Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 020549
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
149 AM EDT THU OCT 2 2014

.SYNOPSIS...
DRIER HIGH PRESSURE WILL LINGER OVER THE REGION THROUGH THURSDAY. A
STRONG COLD FRONT WILL THEN APPROACH THE CAROLINAS FROM THE
NORTHWEST ON FRIDAY AND MOVE OFFSHORE BY EARLY SATURDAY. IN THE
FRONTS WAKE...A COOL AND DRY AIRMASS WILL MOVE BACK OVER THE
REGION AND REMAIN IN PLACE OVER THE WEEKEND. ANOTHER COLD FRONT WILL
APPROACH THE SOUTHERN APPALACHIAN REGION FROM THE NORTHWEST EARLY
NEXT WEEK.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 130 AM...SOME FOG DEVELOPING ACROSS THE PIEDMONT...WITH MORE
FOG DEVELOPING IN EARNEST IN THE MTN VALLEYS. EXPECT MOST OF THE FOG
OUTSIDE THE MTNS TO REMAIN LIGHT...WHILE THE FOG SHOULD BE LOCALLY
DENSE IN THE MTN VALLEYS. THE FOG SHOULD REMAIN UNTIL AN HOUR OR SO
AFTER DAYBREAK. TEMPS LOOK OK.

PREVIOUS DISCUSSION...
THE EVENING GSO RAOB SHOWS A STRONG TEMPERATURE INVERSION AROUND 700
MB...AND WEAK UPGLIDE UNDER THIS LEVEL HAS PRODUCED SOME HIGH BASED
STRATOCUMULUS AROUND THE REGION. THIS AREA OF MOISTURE AND WEAK LIFT
WILL GRADUALLY MOVE EWD OVERNIGHT. THE OPERATIONAL NAM AND LATEST
SREF MEAN PRODUCE SOME SPOTTY LIGHT QPF OVERNIGHT ACROSS THE
REGION...BUT THIS IS NOT SUPPORTED BY THE DRY SUB CLOUD LAYER AND
THE OFFICIAL FORECAST WILL REMAIN DRY. ONCE THE CLOUDS THIN FROM THE
WEST...PATCHY DENSE MOUNTAIN VALLEY FOG AND LIGHT FOOTHILL FOG WILL
BE POSSIBLE OVERNIGHT THROUGH DAYBREAK.

OTHERWISE...AN UPPER RIDGE WILL BUILD OVER THE SOUTHEAST U.S.
THROUGH THU. AT THE SURFACE...HIGH PRESSURE WILL CONTINUE TO RIDGE
SOUTH INTO THE REGION. THE MID LEVEL INVERSION WILL BE MAINTAINED
THROUGH THE PERIOD. QUIET/DRY WEATHER IS THUS EXPECTED TO CONTINUE
THROUGH THU...WITH MAX TEMPS REMAINING ABOVE CLIMO.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
AS OF 215 PM WEDNESDAY...MODELS STILL IN GOOD AGREEMENT ON TIMING A
COLD FRONT THRU THE CWFA ON FRIDAY. IT LOOKS LIKE THERE WILL BE ONLY
A BRIEF PERIOD OF MOIST SWLY 850 MB FLOW AHEAD OF THE FRONT THURSDAY
NIGHT THRU FRIDAY MIDDAY. SO I HAVE POPS SLOWLY RAMPING UP IN THE
WESTERN ZONES (ESP THE SW-UPSLOPE AREAS)...WHILE THE REST OF THE
AREA SHUD BE RELATIVELY DRY OVERNIGHT. LOW TEMPS THURSDAY NIGHT WILL
REMAIN ELEVATED ABOVE NORMAL WITHIN THE RETURN FLOW AND CLOUD COVER.

DURING THE DAY ON FRIDAY...A PRE-FRONTAL BAND OF SHWRS AND PERHAPS A
FEW TSTMS SHUD CROSS THE CWFA FROM WEST TO EAST. AS USUAL WITH THESE
TYPE OF EVENTS...THE LINE MAY SLOW DOWN AS IT CROSSES THE MTNS.
GUIDANCE HAS TRENDED A TAD SLOWER WITH THE TIMING AS WELL. I WILL
CONTINUE THE HIGH-END LIKELY EAST TO CATEGORICAL WEST FOR
FRIDAY...WITH LIKELY POP LINGERING IN THE EASTERN ZONES FRIDAY
EVENING. QPF WILL BE MODEST DUE TO THE FAST-MOVING NATURE OF THE
CONVECTION...GENERALLY 0.5 TO 1.0". AS FOR SEVERE
POTENTIAL...GUIDANCE HASN/T TRENDED ANY MORE UNSTABLE WITH THE
LINE...WITH REALLY ONLY 500-1000 J/KG OF SBCAPE...HIGHEST ALONG I-85
CORRIDOR. CONFIDENCE ON ANYTHING MORE THAN AN ISOLD WIND EVENT HERE
AND THERE IS STILL LOW...SO WILL CONTINUE TO LEAVE MENTION OUT OF
THE HWO. TEMPS WILL REMAIN AT OR BELOW NORMAL ON FRIDAY...ASSUMING
CLOUDS/PRECIP MOVE IN DURING THE DAY.

DECENT 850 MB CAA IS EXPECTED BEHIND THE FRONT OVERNIGHT FRIDAY
NIGHT THRU SATURDAY. THIS SHUD CUT OFF SHWR ACTIVITY...SAVE FOR A
LINGERING SLGT CHC NWLY UPSLOPE SHWR THREAT. CLOUDS SHUD CLEAR OUT
FOR THE MOST PART...BUT TEMPS WILL BE ABOUT 8-10 DEG BELOW
NORMAL...WITH A LIGHT NWLY BREEZE. IT WILL DEFINITELY FEEL LIKE FALL.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 155 PM WEDNESDAY AFTERNOON...THE MEDIUM RANGE FCST PICKS UP AT
00Z ON SUNDAY WITH A NEGATIVELY TILTED...STEEP UPPER TROF TO OUR
NORTH AND BROAD UPPER RIDGING BUILDING OVER THE WEST COAST. OVER THE
NEXT DAY OR SO...THE TROF AXIS LIFTS NE OF THE REGION. FOR THE NEXT
FEW DAYS...THE MODELS CONTINUE TO INDICATE THAT WE WILL REMAIN UNDER
BROAD UPPER TROFFING WITH SOME DEAMPLIFICATION EXPECTED BY NEW DAY 7
ON WED. THE ECMWF CONTINUES TO REAMPLIFY THE TROF MORE THAN THE GFS
ON MON AND TUES...YET IT DOES INCREASE HEIGHTS BY THE VERY END OF
THE MEDIUM RANGE MUCH LIKE THE GFS. THE GFS CONTINUES TO DEVELOP A
LARGE CLOSED H5 LOW OVER ONTARIO EARLY IN THE PERIOD AND MAINTAINS A
LONGER WAVELENGTH TROF THRU TUES.

AT THE SFC...COOL AND DRY HIGH PRESSURE WILL BE IN PLACE OVER THE
REGION ON SUN AND THEN SHIFT EASTWARD ON MON AND TUES. THIS PUTS THE
FCST AREA BACK UNDER LIGHT SLY FLOW FOR THE REST OF THE MEDIUM
RANGE. THE MODELS CONTINUE TO DEVELOP SOME SORT OF LARGE SFC LOW
NORTH OF THE GREAT LAKES EARLY NEXT WEEK AND MOVE A COUPLE OF WEAK
FRONTS OVER OUR AREA. THE MODELS ARE NOW SUGGESTING THAT MORE
MOISTURE COULD BE ASSOCIATED WITH THE FROPA(S) AND MORE QPF IS
POSSIBLE...HOWEVER I DONT THINK THE CURRENT GUIDANCE WARRANTS ANY
POPS MORE THAN SLIGHT CHANCE WITH SOME ISOLATED SOLID CHANCE POPS
OVER THE HIGHER TERRAIN FOR TUES AFTERNOON/EVENING.
OTHERWISE...TEMPS WILL START OUT WELL BELOW NORMAL FOR EARLY OCT AND
STEADILY WARM THRU THE PERIOD WITH HIGHS APPROACHING 80 OVER THE
LOWER ELEVATIONS BY DAY 7.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AT KCLT...SCATTERED VFR STRATOCUMULUS EXPECTED FOR MUCH OF THE EARLY
MORNING HOURS AS VERY WEAK UPGLIDE DEVELOPS UNDER A MID LEVEL
INVERSION. AS EXPECTED...FOG WAS DEVELOPING IN THE OUTLYING AREAS
WHICH HAD REDUCED THE VISIBILITY TO MVFR/IFR...AND EXPECT THE FOG TO
EXPAND OVER THE PIEDMONT AS IT DID LAST NIGHT. SIMILAR TO LAST
NIGHT...THE RESTRICTION SHOULD RING KCLT...BUT THE FOG WILL HAVE A
DIFFICULT TIME DEVELOPING AT THE AIR FIELD. HAVE INCLUDED A TEMPO
FOR MVFR BASED ON THE LAMP GUIDANCE...BUT CONFIDENCE IS ONLY
MODERATE. OTHERWISE...EXPECT SCT CLOUDS TO REMAIN THROUGH THURSDAY
WITH A CONTINUED VERY LIGHT SRLY FLOW THROUGH THE END PERIOD.

ELSEWHERE...THE BIG PROBLEM WILL BE MOUNTAIN VALLEY FOG AT
KAVL...WHICH WAS ALREADY LIFR AT ISSUANCE TIME. EXPECT SOME
VARIABILITY TO THE FOG RESTRICTION THROUGH DAYBREAK...BUT GENERALLY
LIFR/VLIFR. OTHER TAF SITES MAY SEE A PERIOD OF MVFR VISIBILITY AND
THAT WAS INCLUDED. THE FOG SHOULD LIFT AND BURN OFF BY 13Z TO 14Z.
OTHERWISE...SCT/FEW HIGH BASED STRATOCU AGAIN THURSDAY WITH A LIGHT
WIND FROM THE S TO SW. ANY CLOUD UP WILL REMAIN W OF THE NC MTNS
THROUGH THE END OF THE TAF PERIOD.

OUTLOOK...A COLD FRONT WILL MOVE ACROSS THE AREA ON FRI WHICH WILL
TRIGGER SHOWERS AND THUNDERSTORMS...WITH ASSOCIATED RESTRICTIONS
POSSIBLE. BEHIND THE FRONT FRI NIGHT...CLEARING WILL OCCUR WITH AN
EXTENDED PERIOD OF VFR WEATHER ANTICIPATED THROUGH EARLY NEXT WEEK.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-05Z
KCLT       HIGH 100%     HIGH  94%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH  97%     HIGH 100%     HIGH 100%
KAVL       HIGH  81%     HIGH  85%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH  97%     HIGH 100%     HIGH 100%
KAND       HIGH  94%     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...JPT
NEAR TERM...HG/PM
SHORT TERM...ARK
LONG TERM...JPT
AVIATION...PM






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