Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 250019
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
819 PM EDT THU APR 24 2014

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE EASTERN SEABOARD TONIGHT AS A COLD
FRONT AND UPPER LEVEL DISTURBANCE APPROACH FROM THE WEST. THE COLD
FRONT WILL CROSS THE AREA ON FRIDAY...WITH DRY HIGH PRESSURE
RETURNING THROUGH THE WEEKEND. A WET AND POSSIBLY STORMY PATTERN
WILL SET UP MONDAY THROUGH WEDNESDAY...FOLLOWED BY COOLER WEATHER.

&&

.NEAR TERM /THROUGH FRIDAY/...
730 PM UPDATE...WARM FRONT IS BASICALLY KNOCKING ON OUR
DOORSTEP...HAVING MOVED INTO CENTRAL GA/SC DURING THE LATE AFTN.
MANY SITES JUST SOUTH OF THE FA ARE REPORTING DEWPOINTS IN THE 50S.
REVISED POPS OVERNIGHT GENERALLY TO MOVE THE PRECIP CHANCES CLOSER
TO DAYBREAK...WITH ISENTROPIC FIELDS NOT INDICATING MUCH POTENTIAL
UNTIL WELL AFTER MIDNIGHT. MESO MODELS DON/T DEVELOP MUCH UNTIL LATE
TONIGHT EITHER. GIVEN THE SOUTHERLY FLOW...ON MOST MODEL GUID THE
EVOLUTION OF CLOUD/PRECIP DEVELOPMENT IN THE PREFRONTAL ENVIRONMENT
REFLECTS ENHANCEMENT FROM THE BLUE RIDGE. THIS SEEMS APPROPRIATE.
WHILE PROG SOUNDINGS MAINLY INDICATE LOW STRATUS...SOME VSBY
GUIDANCE IS LOW ALONG IT. THIS MAY ACTUALLY BE A RESULT OF THE RIDGE
BEING /IN THE CLOUDS/. NONETHELESS INCLUDED A MENTION OF RESTRICTED
VSBYS IN THE GRIDS AT ASHEVILLE AND MTN AREAS SOUTH. SEVERE WX
THREAT TOMORROW STILL APPEARS LIMITED...WITH SHEAR MARGINAL ACRS THE
AREA AND INSTABILITY RELATIVELY LOW IN THE WEST. STILL SEEING BETTER
SBCAPE EAST WHERE THE FRONT ARRIVES LATER ALLOWING FOR MORE WARMING
AHEAD OF IT.

AT 200 PM EDT THURSDAY...AN UPPER RIDGE AXIS WILL CROSS THE EAST
COAST TONIGHT...WHILE AN UPPER TROUGH CROSSES THE MID MS RIVER
VALLEY. MOISTURE WILL INCREASE AHEAD OF AN APPROACHING COLD
FRONT...SUPPORTING PRECIPITATION AS EARLY AS MIDNIGHT IN THE
MOUNTAINS. GULF INFLOW IS RATHER LIMITED...AS IS ISENTROPIC
UPGLIDE...AND PRECIPITATION IS NOT EXPECTED TO BE EXCESSIVE. MODEST
INSTABILITY WILL REACH THE UPPER SAVANNAH RIVER VALLEY BY DAWN.
MINIMUM TEMPERATURES WILL RUN AROUND FIVE DEGREES ABOVE NORMAL WITH
INCREASING CLOUD COVER AND MOISTURE.

THE COLD FRONT WILL CROSS OUR AREA ON FRIDAY...PRECEDED BY
INCREASING INSTABILITY AND SHEAR. THE GREATEST CHANCE OF SEVERE
WEATHER WILL BE IN THE PIEDMONT IN THE EARLY AFTERNOON...ESPECIALLY
IN SC...GA...AND THE KCLT METRO AREA. DRYING FROM THE SW WILL OCCUR
IN THE LATE AFTERNOON BEHIND FRONT...ALTHOUGH SOME PRECIPITATION
ASSOCIATED WITH MOIST NW FLOW MAY LINGER IN THE NC MOUNTAINS...
MAINLY NEAR THE TN BORDER. HIGH TEMPERATURES WILL RUN AROUND NORMAL.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 2 PM EDT THURSDAY...EXPECT SOME LINGERING SHOWERS OVER THE NRN
MOUNTAINS EARLY FRIDAY EVENING. ANY REMAINING THUNDERSTORM ACTIVITY
OVER THE WESTERN PIEDMONT SHOULD MOVE EAST QUICKLY AND OUT OF THE
FCST AREA BY SUNSET.  AFTER THAT...THE WEATHER SHOULD BE QUIET. THE
WHOLE WEEKEND LOOKS TO BE DRY COURTESY OF AN UPPER RIDGE BUILDING IN
FROM THE WEST...SUPPORTING SURFACE HIGH PRESSURE THAT MOVES ACROSS
THE DEEP SOUTH. THE UPPER RIDGE AXIS FINALLY REACHES THE WESTERN
CAROLINAS SUNDAY EVENING WITH THE SURFACE HIGH OFF THE SOUTHEAST
COAST...BUT MOISTURE IS NOT EXPECTED TO RETURN QUICK ENOUGH TO ALLOW
FOR ANY SHOWER DEVELOPMENT BEFORE THE END OF THE DAYTIME PERIOD.
TEMPS ARE EXPECTED TO RUN ABOUT FIVE DEGREES ABOVE NORMAL THROUGH
THE PERIOD...BUT THE AIR MASS SHOULD REMAIN RELATIVELY DRY...SO IT
SHOULD AMOUNT TO A SEASONALLY WARM WEEKEND...BUT STILL COMFORTABLE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 200 PM EDT THU...THE WORD OF THE DAY IS REX BLOCK AS A LARGE
POSITIVE HEIGHT ANOMALY WILL BUILD ACROSS CENTRAL CANADA EARLY IN
THE EXTENDED RANGE...CAUSING A BROAD UPPER LOW TO DEVELOP OVER MUCH
OF THE CENTRAL AND EASTERN STATES. THE CENTER POINT OF THE UPPER LOW
IS EXPECTED TO SET UP SHOP OVER THE ERN PLAINS OR UPPER MIDWEST BY
TUESDAY...WITH LITTLE MOVEMENT WED AND THURSDAY. THE EC...CANADIAN
AND GFS ARE IN GOOD AGREEMENT WITH THE LARGER WAVELENGTH
FEATURES...THOUGH THERE ARE PLENTY OF DIFFERENCES WITH THE EMBEDDED
SHORT WAVE ENERGY LATER IN THE PERIOD.

EARLY IN THE EXTENDED THE UPPER LOW WILL BEGIN TO CUT OFF OVER THE
CENTRAL PLAINS...WHICH BUILDS THE LARGE POSITIVE HEIGHT ANOMALY FROM
THE SE STATES UP ACROSS THE GREAT LAKES. OVERALL THE LATEST GFS AND
CANADIAN HAVE BEEN SLOWER WITH THE PATTERN. THIS MAKES PLENTY OF
SENSE AND I WOULD EXPECT THAT WE WILL CONTINUE TO SEE SOME SLOWING
IN SUCH A BLOCKY PATTERN. THE UPSHOT OF THIS IS THAT THE STRONG LLVL
JET THAT LOOKED AS THOUGH THE WOULD SPREAD MODERATE TO HEAVY RAIN
AND POSSIBLY STRONG STORMS ACROSS THE REGION MONDAY NIGHT AND
TUESDAY NOW STAYS WEST OF THE APPALACHIANS. I/D SAY IT/S A GOOD 500
MILES FARTHER WEST TODAY. IF THIS PATTERN HOLDS...THE HEAVY PCPN
MONDAY INTO TUESDAY SHOULD GENERALLY BE WEST OF THE REGION.

HOWEVER...WE SHOULD STILL SEE A FAIR AMOUNT OF SHOWER AND
THUNDERSTORM ACTIVITY STARTING MONDAY NIGHT...IT JUST SHOULDN/T BE
AS WIDESPREAD OF HEAVY AS ORIGINALLY EXPECTED. ALSO...IF THE RIDGE
BECOMES ANY STRONGER OVER THE REGION...WE COULD SEE MORE OF A DELAY
IN PCPN ONSET INTO LATE TUE OR TUE NIGHT. I HAVEN/T PUSHED THINGS
BACK QUITE THAT FAR YET.

WITH THE UPPER LOW HANGING AROUND AT LEAST THROUGH DAY 7...WE WILL
SEE A CHANCE OF SHOWERS AND TSTMS WED AND THU AS WELL. A PERIOD OF
HEAVIER RAIN OR STRONGER CONVECTION IS POSSIBLE EITHER
DAY...DEPENDING ON THE LOCATION OF ANY STRONGER...ADVECTIVE
SHORTWAVE FEATURES WITHIN THE TROUGH. TEMPERATURES SHOULD GRADUALLY
FALL DURING THE EXTENDED PERIOD...STARTING A LITTLE ABOVE NORMAL ON
MONDAY...AND ENDING WELL BELOW NORMAL WED AND THU.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
AT KCLT...VFR UNDER BANDS OF CIRRUS FOR MOST OF TONIGHT...WITH
MIDLEVEL STRATOCU DEVELOPING LATE IN THE EVENING. EVENTUALLY A LOW
STRATUS DECK IS EXPECTED TO FORM AND BRING CIGS TO IFR...AS MOIST
SOUTHERLY FLOW BUILDS AHEAD OF COLD FRONT. THESE LOW CIGS WILL LIFT
GRADUALLY THRU THE MRNG. SOME SHRA WILL BE POSSIBLE FROM THE EARLY
MRNG ONWARD AND TSRA BECOME MORE LIKELY AS THE CIG LIFTS...ALLOWING
SFC DESTABILIZATION. BEST CHANCES FROM MIDDAY TO LATE AFTN WHEN THE
FRONT MOVES THRU AND DRYING OCCURS. SELY WINDS CONTINUE
TONIGHT...VEERING TO SW PRIOR TO FROPA AND BECOMING GUSTY.

ELSEWHERE...TRENDS MUCH LIKE KCLT. AREAS WITH THE BEST CHANCE OF LOW
CIGS...AND THE EARLIEST AREAS TO SEE SHRA DEVELOP TONIGHT...WILL BE
ALONG AND JUST SOUTH OF THE BLUE RIDGE. GUIDANCE ALSO BRINGS VSBYS
DOWN IN THESE AREAS. HAVE GONE IFR VSBY AT KAVL...AND INCLUDED AN
IFR CIG AT THE OTHER SITES. ALL SITES HAVE A VC MENTION FOR A
PORTION OF THE DAY TO REFLECT SCATTERED NATURE OF CONVECTION...BUT
ALSO A PROB30 DURING THE PEAK CHANCES. WINDS REMAIN SOUTHERLY BUT
WILL VEER AS THE FRONT APPROACHES.

OUTLOOK...DRY HIGH PRES RETURNS SATURDAY THRU SUNDAY. INCREASED
MOISTURE RETURNS TO THE REGION EARLY NEXT WEEK...WITH A BLOCKED
PATTERN SETTING UP WHICH COULD BRING PERIODS OF SHRA/TSRA AND
ASSOCIATED RESTRICTIONS INTO MIDWEEK.

CONFIDENCE TABLE...

            00-06Z        06-12Z        12-18Z        18-24Z
KCLT       HIGH 100%     HIGH  92%     HIGH  94%     HIGH 100%
KGSP       HIGH 100%     HIGH  93%     HIGH  94%     HIGH 100%
KAVL       HIGH 100%     MED   72%     MED   66%     HIGH 100%
KHKY       HIGH 100%     HIGH  93%     HIGH  91%     HIGH 100%
KGMU       HIGH 100%     HIGH  92%     HIGH  91%     HIGH 100%
KAND       HIGH 100%     HIGH  92%     HIGH  84%     HIGH  94%

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...DEO
NEAR TERM...JAT/WIMBERLEY
SHORT TERM...PM
LONG TERM...MCAVOY
AVIATION...WIMBERLEY






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