Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 241814
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
214 PM EDT THU JUL 24 2014

.SYNOPSIS...
A COLD FRONT WILL THE CROSS AREA THROUGH THIS EVENING AND MOVE
SOUTHEAST OF THE REGION OVERNIGHT. HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT FOR FRIDAY AND THE WEEKEND. ANOTHER FRONT IS
EXPECTED TO REACH THE AREA ON MONDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
AT 215 PM...RADAR BEGINNING TO LIGHT UP WITH QUITE A BIT OF
CONVECTION DEVELOPING. AT THIS TIME...IT IS JUST SCT IN NATURE...BUT
WOULD EXPECT TO SEE SOME CONSOLIDATION LATER IN THE AFTERNOON OVER
THE PIEDMONT WHEN THE APPROACHING FRONT/LEE TROUGH PROVIDE MORE OF A
FOCUS. WITH CAPES BETWEEN 2500-3000J AND 0-6KM BULK SHEAR 25-30KTS A
FEW SEVERE STORMS STILL LOOK TO BE A GOOD BET. SOME STORMS MY PERIST
INTO THE 00Z-03Z TIMEFRAME AS THE COLD FRONT ONLY SLOWLY SLIPS
SOUTHEAST OF THE REGION.

OTHERWISE AS THE FRONT MOVES OUT OF THE AREA TONIGHT...HIGH PRESSURE TO
THE NORTH WILL BUILD SOUTHWARD BRINGING A SOMEWHAT DRYER AIRMASS
INTO THE AREA. HOWEVER...LOW LEVEL MOISTURE WILL REMAIN ELEVATED
OVERNIGHT AND WITH WINDS BECOMING LIGHT FOG SHOULD DEVELOP
THROUGHOUT THE MOUNTAIN VALLEYS...AND ALSO ACROSS PARTS OF THE
PIEDMONT.

ON FRIDAY...EVEN WITH THE REMANTS OF THE FRONT REMAINING SOUTH OF
THE AREA...WINDS ARE FORECAST TO VEER TO THE SE DURING THE
AFTERNOON. THE LIGHT UPSLOPE COMPONENT AND WEAKENING CAP MAY ALLOW FOR
A FEW ISOLATED MOUNTAIN SHOWERS FRIDAY AFTERNOON. MAX TEMPS WILL TOP
OUT A COUPLE DEGREES BELOW CLIMO.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 130 PM THU...UPPER HEIGHTS INITIALLY RISE FRI NIGHT AS A TROUGH
LIFTS AWAY FROM THE EAST COAST...BUT REMAIN NEARLY STEADY THEREAFTER
LEAVING OUR REGION UNDER SLIGHTLY CYCLONIC FLOW OVER THE WEEKEND. BY
LATE SUNDAY HOWEVER HEIGHTS BEGIN TO FALL AGAIN AS ANOTHER SHORTWAVE
DIGS INTO THE MIDWEST. AT THE SFC WEAK HIGH PRESSURE WILL PERSIST
OVER THE SERN CONUS ALONG WITH LIGHT SWLY TO WLY FLOW.

FOR SATURDAY THE MAIN DIFFICULTY IS TO DETERMINE WHETHER THE SFC HIGH
WILL PROVIDE ENOUGH SUBSIDENCE TO STIFLE DIURNAL CONVECTION. MODELS
DIFFER RATHER WIDELY IN THEIR DEPICTION OF THE CAP. 09Z SREF MEMBER
SOUNDINGS MOSTLY SHOW A SIGNIFICANT MIDLEVEL INVERSION...BUT THE
MEMBERS WHICH ARE UNCAPPED SHOW CAPE VALUES A BIT HIGHER THAN CLIMO
GIVEN THE LACK OF RIDGING ALOFT. DRY MID-UPPER LEVELS AND LACK OF
SHEAR IMPLY PULSE-MODE THREATS IF ANY CELLS ARE TO FIRE. ON THE OTHER
HAND...GFS/GEFS IMPLY CAPPING AND ACCORDINGLY HAVE NO QPF RESPONSE.
OVERALL SUPPORT SEEMS TO BE BETTER FOR A DRY FCST...THUS I HAVE
MAINTAINED IT. HIGH TEMPS WILL BE ABOUT NORMAL FOR SATURDAY.

THE POTENTIAL CAPPING IS A CRITICAL QUESTION FOR SUNDAY...BUT AT THAT
TIME THERE IS THE ADDED ISSUE OF WHETHER THE COLD FRONT PLOWING ACRS
THE OH/TN VALLEYS WILL HAVE ANY IMPACT DURING PEAK HEATING.  EARLIER
MODEL RUNS SUGGESTED THE FRONT WOULD BE NEAR ENOUGH TO PUT OUR AREA
IN A MORE FAVORABLE ENVIRONMENT FOR STRONG STORMS SUNDAY AFTN...BUT
LATEST GUIDANCE HAS DELAYED IT AND A FAIR NUMBER OF THE LATEST RUNS
AGAIN KEEP CONVECTION TO A MINIMUM OVER THE CWFA. ENSEMBLE SOLUTIONS
LEND SOME SUPPORT THOUGH...AND IN LIGHT OF THE UNCERTAIN MODEL TRENDS
AND CONTINUED EXPECTATION THAT THE FRONT WILL BE NEARBY...LOW POPS
HAVE BEEN KEPT SUNDAY AFTN...RAMPING UP INTO SUNDAY NIGHT. TEMPS WILL
INCH UP SLIGHTLY FURTHER SUNDAY UNDER HIGHER THICKNESSES IN THE SWLY
FLOW.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 150 PM THURSDAY...SUBSTANTIAL/ANOMALOUSLY STRONG UPPER HEIGHT
FALLS WILL BE INTRODUCED TO THE EASTERN CONUS EARLY IN THE MEDIUM
RANGE PERIOD...ALLOWING A COLD FRONT TO PUSH TOWARD THE REGION. THE
LATEST GLOBAL MODEL RUNS HAVE CONTINUED A RECENT TREND OF DRIER
PRE-FRONTAL AIR AND A WEAKER QPF RESPONSE WITH THE FRONT IN THE LATE
SUNDAY NIGHT/EARLY MONDAY TIME FRAME. IN FACT...A CONSENSUS SEEMS TO
BE DEVELOPING THAT PROBABILITIES FOR SHOWERS WILL BE VERY LOW...
EXCEPT PERHAPS ACROSS THE SOUTHERN AND EASTERN FRINGE OF OUR
PIEDMONT AREAS MON AFTERNOON...WHEN THE FRONT WILL HAVE A LITTLE
MORE IN THE WAY OF BUOYANCY TO WORK WITH. NEVERTHELESS...EARLY NEXT
WEEK IS STILL TOO FAR IN THE FUTURE FOR US TO GET TOO CUTE WITH
TIMING THE POSITION OF THE FRONT...AND THESE SCENARIOS TYPICALLY
EVOLVE MORE SLOWLY THAN ADVERTISED BY THE MODELS THIS TIME OF YEAR.
THEREFORE...WILL GENERALLY FEATURE A SHOTGUNNED CHANCE POP ACROSS
THE CWFA THROUGHOUT MONDAY...DIMINISHING TO SLIGHT CHANCE OR LESS BY
EVENING.

THE REMAINDER OF THE FORECAST PERIODS LOOKS VERY SIMILAR TO WHAT WAS
EXPERIENCED ABOUT A WEEK AGO...WHEN AN UNUSUALLY COOL/DRY AIR MASS
BECAME ESTABLISHED OVER THE REGION UNDERNEATH AN ANOMALOUSLY STRONG
EASTERN TROUGH. IF ANYTHING...THIS AIR MASS PAY PROVE TO BE A LITTLE
MORE PERSISTENT THAN LAST WEEK/S. TEMPS ARE EXPECTED TO BE 5-10
DEGREES BELOW CLIMO THROUGH THE PERIOD...WHILE A HALT IN DIURNAL
CONVECTION IS EXPECTED THROUGH AT LEAST WED.

BY THE END OF THE PERIOD...THERE ARE SIGNS THAT...AGAIN SIMILAR TO
LAST WEEK/S EVENTS...THE TROUGH WILL EFFECTIVELY RETROGRADE...
ALLOWING MOISTURE TO RETURN WITHIN A DEVELOPING WEDGE-LIKE SCENARIO.
POPS AND CLOUDS WILL THEREFORE BEGIN TO INCREASE BY THE END OF THE
PERIOD...WITH TEMPS REMAINING COOL WITHIN A DEVELOPING EASTERLY LOW
LEVEL FLOW REGIME.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AT KCLT...A COLD FRONT APPROACHING ALONG WITH AN UPPER TROUGH SHOULD
TRIGGER NUMEROUS SHOWERS/THUNDERSTORMS NEAR AND/OR OVER THE AIRFIELD
THIS AFTERNOON. HENCE...HAVE A TEMPO FOR TSRA WITH RESTRICTIONS AND GUSTY
WINDS UNTIL 23Z. THINGS WILL CALM DOWN OVERNIGHT. HOWEVER...MOST
GUIDANCE SUGGESTS THAT MVFR CLOUDS WILL DEVELOP TOWARD SUNRISE WITH
SOME LIGHT FOG. THIS SHOULD DISSIPATE BY 14Z.

ELSEWHERE...ALL TERMINALS WILL LIKELY SEE THUNDERSTORMS WITH
RESTRICTIONS AND GUSTY WINDS THIS AFTERNOON AS A COLD FRONT MOVES
INTO THE AREA. THE STORMS WILL MOVE OUT OF THE AREA THIS EVENING.
THE OVERNIGHT WILL QUIET DOWN BUT SOME IFR FOG IS A GOOD BET AT KAVL
WHERE CROSS OVER OVER TEMP WILL BE MET.

OUTLOOK...FRI NIGHT THROUGH SUNDAY MORNING SHOULD BE QUIET AND
VFR...EXCEPT FOR THE MTN VALLEYS WHERE EARLY MORNING FOG MAY OCCUR.
THUNDERSTORMS WILL RETURN TO THE FORECAST FOR SUNDAY AFTERNOON
THROUGH MON AS ANOTHER COLD FRONT APPROACHES AND THEN MOVES THROUGH
THE AREA ON MON.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH  85%     MED   76%     MED   73%
KGSP       HIGH  95%     HIGH  93%     HIGH 100%     HIGH 100%
KAVL       MED   78%     MED   78%     MED   71%     HIGH  91%
KHKY       HIGH  84%     HIGH  93%     HIGH 100%     HIGH 100%
KGMU       HIGH  95%     HIGH  93%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     MED   75%

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






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