Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 201032
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
632 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/...
1030 UTC UPDATE...POPS HAVE BEEN ADJUSTED PER RADAR TRENDS...WITH A
DECREASE EARLY ON. SKY COVER WAS UPDATED FROM INFRARED SATELLITE
IMAGERY...ALSO RESULTING IN A DECREASE. AREAS OF FOG WERE REDUCED
BASED ON OBSERVATIONS AND DEW POINT DEPRESSIONS.

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 /12Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...FOG HAS FAILED TO DEVELOP...AND THE DEW POINT DEPRESSION
REMAINS THREE DEGREES. CALM WINDS ARE EXPECTED TO BECOME LIGHT NE
THIS MORNING...THEN BACK TO SW BY AFTERNOON...BEFORE VEERING TO WNW
THIS EVENING. CONVECTIVE CHANCES REMAINS TOO LOW TO MENTION. LOW
CLOUDS ARE EXPECTED TO INCREASE TODAY...BUT WITHOUT ENOUGH COVERAGE
FOR A LOW VFR CIG. GUIDANCE DID NOT FAVOR FOG WEDNESDAY MORNING...
BUT IF IT RAINS THIS AFTERNOON OR EVENING...FOG WOULD BE MORE LIKELY.

ELSEWHERE...FOG HAS NOT DEVELOPED AS EXPECTED...EXCEPT IN A FEW NON
TAF SITES THAT RECEIVED BETTER RAINFALL YESTERDAY...AND THE LITTLE
TN RIVER VALLEY. CALM FOOTHILL WINDS MAY BRIEFLY COME UP FROM THE N
OR W THIS MORNING...BEFORE BACKING TO SW. KAVL WINDS WILL REMAIN
CHANNELED FROM THE NW. CONVECTIVE CHANCES ARE ONLY GREAT ENOUGH FOR
A MENTION AT KAVL THIS AFTERNOON. GUIDANCE FAVORED VERY LOW VSBY IN
FOG IN THE MOUNTAINS TONIGHT...BUT BASED ON RECENT PERFORMANCE...
ONLY MVFR VSBY WILL BE CARRIED AT KAVL.

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...

            10-16Z        16-22Z        22-04Z        04-10Z
KCLT       HIGH  87%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH  87%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       MED   79%     HIGH 100%     HIGH 100%     HIGH  89%
KHKY       HIGH  83%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH  91%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  87%     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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