Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 131534
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1134 AM EDT SAT SEP 13 2014

.SYNOPSIS...
A STATIONARY FRONT WILL REMAIN JUST TO OUR SOUTH OVER THE WEEKEND
AND INTO EARLY NEXT WEEK WITH UNSETTLED WEATHER EACH DAY. A BACK
DOOR COLD FRONT WILL CROSS THE AREA BY THE MIDDLE OF NEXT WEEK WITH
A COOL AIR WEDGE PATTERN SETTING UP BY THE END OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1125 AM...NOT MUCH ON RADAR AT THE MOMENT EXCEPT FOR SOME SCT
-SHRA NC PIEDMONT. LATEST SFC MAP INDICATES THAT THE COLD FRONT WAS
LOCATED FROM JUST NW OF CLT...SW THROUGH THE NORTHERN UPSTATE INTO
NE GA. 12Z NAM MOVES THE FRONT SLOWLY SE AND BY 00Z LAYS IT OUT
ACROSS THE SOUTHERN UPSTATE INTO NE GA. THE CAMS STILL LIKE THE IDEA
OF DEVELOPING CONVECTION ALONG THE FRONT DURING THE AFTERNOON HOURS.
CAN`T ARGUE WITH THAT IN THAT DESPITE EXTENSIVE CLOUD COVER THIS
MORNING SBCAPES ALREADY EXCEED 1000J/KG WITH DEWPOINTS IN THE LOW
70S AND PRECIP WATER AROUND 2 INCHES. HENCE...WILL CONTINUE WITH THE
NUMEROUS TYPE POPS FOR THIS AFTERNOON FROM THE SOUTHERN NC PIEDMONT
ACROSS THE UPSTATE INTO NE GA. MAIN THREAT WITH THE STORMS WILL BE
LOCALLY HEAVY RAIN.

12Z NAM IS INTERESTING IN THAT IT CONTINUES TO LIGHT UP THE BOUNDARY
TONIGHT WITH CONVECTION AND HEAVY PRECIP AS IT KEEPS QUASI-STATINARY
ACROSS OUR SOUTHERN TIER OF COUNTIES IN THE UPSTATE. 3-4 INCHES
OF RAINFALL IS FORECAST FROM CHESTER COUNTY WEST INTO GREENWOOD
COUNTY. I AM NOT QUITE READY TO BUY INTO THIS COMPLETELY BUT HAVE
GIVEN IT A NOD AND HELD ONTO THE LIKELY POPS INTO TONIGHT ACROSS
THAT AREA. WILL AWAIT THE 12Z GFS BEFORE ENTERTAINING ANY TYPE OF
FLOOD WATCH IDEA.

AS OF 845 AM...UPDATED THE POPS BASED ON CURRENT RADAR TRENDS WHICH
FEATURES A BAND OF SHOWERS FROM AVERY COUNTY DONW INTO BUNCOMBE
COUNTY...APPARENTLY ASSOCIATED WITH THE COLD FRONT. CAMS ARE STILL
FAVORING THE BEST COVERAGE OF SHOWERS/STORMS TO BE THIS AFTERNOON
FROM ABOUT THE CHARLOTTE METRO AREA...SW THROUGH UPSTATE SC.
HENCE...HAVE MAINTAINED GENERALLY LIKELY POPS IN THAT AREA. POPS
THIS AFTERNOON WERE ADJUSTED BY BLENDING IN CONSHSORT. TEMP FIELDS
WERE POPULATED WITH CONSHSORT. THIS BUMPED MAX TEMPS UPWARD A COUPLE
DEGREES OUTSIDE OF THE MOUNTAINS.

OF 645 AM EDT...THOUGH WEDGE OF HIGH PRESSURE IS HANGING ON BY A
THREAD OVER THE NW NC PIEDMONT...THE WEAKENING ACTIVITY THERE IS
FORCED BY A WEAK WAVE OF LOW PRESSURE INVOF WITH THE COLD FRONT
EXTENDING DOWN FROM THE MIDWEST SYSTEM DESCRIBED BELOW. INCREASING
ACTIVITY JUST W OF THE MTNS SUGGESTS POPS WILL RAMP UP QUICKLY THIS
AM IN THE TENN BORDER ZONES...THEN SPREAD EAST AS FRONT MOVES ACRS
THE CWFA TODAY. ON ANOTHER NOTE...LOCALLY DENSE FOG IS PRESENT OUT
THERE. UNLESS SFC OBS BEGIN TO SHOW A CONTIGUOUS AREA OF 1/4SM
VSBY...NO ADVY WILL BE NEEDED. HOWEVER CAUTION IS ADVISABLE ON RURAL
ROADS AND IN VALLEYS THRU 8-9 AM.

THIS MRNG...LOW PRESSURE WILL DEEPEN OVER THE UPPER OH VLY IN
RESPONSE TO THE SHARP SHORTWAVE OVER THE GREAT LAKES REGION. A COLD
FRONT EXTENDS SWD FROM THAT LOW AND WILL CROSS THE MTNS AROUND
MIDDAY. IT WILL THEN PROGRESS ACRS THE CWFA THIS AFTN/EVENING ACTING
TO FOCUS CONVECTION. THE FRONT IS THEN EXPECTED TO STALL OUT ACROSS
SC BY SUNDAY MRNG ALLOWING ANOTHER WEDGE TO FORM AS HIGH PRESSURE
MOVES FROM THE MISSISSIPPI VALLEY TO THE EAST COAST.

POPS TODAY WILL PEAK EARLIER THAN CLIMO IN THE MTNS BEFORE COLD
ADVECTION INHIBITS CONVECTION...BUT ABUNDANT MOISTURE AND UPSLOPING
WARRANT KEEPING A MENTIONABLE POP THRU THE NEAR TERM. OVER THE
FOOTHILLS/PIEDMONT MODELS PRODUCE MODEST CAPES OF 1000-1500 J/KG
STILL WITH WEAK SHEAR...AS ANY SIGNIFICANT UPPER FEATURES REMAIN WELL
TO OUR NORTH DURING THE PERIOD. THERE IS HOWEVER ENOUGH FLOW ALOFT TO
KEEP CELLS MOVING TO SOME DEGREE. PWAT VALUES WILL BE ELEVATED...ESP
IN THE LOWER PIEDMONT WHERE THEY WILL REMAIN NEAR 2 INCHES.  THEY
WON/T BE QUITE AS HIGH AS THOSE FRIDAY AND THE FLOW WILL BE AT A
LARGER ANGLE TO THE FRONT. ALTOGETHER THE FLOOD RISK IS NOT THAT
GREAT...THOUGH LOCALIZED FLOODING IS STILL A POSSIBILITY ESPECIALLY
IN URBAN ENVIRONMENTS. THE BRIEF BREAK IN THE WEDGE SHOULD ALLOW
CLOUDS TO LIFT BUT NOT BREAK UP...AND TEMPS WILL BE NEAR TO SLIGHTLY
ABOVE NORMAL.

TONIGHT...WITH A WEDGE AGAIN SETTING UP...WEAK UPGLIDE RETURNS AS THE
LOW LIFTS AWAY AND THE BERMUDA HIGH REGAINS INFLUENCE ACRS THE
SOUTHEAST. THUS HAVE ALLOWED CHANCE POPS TO PERSIST OVER MUCH OF THE
PIEDMONT OVERNIGHT. EASTERLY FLOW WILL PROVIDE SOME ENHANCEMENT INTO
THE BLUE RIDGE AS WELL. LAPSE RATES ARE RATHER POOR ABOVE THE WEDGE
INVERSION SO IT APPEARS THUNDER WILL BE OF LITTLE CONCERN ONCE IT
DEVELOPS. ONLY LIGHT QPF WILL BE ADVERTISED. THOUGH THEY WILL BE
COOLER THAN THOSE SATURDAY MRNG WITHIN THE POSTFRONTAL AIRMASS...MIN
TEMPS STILL WILL BE A CATEGORY OR SO ABOVE NORMAL UNDER CLOUDY SKIES.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 310 AM SATURDAY...A BRIEF BUT SIGNIFICANT COLD AIR DAMMING
EVENT IS ANTICIPATED FOR SUNDAY...AS WEAKENING/MIGRATORY HIGH
PRESSURE OOZES ACROSS THE NORTHEAST CONUS. WHILE CONFIDENCE IS
REASONABLY HIGH THAT MAXES SUNDAY WILL BE 10-15 DEGREES BELOW
CLIMO...THERE IS UNCERTAINTY REGARDING HOW MUCH PRECIP WILL AFFECT
THE CWA SUNDAY. THE AIR MASS IS EXPECTED TO BE VERY STABLE...WITH
THE EXCEPTION OF THE WESTERN MNTNS...AND PERHAPS THE SOUTHERN TIER
OF THE FORECAST AREA. ALTHOUGH MOISTURE WITHIN THE WEDGE AIR MASS
WILL BE ABUNDANT...UPGLIDE OVER THE COOL DOME WILL NOT BE ESPECIALLY
SIGNIFICANT. WHILE SCT CONVECTION WILL BE POSSIBLE AROUND THE
PERIPHERY OF THE CAD AIR MASS...THERE MAY BE MORE OF A PATCHY
DRIZZLE/SPOTTY -RA SCENARIO OVER THE VAST MAJORITY OF THE FORECAST
AREA. WE DIDN/T DEVIATE TOO MUCH FROM THE INHERITED 30-40 POPS...BUT
ANY PRECIP AMOUNTS SHOULD BE VERY LIGHT ACROSS THE VAST MAJORITY OF
THE FORECAST AREA.

OTHERWISE...WEDGE EROSION SHOULD BE IN FULL EFFECT BY MONDAY...AS
THE WEAKENING PARENT HIGH SLIDES OFF THE NEW ENGLAND COAST. WITH
MOISTURE LINGERING...ADDITIONAL HEATING TUE AFTERNOON SHOULD PROVIDE
THE NECESSARY INGREDIENTS FOR SCATTERED CONVECTION...AND 30-50 POPS
WILL BE MAINTAINED ACROSS MUCH OF THE AREA MON AFTERNOON INTO THE
EVENING HOURS.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 450 AM SATURDAY...A GENERAL LOW AMPLITUDE UPPER FLOW REGIME
WILL PERSIST INTO THE EARLY PORTION OF THE MEDIUM RANGE...WHILE A
WEAK FRONTAL ZONE AND ASSOCIATED MOISTURE WILL REMAIN STALLED ACROSS
THE SOUTHEAST. IT APPEARS THAT A RATHER POTENT SHORT WAVE TROUGH
TRAVERSING THE GREAT LAKES REGION WILL SEND A REINFORCING FRONTAL
ZONE THROUGH OUR AREA TUESDAY...WHICH MAY FINALLY ALLOW SOME DRIER
AIR TO TRICKLE INTO THE AREA. THIS SHOULD GIVE US A DAY OR SO WITH
LIMITED CONVECTIVE COVERAGE. HOWEVER...MOISTURE MAY RETURN BY
MID-WEEK IN ADVANCE OF AN EVEN STRONGER SHORT WAVE PASSING TO OUR
NORTH...ALLOWING FOR AN INCREASE IN DIURNAL CONVECTIVE COVERAGE BY
WEDNESDAY/THU. STRONG/EARLY AUTUMN HIGH PRESSURE BUILDING INTO NEW
ENGLAND BY EARLY FRIDAY SHOULD THEN SET THE STAGE FOR ANOTHER ROUND
OF COLD AIR DAMMING ACROSS THE SOUTHEAST/MID-ATLANTIC LATE IN THE
WEEK...ALTHOUGH IT REMAINS SOMEWHAT UNCERTAIN AS TO HOW MUCH
MOISTURE WILL BE PRESENT DURING THIS PARTICULAR CAD EVENT.

&&

.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...CIG SHOULD BE LOCKED IN AT LIFR UNTIL MID MRNG UNDER
PERSISTENT COOL WEDGE. WINDS ALOFT VEER AT MIDDAY AHEAD OF ANOTHER
COLD FROPA EXPECTED EARLY THIS EVENING. THIS WILL ALLOW CIGS TO
LIFT...BUT DIURNAL INSTABILITY WILL BE ABLE TO GROW WITH THAT FRONT
COMING IN NEAR PEAK HEATING. SHRA/TSRA WILL CONTINUE TO BE CAPABLE
OF PROLIFIC RAINFALL AND PERIODIC MVFR CIGS/VSBY...HENCE TEMPO. MVFR
TONIGHT AS WEDGE RETURNS IN THE WAKE OF THE COLD FRONT. WINDS WILL
GENERALLY BE SOUTHERLY DURING THE DAY TODAY BUT WILL PREVAIL NE IN
THE NEW WEDGE.

ELSEWHERE...PATCHY IFR CIGS WILL SLOWLY LIFT THRU THE MORNING...WITH
KHKY LIKELY THE LAST SITE TO GO MVFR AS IT IS MOST UNDER THE
INFLUENCE OF A WEDGE OF COOL HIGH PRESSURE. COLD FRONT WILL MOVE
THRU THE REGION ACTING TO FOCUS DIURNAL INSTABILITY AND CONVECTIVE
DEVELOPMENT. HAVE PREVAILED SHRA/TSRA NEAR TIME OF FROPA. THE FRONT
WILL THEN STALL ACRS GA/SC BASICALLY REINFORCING THE ONE WHICH IS
ALREADY STATIONARY IN THAT AREA...AND A WEDGE DEVELOPS TONIGHT ONCE
AGAIN. MVFR CIGS ARE LIKELY AT ALL THE SITES EXCEPT KAND AFTER
MIDNIGHT...MOST LIKELY PREVENTING COOLING OF THE SFC LAYER SO IFR IS
NOT ALLOWED TO PREVAIL. KAND WILL BE OUT OF THE INFLUENCE OF THE
WEDGE AND STANDS A BETTER CHANCE OF IFR.

OUTLOOK...A FRONTAL BOUNDARY WILL REMAIN STALLED ACROSS THE
SOUTHEAST THRU THE WEEKEND WHILE A WEAK WEDGE OF HIGH PRESSURE
SLIDES DOWN THE EAST SIDE OF THE MOUNTAINS. MORNING VSBY/CIG
RESTRICTIONS POSSIBLE AT ALL SITES EACH MORNING WITH THE HIGHEST
PROBABILITIES RESIDING ACROSS THE HIGH TERRAIN AND IN THE MOUNTAIN
VALLEYS.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-14Z
KCLT       HIGH  85%     HIGH 100%     HIGH 100%     HIGH  84%
KGSP       MED   76%     HIGH 100%     HIGH  95%     MED   67%
KAVL       HIGH  81%     HIGH  99%     HIGH  88%     HIGH  93%
KHKY       MED   77%     HIGH 100%     HIGH  93%     MED   67%
KGMU       HIGH  82%     HIGH 100%     HIGH 100%     MED   67%
KAND       HIGH  86%     HIGH 100%     HIGH  98%     HIGH  97%

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...WIMBERLEY
NEAR TERM...LG
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...WIMBERLEY





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