Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 021817
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
217 PM EDT SAT MAY 2 2015

.SYNOPSIS...
DEEP LAYERED RIDGING WILL TO CONTINUE ACROSS THE REGION INTO NEXT WEEK
WITH AN OCCASIONAL SHOWER OR THUNDERSTORM POSSIBLE DURING PEAK
HEATING EACH DAY...MAINLY ACROSS THE MOUNTAINS AND FOOTHILLS OF
WESTERN NORTH CAROLINA. TEMPERATURES WILL MODERATE TO ABOVE NORMAL
LEVELS WITH HIGHS TOPPING OUT IN THE LOWER TO MID 80S NEAR PERIODS
END.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 210 PM EDT...WATER VAPOR IMAGERY SHOWS A SHORTWAVE MOVING SE
TOWARD THE SRN APPALACHIANS THIS AFTERNOON. THIS IS PRODUCING SOME
CLOUDINESS BUT VERY LITTLE RETURNS ON UPSTREAM REGIONAL RADARS THUS
FAR. THE SHORTWAVE WILL CROSS THE SRN APPALACHIANS WITH SOME WEAK
DPVA FORCING CIRCA 21Z. SOME SPEED CONVERGENCE AT LOW LEVELS IS ALSO
INDICATED ALONG THE ERN ESCARPMENT. HOWEVER...SFC DEWPOINTS IN THE
UPPER 30S AND LOWER 40S ACROSS MOST OF THE AREA WILL CONTINUE TO
LIMIT SFC BASED INSTABILITY THROUGH THE LATE AFTN HOURS. THE
CONVECTION ALLOWING MODELS CONFINE SHOWER COVERAGE TO THE SRN MTNS
AND ERN ESCARPMENT LATE THIS AFTN...WITH ISOLD COVERAGE AT
BEST.

SFC HIGH PRES WILL BUILD OVERHEAD TONIGHT. WINDS WILL BECOME
LIGHT...BUT FEW TO SCT STRATOCUMULUS COULD REDEVELOP JUST UNDER A
WEAK INVERSION ALOFT. IN ADDITION...AIRMASS RECOVERY WILL HOLD MIN
TEMPS AT LEAST A CATEGORY ABOVE SAT MORNING VALUES. THE LOW LEVEL
RIDGE WILL SLIP TO THE SE COAST ON SUNDAY...AND SOME BAGGINESS IN
THE UPPER LEVEL HEIGHT FIELD WILL DEVELOP. AT LOW LEVELS...FLOW WILL
BECOME MORE SRLY UPSLOPE THROUGH THE DAY. WITH GRADUAL DEWPOINT
RECOVERY...ISOLD TO LOW END SCATTERED SHOWER COVERAGE WILL BE
POSSIBLE IN AND NEAR THE HIGH TERRAIN. MAXES SHOULD REBOUND ANOTHER
DEGREE OR TWO.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 230 PM EDT SATURDAY...THE CURRENT SUITE OF MODEL GUIDE WAS
FAIRLY SIMILAR IN ALLOWING WEAK H5 TROFFING TO SETTLE INTO THE
WESTERN CAROLINA`S AND NORTHEAST GEORGIA SUNDAY NIGHT. LEFT OVER
CONVECTION (FROM SUNDAY AFTERNOON) SHOULD WANE SUNDAY EVENING...AS
INSTABILITY WEAKENS...ALTHOUGH CLOUDINESS MAY FAN OUT ACROSS THE
FORECAST AREA WHICH IS DEPICTED VIA BUFKIT AND PLAIN VIEW MODEL
DATA. WE ARE NOT CONVINCED HOWEVER THAT PRECIPITATION WILL SHIFT OUT
OF THE MOUNTAINS AND FOOTHILLS CONSIDERING THE SELY FETCH IS WEAK...
FORCING WEAK AND POOR TIME OF DAY.

MEANWHILE THE RETROGRESSION OF THE SURFACE HIGH PRESSURE SYSTEM OFF
THE ATLANTIC SEABOARD WILL ALLOW MOISTURE TO GRADUALLY SHIFT (IN A
DEEPER TYPE FASHION) THROUGHOUT THE FORECAST AREA EARLY NEXT WEEK.
THE UPPER AIR PATTERN BOTH MONDAY AND TUESDAY SHOW A RATHER NEBULOUS
PATTERN WITH AN H5 LOW STUCK ACROSS THE REGION...WHILE WEAK SPOKES
OF VORTICITY RIDE AROUND THE UPPER TROUGH.

THE UPSHOT APPEARS TO BE MORE CLOUDINESS MONDAY/TUESDAY...WITH A BIT
STEEPER LAPSE RATES DESPITE THE CLOUDS...AND CONTINUED LOBES OF
ENERGY ARRIVING AND EXITING. WE WILL FOLLOW A DIURNAL POP TREND IN
THE MOUNTAINS AND FOOTHILLS...SLIGHTLY ABOVE DETERMINISTIC GUIDE AND
CLOSER TO A BLEND. THE MODELS CONTINUE TO INSIST ON PRECIPITATION
BREAKING CONTAINMENT...THEREFORE FOR STARTERS WE HAVE BROUGHT LOW
POP CHANCES JUST A BIT FURTHER EAST AND SOUTH OF THE PREVIOUS
FORECAST. THE GENERATION OF INSTABILITY ON BOTH MODELS SUGGEST
THUNDER BOTH MONDAY/TUESDAY AFTERNOON`S AND EVENINGS.

THERE APPEARS TO BE A NOTICEABLE TREND IN KEEPING MINS A LITTLE
HIGHER AT NIGHT...AND MAX TEMPERATURES A LITTLE LOWER DURING THE
DAY...PROBABLY BECAUSE OF THE STUCK UPPER TROUGH AND CLOUDS. AS A
RESULT USED A BLENDING OF GUIDE TO ARRIVE AT TEMPERATURE FORECAST
THROUGH THIS PART OF THE FORECAST CYCLE.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 145 PM EDT SATURDAY...THE EXT RANGE BEGINS WITH AN ULVL
PATTERN TRANSITION FROM A BROAD SUBTROP HIGH TO A REX BLOCK WHICH
WILL PERSIST THROUGHOUT THE PERIOD. RELATIVELY COOL H5 AIR WILL
FILTER INTO REX TROF AND HELP INSTIGATE A HYBRID SUBTROPICAL SFC LOW
AROUND THE BAHAMAS EARLY WED. THE DYNAMIC MODELS AGREE WELL WITH
THIS SCENARIO...ALBEIT WITH THE USUAL AMOUNT OF TIMING/STRENGTH
SPREAD THRU TIME. THE 12Z GFS IS STRONGER AND MORE W/LY THAN THE 00Z
ECMWF...WHICH WOULD AFFECT THE SENSIBLE WX ACROSS THE WRN CAROLINAS
AND NE GA MAINLY THU.

IN ANY SENSE...AN OVERALL SUBSIDENCE PATTERN WILL PREVAIL ACROSS THE
CWFA WITH LITTLE TRIGGERS AVAILABLE FOR NON/MTN SHRA AND CONVECTION
WED AFTERNOON. MODEL SOUNDINGS INDICATE CIN VALUES OUTSIDE THE MTNS
WILL NOT BE OVERCOME IF AT ALL BY 00Z...SO WILL KEEP THE CHANCE POP
MENTION LIMITED TO THE MTNS. ON THU...A BACKDOOR COLD FRONT AIDED BY
THE DEVELOPING SUBTROP SYSTEM WILL MOVE INTO THE NRN ZONES AND WITH
INCREASED LLVL MOISTURE AND MLVL OMEGA...SBCAPE/ELCAPE SHOULD BE
ENOUGH FOR THE NC PIEDMONT AND FOOTHILLS TO SEE SCT SHRA/TSTMS.
PWATS INCREASE TO NEAR 1.3 INCHES THU AND A SUSPECTED WEAK STORM
MOTION MAY ALLOW SOME SPOTTY HYDRO CONCERNS. HOWEVER THERE IS LOW
CONFIDENCE IN THE STEERING FLOW MAGNITUDE. THE MORE AGGRESSIVE GFS
INCREASES THE H85/H5 FLOW TO ARND 25 KTS...WHILE THE ECMWF IS ABOUT
HALF THAT OR LESS. THE SHALLOW FRONT WASHES OUT ON FRI AND A DEEP
SUBS PATTERN RETURNS AS THE NRN REX RIDGE AXIS CROSSES OVERHEAD.
THIS WILL RETURN POPS TO NEAR OR BELOW CLIMO WITH MAINLY LOW END
DIURNAL MTN CHANCE CONVEC. MAX TEMPS WILL INCREASE TO A CAT OR TWO
ABOVE NORMAL THOUGH THE PERIOD WITH SIMILAR MIN CURVES.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS WILL CONTINUE THROUGH THE
PERIOD THROUGHOUT AS SFC HIGH PRESSURE BUILDS OVER THE AREA. EXPECT
SOME MEASURE OF FEW TO SCT HIGH BASED STRATOCUMULUS TO
LINGER...FIRST FROM DAYTIME HEATING THIS AFTERNOON AND THEN FROM
MOISTURE UNDER A WEAK INVERSION OVERNIGHT. A PASSING WEAK SHORTWAVE
LATE THIS AFTN/EARLY EVENING COULD GENERATE ISOLD SRN MTN
SHOWERS...BUT THESE WILL STAY AWAY FROM ANY TAF SITES. NRLY FLOW AT
10 KT OR LESS EARLY IN THE PERIOD WILL TURN LIGHT NE OVERNIGHT THEN
COME UP FROM THE SE THROUGH SUNDAY MORNING.

OUTLOOK...RELATIVELY DRY CONDITIONS WILL PERSIST THROUGH THE
PERIOD...BUT WITH RETURN FLOW MOISTURE SLOWLY REDEVELOPING OVER THE
MTNS AND PRODUCING ISOLD TO SCATTERED DIURNAL CONVECTION 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 100%     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...SBK
NEAR TERM...HG
SHORT TERM...TS
LONG TERM...SBK
AVIATION...HG



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