Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 061758
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
158 PM EDT MON JUL 6 2015

.SYNOPSIS...
AS AN UPPER LEVEL LOW PRESSURE SYSTEM DEPARTS THE REGION...SLIGHTLY
DRIER AIR ARRIVES FROM THE WEST TODAY. A BROAD UPPER RIDGE WILL
STRENGTHEN AND MIGRATE OVER THE SOUTHEAST THROUGH THE REMAINDER OF
THE WEEK AND INTO THE WEEKEND.  AS A RESULT...SHOWER AND
THUNDERSTORM CHANCE WILL BECOME INCREASINGLY DIURNAL IN NATURE.
TEMPERATURES ARE ALSO EXPECTED TO MODERATE TO ABOVE NORMAL LEVELS.

&&

.NEAR TERM /THROUGH TONIGHT/...
BASED ON CURRENT TRENDS...HAVE REALIGNED POPS TO FAVOR CONVECTIVE
DEVELOPMENT INITIALLY OVER THE SOUTHER UPSTATE/NE GA THIS AFTERNOON
WHERE BEST INSTABILITY RESIDES. THIS IDEA IS SUPPORTED BY THE LATEST
HRRR. STILL LOOKS LIKE EASTERN SECTIONS WILL SEE SOME WIDELY SCT
TSRA LATE THIS AFTERNOON AND EARLY EVENING. LOWERED POPS SOMEWHAT
OVER THE MOUNTAINS IN DEFERENCE TO CAPE MINIMA ACROSS THAT AREA.

AT 1225 PM...GOING FORECAST ESSENTIALLY ON TRACK WITH NO ECHOES ON
RADAR AT THE MOMENT. WILL STAY THE COURSE WITH POP FORECAST ALTHOUGH
THE BLUE RIDGE IS CURRENTLY IN A CAPE MINIMA...THOUGH EDGING UPWARD
TO AROUND 1000J. 16Z HRRR DEVELOPS RANDOM WIDELY SCATTERED SHRA/TSRA
THIS AFTERNOON NOT FAVORING ANY PARTICULAR LOCATION. BOTTOM LINE IS
THAT IT LOOKS LIKE CONVECTIVE COVERAGE WILL BE ON THE LOW SIDE.
CAN`T COMPLETELY RULE OUT A STRONG TO SEVERE STORM AS CAPES CREEPING
UP TO AROUND 2000J OVER THE PIEDMONT ALONG WITH SOME MID LEVEL DRY
AIR SHOWING UP IN BUFKIT PROFILES. MAX TEMPS WILL TOP OUT IN THE
UPPER 80S TO LOW 90S OUTSIDE THE MOUNTAINS...WITH THE HIGHEST VALUES
TO THE EAST WHERE BEST INSOLATION RESIDES.

AS OF 10 AM...RADAR SHOWS SOME DISSIPATING LIGHT SHOWERS OVER THE
NORTHERN NC PIEDMONT. THE FOCUS FOR ADDITIONAL PRECIP WILL SHIFT TO
THIS AFTERNOON. THE REMNANTS OF THE UPPER TROUGH IS STILL LINGERING
ACROSS THE WESTERN CAROLINAS INTO NE GA. SATELLITE PICS SHOW QUITE A
BIT OF CLOUDINESS FROM FAR WESTERN NC INTO GA APPARENTLY ASSOCIATED
WITH A VORT MAX. THE 12Z NAM LIFTS THIS FEATURE SLOWLY E-NE. THE NAM
IS THE MOST BULLISH IN TRIGGERING DEEP CONVECTION ALONG THE
ESCARPMENT EARLY THIS AFTERNOON AND THEN DEVELOPING MORE SCT TSRA
OVER EASTERN SECTIONS THIS EVENING. THE LATEST CAMS ARE MUCH MORE
MUTED. USED A BLEND OF THE LATEST CONSSHORT AND NAM ND5 POPS. THIS
RESULTS IN CHANCE POPS ALONG THE ESCAPRMENT THIS AFTERNOON AND ALSO
OVER PARTS OF THE I-77 CORRIDOR THIS EVENING. OTHERWISE...ANY
CONVECTION WILL BE ISOLATED IN NATURE. ALSO TRENDED TEMPS/DEWPOINTS
AND SKY TO LATEST CONSHORT DATA.

AS OF 645 AM...THE UPPER TROUGH THAT HAS LINGERED OVER THE CWFA THE
PAST COUPLE OF DAYS IS LOSING INFLUENCE AS IT DRIFTS NEWD. THE BEST
DPVA IS ALREADY OFF TO OUR NORTHEAST. A BAND OF LIGHT SHOWERS
HOWEVER ILL CONTINUE TO ROTATE ACRS THE NRN MTN/FOOTHILL ZONES OVER
THE NEXT COUPLE OF HRS. THESE WILL PROBABLY BE NO MORE THAN
SPRINKLES IN MANY AREAS. PATCHY FOG AND LOW CLOUDS WILL BE SEEN OVER
THE PIEDMONT...BUT THESE SHOULD MIX OUT BY 9 A.M. OR SO.

CYCLONIC MID-UPPER FLOW WILL REMAIN OVERHEAD THRU MOST OF THE DAY.
THOUGH EMBEDDED VORTICES MIGHT PROVIDE MESOSCALE ENHANCEMENT TO
LIFT...THE UPPER PATTERN IS EXPECTED TO HAVE LITTLE IMPACT ON POPS
EXCEPT PERHAPS TO ALLOW THE LIGHT SHOWERS OVER THE NRN CWFA AT
DAYBREAK TO CONTINUE SPREADING EAST THRU THE MRNG. MAJOR MODELS
INCLUDING THE CONVECTION ALLOWING SPC AND NSSL WRF RUNS MAINLY KICK
OFF ACTIVITY ALONG THE SRN END OF THE BLUE RIDGE AT
MIDDAY...PROPAGATING IT EWD AND FEATURING THE BEST COVERAGE OVER THE
PIEDMONT BY MID-AFTN. SOME DIFFERENCES CONTINUE TO BE SEEN BETWEEN
NAM AND GFS IN TERMS OF INSTABILITY...MORESO THAN USUAL. GFS SHOWS
POORER LAPSE RATES PERHAPS ON ACCOUNT OF SUBSIDENCE IN THE WAKE OF
THE TROUGH. NONETHELESS BOTH MODELS SUPPORT SCATTERED ACTIVITY.
TSTMS ARE EXPECTED TO REMAIN MORE ISOLATED THAN SHOWERS WITH
BUOYANCY IN QUESTION. PROFILES WILL BE QUITE A BIT DRIER IN THE
UPPER LEVELS WHICH MIGHT ALLOW TSTMS TO PRODUCE ROBUST
OUTFLOWS...PARTICULARLY IF THE HIGHER NAM CAPES VERIFY. HOWEVER I
WILL NOT VENTURE TO SAY THAT DAMAGING WINDS CAN BE EXPECTED. MAX
TEMPS WILL BE CLOSE TO NORMAL...MAYBE A DEGREE OR TWO BELOW.

TONIGHT POPS DIMINISH WITH NOCTURNAL STABILIZATION AND CONTINUED
DEPARTURE OF THE TROUGH. HOWEVER WITH WARM ADVECTION RAMPING UP OVER
THE TENN VALLEY IN SW FLOW AHEAD OF THE MIDWEST TROUGH...I KEPT AN
ISOLD SHOWER MENTION AND MCLDY SKIES OVER THE MTNS. MIN TEMPS WILL
BE SIMILAR TO THOSE THIS MORNING...ABOUT NORMAL.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
OF 230 PM EDT MONDAY... THE SHORT TERM PART OF THE FORECAST STILL
CONTINUES A THEME FOR THE RETROGRESSION OF THE BERMUDA HIGH INTO OUR
FORECAST AREA (FA) TUESDAY NIGHT AND WEDNESDAY...ALBEIT NOT YET
FIRMLY ENTRENCHED. THE UPPER AIR PATTERN THEN TAKES ON A W-SWLY LOOK
AT THAT TIME...WITH PACKETS OF ENERGY MOVING THROUGH THE FLOW...
ESPECIALLY ON OUR NORTHERN AND WESTERN PERIPHERY.

CONVECTION TUESDAY NIGHT IN THE MOUNTAINS SHOULD WANE WITH LOSS OF
HEATING...ALTHOUGH ALONG THE TENNESSEE/NORTH CAROLINA STATE LINE A
FEW CELLS MAY TRY TO HOLD ON A LITTLE LONGER WITH WEAK FORCING
ALOFT.

MEANWHILE ON WEDNESDAY...THERE APPEARS TO BE ENOUGH INSTABILITY...
AND HEIGHTS HAVE NOT REACHED THEIR APEX YET...PLUS TAIL OF ENERGY
PACKETS (DPVA) MOVING THROUGH THE MEAN FLOW...FOR A CHANCE POP
FORECAST IN THE MOUNTAIN AND SLIGHT CHANCE ELSEWHERE. WE JUST NEED
TO KEEP AN EYE ON ANY CONVECTION NORTH OF OUR REGION...IN A WAFFLING
FRONTAL PATTERN...TRYING TO TURN SEWD TOWARD OUR NORTHERN FA. THE
NAM SUBTLY IMPLIES SOMETHING LIKE THIS HEADING OFF TO OUR EAST...
THEREFORE A NOTE OF CAUTION.

ONCE AGAIN CONVECTION WILL WANE WEDNESDAY NIGHT. IT APPEARS RIDGING
ALOFT WILL BE BUILDING IN FULL FORCE THURSDAY. WE HAVE KEPT THE POPS
ON THE VERY LOW SIDE...BASICALLY TRYING TO EMPHASIS THE HIGHER
TERRAIN LOCATIONS. WE WERE A LITTLE CONCERNED WITH THE LEE SIDE
TROFFING PROVIDING A WEAK FOCUS AROUND THE REGION...THUS POPS JUST
INTO THE SLIGHT CATEGORY...WHICH FITS WELL WITH OUR NEIGHBORS.

WE HAVE FOLLOWED THE TEMPERATURE PROFILE OF THE MODELS WHICH BRING
TEMPERATURES UP DURING THIS PART OF THE CYCLE...AS RIDGING AND HEAT
BEGIN ANOTHER SURGE.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AT 200 PM EDT MONDAY...ON FRIDAY AN UPPER RIDGE WILL EXTEND FROM THE
GULF STATES TO THE GREAT LAKES. THE RIDGE AMPLIFIES ALMOST TO HUDSON
BAY ON SATURDAY...THEN RETROGRESSES TO THE SOUTHERN PLAINS BY
SUNDAY...AND TO THE SOUTHERN ROCKIES BY MONDAY.

AT THE SURFACE...HIGH PRESSURE WILL BE CENTERED OVER THE SOUTHERN
APPALACHIANS ON FRIDAY...WITH A LEE TROUGH OVER THE PIEDMONT...WHILE
A STATIONARY FRONT RESIDES OVER THE OH RIVER VALLEY. ON SATURDAY THE
WESTERN PORTION OF THE FRONT DIPS SOUTH INTO NC...BUT BY SUNDAY IT
IS EXPECTED TO RETURN NORTH AS A WARM FRONT. MONDAY FEATURES A AN
IMPROVED PRESSURE GRADIENT AND RESULTING WESTERLY FLOW...AS THE
RETROGRESSING UPPER RIDGE ALLOWS FOR EAST COAST TROUGHING AND A DIP
OF THE WESTERLIES TO OUR LATITUDE.

INSTABILITY IS EXPECTED TO BE LIMITED EARLY ON UNDER THE UPPER
RIDGE...ALTHOUGH NO CAPPING INVERSION IS DEPICTED IN MODEL
SOUNDINGS. AS THE UPPER RIDGE SLIDES WEST...MORE ROBUST INSTABILITY
APPEARS BY THE WEEKEND. STEERING FLOW WILL BE QUITE LIGHT UNDER THE
RIDGE...BUT IMPROVES AS THE RIDGE DEPARTS AND WINDS PICK UP WITH
EAST COAST TROUGHING. TEMPERATURES WILL RUN ABOVE NORMAL...WITH A
SLIGHT DECLINE LATE IN THE FORECAST AS HEIGHTS FALL ALOFT WITH THE
DEPARTURE OF THE RIDGE.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
AT KCLT...MAIN CONCERN IS WHETHER ANY CONVECTION WILL AFFECT THE
AIRFIELD THIS AFTERNOON AND/OR EARLY EVENING. BEST INSTABILITY AXIS
IS TO THE S-SW AND THAT IS WHERE SOME RADAR ECHOES ARE CURRENTLY
NOTED OVER THE SW UPSTATE OF SC. LATEST HRRR DEVELOPS SCT TSRA
EASTWARD ALONG THAT INSTABILITY AXIS BY 20Z AND THEN TO THE NORTH
CIRCA 21-22Z. CONFIDENCE STILL NOT HIGH ENUF TO GO WITH A TEMPO
TSRA...SO WILL STAY THE COURSE WITH A VCSH. NO RESTRICTIONS EXPECTED
EXCEPT IF A TSRA AFFECTS THE AIRFIELD.

ELSEWHERE...SAME CONCERNS AS TO WHETHER ANY CONVECTION WILL AFFECT
THE AIRFIELDS. LOOKS LIKE THE SC AIRFIELDS WILL HAVE THE BEST CHANCE
AS THEY ARE CLOSER TO THE INSTABILITY MAXIMUM OVER THE SOUTHERN
UPSTATE AND THE LEE TROUGH. HENCE...WILL CARRY A VCTS AT
KAND/KGSP/KGMU FROM 20-23Z. THUNDER CHANCES LESS AT AVL AND HKY
SO WILL JUST CARRY A VCSH THERE. THE ONLY OTHER RESTRICTION IS FOR
SOME FOG AT KAVL EARLY TUE MORNING. CURRENTLY FORECASTING VSBY`S
TO LOWER TO AROUND 2 MILES AT KAVL IN FOG JUST BEFORE SUNRISE.

OUTLOOK...THE WEATHER REGIME WILL RETURN TO A MORE TYPICAL DIURNAL
SUMMERTIME PATTERN THROUGH THE WEEK. THIS WILL MEAN SCATTERED
AFTN/EVENING THUNDERSTORMS OVER THE AREA...MAINLY IN THE MTNS...WITH
ASSOCIATED RESTRICTIONS UNDER THE HEAVIEST SHOWERS...AND SPOTTY LOW
CLOUDS AND FOG THE FOLLOWING MORNING.

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  94%     HIGH  94%
KHKY       HIGH 100%     HIGH 100%     HIGH  97%     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...CDG/WIMBERLEY
NEAR TERM...LG
SHORT TERM...CDG
LONG TERM...CDG
AVIATION...LG


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