Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 110519
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
119 AM EDT FRI JUL 11 2014

.SYNOPSIS...
A FRONTAL BOUNDARY WILL BE SOUTH OF OUR AREA TODAY AND GRADUALLY
WEAKEN AND DISSIPATE TONIGHT. WEAK HIGH PRESSURE WILL RETURN THROUGH
THE WEEKEND. A STRONG COLD FRONT IS EXPECTED TO REACH THE AREA ON
TUESDAY WITH THE POSSIBILITY OF STRONG STORMS.

&&

.NEAR TERM /THROUGH TODAY/...
0515 UTC UPDATE...POPS AND QPF HAVE BEEN PER RADAR TRENDS TO ACCOUNT
FOR CONVECTION ON THE WESTERN BLUE RIDGE...AND IN THE SOUTHERN SC
PIEDMONT. WINDS WERE UPDATED WITH A BLEND OF THE LATEST ADJMAV AND
NAM.

AS OF 750 PM...A WEAK FRONT WILL SLIDE ACROSS THE REGION OVERNIGHT.
LATEST MESO ANALYSIS AND RADAR TRENDS INDICATE THAT THE ATMOS HAS
BEEN WORKED OVER...I WILL UPDATE TO REDUCE POPS. HOWEVER...LIGHT
WINDS...WET GROUND...AND LINGERING MOISTURE IS EXPECTED TO SUPPORT
AREAS OF FOG AND LOW CLOUDS BY LATE TONIGHT. THE LOWEST CONDENSATION
PRESSURE DEFICITS ON THE NAM REMAIN ACROSS THE MTNS AND I-40
CORRIDOR. I WILL INDICATE IFR TO LIFR VIS AND CEILINGS WITHIN THE
MTN VALLEYS LATE TONIGHT...WITH MVFR FOG POSSIBLE ACROSS THE I-40
CORRIDOR AND AROUND LAKES. OTHERWISE...CONDITIONS SHOULD FAVOR LIGHT
VEERING WINDS.

AS OF 245 PM EDT THURSDAY...BROAD UPPER LONGWAVE TROF CONTINUES TO
DOMINATE THE PATTERN ACROSS THE CENTRAL/EASTERN CONUS.  A SURFACE
CYCLONE CONTINUES TO EJECT NORTHEAST ACROSS EASTERN QUEBEC WHILE ITS
ASSOCIATED TRAILING COLD FRONT REMAINS LAID ACROSS THE SOUTHERN OHIO
AND TENNESSEE VALLEYS.  AN UPPER SHORT WAVE TROF PUSHING THROUGH THE
MEAN UPPER FLOW IS BEGINNING TO MOTIVATE THE OLD FRONT ACROSS THE
SPINE OF THE APPS AND INTO WESTERN NC.  CURRENT RADAR IMAGERY
INDICATES EXPANDING CONVECTION AHEAD OF THE INTRUDING BOUNDARY
ACROSS THE MOUNTAINS AND FOOTHILLS OF WESTERN NC.  MEANWHILE FURTHER
EAST ACROSS THE PIEDMONT...EARLIER LOW/MID STRATUS HAS STUNTED
HEATING SLIGHTLY ALLOWING FOR A LAG IN ACTIVITY.  THAT
SAID...INSTABILITY CONTINUES TO BUILD ACROSS THESE ZONES AS LATEST
SPC MESOANALYSIS INDICATES UPWARDS OF 1500J/KG OF SBCAPE PRESENT.
THIS COMBINED WITH POTENTIAL SURFACE CONVERGENCE ASSOCIATED WITH A
WEAK LEE TROF WILL LIKELY PROVIDE ADDITIONAL FOCUS FOR CONVECTION
OUTSIDE OF THE HIGH TERRAIN LATER IN THE AFTERNOON.  THUS...THE
FORECAST WILL FEATURE LIKELY LEVEL POPS ACROSS PORTIONS OF THE HIGH
TERRAIN AND NC/SC PIEDMONTS WHILE SOLID CHANCE LEVEL POPS ARE
HIGHLIGHTED ELSEWHERE.  EXPECTING THE PRIMARY THREAT FROM ANY OF
THESE THUNDERSTORMS TO BE DAMAGING DOWNBURST WINDS AS DCAPE RECOVERS
THROUGH THE AFTERNOON.  SECONDARY THREATS WILL INCLUDE SMALL HAIL
AND HEAVY RAINFALL WHICH COULD LEAD TO MINOR FLOODING.

CONDITIONS WILL IMPROVE BY LATE EVENING INTO THE OVERNIGHT AS
HEATING SUBSIDES AND REGION OF ENHANCED DPVA ADVECTS TO THE EAST.
IN RESPONSE...POPS WILL TAPER DOWN BY MORNING WITH ONLY SLIGHT
CHANCE POPS REMNANT ACROSS THE NC/SC PIEDMONTS.  THE ABOVE MENTIONED
UPPER TROF WILL LIFT TO THE NORTHEAST ON FRIDAY AS CONFLUENT FLOW
AIDS SURFACE RIDGE DEVELOPMENT ACROSS THE EASTERN GREAT LAKES.  THE
FRONTAL BOUNDARY THAT IS CURRENTLY PUSHING THROUGH THE REGION WILL
LIKELY STALL ACROSS THE MIDLANDS...NORTHEAST INTO CENTRAL NC.  THIS
WILL LEAD TO A SLIGHTLY MORE STABLE ENVIRONMENT ACROSS THE ENTIRE
CWFA ON FRIDAY.  FORECAST SOUNDINGS INDICATE DEVELOPMENT OF MID
LEVEL INHIBITION AS HEIGHTS RISE THUS DECIDED TO CAP POPS AT SLIGHT
CHANCE LEVELS OUTSIDE OF THE HIGH TERRAIN WHERE WEAK EASTERLY
UPSLOPE FLOW MIGHT AID CONVECTION WARRANTING LOW END CHANCE LEVEL
POPS.  NOT EXPECTING MUCH IMPACT IN REGARDS TO TEMPERATURES BEHIND
THE FRONT AS HIGHS ON FRIDAY WILL ONCE AGAIN APPROACH OR JUST EXCEED
NORMAL LEVELS AMONGST PARTLY CLOUDY SKIES.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...
AS OF 107 AM FRI...WEAK HIGH PRESSURE WILL REMAIN RIDGED OVER THE
AREA SATURDAY THROUGH SUNDAY AS AN EXTENSION OF THE BERMUDA HIGH.
LIGHT LOW LEVEL E TO SE FLOW INDICATED ON THE GFS SATURDAY THEN
SHIFTS TO LIGHT SOUTHERLY WIND ON SUNDAY. LOW COVERAGE OF DIURNAL
CONVECTION IS EXPECTED ALMOST COMPLETELY OVER THE MTNS AND ADJACENT
FOOTHILLS SATURDAY PM WITH LIGHT UPSLOPE AND LIGHT LOW LEVEL
DIRECTIONAL CONVERGENCE FOCUSED ON MTNS. A BIT MORE
MOISTURE...SLIGHTLY MORE UNSTABLE ON SUNDAY ALONG WITH CONTINUED
LIGHT DIRECTIONAL LOW LEVEL WIND CONVERGENCE TO PRODUCE SOMEWHAT
MORE COVERAGE OF PM CONVECTION MAINLY OVER MTNS. MAX TEMPS SAT AND
SUN WILL BE AT OR JUST A DEGREE OR TWO ABOVE CLIMO NORMALS WITH MIN
TEMPS SAT NIGHT AND SUN NIGHT AT OR JUST ABOVE CLIMO NORMS AS WELL.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 300 PM THU...A DISTINCT UPPER LEVEL PATTERN CHANGE IS FORECAST TO
OCCUR NEXT WEEK ACROSS THE EASTERN U.S. AS A DEEP UPPER LOW SWINGS
SOUTH OUT OF NORTHERN CANADA AND ESTABLISHES AN ANOMALOUS UPPER
TROUGH OVER THE EAST BY MIDWEEK. AS THE UPPER LOW MOVES SE AND
HEIGHTS FALL...A SURFACE COLD FRONT WILL BE DRIVEN SOUTHEASTWARD.
MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT THAT THE COLD FRONT WILL
MOVE THROUGH DURING THE TUESDAY AFTERNOON AND EVENING TIME PERIOD.
THE FRONT WILL BE WELL FORCED FOR JULY AND CAPES SHOULD POOL AHEAD
OF THE FRONT TO PERHAPS 2000J/KG...SO THERE IS A DISTINCT
POSSIBILITY OF AN ORGANIZED SEVERE STORM EVENT WITH THE FRONTAL
PASSAGE. THE FRONT MAY NOT CLEAR THE AREA COMPLETELY ON WED SO SOME
LINGERING SHOWERS MAY OCCUR PRIMARILY OVER THE UPSTATE AND NE GA.
THE BIG STORY BEHIND THE FRONT WILL BE THE COOLING. TEMPS ARE
FORECAST TO BE AT LEAST 2 STANDARD DEVIATIONS BELOW AVERAGE WED AND
THU. IN FACT THE CONSRAW GUIDANCE KEEPS MAX TEMPS IN THE 70S EVEN
OVER PARTS OF THE PIEDMONT ON WED. WE WILL NOT BE GOING THAT COOL
YET...BUT THE POTENTIAL IS THERE FOR EVEN COOLER THAN FORECAST
TEMPS. THE ANOMOLOUSLY COOL WEATHER WILL BE EVEN MORE PRONOUNCED TO
THE NORTH. TO SUMMERIZE...MONDAY SHOULD BE A TYPICAL JULY DAY WITH
DIURNALLY DRIVEN SCATTERED SHOWERS AND THUNDERSTORMS WITH TEMPS A
COUPLE DEGREES ABOVE CLIMO. THUNDERSTORMS...POSSIBLY SEVERE ARE A
GOOD BET FOR TUE WITH THE COLD FRONT. MUCH COOLER WEATHER IS
EXPECTED WED AND THU WITH SOME LINGERING SHOWERS POSSIBLE ON THU.

&&

.AVIATION /05Z FRIDAY THROUGH TUESDAY/...
AT KCLT...ALTHOUGH THE MAIN CLOUD DECK APPROACHING FORM THE WEST IS
HIGH LEVEL CIRRUS...OBSERVATIONS AND MODEL TIME HEIGHTS SHOW THAT A
LOW MVFR CIG IS POSSIBLE OVERNIGHT. MODEL GUIDANCE IS BECOMING MORE
SUPPORTIVE OF LOW VFR FOG TOWARD DAYBREAK. LOW CLOUDS WILL INCREASE
TODAY AS NE WINDS VEER TO THE WEST...SETTING UP A MOIST UPSLOPE
FLOW...BUT CONFIDENCE IS LIMITED ON THE CHANCE OF LOW VFR CIGS.
AFTERNOON CONVECTIVE CHANCES ARE TOO LOW AT THIS POINT TO MENTION IN
THE TAF. LIGHT WINDS VEER SE FRIDAY EVENING.

ELSEWHERE...A WEAK FRONT WILL SLIDE ACROSS THE REGION OVERNIGHT.
LIGHT WINDS...WET GROUND...AND LINGERING MOISTURE WILL SUPPORT AREAS
OF FOG AND LOW CLOUDS OVERNIGHT. MODEL GUIDANCE HAS BECOME MORE
SUPPORTIVE OF CIG AND VSBY RESTRICITONS AT DAWN...WITH IFR OR LOWER
EXPECTED IN MOUNTAIN VALLEYS...AND MVFR IN THE FOOTHILLS...EXCEPT
BRIEFLY IFR AT KHKY. WINDS WILL VEER FROM NE TO W TODAY...WITH THE
RESULTING MOIST UPSLOPE FLOW SUPPORTING THE MOST CLOUD COVER AND
CONVECTION OVER THE MOUNTAINS. WINDS VEER TO SE THIS EVENING.

OUTLOOK...HIGH PRESSURE WILL SLOWLY SETTLE OVER THE AREA THIS
WEEKEND. ANY RESTRICTIONS SHOULD MAINLY BE CONFINED TO DIURNAL TSTMS
AND MORNING VALLEY FOG EACH DAY.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-05Z
KCLT       HIGH 100%     HIGH  90%     HIGH 100%     HIGH 100%
KGSP       HIGH  97%     HIGH  97%     HIGH 100%     HIGH 100%
KAVL       MED   79%     HIGH  81%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH  88%     HIGH 100%     HIGH 100%
KGMU       HIGH  91%     HIGH  97%     HIGH 100%     HIGH 100%
KAND       HIGH  97%     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...LG
NEAR TERM...CDG/JAT/NED
SHORT TERM...LG
LONG TERM...LG
AVIATION...JAT





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