Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 200834
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
434 AM EDT WED AUG 20 2014

.SYNOPSIS...
A BROAD UPPER LEVEL RIDGE OF HIGH PRESSURE WILL BUILD ACROSS THE
MISSISSIPPI RIVER VALLEY OVER THE NEXT FEW DAYS AND LINGER FOR THE
REST OF THE WORK WEEK...RESULTING IN ABOVE NORMAL TEMPERATURES. A
WEAK COLD FRONT WILL THEN PUSH INTO THE AREA FROM NORTHEAST SATURDAY
AND BRING SOME MINOR RELIEF FROM THE HEAT.

&&

.NEAR TERM /THROUGH TONIGHT/...
0830 UTC UPDATED...POPS HAVE BEEN ADJUSTED PER RADAR TRENDS...WITH A
DECREASE IN MOST PLACES...BUT AN INCREASE IN THE NW NC PIEDMONT
WHERE A LIGHT SHOWER HAS DEVELOPED. SKY COVER WAS UPDATED FROM
INFRARED SATELLITE IMAGERY.

AT 300 AM EDT TUESDAY...AN UPPER TROUGH WILL AMPLIFY ALONG THE EAST
COAST TODAY...WHILE AN UPPER RIDGE BUILDS NORTH OVER THE MS RIVER
VALLEY. SEVERAL WEAK SHORTWAVES WILL CROSS OUR AREA TODAY AND
TONIGHT IN NW FLOW ALOFT....WHILE A COLD FRONT ADVANCES SLOWLY FORM
THE NE. IT IS UNCLEAR WHETHER THE FRONT WILL MAKE IT VERY FAR INTO
OUR AREA...BUT ITS GENERAL PROXIMITY MAY FOCUS CONVECTION ACROSS OUR
NORTHERN TIER OF COUNTIES. EVEN IF THE FRONT REMAINS OFF TO THE
NORTHEAST...OUR AREA WILL BE IN A MOIST UNSTABLE AIR MASS...AND
PASSING SHORTWAVES WILL PROVIDE SUPPORT FOR CONVECTION. MOISTURE
WILL BE SOMEWHAT LIMITED...AND STEERING FLOW GREAT ENOUGH TO KEEP
CELLS MOVING...LIMITING THE POTENTIAL FOR HEAVY RAINFALL. ROBUST
CAPE WILL BE PRESENT...AND DRY AIR WILL BE AVAILABLE FOR EVAPORATIVE
COOLING...PROVIDING SUPPORT FOR WIND GUSTS AND HAIL. HIGH
TEMPERATURES WILL BE SLIGHTLY ABOVE NORMAL.

SOME ELEVATED INSTABILITY WILL LINGER THROUGH TONIGHT...AND IF ANY
MCS ROUNDING THE CORNER OF THE RIDGE REACHES OUR AREA...IT MAY WELL
SURVIVE. STEERING FLOW AND A LACK OF DEEP MOISTURE WILL LIMIT HEAVY
RAINFALL POTENTIAL. MINIMUM TEMPERATURES WILL RUN ABOVE NORMAL IN A
MOIST AIRMASS.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 AM WEDNESDAY...A LARGE UPPER RIDGE WILL PERSIST ACRS THE
LWR-MID MS VALLEY...EXTENDING EAST ACRS THE SOUTHEAST STATES THRU
THE SHORT TERM. THE LATEST GUIDANCE SHOWS THAT A RING OF FIRE
PATTERN WILL SET UP...WITH A SERIES OF SHORTWAVES AND ASSOCIATED
CLUSTERS OF CONVECTION WILL RIDE OVER TOP OF THE RIDGE...FROM THE
UPR MIDWEST/SRN GREAT LAKES...TO THE MID ATLANTIC. IT LOOKS LIKE
MOST OF THE ASSOCIATED ACTIVITY WILL STAY NORTH OF THE CWFA.
HOWEVER...THE NRN ZONES (GENERALLY I-40 CORRIDOR AND NORTH)...MAY
GET BRUSHED BY A POSSIBLE MCS AT SOME POINT. NOT MUCH CHANGE WAS
MADE TO THE POPS. STILL EXPECT AT LEAST A HANDFUL OF
DIURNALLY-DRIVEN CONVECTION...AS STEEP MID LVL LAPSE RATES REMAIN
ATOP THE REGION. MODELS ARE TRENDING WARMER FOR THURSDAY AND
FRIDAY...SO I BUMPED UP TEMPS ABOUT A CATEGORY...EVEN MORE IN THE NW
NC PIEDMONT...WHERE WE PREVIOUSLY THOUGHT A BACKDOOR COLD FRONT
WOULD PUSH IN BY FRIDAY. THIS RESULTS IN ABOVE NORMAL TEMPS...WITH
UPR 80S IN THE MTN VALLEYS AND MID-UPR 90S ACRS THE PIEDMONT.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 315 AM WEDNESDAY...THE UPPER FLOW LOOKS TO BECOME MORE
NORTHERLY ATOP THE CWFA FOR SATURDAY AND SUNDAY...AS RIDGE AXIS
DRIFTS SLIGHTLY EAST...WHILE A LARGE TROF REMAINS NEARLY STATIONARY
JUST OFF THE EAST COAST. WHILE THE MEDIUM RANGE GUIDANCE HAS DELAYED
THE TIMING OF A BACKDOOR COLD FRONTAL PASSAGE BY A FULL DAY...THEY
STILL SHOW IT COMING THRU...WITH SLIGHTLY COOLER TEMPS AND INCREASED
CHC FOR PRECIP. BOTH THE 00Z/20 GFS AND ECMWF SHOW WEDGE-LIKE
CONFIGURATION FOR SUNDAY...WITH A 1021-1023 MB SFC HIGH OVER THE
CANADIAN MARITIMES...NOSING A RIDGE AXIS SW ALONG THE EAST COAST.
LIGHT NELY LLVL FLOW AND INCREASED CLOUDS SHUD KEEP TEMPS CLOSER TO
NORMAL...ESP SUNDAY.

FOR MONDAY AND TUESDAY...THE SFC HIGH SINKS SOUTHWARD...KEEPING
COOLER LLVL THICKNESSES ACRS THE REGION...AND CONTINUED LIGHT ELY
LLVL FLOW. I WILL FCST TEMPS BACK TO NORMAL...EVEN SLIGHTLY BELOW
NORMAL IN THE NW NC PIEDMONT...WITH CONTINUE SLGT CHC TO CHC POPS.

&&

.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...RAIN EARLIER TODAY WILL FAVOR FOG FORMATION BY DAWN. MVFR
CIG AND VSBY WILL BE INTRODUCED BEFORE DAYBREAK. MODEL TIME HEIGHTS
SHOW LOW VFR CLOUDS LINGERING THROUGH THE FORECAST. ALTHOUGH A COLD
FRONT WILL APPROACH FORM THE NE OVERNIGHT...IT IS UNCLEAR IF THE
FRONT WILL REACH KCLT OR NOT...AND SERVE AS A FOCUSING MECHANISM FOR
BOTH CLOUDS AND CONVECTION. CURRENTLY...VERY LITTLE CLOUD COVER IS
ASSOCIATED WITH THIS BOUNDARY. AT THIS TIME GUIDANCE VEERS WINDS
FROM SW TO NE OVERNIGHT...THEN BACKS THEM TO SW TODAY...AND ONLY
VEERS THEM NW TONIGHT. CONVECTIVE CHANCES ARE TOO LOW TO WARRANT A
MENTION IN THE TAF THIS AFTERNOON...AND LOW VFR CIGS WILL NOT BE
CARRIED WITHER.

ELSEWHERE...GUIDANCE FAVORS FOG AT DAYBREAK...BUT MAY BE  TOO
AGGRESSIVE. FOR NOW DAYBREAK MVFR VSBY AND CIGS WILL BE CARRIED AT
ALL SITES BUT KGMU. WINDS VEER FROM SW TO NE OVERNIGHT AS A COLD
FRONT APPROACHES FORM THE NE...BUT NEVER VEER NE AT ANY TAF SITES.
WINDS BACK TO SW TODAY...THEN VEER NW TONIGHT. THE PROXIMITY OF THIS
FRONT COULD SERVE AS A FOCUSING MECHANISM FOR CLOUDS AND CONVECTION
DURING THE DAY...BUT AT THIS TIME LITTLE CLOUDS COVER WAS NOTED WITH
THIS FEATURE. AFTERNOON CONVECTION WILL BE FEATURED AT KAVL ONLY...
WITH LOW VFR CIGS AND VSBY CARRIED WITH CONVECTION.

OUTLOOK...SCT AFTERNOON CONVECTION AND PATCHY EARLY MORNING FOG WILL
REMAIN IN THE FORECAST THROUGH THE WEEK. THERE WILL ALSO BE
INCREASING CHANCES FOR REMNANT ORGANIZED CONVECTION APPROACHING THE
AREA FROM THE NW DURING THE LATE NIGHT/EARLY MORNING HOURS.

CONFIDENCE TABLE...

            08-14Z        14-20Z        20-02Z        02-08Z
KCLT       MED   71%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH  87%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  94%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH  91%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     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...ARK
NEAR TERM...JAT
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...JAT






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