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Area Forecast Discussion

409
FXUS62 KGSP 251548
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1148 AM EDT FRI JUL 25 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD IN BEHIND A DEPARTING COLD FRONT ON FRIDAY
LASTING THROUGH THE MAJORITY OF THE WEEKEND. ANOTHER COLD FRONT IS
EXPECTED TO REACH THE AREA FROM THE NORTHWEST ON MONDAY MORNING AND
INTO MONDAY AFTERNOON POTENTIALLY LEADING TO SCATTERED
THUNDERSTORMS.  HIGH PRESSURE WILL ONCE AGAIN REGAIN CONTROL ON
TUESDAY LASTING THROUGH THE REMAINDER OF THE WORK WEEK WITH ONLY
MINIMAL PRECIPITATION THREATS BY WEEKS END.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 11 AM...ALTHOUGH THE WEAK FRONT HAS SAGGED INTO THE SC
MIDLANDS AND CENTRAL GA THIS MORNING...A MOIST E/NE FLOW NORTH OF
THE BOUNDARY IS RESULTING IN AREAS OF LOW STRATUS AND STRATOCU
ACROSS THE AREA. THIS SHOULD CONTINUE TO LIFT/EVOLVE INTO A FAIRLY
EXTENSIVE AFTERNOON CUMULUS FIELD. THE PRIMARY CONCERN FOR THIS
PERIOD WILL BE WHETHER A FEW OF THESE CUMULUS CLOUDS CAN DEVELOP
INTO THUNDERSTORMS THIS AFTERNOON. THE DIFFERENCE BETWEEN FORECAST
RAP AND NAM SOUNDINGS IS QUITE STRIKING...AS THE RAP MAINTAINS A
RATHER FORMIDABLE CAP ACROSS THE AREA THROUGH THE AFTERNOON...WHILE
THE NAM TRIES TO ELIMINATE IT. ALTHOUGH DEWPOINTS WILL BE A LITTLE
LOWER THAN TYPICAL OF THIS TIME OF YEAR...THEY SHOULD STILL BE HIGH
ENOUGH TO YIELD MODEST AMOUNTS OF CAPE THIS AFTERNOON. THUS...IF THE
CAP DOES INDEED ERODE...IT SEEMS REASONABLE THAT A FEW SHOWERS/TSRA
WILL DEVELOP ACROSS THE HIGH TERRAIN...AS IS INDICATED IN THE
CURRENT FORECAST. THE ONLY REAL CHANGE OF NOTE WILL BE TO INCLUDE A
SLIGHT CHANCE POP NEARER THE FRONT ACROSS THE FAR SOUTHERN PIEDMONT
AREAS. OTHERWISE...MAX TEMPS SHOULD BE ABOUT A CATEGORY BELOW CLIMO
OWING TO THE COOL E/NE FLOW AND CONSIDERABLE CUMULUS COVER.

AS OF 640 AM...LOW CLOUDS SPREADING IN FROM THE EAST OR ALREADY IN
PLACE ACROSS THE MTNS SHUD LIFT OR SCATTER OUT BY NOON. OTHERWISE...
GOING FCST STILL LOOKS ON TRACK. UPDATES MAINLY FOR CURRENT
CONDITIONS.

AS OF 305 AM...SLOW MOVING COLD FRONT KEEPING ENUF LOW LEVEL
CONVERGENCE ACROSS THE SRN UPSTATE TO BREAK THE CAP AND PRODUCE
ISOLATED SHRA. THESE SHUD END OR MOVE SOUTH OF THE AREA BY DAYBREAK
AS THE FRONT MOVES OUT OF THE AREA.

ALTHOUGH THE FRONT MOVES SOUTH OF THE AREA...GUIDANCE IS NEARLY
UNANIMOUS KEEPING LOW LEVEL MOISTURE ACROSS THE AREA. IN ADDITION...
LOW LEVEL FLOW BECOMES SELY LEADING TO WEAK UPSLOPE FLOW. THIS IS
FORECAST TO PROVIDE ENUF LIFT TO TAP THE ELEVATED INSTABILITY AND
PRODUCE ISOLATED TO SCT CONVECTION ALONG THE BLUE RIDGE AND WEST
ACROSS THE MTNS. GIVEN THE MDL SUPPORT...HAVE CHANGED THE FORECAST
TO INCLUDE POP IN THIS AREA. THERE MAY ALSO BE SOME CONVECTION
ACROSS THE FAR SRN CWFA AS THAT AREA WILL BE CLOSE TO THE FRONT.
HOWEVER...BEST CHC WILL BE SOUTH OF THE CWFA. CLOUDS WILL LINGER
THRU THE MORNING ACROSS MUCH OF THE NRN AND ERN CWFA...BEFORE MIXING
OUT BY AFTERNOON. THIS AND THE COOLER AIR MASS BEHIND THE FRONT WILL
LEAD TO HIGHS A LITTLE BELOW NORMAL.

CONVECTION SHUD DISSIPATE DURING THE EVENING WITH LOSS OF HEATING.
HOWEVER...CANNOT RULE OUT SOME LINGERING SHRA OVER THE BLUE RIDGE
LATE INTO THE EVENING OR EARLY OVERNIGHT BEFORE THE LOW LEVEL FLOW
BECOMES SWLY. LOWS SHUD BE NEAR NORMAL.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 230 AM EDT FRIDAY...THE SHORT TERM PERIOD INITIALIZES SATURDAY
MORNING WITH REMNANT FRONT WELL TO THE SOUTHEAST ALONG THE
CAROLINA/GEORGIA COASTLINE.  SURFACE HIGH PRESSURE WILL QUICKLY
BUILD UNDER RISING HEIGHTS ALOFT.  DESPITE WEAK LEE TROF DEVELOPING
JUST EAST OF THE FORECAST AREA POTENTIALLY PROVIDING A FOCUS FOR
AFTERNOON CONVECTION...SOUNDINGS INDICATE A SUBSTANTIAL LOW/MID
LEVEL CAP IN PLACE.  NOT EXPECTING ANY POTENTIAL UPDRAFTS TO BREAK
THROUGH THE DEEP INHIBITION THEREFORE KEPT THE FORECAST DRY FOR
SATURDAY.

ALSO KEPT FORECAST DRY THROUGH SUNDAY MORNING AS UPPER HEIGHTS ARE
SLOW TO FALL DUE TO APPROACHING UPPER TROF AND ASSOCIATED SURFACE
COLD FRONT.  STILL THINK AREA OF GREATEST LIFT AND LOWEST INHIBITION
WILL REMAIN TIED TO LEE TROF REDEVELOPMENT EAST OF THE I77 CORRIDOR
THEREFORE CONTINUE WITH DRY FORECAST FOR THE PIEDMONT REGION THROUGH
THE AFTERNOON.  FURTHER WEST...HEIGHTS WILL BEGIN TO FALL RAPIDLY AS
UPPER SHORT WAVE AND ASSOCIATED MOISTURE ADVECT INTO THE
CENTRAL/SOUTHERN APPS.  MODELS TEND TO AGREE ON AT LEAST SOME
PRECIPITATION PUSHING INTO THE NORTHERN MOUNTAINS BY MID/LATE
AFTERNOON ON SUNDAY...WITH CHANCES INCREASING AHEAD OF THE
APPROACHING FRONT THROUGH THE OVERNIGHT.  THEREFORE...SOLID CHANCE
POPS ARE FEATURED SUNDAY EVENING ALONG THE HIGHER TERRAIN OF NC
INCREASING TO NEAR LIKELY POPS BY MONDAY MORNING NEAR THE TN
BORDER.  ELSEWHERE POPS TAPER DOWN SHARPLY TO SLIGHT CHANCE LEVELS
OVER THE NC/SC FOOTHILLS AND WESTERN MOST AREAS OF THE PIEDMONT.
TEMPERATURES THROUGH THE SHORT TERM PERIOD WILL GRADUALLY WARM AS
SOUTHERLY FLOW RAMPS UP AHEAD OF APPROACHING SURFACE TROF.
EXPECTING HIGHS ON BOTH SATURDAY AND SUNDAY TO SURGE TO ABOVE NORMAL
LEVELS WITH MID 90S POSSIBLE FOR SOUTHERN PORTIONS OF THE FORECAST
AREA ON SUNDAY.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 315 AM EDT FRIDAY...THE EXTENDED RANGE PERIOD WILL BEGIN WITH
A RATHER ACTIVE PATTERN ON MONDAY MORNING.  STRONG HEIGHT FALLS WILL
BE ADVECTING IN FROM THE WEST AS A COLD FRONT STRETCHES ALONG THE
APPALACHIAN CHAIN FROM A PARENT SURFACE CYCLONE ACROSS THE EASTERN
GREAT LAKES.  POPS WILL INITIALIZE AT HIGH END CHANCE LEVELS ACROSS
THE HIGHER TERRAIN AS THE PRE-FRONTAL ACTIVITY PUSHES INTO THE REGION
AROUND OR JUST BEFORE DAYBREAK MONDAY.  THE ENTIRE COMPLEX WILL
CONTINUE ADVECTING EAST THROUGH THE MORNING AND EARLY AFTERNOON
HOURS ALLOWING FOR SOME DIURNAL DESTABILIZATION AHEAD ACROSS THE
NC/SC PIEDMONT REGIONS.  THERE IS STILL SOME UNCERTAINTY REGARDING
OVERALL MAGNITUDE OF INSTABILITY THAT WILL BUILD AHEAD OF THE FRONT
AS ABUNDANT SKY COVER WILL WORK TO LIMIT HEATING.  THAT
SAID...MODEST WARM SECTOR ALREADY IN PLACE WILL NOT NEED MUCH
HEATING FOR LAPSE RATES TO SUPPORT SUBSTANTIAL LOW LEVEL LIFT.
ALOFT DRIER AIR WILL BE ADVECTING IN AS STRONG WNW FLOW ASSOCIATED
WITH TROF AXIS PUSHES INTO THE REGION.  THIS WILL ALLOW MID LEVEL
LAPSE RATES TO STEEPEN...POTENTIALLY LEADING TO A FAIRLY UNSTABLE
PROFILE.  SPEAKING OF...LATEST GFS FORECAST SOUNDINGS INDICATE
NEARLY 1500J/KG SBCAPE AND LONG STRAIGHT HODOGRAPHS PRODUCING DEEP
LAYER SHEAR IN EXCESS OF 35KTS SUGGESTING MULTICELL STRONG/SEVERE
THUNDERSTORMS. ALL THAT SAID...THERE IS STILL PLENTY OF TIME FOR THE
PATTERN TO CHANGE SLIGHTLY WHICH COULD SUBSTANTIALLY ALTER THE
OUTCOME.  THUS...DUE TO RANGE IN THE FORECAST...KEPT POPS CAPPED AT
CHANCE LEVELS FOR THE ENTIRE REGION ON MONDAY AFTERNOON.

SURFACE HIGH PRESSURE WILL BUILD INTO THE REGION BEHIND THE FRONT
FOR TUESDAY AND WEDNESDAY LEADING TO LOWER PRECIPITATION CHANCES
DESPITE PERSISTENT UPPER TROF REMAINING NEARLY STATIONARY.  FORECAST
WILL FEATURE SLIGHT CHANCE POPS ACROSS THE HIGH TERRAIN THROUGH
WEDNESDAY MORNING AMIDST STRONG NW FLOW.  THE SURFACE RIDGE REMAINS
DOMINATE THROUGH THE REMAINDER OF THE PERIOD AS IT REPOSITIONS
ITSELF TO THE NORTHEAST AND EXTENDS IN A WEDGE LIKE PATTERN ALONG
THE LEE SIDE OF THE APPALACHIANS BY THURSDAY.  SURFACE FLOW WILL
SHIFT TO MORE OF AN EAST TO SOUTHEAST COMPONENT LEADING TO POTENTIAL
UPSLOPE/UPGLIDE PRECIPITATION INTO FRIDAY.  THUS CHANCE LEVEL POPS
ARE ONCE AGAIN FEATURED THROUGH THE REMAINDER OF THE FORECAST ALONG
THE HIGH TERRAIN WITH SLIGHT CHANCE POPS HIGHLIGHTED ELSEWHERE.
TEMPERATURES WILL GRADUALLY COOL BEHIND THE FROPA ON MONDAY WITH
HIGHS TOPPING OUT NEARLY A CATEGORY BELOW NORMAL BY THURSDAY FOR
SOME LOCATIONS.

&&

.AVIATION /16Z FRIDAY THROUGH TUESDAY/...
AT KCLT...IFR STRATUS HAS SPREAD ACROSS THE AIRFIELD AND WILL
CONTINUE THRU MID-MORNING WHEN A SLOW RISE TO LOW VFR BY 18Z
DEVELOPS. THAT SAID...MOISTURE IS SHALLOW AND CIGS COULD SCATTER OUT
BEFORE LIFTING. FEW TO SCT LOW VFR CLOUDS EXPECTED THRU THE EVENING
AND OVERNIGHT. NELY WIND BECOMES ENE THIS AFTERNOON AND EVENING THEN
CALM OVERNIGHT. RIGHT NOW...DO NOT EXPECT ANY RESTRICTIONS
OVERNIGHT.

ELSEWHERE...LOW STRATUS IS MAKING A RUN FROM THE EAST AT THE NON MTN
SITES. LOW VFR CIGS HAVE DEVELOPED AND MVFR OR EVEN THE IFR DECK
COULD DEVELOP. IF SO...SHUD BE A RELATIVELY QUICK RETURN TO VFR...
GENERALLY BEFORE NOON. THEN VFR EXPECTED THRU THE REST OF THE
PERIOD. NELY WIND BECOMES ELY OR SELY BY LATE AFTERNOON WITH
GENERALLY CALM WIND OVERNIGHT. KAVL WILL SEE MVFR OR IFR THIS
MORNING WITH LOW VFR DEVELOPING BY NOON. NLY WIND BECOMES SLY FOR
THE AFTERNOON...THEN CALM OVERNIGHT. ISOLATED CONVECTION WILL
DEVELOP ACROSS THE MTNS...BUT CHC TOO LOW FOR TAF INCLUSION. KAVL
COULD SEE RESTRICTIONS FROM FOG TOWARD DAYBREAK SAT.

OUTLOOK...SAT THROUGH SUNDAY MORNING SHOULD BE QUIET AND VFR...
EXCEPT FOR THE MTN VALLEYS WHERE EARLY MORNING FOG MAY OCCUR. SCT
THUNDERSTORMS MAY RETURN TO THE FORECAST AREA FOR SUNDAY
AFTERNOON...THOUGH MORE LIKELY MON...AS ANOTHER COLD FRONT
APPROACHES AND THEN MOVES THROUGH THE AREA BY MON NIGHT.

CONFIDENCE TABLE...

            15-21Z        21-03Z        03-09Z        09-15Z
KCLT       HIGH  88%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH  97%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  88%     HIGH 100%     HIGH  89%     HIGH  90%
KHKY       HIGH  89%     HIGH 100%     HIGH 100%     HIGH  87%
KGMU       HIGH  98%     HIGH  97%     HIGH 100%     HIGH 100%
KAND       HIGH  88%     HIGH 100%     HIGH 100%     HIGH  93%

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
NEAR TERM...JDL/RWH
SHORT TERM...CDG
LONG TERM...CDG
AVIATION...RWH






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