Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 202031
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
431 PM 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 THURSDAY/...
AS OF 425 PM...CLUSTER OF TSRA ASSOCIATED WITH THE PREVIOUS MCS HAVE
FINALLY DISSIPATED AS THEY MOVED SOUTH OF THE CWFA. ADDITIONAL
STORMS ARE FORMING ACROSS THE MTNS AHEAD OF ANOTHER SHORTWAVE. THESE
STORMS WILL MOVE SOUTH INTO THE UPSTATE AND NE GA...AND ACROSS THE
NC MTNS THRU THE AFTERNOON AND POSSIBLY INTO THE EARLY EVENING...
ESPECIALLY ACROSS THE NC MTNS. WITH THE AMOUNT OF INSTABILITY AND
DCAPE VALUES OVER THE AREA...CANNOT RULE OUT ADDITIONAL SEVERE
STORMS. HAVE UPDATED POP TO INCLUDE THESE FEATURES. OTHERWISE...
UPDATES FOR CURRENT CONDITIONS.

PREVIOUS DISCUSSION...A PERSISTENT SMALL/STRONG TO OCCASIONALLY
SEVERE CONVECTIVE CLUSTER CONTINUES TO DROP SOUTHEAST TOWARD
SPARTANBURG COUNTY. SCT CONVECTION IS FINALLY BEGINNING TO UNZIP A
BIT ALONG THE OUTFLOW BOUNDARY ALONG THE I-40 CORRIDOR INTO THE NC
PIEDMONT. OTHERWISE... THE LATEST SPC MESOANALYSIS DEPICTS A MINIMA
IN CAPE ACROSS THE AREA...WITH CAPE EXCEEDING 3000 J/KG JUST TO OUR
EAST... AND MORE THAN 4000 J/KG ACROSS EAST TENN INTO NRN/CTRL
GEORGIA. OTHER THAN FEATURING 40-60 POPS DOWNSTREAM OF THE ONGOING
ACTIVITY...THE HIGHEST POPS HAVE BEEN DELAYED UNTIL EVENING ACROSS
WESTERN AREAS. ROBUST CONVECTION IS DEVELOPING WITHIN THE VERY
UNSTABLE AIR ACROSS EAST TENN...AND IT APPEARS COVERAGE WILL ONLY
INCREASE THERE THROUGH THE AFTERNOON...WITH SOME UPSCALE GROWTH
POSSIBLE IF NOT LIKELY IN LIGHT OF 0-3KM SHEAR OF AROUND 20 KTS. WE
HAVE THEREFORE INCREASED POPS TO LIKELY THIS EVENING ACROSS THE
SOUTHWEST MTNS OF NC. BRIEF LARGE HAIL AND DAMAGING WINDS WILL
REMAIN POSSIBLE...WITH DOWNBURST POTENTIAL ENHANCED WITH ANY
ORGANIZED CLUSTERS.

CONVECTION SHOULD WANE AND/OR PUSH SOUTH OF THE FORECAST AREA BY
LATE EVENING. HOWEVER...LOW CHANCE POPS WILL BE MAINTAINED ACROSS
THE FAR WESTERN MTNS...ESP THE NORTHERN MTNS...AS ADDITIONAL SHORT
WAVE TROUGHS AND/OR MCV/S DROPPING SOUTHEAST...DOWNSTREAM OF
BUILDING UPPER RIDGE WILL CONTINUE TO CLIP THE FORECAST AREA.
OTHERWISE...UPPER HEIGHTS WILL CONTINUE TO BUILD ACROSS THE
SOUTHEAST INTO THURSDAY...RESULTING IN WARMER MID-LEVEL TEMPS AND A
DEEPER/RELATIVELY DRIER BOUNDARY LAYER WITH HIGHER LFC/S.
NEVERTHELESS...FORECAST SOUNDINGS ARE LARGELY UNCAPPED AND QUITE
UNSTABLE BY AFTERNOON. POPS WILL BE ADVERTISED NEAR-CLIMO...WITH
SLIGHT/LOW CHANCE POPS OUTSIDE THE MTNS...AND CHANCES OVER THE HIGH
TERRAIN. TEMPS WILL BE A BIT ABOVE NORMAL THROUGH THE PERIOD.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 255 PM EDT WEDNESDAY... THE UPPER RIDGE CURRENTLY IN PLACE
FROM THE WESTERN GULF OF MEXICO TO THE NORTHERN PLAINS...WILL
RETROGRADE OR BECOME SLIGHTLY RE-ORIENTED BY SATURDAY. MEANWHILE THE
UPPER LOW PIN-WHEELING ACROSS THE GREAT LAKES...WILL DRIFT TOWARD
THE NEW ENGLAND COAST.

THEREFORE SENSIBLE WEATHER IN THE SHORT TERM SUGGESTS A CONTINUOUS
FLOW OF S/W`S WILL SLIDE SEWD (IN THE NWLY FLOW ALOFT) TOWARD OUR
REGION THIS PERIOD. IT APPEARS ONE SUCH S/W COULD CLIP PARTS OF THE
NORTHERN AND EASTERN SECTIONS OF OUR FORECAST AREA THURSDAY NIGHT.
THEREFORE...AFTER SOME THURSDAY EVENING NC POPS FOR UPSLOPING ON THE
WEST FACING SLOPES...WE WILL ADJUST POPS ACROSS OUR NRN AND ERN
COUNTIES FOR CHANCE OF SHOWERS AND THUNDERSTORMS OVERNIGHT.

OTHER THEN RIDGE TOP STORMS FRIDAY...IT IS HARD TO NAIL DOWN ANY
OTHER AREA FOR HIGHER POPS...ALTHOUGH FLOW ALOFT SUGGESTS OUR NRN
SECTIONS MAY HAVE A BETTER CHANCE. WITH MOISTURE AND INSTABILITY IN
PLACE WILL CARRY CHANCE IN THE NORTH AND SLIGHT CHANCE SOUTHERN
SECTIONS.

IT APPEARS A BACK DOOR COLD FRONT WILL EDGE TOWARD THE REGION
SATURDAY WITH MORE CLOUD COVER...AND PERHAPS AN INCREASE IN OVERALL
PRECIPITATION POTENTIAL. WE HAVE NOT GONE OVERBOARD YET TO SEE IF
THE TREND CONTINUES DURING THIS TIME-FRAME.

GUIDE TEMPERATURES ON FRIDAY SHOULD BE VERY WARM OR HOT...WITH
APPARENT TEMPERATURES CLIMBING TO 100 DEGREES OR BETTER IN OUR SC
PIEDMONT ZONES. WE HAVE USED MORE OF A CONSENSUS OF TEMPERATURES...
RATHER THAN MOS VALUE GUIDE ON FRIDAY AND SATURDAY. TEMPERATURE
TREND AS MENTIONED HOT ON FRIDAY...BUT KNOCKED BACK SOMEWHAT ON
SATURDAY...BECAUSE OF CLOUDS AND POTENTIAL PRECIPITATION. THERMAL
PROFILE ALSO SUGGESTS THIS PLAN.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 1230 PM WEDNESDAY...MEDIUM RANGE MODELS ARE IN DECENT ENUF
AGREEMENT WITH RESPECT TO THE MEAN PATTERN FOR THE FIRST HALF OF THE
EXTENDED PERIOD FEATURING LLVL RIDGING POKING SSW INTO THE CWFA. THE
COMBINATION OF THE LLVL EASTERLY FLOW AND THE HIGHLY AMPLIFIED NLY
FLOW SHOULD RESULT IN ENUF FORCING FOR AT LEAST SCATTERED
SHOWERS...AND MAX TEMPERATURES A FEW DEG F BELOW PERSISTANCE AND A
CATEGORY OR TWO BELOW CLIMO SUNDAY AND MONDAY.

WITH LLVL RIDGING LIKELY TO LINGER THRU TUESDAY...THERE REMAINS ABOVE
NORMAL CONFIDENCE THAT MAXIMUM TEMPERATURES WILL CONTINUE TO AVERAGE
BELOW CLIMO. IT REMAINS TO BE SEEN ON JUST HOW MUCH FORCING IS
AVAILABLE TO TRIGGER SHOWER ACTIVITY...SO JUST A TOKEN SLIGHT AND/OR
SMALL POP WILL REMAIN.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...CONVECTION OVER THE NC PIEDMONT HAS
DISSIPATED BUT IS DEVELOPING ACROSS THE NC MTNS AND MOVING INTO THE
UPSTATE. WILL HAVE TO WATCH ALL THE WRN SITES FOR AMD AS CELLS COULD
MOVE OVERHEAD THRU THE AFTERNOON AND POSSIBLY THE EARLY EVENING.
KCLT HAS THE LEAST CHC OF ANY ADDITIONAL CONVECTION.

EVEN OUR MOST RELIABLE GUIDANCE IS ONCE AGAIN HITTING THE FOG HARD
LATE TONIGHT...AS IT HAS BEEN DOING THE PASTS SEVERAL MORNINGS...
WITH VERY POOR VERIFICATION RESULTS. THEREFORE...WE HAVE IMPROVED
THE VISBY FORECAST CONSIDERABLY OVER WHAT GUIDANCE IS ADVERTISING...
BUT THIS IS STILL RESULTING IN A 3SM FORECAST AT KAVL. OTHERWISE...
VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD OUTSIDE OF SHRA/
TSRA.

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

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-20Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  91%     HIGH  94%     HIGH  95%
KHKY       HIGH 100%     HIGH 100%     HIGH  94%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  83%     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...CSH
NEAR TERM...JDL/RWH
SHORT TERM...TS
LONG TERM...CSH
AVIATION...JDL/RWH





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