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Area Forecast Discussion

506
FXUS62 KGSP 260018
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
818 PM EDT FRI JUL 25 2014

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN ACROSS THE AREA THROUGH THE WEEKEND.
ANOTHER COLD FRONT IS EXPECTED TO REACH THE AREA FROM THE NORTHWEST
BY EARLY MONDAY. HIGH PRESSURE WILL REGAIN CONTROL ON TUESDAY...
LASTING THROUGH AT LEAST MID-WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 745 PM EDT...CONVECTION HAS FINALLY DEVELOPED THIS EVENING
ALONG THE NRN BLUE RIDGE...AND ISOLD TO SCT COVERAGE SHOULD LINGER
THERE IN LIGHT WESTERLY STEERING FLOW THROUGH 10 PM. IT CONTINUES TO
LOOK UNLIKELY THAT MUCH OF ANY COVERAGE WILL GET GOING FROM THE
MIDLANDS ACTIVITY AS ANY WWD PROPAGATING OUTFLOWS HAVE BEEN FEW AND
SHORT LIVED. HAVE THUS ACCOUNTED FOR MAINLY ERN MTN SLOPE
ACTIVITY...WITH A SLIGHT BOOST IN POPS OVER PREVIOUS VALUES. THE
CONVECTION SHOULD DIMINISH FAIRLY QUICKLY LATER THIS...BUT LOW LEVEL
MOISTURE REMAINS SUFFICIENT FOR THE DEVELOPMENT OF VALLEY FOG AND
LOW STRATUS LATE TONIGHT/EARLY SATURDAY. THERE COULD BE ANOTHER
ROUND OF LOW STRATUS OUTSIDE THE MTNS AS WELL...ALTHOUGH VEERING LOW
LEVEL FLOW MAKES THAT LESS LIKELY THAN OBSERVED FRI MORNING. MIN
TEMPS SHOULD SETTLE VERY CLOSE TO CLIMO.

SATURDAY...FORECAST SOUNDINGS ARE CAPPED UNDER THE INFLUENCE OF
RISING HEIGHTS ALOFT...AS A RIDGE AXIS ASSOCIATED WITH THE
SUBTROPICAL HIGH OVER THE GREAT PLAINS NOSES ITS WAY TOWARD THE
SOUTHEAST COAST. AS A RESULT...THERE IS LITTLE TO NO MODEL QPF
RESPONSE ACROSS THE AREA SAT AFTERNOON...AND A DRY FORECAST WILL BE
MAINTAINED. OTHERWISE...TEMPS WILL WARM NOTICEABLY FROM TODAY/S
READINGS...WITH MAXES EXPECTED TO REACH THE LOWER 90S IS MOST
LOCATIONS EAST OF THE MTNS...AND MID/UPPER 80S EXPECTED IN THE MTN
VALLEYS.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 100 PM FRI...BROADLY CYCLONIC UPPER LEVEL FLOW WILL CONTINUE
ACRS THE ERN HALF OF THE CONUS SATURDAY NIGHT AND SUNDAY...BEFORE
BEGINNING TO AMPLIFY MONDAY AS A POTENT SHORTWAVE MOVES THRU THE
GREAT LAKES. A COLD FRONT ACCOMPANYING THE TROUGH WILL MOVE THRU THE
OHIO VALLEY SUNDAY...WITH MOST GUIDANCE INDICATING A PASSAGE ACRS THE
SRN APPALACHIANS EARLY MONDAY...BUT STILL IN PLACE TO AFFECT THE
PIEDMONT THAT AFTN.

SATURDAY NIGHT SHOULD BE QUIET WITHIN OUR CWFA...AND SUNDAY SHOULD
START OFF QUIET. VARIOUS GUIDANCE SOURCES CONTINUE TO SHOW NOTABLE
DIFFERENCES IN QPF RESPONSE TO DIURNAL DESTABILIZATION. GFS IS
ESSENTIALLY THE DRIEST MODEL...WITH A WARM LAYER ALOFT CAPPING OFF
CONVECTION. OPNL NAM ALSO INDICATES SOME DEGREE OF CAPPING THOUGH IT
WEAKENS LATE IN THE DAY...PARTICULARLY OVER THE MTNS. SREF MEMBERS
ARE FAIRLY EVENLY SPREAD BETWEEN STRONG CAPPING AND FREE CONVECTION.
LAPSE RATES ABOVE THE WARM LAYER ARE DECENT...WHICH IN CONJUNCTION
WITH SFC TEMPS/DEWPTS SLIGHTLY ABOVE NORMAL MEANS UNCAPPED PARCELS
WILL BE SOMEWHAT MORE UNSTABLE THAN USUAL. THIS WOULD BE CONCURRENT
WITH STRENGTHENING UPPER FLOW AHEAD OF THE DIGGING TROUGH...SO IF THE
TIMING IS RIGHT THERE COULD BE A SEVERE THREAT. THIS BECOMES MORE OF
A CONCERN OVERNIGHT IN THE MTNS WHERE SOME PROG SOUNDINGS ARE
UNCAPPED FOR NEAR-SURFACE PARCELS AS SHEAR RISES TO 40-50 KT. SPC HAS
ALREADY INCLUDED A PORTION OF OUR MTNS IN A SLIGHT RISK ON THE DAY 3
OTLK VALID THRU 12Z MON...WITH MOST OF THE REST OF THE CWFA WITHIN
THE 5 PERCENT CONTOUR. REGARDLESS OF ANY CONVECTION...WINDS WILL
BEGIN TO BECOME RATHER GUSTY IN THE HIGHER ELEVATIONS SUNDAY NIGHT.
THIS WILL CONTINUE MONDAY EVEN POST-FROPA.

COOLER AND DRIER AIR ARE PROGGED TO BEGIN FILTERING INTO THE MTNS BY
MIDDAY MONDAY...AND THRU THE PIEDMONT BY 00Z TUE IN THE WAKE OF THE
FRONT. THERE STILL APPEARS TO BE TIME FOR DESTABILIZATION AHEAD OF
THE WIND SHIFT LINE SO FRONTAL ENHANCEMENT TO TSTM CHANCES APPEARS
LIKELY AT LEAST ALONG AND SOUTH OF I-85 IF NOT UP INTO THE FOOTHILLS.
HODOGRAPHS IN THIS AREA WILL BE RATHER LONG WITH H5 FLOW NEARING 50
KT INDICATING A SUPERCELL RISK IN OUR AREA. SPC IS CURRENTLY
HIGHLIGHTING AREAS OF ERN NC/VA ON THE DAY 4 GRAPHIC BUT THE RISKS
THEY DESCRIBE APPEAR TO BE PRESENT IN OUR ERN/SERN ZONES AS WELL.
MONDAY AFTN MAX TEMPS IN THE MTNS REFLECT THE COOL AIRMASS THAT WILL
REMAIN OVER THE REGION THRU MOST OF NEXT WEEK...BEING 2 OR 3
CATEGORIES BELOW NORMAL. THE PIEDMONT APPEARS TO STILL BE CAPABLE OF
MAXES NEAR NORMAL.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 2 PM EDT FRIDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
TUESDAY WITH A SIGNIFICANT UPPER TROF DIGGING DOWN OVER THE EASTERN
CONUS WHILE AN EQUALLY STEEP UPPER RIDGE IS IN PLACE OVER THE WEST.
NO MAJOR PATTERN CHANGES ARE EXPECTED AS THIS TROF WILL REMAIN
LARGELY IN PLACE THRU DAY 7 WITH SOME DEAMPLIFICATION LIKELY ON DAYS
6 AND 7.

AT THE SFC...A FAIRLY STRONG WARM SEASON COLD FRONT WILL BE MOVING
THRU THE FCST AREA LATE MON/EARLY TUES WITH CONSIDERABLY COOLER AND
DRIER AIR SPREADING OVER THE CAROLINAS ON TUES. BEHIND THE DEPARTING
FRONT CANADIAN HIGH PRESSURE WILL KEEP NLY FLOW OVER THE AREA THRU
WED AS IT GRADUALLY SLIDES SOUTHEASTWARD. BY THURS...BNDRY LYR FLOW
SHOULD BE PRETTY WEAK AND POSSIBLY BECOME VRB FOR MOST OF THE
DAY/EVENING. ON FRI...THE LONG RANGE MODELS VEER THE LOW LVL FLOW
MORE FROM THE EAST TO NE AND MOVE A LARGE PLUME OF DEEPER LYR
MOISTURE OVER THE CWFA FROM THE SOUTH. THIS WILL PROVIDE OUR BEST
OPPORTUNITY FOR WIDESPREAD SHOWERS AND TS IN THE MEDIUM RANGE.
OTHERWISE...I EXPECT DRY CONDITIONS WITH UNSEASONABLY COOL TEMPS
THRU DAY 7.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT AND ELSEWHERE EXCEPT KAVL...CUMULUS FROM HEATING TODAY HAS
THINNED OUT IN MOST AREAS THIS EVENING. THE PRIMARY EXCEPTION
REGARDING CLOUDS IS KHKY...WHERE SOME CONVECTIVE DEBRIS FROM THE
NEARBY BLUE RIDGE ACTIVITY MAY PROVIDE VFR CIGS THROUGH LATE
EVENING. STILL SEE LITTLE CHANCE OF THIS CONVECTION MAKING A RUN
ACROSS THE FOOTHILLS IN THE LIGHT WESTERLY STEERING FLOW GIVEN THE
TIME OF DAY. EXPECT MAINLY LIGHT SE WINDS...WHICH MIGHT GO CALM AT
TIMES TONIGHT. WITH LOW LEVEL MOISTURE PERSISTING...THERE IS A
CHANCE FOR BR AND POSSIBLY A RETURN OF LOW STRATUS TOWARD DAYBREAK
SAT. HOWEVER...WITH LOW LEVEL FLOW EXPECTED TO VEER TOWARD THE
SW...THE PROBABILITY OF LOW CLOUDS DEVELOPING APPEARS A BIT LOWER
THAN OBSERVED FRI MORNING...SO VFR SKY CONDITIONS WILL BE
MAINTAINED...WITH 6SM BR NEAR DAYBREAK EXCEPT FOR MVFR FOG AT KHKY.
HAVE ALSO HINTED AT THE LOW CLOUD POTENTIAL FROM KHKY TO KCLT WITH
FEW TO SCT010 PENDING BETTER AGREEMENT ON MOS AND MODEL PROFILES.
VFR CONDITIONS WITH SW WINDS LESS THAN 10 KT ARE EXPECTED THROUGHOUT
ON SAT.

AT KAVL...HAVE ADDED A WINDOW OF VCSH FOR NEARBY WEAK CONVECTION
SLIDING EWD OFF THE BLUE RIDGE. THUNDER IS NOT EXPECTED GIVEN THE
WANING INSTABILITY AND THIS ACTIVITY SHOULD DIMISH FAIRLY QUICKLY
THROUGH 02Z. OTHERWISE...SCT TO BKN VFR CLOUDS CAN BE EXPECTED INTO
THE EARLY OVERNIGHT. PLENTIFUL LOW LEVEL MOISTURE WILL THEN MEAN
THAT FOG AND PERHAPS LOW STRATUS ARE IN STORE FOR THE EARLY MORNING
HOURS. WILL FEATURE TEMPO IFR CONDITIONS 08Z TO 12Z. A QUICK
RECOVERY TO VFR CONDITIONS WITH STEADY NW FLOW AND DRY CONDITIONS IS
EXPECTED ON SAT.

OUTLOOK...GENERALLY VFR THROUGH SUNDAY MORNING...EXCEPT FOR POSSIBLY
MORNING MTN VALLEY FOG. SCT THUNDERSTORMS MAY RETURN TO THE FORECAST
AREA FOR SUNDAY AFTERNOON THROUGH MON AS ANOTHER COLD FRONT
APPROACHES AND THEN MOVES THROUGH THE AREA BY MON NIGHT. VFR
CONDITIONS WILL THEN LINGER THROUGH MID WEEK.

CONFIDENCE TABLE...

            00-06Z        06-12Z        12-18Z        18-24Z
KCLT       HIGH  98%     HIGH  84%     HIGH  99%     HIGH 100%
KGSP       HIGH  96%     HIGH  93%     HIGH 100%     HIGH 100%
KAVL       HIGH  93%     MED   64%     MED   76%     HIGH 100%
KHKY       HIGH  98%     HIGH  89%     HIGH 100%     HIGH 100%
KGMU       HIGH  93%     HIGH  90%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH  94%     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...JDL
NEAR TERM...HG
SHORT TERM...WIMBERLEY
LONG TERM...JPT
AVIATION...HG






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