Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 272026
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
426 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 THURSDAY/...
415 PM UPDATE...CONVECTION OVER THE MTNS REMAINS ISOLATED...WITH
MOST CU IN THAT AREA LOOKING UNLIKELY TO PRECIPITATE ON VISIBLE SAT.
FOR THE PIEDMONT THE MAIN FOCUS CONTINUES TO BE AN EXPANDING OUTFLOW
BDY S AND E OF CHARLOTTE...KICKING OFF SOME SMALL CELLS. WHILE THE
AREA APPEARS UNSTABLE ENOUGH THAT A FEW MORE ISOLATED CELLS COULD
DEVELOP AWAY FROM THE EXISTING ACTIVITY...LOW CHC POPS AT BEST SEEM
FINE INTO THE EVENING. TOUCHED UP TEMPS/DEWPTS THOUGH THEY WERE MORE
OR LESS ON TRACK.

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 INTO THE EVENING HOURS...
WITH SLIGHTLY HIGHER PROBABILITIES ALONG/NEAR THE EASTERN
ESCARPMENT. ALTHOUGH THE LIMITED INSTABILITY SHOULD GENERALLY LIMIT
COVERAGE OF ROBUST UPDRAFTS...STRONG THETA-E LAPSES/DECENT DCAPE
AND WEAK SHEAR COULD SUPPORT A COUPLE OF MICROBURSTS.

A SHORT WAVE TROUGH WILL APPROACH THE AREA FROM THE TENN VALLEY THIS
EVENING. THERE IS A CONSIDERABLE AMOUNT OF CONVECTION AHEAD OF THIS
FEATURE ACROSS THE MISS VALLEY THIS AFTERNOON. MUCH OF THIS ACTIVITY
WILL PUSH ACROSS THE TENN VALLEY INTO THE EVENING HOURS...BUT
MESOSCALE AND SHORT TERM GUIDANCE ARE IN GENERAL AGREEMENT THAT THIS
ACTIVITY WILL TEND TO LOSE STEAM AS IT APPROACHES OUR AREA TONIGHT
IN THE WEAKLY SHEARED/STABILIZING ENVIRONMENT. THUS...ONLY TOKEN
SLIGHT/LOW CHANCE POPS WILL BE RETAINED THROUGH THE OVERNIGHT.

BY THURSDAY AFTERNOON...PWATS WILL RETURN TO ABOVE CLIMO LEVELS...AS
DEEPER MOISTURE PUSHES INTO THE SOUTHERN APPALACHIANS AND
SURROUNDING AREAS IN ASSOCIATION WITH DAMPENING SHORT WAVE TROUGH.
ON THE OTHER HAND...INSTABILITY MAY END UP BEING LIMITED BY
CONSIDERABLE MID-LEVEL CLOUD COVER TOMORROW AFTERNOON.
ADDITIONALLY...THE DEEP LAYER FLOW WILL BE EXTREMELY WEAK. IN
FACT...2-8KM MEAN WINDS ARE LESS THAN 5 KTS IN THE LATEST NAM
FORECAST SOUNDINGS. THEREFORE...ANY CELLS THAT DO DEVELOP TOMORROW
AFTERNOON WILL NOT COVER MUCH AREA. WE WILL CONTINUE TO ADVERTISE
HIGHER-THAN-CLIMO POPS IN LIGHT OF THE HIGH PWATS...BUT CONVECTION
IS NOT EXPECTED TO BE ESPECIALLY ROBUST IN THE WEAK LAPSE RATE/
MODESTLY UNSTABLE REGIME. LOCALIZED HEAVY RAINFALL WILL BE OF SOME
CONCERN IN LIGHT OF THE HIGH MOISTURE CONTENT AND WEAK STEERING
FLOW.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
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. LIMITED
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 NIGHT THROUGH WEDNESDAY/...
AS OF 230 PM WEDNESDAY...MODELS REMAIN IN GOOD AGREEMENT WITH A
BROAD UPPER TROF CROSSING THE NORTHEASTERN CONUS AND ERODING THE
UPPER RIDGE OVER THE EASTERN SEABOARD ON SUNDAY. A BROAD SURFACE
HIGH WILL BUILD INTO THE MIDWEST...SLOWLY PUSHING A COLD FRONT
TOWARDS THE SOUTHEAST LATE SUNDAY AND INTO MONDAY. THE BOUNDARY WILL
THEN STALL OUT OVER THE APPALACHIANS AND WEAKEN SLIGHTLY EARLY IN
THE WORK WEEK.

AS THE FRONTAL BOUNDARY APPROACHES SUNDAY AND MONDAY...POPS INCREASE
ONCE AGAIN...WITH THE GFS DRIVING THE BOUNDARY IN SLIGHTLY FASTER
THAN THE ECMWF. WHILE NOT PARTICULARLY IMPRESSIVE AT THIS
TIME...WEAK SHEAR AND INSTABILITY LOOK TO BE PRESENT MONDAY THROUGH
THE END OF THE EXTENDED PERIOD...SUGGESTING STORMS WITH SOME
ORGANIZATION ARE POSSIBLE WITH A DIURNAL PEAK. CONFIDENCE IS LOWER
TUESDAY-WEDNESDAY...BUT MODELS SUGGEST THE BOUNDARY WILL BE SLOW TO
CLEAR THE AREA...SO POPS WILL REMAIN ABOVE CLIMO THROUGH THE END OF
THE PERIOD. MOIST SOUTH/SOUTHWESTERLY FLOW WILL WILL KEEP HIGHS AND
LOWS WELL ABOVE CLIMO ON SUNDAY...WITH CLOUD COVER DROPPING HIGHS TO
NEAR NORMAL AND LOWS REMAINING ABOVE AVERAGE FOR THE WORK WEEK.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...SCT/BKN CLOUDS JUST ABV THE MVFR THRESHOLD
ARE 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. THE BEST CHANCES THROUGH THE REMAINDER OF THE
AFTERNOON WILL BE JUST S AND E OF KCLT ALONG AN OUTFLOW BOUNDARY.
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...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH  95%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH  85%     HIGH 100%
KAVL       HIGH 100%     HIGH  95%     HIGH  91%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH  95%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH  91%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  97%     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...SBK
NEAR TERM...JDL/WIMBERLEY
SHORT TERM...JAT
LONG TERM...LEV
AVIATION...JDL/WIMBERLEY



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