Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 032110
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
510 PM EDT FRI JUL 3 2015

.SYNOPSIS...
A BROAD UPPER LEVEL TROUGH WILL REMAIN OVER THE SOUTHEAST THROUGH
MONDAY...STEERING A SERIES OF WEAK DISTURBANCES OVER THE REGION.
THESE FEATURES WILL INCREASE RAIN AND THUNDERSTORM CHANCES EACH
AFTERNOON AND EVENING...AND KEEP SKIES CLOUDIER THAN USUAL. SLIGHT
DRYING WILL OCCUR TUESDAY...BEFORE ANOTHER FRONT PUSHES THROUGH IN
THE MIDDLE OF THE WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
500 PM UPDATE...BEST CHANCES FOR ROBUST DEEP CONVECTION THROUGH
SUNSET WILL LIE WITHIN THE LLVL CONVERGENCE AXIS ALONG THE I-40
CORRIDOR. ELSEWHERE...SBCAPES ARE RATHER MODEST...AND SINCE WE
ARE IN A TEMPORARY FORCING MINIMUM...CVRG SHOULD REMAIN ISOLATED.

AS OF 235 PM EDT...A FLASH FLOOD WATCH WILL BE POSTED FOR THE
EXTREME SOUTHERN APPALACHIANS TONIGHT THROUGH SATURDAY GIVEN THE
DEEP MOISTURE AND PERSISTENT UPSLOPE FLOW AND UPPER FORCING.

WATER VAPOR IMAGERY SHOWS A MID/UPPER LEVEL TROUGH DIGGING SE INTO
LOWER OH VALLEY THIS AFTERNOON...WITH NUMEROUS SHORTWAVES RIPPLING
EAST IN THE WESTERLY FLOW ACROSS KY/TN/GA. MEANWHILE...A WAVY
SURFACE BOUNDARY PERSISTS ROUGHLY WEST TO EAST ALONG THE INTERSTATE
40 CORRIDOR...AND THIS BOUNDARY IS EXPECTED TO REMAIN STALLED ALONG
OR NEAR THE NRN BORDER OF OUR FORECAST AREA THROUGH THE NEAR TERM.
THESE FEATURES WILL INTERACT WITH PRECIPITABLE WATER VALUES OF 1.75
INCHES OR GREATER ACROSS THE FORECAST AREA TO GENERATE FAIRLY HIGH
COVERAGE OF PRECIPITATION AND LOCALLY HEAVY RAINFALL...ESPECIALLY
OVER THE MTNS. A FLASH FLOOD WATCH WILL BE POSTED IN SW MTN AREAS
GIVEN THE ANTECEDENT CONDITIONS AND LOCAL UPSLOPE FOCUS IN THE
PERSISTENT WSW SFC TO 850 MB FLOW.

AT PRESENT...REGIONAL RADARS SHOW PRECIPITATION MOVING EAST IN THE
CYCLONIC FLOW ACROSS ERN KY...ERN TN...AND AL/GA. THROUGH LATE AFTN
AND INTO THE EVENING HOURS...COVERAGE WILL BE BEST ALONG THE NRN
TIER CLOSER TO THE LOW LEVEL CONVERGENCE AXIS NEAR AND NORTH OF
INTERSTATE 40 AS A SFC WAVE MOVES EAST ALONG THE BOUNDARY. THE HRRR
HAS ADDITIONAL CONVECTION DEVELOPING ALONG THE ERN SLOPES OF THE
BLUE RIDGE LATE THIS AFTN AND MAKING A RUN EASTWARD THROUGH THE NC
PIEDMONT. THIS SEEMS REASONABLE SINCE MUCH OF THIS AREA DID NOT GET
WORKED OVER BY MORNING CONVECTION/RAIN AND SOME 1500+ SBCAPE VALUES
ARE APPARENT IN SFC LAPS DATA.

OTHERWISE...A SERIES OF SHORTWAVES WILL LIKELY CROSS THE REGION
TONIGHT THROUGH SAT...BUT WITH THE ASSOCIATED FORCING HARD TO TIME.
WILL PARE BACK POPS W TOWARD THE MTNS FOR MUCH OF THE NIGHTTIME
HOURS...WITH A FOCUS MAINLY ON THE TN BORDER COUNTIES OVERNIGHT
WHERE WESTERLY LOW LEVEL UPSLOPE WILL BE BEST. THERE IS GOOD
CONSENSUS ON INCREASING UPPER JET SUPPORT LATE TONIGHT INTO
SATURDAY...AND COVERAGE MAY BE RESURGENT FROM THE SW TOWARD
DAYBREAK. CLOUD COVER AND EARLY DAY PRECIPITATION COULD ONCE AGAIN
KEEP INSTABILITY LIMITED FOR SATURDAY...BUT THE CONTINUED MOISTURE
EAST OF THE TROUGH WILL REQUIRE CATEGORICAL POPS ACROSS THE WRN MTNS
TO CHC POPS EAST OF INTERSTATE 77 THROUGH THE DAY. EXPECT A SMALLER
THAN CLIMO DIURNAL RANGE ON TEMPS WITH CLOUDS/PRECIP.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM FRIDAY..THE UPPER TROUGH ACROSS THE TENN/LOWER MISS
VALLEYS IS EXPECTED TO EVOLVE INTO A CLOSED LOW DURING THE SHORT
TERM...RESULTING A SLOWLY EVOLVING SYNOPTIC PATTERN. IN FACT...THE
TREND IN THE LATEST NUMERICAL GUIDANCE IS TO SLOW THE PROGRESSION OF
THE TROUGH AXIS INTO THE EASTERN SEABOARD EARLY NEXT WEEK.
THEREFORE...LITTLE IN THE WAY OF AN AIR MASS CHANGE OR SENSIBLE
WEATHER CONDITIONS IS EXPECTED THROUGH AT LEAST THE END OF THE
WEEKEND. IN OTHER WORDS...PERIODS OF SHOWERS AND THUNDERSTORMS WILL
REMAIN POSSIBLE AT JUST ABOUT ANY TIME DURING THE PERIOD...AND POPS
WILL REMAIN WELL ABOVE CLIMO...WITH THE HIGHEST POPS FAVORED ACROSS
THE WESTERN AND NORTHERN ZONES. EXTENSIVE CLOUD COVER SHOULD CONTINUE
TO KEEP THE DIURNAL TEMP RANGE SOMEWHAT SMALL...WITH BELOW-NORMAL
MAX TEMPS EXPECTED. THIS WILL ALSO SUPPORT MUTED INSTABILITY...AND
AN UNSEASONABLY LOW SEVERE STORM THREAT THROUGH THE PERIOD.
HOWEVER...PWATS WILL REMAIN HIGHER THAN TYPICAL THROUGH THE
PERIOD...SUPPORTING THE THREAT OF LOCALIZED HEAVY OR EVEN EXCESSIVE
RAINFALL. IN FACT...WITH ANOMALOUSLY STRONG WESTERLY LOW LEVEL FLOW
EXPECTED TO CONTINUE...AND GRADUALLY DETERIORATING ANTECEDENT
CONDITIONS...PORTIONS OF THE FAR WESTERN NC MTNS WILL LIKELY SEE A
MORE ORGANIZED HYDRO THREAT DEVELOP OVER THE WEEKEND.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 130 PM FRIDAY...WE WILL HAVE BRIEF UPPER RIDGING MONDAY NIGHT
INTO TUESDAY AHEAD OF THE NEXT UPPER TROUGH WITH ITS ASSOCIATED
SURFACE COLD FRONT. THERE WILL STILL BE ENOUGH LOW LEVEL MOISTURE
MONDAY EVENING AND LATE DAY CONVECTION WILL GRADUALLY DIMINISH
OVERNIGHT. LOW LEVEL CONVERGENCE WILL BE WEAK TUESDAY...ESPECIALLY
FOR THE FOOTHILLS AND PIEDMONT. THE APPROACHING COLD FRONT WILL BE
ORIENTED SW TO NE FROM NORTH TX TO THE EASTERN GREAT LAKES
TUESDAY. THE FRONT WILL BECOME NEARLY STATIONARY WED TO FRI WHILE
ORIENTED WEST TO EAST WITH WAVES OF ENERGY RIDING ALONG THE FRONT
CREATING PERIODS OF ENHANCED CONVECTIVE ACTIVITY. THE VARIOUS MODELS
HAVE DIFFERING SOLUTIONS FOR DAYS 6 AND 7 WITH THE ECMWF PUSHING THE
COLD FRONT FARTHER SOUTH WITH SOME SUPPORTIVE UPPER TROFINESS.  THE
GFS HAS MCS FEATURES PASSING FROM THE MISS VALLEY TO OHIO VALLEY
WITH LITTLE EFFECTS ON THE NC MTNS. OVERALL...THE WEATHER PATTERN
WILL CONTINUE TO BE UNSETTLED FOR OUR REGION WITH MAX TEMPS SLIGHTLY
BELOW NORMAL TUES WITH SLIGHT WARMING TO AT LEAST NORMAL MAXES AND
EVEN A LITTLE ABOVE NORMS.

&&

.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT...THERE WAS LITTLE MORE THAN ISOLD SHOWERS NEAR THE AIRFIELD
AT ISSUANCE TIME...BUT MESOSCALE MODELS INDICATE CONVECTION
DEVELOPING EAST OFF THE MTNS THIS AFTN AND MAKING A RUN OUT ACROSS
THE NC PIEDMONT THROUGH LATE AFTN. WILL THUS FEATURE TEMPO TSRA
STARTING AT 19Z. NONE OF THE PROFILES OR MOS INDICATE LOW CLOUDS
DEVELOPING OVERNIGHT...BUT THE GUIDANCE WAS POOR FOR LOW CLOUDS THIS
MORNING. WILL HINT AT STRATUS DEVELOPMENT WITH FEW020 IN THE TAF FOR
THE OVERNIGHT HOURS. EXPECT SW WINDS TO GUST OCCASIONALLY...BUT
LIMITED HEATING IS CAPPING MIXING AND GUST POTENTIAL. SW FLOW WILL
PICK UP AGAIN MID MORNING ON SAT.

ELSEWHERE...KAVL AND THE FOOTHILLS TAFS HAVE BEEN LARGELY FREE OF
CONVECTION SINCE THE MORNING SYSTEM. HOWEVER...PROFILES ARE
REBOUNDING AND SBCAPE VALUES ARE BUILDING SLIGHTLY TO PERMIT SHOWER
REDEVELOPMENT. THE BEST CHANCE OF LATE AFTN THUNDER WILL BE FROM
KAVL TO KHKY NEARER THE LOW LEVEL CONVERGENCE AXIS. ANTICIPATE
MOSTLY LOWER END VFR CIGS...EXCEPT WITH RESTRICTIONS IN ANY
SHRA/TSRA...AND THEN LOWER STRATUS DEVELOPING AGAIN TONIGHT. THE
GUIDANCE CONSENSUS IS MVFR...BUT IFR WILL ONCE AGAIN BE POSSIBLE.
EXPECT LOW END GUSTS AT THE UPSTATE SITES IN THE SW FLOW WITH MIXING
THIS AFTN...OTHERWISE...STEADY WSW TO SW FLOW THROUGHOUT...EXCEPT
MOSTLY NW AT KAVL. CONVECTION MAY RETURN QUICKLY FROM THE SW EARLY
SAT WITH THE ARRIVAL OF BETTER UPPER SUPPORT.

OUTLOOK...PRECIPITATION COVERAGE WILL REMAIN HIGH THROUGH
SUNDAY...THEN THE PATTERN WILL TRANSITION TO A MORE DIURNAL
PATTERN...BUT WITH CONTINUED MOISTURE IN THE AREA. RESTRICTIONS WILL
BE CONFINED MAINLY TO THUNDERSTORMS AND THEN EARLY MORNING STRATUS
WHERE HEAVY RAIN FELL THE PREVIOUS DAY.

CONFIDENCE TABLE...

            21-03Z        03-09Z        09-15Z        15-18Z
KCLT       HIGH  85%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       LOW   55%     HIGH 100%     MED   61%     LOW   57%
KAVL       HIGH 100%     HIGH 100%     HIGH  96%     MED   79%
KHKY       MED   64%     HIGH  85%     LOW   55%     MED   67%
KGMU       HIGH 100%     HIGH 100%     MED   63%     LOW   57%
KAND       HIGH 100%     HIGH 100%     MED   63%     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...FLASH FLOOD WATCH THROUGH SATURDAY EVENING FOR GAZ010-017.
NC...FLASH FLOOD WATCH THROUGH SATURDAY EVENING FOR NCZ048-051-052-
     058-059-062.
SC...NONE.

&&

$$
SYNOPSIS...DEO
NEAR TERM...CSH/HG
SHORT TERM...JDL
LONG TERM...DEO
AVIATION...HG



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