFLOWS WITH THIS ONGOING ACTIVITY AND THE
PASSING UPPER WAVE THROUGH EARLY EVENING...WILL FOCUS POP COVERAGE
JUST EAST OF THE MTNS EARLY...BUT WITH COVERAGE THEN TURNING BACK TO
THE WESTERN MOUNTAINS LATER TONIGHT AS PRE/FRONTAL CONVECTION
ARRIVES FROM ERN TN AND STOUT WESTERLY FLOW TRIGGERS UPSLOPE
FORCING. IN FACT...850 MB WINDS WILL VEER AND STRENGTHEN TO SOME
UNSEASONABLY HIGH VALUES OF 30 TO 35 KT BY 06Z...BUT INSTABILITY
SHOULD WANE OVERNIGHT. THE MAIN CONCERN FOR ANY OVERNIGHT SEVERE WX
WOULD BE WITH THE ARRIVAL OF A DECAYING PRE/FRONTAL LINE ACROSS THE
WRN NC MTNS.

A BROAD AREA OF WEAK Q VECTOR CONVERGENCE WILL DEVELOP FROM THE WEST
THROUGH WED AHEAD OF THE AXIS OF THE BROAD ERN CONUS TROUGH. THIS
WILL ARRIVE COINCIDENT WITH THE DEEPEST FRONTAL ZONE MOISTURE...WITH
THE BOUNDARY LIKELY BISECTING THE FORECAST AREA BY WED AFTN AND THEN
SETTLING SLOWLY SOUTHEAST. BOTH TRIGGERING AND INSTABILITY SHOULD BE
SOMEWHAT LIMITED GIVEN THE WEAK FRONT...LACK OF VIGOROUS WAVES IN
THE TROUGH ALOFT...AND CLOUDS TO INHIBIT HEATING. WILL ORIENT POPS
WITH LIKELY MTNS/CHC EAST EARLY...TRANSITIONING TO SHOTGUN HIGH CHC
THROUGHOUT DURING THE AFTN. CLOUDS SHOULD BE THINNEST IN SE SECTIONS
TO SUPPORT AT LEAST LOWER 90S FOR HIGHS...BUT EXPECT MAXES TO BE AT
LEAST A CATEGORY COOLER ELSEWHERE.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 200 PM TUE...AN EASTERN U.S. TROUGH WILL PREVAIL THROUGH THER
SHORT TERM. AT THE SURFACE...MODELS ARE IN DECENT AGREEMENT THAT  A
BOUNDARY WILL LIE ACROSS UPSTATE SC INTO NE GA AT THE ONSET OF THE
PERIOD. SOME ONGOING CONVECTION IS LIKELY TO PERSIST IN THE VICINTY
OF THE BOUNDARY WED EVENING...BUT EXPECT WITH FORCING REMAINING WEAK
THAT COVERAGE OF PRECIP WILL DECREASE DIURNALLY WED NIGHT. FOR
THU...THE NAM HAS COME INTO AGREEMENT WITH THE GLOBAL MODELS THAT
THE SURFACE BOUNDARY WILL CONTINUE TO LIE ACROSS THE UPSTATE INTO NE
GA. IN FACT...THE NAM SUGGESTS THAT A WEAK WAVE WILL DEVELOP ALONG
THE BOUNDARY INCREASING THE LIKELIHOOD OF SCATTERED TO EVEN
NUMEROUS SHOWERS/THUNDERSTORMS WITH THE BEST COVERAGE FROM THE
CHARLOTTE AREA...THROUGH THE UPSTATE INTO NE GA. AS THE WAVE EXITS
THE AREA...DRYER AIR IS FORECAST TO FILER INTO THE REGION FROM THE
NNW THU NIGHT. HENCE...POPS THU NIGHT AND FRI WILL BE PAIRED BACK. MODELS
DO SHOW SOME LIGHT QPF RESPONSE ON FRI AFTERNOON MAINLY IN UPSLOPE
AREAS AS WINDS BEGIN TO VEER THE SE. MAX TEMPS ARE EXPECTED TO BE A
CATEGORY BELOW AVERAGE EACH DAY.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 130 PM EDT TUESDAY...UPPER H5 HEIGHTS WILL FALL ACROSS THE
SOUTHEAST FRI NIGHT INTO SAT AS AN UPPER RIDGE OF HIGH AMPLIFIES
ACROSS THE WESTERN CONUS WHILE AN UPPER LOW PRESSURE TROUGH OVER
SOUTH CENTRAL CANADA DIGS INTO THE GREAT LAKES REGION. MODELS
SUGGEST THAT THIS UPPER LOW PRESSURE TROUGH APPEARS TO BE
UNSEASONABLY STRONG WITH ITS CENTER HEIGHTS FALLING TO AROUND 545DM.
OUR FORECAST AREA WILL BE UNDER RATHER STRONG W/WNWLY FLOW LOFT
THROUGH TUESDAY AS THE TROUGH SWINGS ACROSS THE EASTERN CONUS.

AT THE SURFACE...A FRONTAL BOUNDARY JUST TO OUR SOUTH FRI NIGHT IS
FORECAST TO LIFT NORTH OF THE AREA BY SAT AFTERNOON AS BERMUDA HIGH
STRAIGHTENS ACROSS THE SE. THE REGION WILL BE UNDER THE INFLUENCE OF
BERMUDA HIGH THROUGH SUN NIGHT BEFORE IT WEAKENS AND SHIFT EAST AS A
COLD FRONT APPROACHES THE REGION FROM THE NW BY MON. THIS FRONT IS
PROGGED TO CROSS THE REGION LATE MONDAY INTO TUESDAY AND OFF THE SE
COAST BY TUE NIGHT. AS FOR OUR SENSIBLE WEATHER...MODEL SOUNDINGS
SUGGEST THAT WE WILL SEE UNCAPPED ALOFT WITH SEASONABLY UNSTABLE
ENVIRONMENT DURING THE AFTERNOON HOURS. HENCE...POPS REMAIN NEAR
CLIMO FAVORING IN THE HIGHER TERRAIN GIVEN BETTER UPSLOPE W/WSWLY
FLOW. THE BEST CHANCE FOR CONVECTION WILL BE ON LATE MONDAY AS THE
FRONT PUSHES THROUGH THE REGION. TEMPERATURES SHOULD REMAIN A FEW
DEGREES BELOW NORMAL THROUGH THE PERIOD.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
AT KCLT...DEWPOINTS HAVE ONCE AGAIN MIXED INTO THE LOWER 60S AND
WEAK CAPPING ALOFT IS KEEPING MOST CUMULUS AND ANY CONVECTION AWAY
FROM THE AIRFIELD. ACTIVITY DEVELOPING CLOSER TO THE MTNS COULD MAKE
A RUN EWD THROUGH EVENING...BUT WITH CONFIDENCE TOO LOW TO MENTION
ANYTHING AT THE TERMINAL. WILL KEEP MAINLY SCT CLOUDS IN THE
FORECAST THROUGH EVENING...WITH SOME LOW END GUSTS PERSISTING UNTIL
MIXING WANES WITH SUNSET. DEEPER MOISTURE AND THE APPROACHING FRONT
WILL WARRANT A PROB30 FOR TSRA AFTER 15Z ON WED.

ELSEWHERE...CONVECTION DEVELOPING ALONG A LINE OF DIFFERENTIAL
HEATING AND AHEAD OF A WEAK UPPER SHORTWAVE WILL THREATEN MAINLY
KGSP AND KGMU THROUGH 20Z...WITH A VCTS MENTION NEEDED AT KAVL AND
KAND. EXPECT SCT TO BKN VFR CLOUDS THROUGHOUT...EXCEPT THICKENING
OVERNIGHT AS DEEPER MOISTURE ALONG THE APPROACHING COLD FRONT
ARRIVES. NO RESTRICTIONS ARE EXPECTED OUTSIDE OF THE MTNS...AND
NOTHING WORSE THAN MVFR AT KAVL...UNLESS A VERY HEAVY SHOWER ARRIVES
WITH A DECAYING FRONTAL ZONE LINE OVERNIGHT. PROB30 SEEMS WARRANTED
THROUGHOUT LATE WED MORNING THROUGH EARLY AFTN WITH THE FRONT IN
PLACE AND WEAK FORCING OVERHEAD.

OUTLOOK...SCATTERED MAINLY AFTN THUNDERSTORMS WILL CONTINUE BEHIND
THE WEAK DEPARTING FRONT LATE THIS 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...

            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  88%     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 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...STAARMANN
NEAR TERM...HG
SHORT TERM...WIMBERLEY
LONG TERM...JOH
AVIATION...HG






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