Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 271803
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
203 PM EDT WED MAY 27 2015

.SYNOPSIS...
A BERMUDA HIGH PATTERN WILL REMAIN ACROSS THE REGION INTO THE
WEEKEND BEFORE A COLD FRONT PUSHES IN FROM THE NORTH LATE SUNDAY.
THIS FRONT WILL THEN WEAKEN AND BECOME STATIONARY OVER THE AREA
THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 2 PM...STUBBORN STRATOCU PERSISTS IN MOST AREAS EAST OF THE
MTNS...WHICH HAS LIMITED CAPE TO LESS THAN 1000 J/KG THUS FAR.
MEANWHILE...DESPITE PERSISTENCE OF GOOD INSOLATION OVER THE MTNS...
THE CU FIELD APPEARS RATHER PALTRY ATTM. NEVERTHELESS...BASED UPON
THE LATEST MESOSCALE/CONVECTION-ALLOWING MODELS...OPTED TO STAY THE
COURSE WITH PRIMARILY 30 POPS ACROSS MUCH OF THE AREA THIS
AFTERNOON...WITH SLIGHTLY HIGHER PROBABILITIES ALONG/NEAR THE
EASTERN ESCARPMENT.

AS OF 1030 AM...WIDESPREAD STRATUS PERSISTS ACROSS THE PIEDMONT AND
FOOTHILLS THIS MORNING...WITH JUST A FEW BREAKS SHOWING HERE AND
THERE. MEANWHILE...VALLEY FOG/LOW STRATUS HAS BURNED OFF ACROSS MOST
OF THE MTN VALLEYS...AND THE VAST MAJORITY OF THE MTNS ARE
EXPERIENCING MOSTLY SUNNY SKIES ATTM. THIS CREATES SOMEWHAT OF A
CONUNDRUM IN TERMS OF DEEP CONVECTIVE CHANCES THIS PM...AS IT/S NOT
ENTIRELY CLEAR EXACTLY WHEN THE PIEDMONT STRATUS WILL BURN OFF...
AND THUS JUST HOW MUCH INSTABILITY WILL BE REALIZED THERE. A FEW
SHOWERS HAVE DEVELOPED ACROSS THE EASTERN ZONES THIS MORNING...AS
WAS SUGGESTED BY THE SHORT TERM AND SOME MESOSCALE MODEL GUIDANCE
(HOWEVER...NOT NEARLY TO THE EXTENT AS WAS SUGGESTED BY SAID
MODELS). THIS ACTIVITY IS FIRING WITHIN A PLUME OF DEEPER
MOISTURE...WHICH IS EXPECTED TO SHIFT EAST OF THE FORECAST AREA THIS
AFTERNOON. AS SUCH...THERE IS A FAIRLY CLEAR CONSENSUS IN THE
MESOSCALE/CONVECTION ALLOWING MODEL GUIDANCE THAT THERE WILL NOT BE A
GREAT DEAL OF DEEP CONVECTIVE COVERAGE...ESP OUTSIDE THE MTNS. THIS
CERTAINLY MAKES SENSE IN LIGHT OF THE DELAY IN DESTABILIZATION THAT
IS UNDERWAY ACROSS THE PIED/FHILLS. THE UPSHOT IS THAT POPS HAVE
BEEN RAISED A BIT ACROSS THE MTNS...ESP NEAR THE BLUE RIDGE...AND
DECREASED A BIT ACROSS THE PIED/FHILLS. THIS GENERALLY RESULTED IN
WIDESPREAD 30 POPS...WITH A COUPLE OF POCKETS OF 20 AND 40 (HIGHEST
NEAR THE ESCARPMENT).

BULK SHEAR WILL BE VERY WEAK THIS PM (GENERALLY LESS THAN 10 KTS) IN
THE 0-3KM AND 0-6KM LAYERS)...THUS CHANCES FOR UPSCALE ORGANIZATION
WILL BE VERY LOW. HOWEVER...DRYING ALOFT SHOULD RESULT IN
RESPECTABLE LEVELS OF DCAPE THIS AFTERNOON...WHICH SHOULD POSE A
THREAT OF ISOLATED PULSE STORMS/BRIEF MICROBURST-PRODUCERS IN THE
WEAKLY SHEARED ENVIRONS.

AS OF 650 AM...RADAR REMAINS PPINE THIS MORNING AND ANY CONVECTION
SHUD HOLD OFF UNTIL AFTERNOON. HAVE UPDATED POP TO REFLECT THIS.
PATCHY FOG SHUD BURN OFF QUICKLY THIS MORNING...BUT LOW CLOUDS WILL
ONLY SLOWLY LIFT AND/OR SCATTER OUT BY EARLY AFTERNOON. OTHERWISE...
FCST MAINLY ON TRACK WITH UPDATES NEEDED FOR CURRENT CONDITIONS.

AS OF 325 AM...SHRA HAVE DISSIPATED AND LOW CLOUDS AND FOG ARE
DEVELOPING IN ITS PLACE. THAT SAID...CANNOT RULE OUT A SPRINKLE OR
TWO HERE AND THERE EARLY THIS MORNING. THE FOG WILL BURN OFF BY MID
MORNING WHILE THE LOW CLOUDS WILL ONLY SLOWLY LIFT INTO THE EARLY
AFTERNOON...POSSIBLY SCATTERING OUT AS WELL. THE GUIDANCE SHOWS
QUITE A BIT OF DRYING ACROSS THE CWFA TODAY AS PW VALUES FALL THRU
THE DAY. HOWEVER...LOW LEVEL MOISTURE REMAINS HIGH AND MODERATE
INSTABILITY SHUD DEVELOP ONCE AGAIN. BEST INSTABILITY WILL BE EAST
AND SOUTH OF THE MTNS THIS AFTERNOON. MODERATE SHEAR DEVELOPS AS
ANOTHER SHORT WAVE MOVES INTO THE AREA. DECENT FORCING SHUD DEVELOP
EAST AND SOUTH OF THE MTNS WITH THE SHORT WAVE AND UPPER DIVERGENCE
MOVING IN. THEREFORE...EXPECT BEST COVERAGE EAST AND SOUTH OF THE
MTNS THIS AFTERNOON AND EARLY EVENING. SREF MEAN DCAPE VALUES ARE
OVER 500 J/KG THIS AFTERNOON...BUT MINIMAL CHC OF VALUES ABOVE 1000
J/KG. NAM IS FORECASTING QUITE A BIT OF SFC DELTA THETA-E AS WELL.
THEREFORE...SPC HAS MOST OF THE CWFA IN A MARGINAL RISK WITH
DAMAGING WINDS THE MAIN THREAT. EXPECT COVERAGE TO DIMINISH TO
ISOLATED OVERNIGHT WITH LOSS OF HEATING AND FORCING. HIGHS WILL BE
NEAR TO A LITTLE ABOVE NORMAL WITH LOWS AROUND 5 DEGREES ABOVE
NORMAL.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AT 200 PM EDT WEDNESDAY...ON FRIDAY MORNING AN UPPER RIDGE WILL BE
ALONG THE EASTERN SEABOARD...WHILE A TROUGH WILL BE OVER THE
ROCKIES. THE EASTERN RIDGE BEGINS TO BREAK DOWN ON SATURDAY.
MEANWHILE...THE DEAMPLIFYING UPPER TROUGH PROGRESSES TO THE SOUTHERN
PLAINS...REACHING THE LOWER MS RIVER VALLEY ON SATURDAY NIGHT.

AT THE SURFACE...ATLANTIC RIDGING WILL OVER THE CAROLINAS AND GA
WILL BE REINFORCED BY HIGH PRESSURE CENTERED OVER EASTERN CANADA.
LOW LEVEL MOISTURE WILL REMAIN BANKED UP AGAINST THE SOUTHERN
APPALACHIANS...WITH ONLY WEAK ISENTROPIC UPGLIDE AND UPSLOPE FLOW
INTO THE BLUE RIDGE. THE SURFACE HIGH MOVES OFFSHORE ON SATURDAY...
BUT THE RIDGE MAINTAINS A FOOTHOLD ON GA AND THE CAROLINAS.
INSTABILITY WILL BE PRESENT BOTH DAYS...CHIEFLY OVER THE MOUNTAINS ON
THE WESTERN PERIPHERY OF THE UPPER RIDGE...BUT SHEAR IS EXPECTED TO
BE RELATIVELY TAME. TEMPERATURES WILL EXHIBIT A REDUCED DIURNAL
RANGE DUE TO CLOUDS AND MOISTURE.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 245 AM WEDNESDAY...MODELS IN GOOD AGREEMENT ON ANOTHER BROAD
SHALLOW UPPER TROF CROSSING THE GREAT LAKES...WITH THE UPPER RIDGE
WEAKENING SLIGHTLY ACRS THE SOUTHEAST STATES OVER THE WEEKEND. THIS
WILL ALLOW A SLOW-MOVING COLD FRONT TO PUSH SOUTHEAST ACRS THE OH/TN
VALLEYS SATURDAY AND SUNDAY...THEN STALL OUT ACRS THE SOUTHERN
APPALACHIANS FOR MONDAY AND TUESDAY.

SATURDAY LOOKS LIKE IT WILL HAVE THE LOWEST POPS OF THE
PERIOD...WITH JUST A LOW-END CHC IN THE MTNS...AND PROBABLY DRY ACRS
MOST OF THE PIEDMONT. POPS RAMP UP AGAIN SUNDAY AND MONDAY...AS THE
RIDGE WEAKENS AND THE FRONT PUSHES IN FROM THE NORTHWEST. SHEAR WILL
STAY FAIRLY WEAK...BUT THERE MAY BE A SMALL SEVERE THREAT. THE GFS
IS MORE BULLISH ON BRINGING MORE STABLE AIR IN ACRS THE NRN HALF OF
THE CWFA...AS A WEAK WEDGE DEVELOPS DUE TO A 1028-1030 MB SFC HIGH
PRES BUILDING IN ACRS THE NORTHEAST STATES. THE ECMWF IS STILL MUCH
WEAKER WITH THE HIGH...AND DOESN/T PUSH THE BACKDOOR FRONT INTO THE
AREA UNTIL TUESDAY. SO MORE UNCERTAINTY FOR EARLY NEXT WEEK...BUT
WILL FEATURE ABOVE CLIMO POPS EACH DAY SUN-TUE...WITH HIGHEST POPS
ON MONDAY. TEMPS WILL BE THEIR WARMEST SAT-SUN AHEAD OF THE
FRONT...THEN BACK TO NEAR OR SLIGHTLY ABOVE NORMAL MON-TUE. MIN
TEMPS WILL REMAIN WELL ABOVE NORMAL EACH NIGHT WITHIN THE SUMMERY
AIR MASS.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...PERIODS OF MVFR CIGS WILL BE POSSIBLE AT
MOST TERMINALS DURING THE FIRST COUPLE OF HOURS OF THE FORECAST
PERIOD...WITH SCT/BKN CLOUDS IN THE 035-045 RANGE EXPECTED INTO THE
EVENING HOURS. THE COMBINATION OF WIDESPREAD LOW CLOUDS AND SOME
MID-LEVEL MOISTURE HAS RESULTED IN MINIMAL INSTABILITY DEVELOPING
ACROSS THE REGION SO FAR THIS AFTERNOON...AND STILL DON/T REALLY SEE
ANY SIGNS THAT DEEP CONVECTION IS IMMINENT NEAR THE TERMINALS...
WHILE THE BEST CHANCES THROUGH THE REMAINDER OF THE AFTERNOON WILL
BE EAST OF KCLT. NEVERTHELESS...EXPECT ISOLATED/WIDELY SCT
CONVECTION TO DEVELOP OVER MUCH OF THE AREA THIS AFTERNOON AS CLOUDS
CONTINUE TO THIN AND INSTABILITY INCREASES. HOWEVER...WITH
INSTABILITY EXPECTED TO REMAIN ON THE WEAK SIDE AND THE EXPECTATION
OF LIMITED COVERAGE...OPTED TO LIMIT THE MENTION TO A VCSH AT ALL
TERMINALS EXCEPT KAVL...WHERE A VCTS WILL E CARRIED. OTHERWISE...
CHANCES FOR VISBY/CIG RESTRICTIONS WILL INCREASE AGAIN TONIGHT...
BUT A TRANSITION TO MORE OF A SW FLOW REGIME IS EXPECTED TO RESULT
IN LOWER CHANCES FOR CIG RESTRICTIONS THAN SEEN IN RECENT DAYS. MVFR
VISBY IS FORECAST AT MOST TERMINALS...WITH IFR CONDITIONS AT KAVL.

OUTLOOK...MOIST SW FLOW WILL CONTINUE TO AFFECT THE TERMINAL
FORECAST AREA THROUGH THE UPCOMING WEEKEND...AS A COLD FRONT LAYS
OVER TO THE NORTH OF THE AREA. EXPECT POCKETS OF MORNING FOG AND/OR
STRATUS MOST DAYS...WITH CONTINUED CHANCES OF AFTN/EVENING SHRA/TSRA
EACH DAY.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH  97%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH  94%     HIGH  94%
KAVL       HIGH 100%     HIGH  97%     HIGH  92%     HIGH  97%
KHKY       HIGH 100%     HIGH 100%     HIGH  91%     HIGH  95%
KGMU       HIGH 100%     HIGH 100%     HIGH  97%     HIGH  94%
KAND       HIGH 100%     HIGH 100%     HIGH  93%     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...ARK
NEAR TERM...JDL/RWH
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...JDL



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