Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 210729
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
329 AM EDT THU AUG 21 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
BACK DOOR COLD FRONT WILL THEN PUSH INTO THE AREA FROM NORTHEAST
SATURDAY AND BRING SOME MINOR RELIEF FROM THE HEAT FOR EARLY NEXT
WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AT 300 AM EDT THURSDAY...AN UPPER TROUGH AXIS WILL PUSH OFF THE EAST
COAST TODAY AND TONIGHT...WHILE AND UPPER RIDGE AXIS CROSSES THE MS
RIVER VALLEY. SEVERAL WEAK SHORTWAVE MOVING INTO THE TROUGH WILL
MOVE FROM THE OH RIVER VALLEY TO CENTRAL NC...BRUSHING NW NC.

MODEL GUIDANCE SUGGEST THAT MOST OF THE CONVECTIVE ACTIVITY
ASSOCIATED WITH THESE FEATURES WILL PASS NORTH OF OUR AREA. THE AREA
FROM THE NORTHERN NC MOUNTAINS...SOUTHEAST TO CHARLOTTE...WILL BE
CLOSEST TO THE TRACK OF THESE SYSTEMS...AND MORE LIKELY TO SEE
CONVECTION THAN AREAS TO THE SOUTH. THE MOUNTAINS ARE ANOTHER AREA
OF CONCERN...DUE TO OROGRAPHIC LIFT AND DIFFERENTIAL HEATING. BOTH
CAPE AND SHEAR APPEAR ROBUST AGAIN TODAY...BUT A BIT LESS SO THAN
YESTERDAY.

WITH PLENTY OF DRY AIR ALOFT FOR EVAPORATIVE COOLING... WIND GUSTS
AND HAIL WILL BE SUPPORTED. STEERING FLOW SHOULD BE ENOUGH TO KEEP
STORMS MOVING ALONG...AND MOISTURE IS NOT VERY DEEP...SO UNLESS
TRAINING FROM NW TO SE OCCURS...HEAVY RAINFALL SHOULD BE LIMITED.
MAXIMUM TEMPERATURES WILL RUN SEVERAL DEGREES ABOVE NORMAL AS
HEIGHTS RISE ALOFT AND A WEAK DOWNSLOPE FLOW SETS UP.

ELEVATED INSTABILITY WILL BE SLOW TO WANE TONIGHT...AND CONVECTION
COULD KEEP GOING WELL INTO THE EVENING...PROVIDED EARLIER ACTIVITY
DOES NOT STABILIZE THE ATMOSPHERE. MINIMUM TEMPERATURES WILL RUN
SEVERAL DEGREES ABOVE NORMAL AS THE UPPER RIDGE BUILDS SLOWLY
EAST...AND A MOIST AIR MASS PERSISTS.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 300 AM THURSDAY...LITTLE CHANGE IN AIR MASS OR PATTERN FROM
THURSDAY TO FRIDAY. UPPER RIDGE CONTINUES TO AMPLIFY ACRS THE MS
RIVER VALLEY...WITH NWLY MID-UPR FLOW PERSISTING ATOP THE CWFA.
ANOTHER EMBEDDED SHORTWAVE IS PROGGED TO DRIFT SE ACRS THE OH VALLEY
FRIDAY AFTN...AND MAY HELP ENHANCE CONVECTION TO OUR NW. OTHER THAN
THAT...EXPECT DIFFERENTIAL HEATING IN THE MTNS TO BE MAIN TRIGGER
FOR AFTN CONVECTION. FCST SNDGS SHOW PLENTY OF SBCAPE...BUT WITH
PERHAPS A LITTLE MORE CAPPING WARM LLVL TEMPS ACRS THE PIEDMONT. SO
I WILL FCST A LOW-END CHC POP IN THE MTNS...AND SLGT CHC TO NO
MENTIONABLE POP ACRS THE PIEDMONT. TEMPS WILL BE SIMILAR TO
THURSDAY/S READINGS...WITH 80S IN THE MTNS AND FROM THE LWR 90S
ALONG THE I-40 CORRIDOR TO UPR 90S ACRS THE UPR SAVANNAH VALLEY.
FRIDAY NIGHT LOOKS LIKE ANOTHER WARM AND MUGGY NIGHT.

SATURDAY...MODELS IN GOOD AGREEMENT ON SHORTWAVE ENERGY CARVING OUT
A DEEPER TROF OFF THE EAST COAST...WHILE UPR RIDGE BEGINS TO EDGE
EAST ACRS THE GREAT LAKES AND OH VALLEY. THIS WILL PLACE THE CWFA
UNDER INCREASING NLY FLOW ALOFT...AND HELP PUSH A BACKDOOR COLD
FRONT THRU THE AREA. THE NAM/GFS/ECMWF ALL SHOW ENHANCED SBCAPE
ALONG THE BNDRY DURING PEAK HEATING. SO EXPECT A LITTLE BETTER
COVERAGE OF CONVECTION SAT AFTN. IT SHUD BE THE LAST REALLY
HOT/MUGGY DAY FOR MOST OF THE AREA FOR AT LEAST A FEW DAYS...AS ELY
FLOW BRINGS MILDER ATLANTIC AIR INTO THE REGION.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 315 AM THURSDAY...MODELS IN GOOD AGREEMENT ON A LARGE AREA OF
HIGH PRES NOSING SOUTHWARD ALONG THE EAST COAST FROM SUNDAY INTO THE
MIDDLE OF NEXT WEEK. THIS WILL KEEP OUR AREA WITHIN A PERSISTENT
NE/ELY LLVL FLOW. ALOFT...THE HIGH-AMPLITUDE RIDGE AXIS WILL
GRADUALLY SHIFT SOUTHEAST AND LAY OVER THE MID ATLANTIC...HELPING
FURTHER KEEP THINGS CAPPED ATOP THE CWFA. SO EXPECT TEMPS TO RETURN
TO BELOW NORMAL THRU THE MEDIUM RANGE...ESP EAST OF THE MTNS. POPS
MAY BE OVERDONE...BUT IT DOES LOOK LIKE THE MTNS WILL STILL BE
UNCAPPED WITH AT LEAST SOME SBCAPE SUNDAY AND MONDAY. NOT SURE HOW
MUCH MAY DEVELOP BELOW THE MID LVL SUBSIDENCE INVERSION. SO POPS
TREND DOWN EACH DAY...TO NO MENTIONABLE POPS BY WEDNESDAY.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
AT KCLT...HIGH LEVEL CIRRUS DEBRIS FOR CONVECTION UPSTREAM WILL BE
THE MAIN CLOUD DECK DURING THIS FORECAST...BUT SOME LOW VFR
CLOUDS SHOULD DEVELOP UNDERNEATH THE CIRRUS WITH DAYTIME HEATING.
FOG IS NOT EXPECTED AT DAYBREAK...AS THE DEW POINT DEPRESSION
REMAINS RATHER HIGH. WNW WINDS ARE EXPECTED TO VEER NNW DURING THE
DAY...THEN BACK TO WSW TONIGHT. CONVECTIVE CHANCES WILL BE BEST IN
THE AFTERNOON...BUT NOT HIGH ENOUGH TO MENTION IN THE TAF...AS THE
BEST ACTIVITY REMAINS TO THE W AND N.

ELSEWHERE...EXTENSIVE UPPER LEVEL CIRRUS REMAINING FROM UPSTREAM
CONVECTION WILL KEEP STREAMING OVER THE AREA FOR SOME TIME.
SATELLITE IMAGERY DOES SHOW SOME MID LEVEL CLOUD IN THE OH VALLEY
HEADED SE...BUT THIS SHOULD PASS NORTH OF THE AREA. WITH DAYTIME
HEATING...SOME LOW VFR CLOUDS ARE EXPECTED TO DEVELOP. GUIDANCE
CONTINUES TO BE AGGRESSIVE WITH FOG FORMATION IN THE MOUNTAINS...BUT
WITH POOR PERFORMANCE LATELY...ONLY MVFR VSBY WILL BE CARRIED AT
KAVL. WITH MOST UPPER ENERGY TRACKING OT THE NORTH OF OUR
AREA...CONVECTIVE CHANCES WILL BE TOO LOW TO MENTION...EXCEPT AT
KAVL...WHERE MOUNTAIN TERRAIN WILL LEND SUPPORT FOR LIFT.

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...

            07-13Z        13-19Z        19-01Z        01-07Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  95%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  91%     HIGH  95%     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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