Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 021447
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1047 AM EDT WED SEP 2 2015

.SYNOPSIS...
HIGH PRESSURE WILL LINGER ACROSS THE REGION THE REST OF THE WEEK
WITH WEAK UPPER LEVEL DISTURBANCES CROSSING OVERHEAD. A BACK DOOR
COLD FRONT IS EXPECTED TO PUSH ACROSS THE REGION ON FRIDAY. IN THE
WAKE OF THE FRONT...A COOL AND MOIST AREA OF HIGH PRESSURE WILL
SETTLE ACROSS THE WESTERN CAROLINAS AND NORTHEAST GEORGIA THIS
WEEKEND INTO EARLY NEXT WEEK. BY TUESDAY...A WARMER AND DRIER AIR
MASS SHOULD BUILD ACROSS THE REGION.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM...MADE SEVERAL MINOR ADJUSTMENTS TO GRIDS BASED ON
OBSERVATIONS. PRETTY THIN CIRRUS SHIELD OUT THERE...OTHERWISE JUST
SOME ISOLATED CU DEVELOPING OVER THE MOUNTAINS. REDUCED SKY COVER
ACCORDINGLY. NEW CAM/HIRES GUIDANCE DELAYING CONVECTIVE INITIATION
BY A COUPLE OF HOURS SO LOWERED POPS THIS MORNING AND PULLED BACK
SOMEWHAT ON AREAL EXTENT. TEMPERATURES LOOK PRETTY GOOD BUT ARE
RISING A LITTLE MORE RAPIDLY THIS MORNING THAN EXPECTED...UPDATED
HOURLY TRENDS AND WILL MONITOR IN CASE HIGHS NEED TO BE ADJUSTED.

AS OF 630 AM...BROAD SUBTROPICAL RIDGE OVER THE SERN CONUS WILL
WEAKEN TODAY AS A SHORTWAVE...NOW CENTERED OVER OHIO...DRIFTS
TOWARD THE MID-ATLANTIC COAST. THE LOW LEVEL FLOW WILL CONTINUE
TO BE PRIMARILY UNDER THE INFLUENCE OF THE RIDGE...MOIST AND
SWLY. WHILE THE BETTER DYNAMIC FORCING AHEAD OF THE SHORTWAVE
WILL BE JUST TO OUR NORTHEAST THE FALLING HEIGHTS ASSOCIATED WITH
IT WILL PRODUCE MORE FAVORABLE BUOYANCY PROFILES THAN THE PAST
COUPLE OF DAYS. CONVECTIVE INITIATION IS EXPECTED ALONG THE BLUE
RIDGE...PRODUCING WIDELY SCTD TSTMS...BUT ISOLD STORMS ARE EXPECTED
TO BE ABLE TO PROPAGATE MORE OR LESS TO THE I-85 CORRIDOR. CAPE
VALUES FROM THE NAM DO SEEM AWFULLY HIGH...WITH MORE MODEST VALUES
ON THE GFS. HOWEVER WITH LATEST CAM GUIDANCE MAINLY SHOWING SPARSE
COVERAGE FOR THE AFTN AND WITH BUFKIT PROFILES NOT LOOKING THAT
GREAT /ASIDE FROM THE NAM/...I HAVE LIMITED POPS TO 30 PERCENT WITH
THIS UPDATE. WEAK SHEAR BUT RELATIVELY DRY MID-UPPER LEVELS WOULD
SUGGEST THE PRIMARY IMPACTS WILL BE GUSTY WINDS. SEVERE WEATHER
IS NOT ANTICIPATED.

AS THE WAVE PLUNGES SWD INTO ERN VA/NC TONIGHT...WINDS WILL VEER TO
NWLY ACRS MOST OF THE CWFA BRINGING IN SLIGHTLY DRIER CONTINENTAL
AIR BY THU MRNG. SOME CLOUD COVER WILL ACCOMPANY THE ACCOMPANYING
BOUNDARY THOUGH NO PRECIP IS EXPECTED TO RESULT. SLIGHTLY WARMER
MIN TEMPS 2-4 DEGREES ABOVE NORMAL ARE THUS FCST.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
AS OF 315 AM WEDNESDAY...ON THURSDAY...H5 RIDGE BUILDS OVER THE
CENTRAL CONUS AS A BROAD TROUGH AMPLIFIES OVER THE WESTERN ATLANTIC.
AT THE SFC...HIGH PRESSURE CENTERED OVER THE OHIO RIVER VALLEY WILL
BUILD ACROSS THE SOUTHERN APPALACHIANS...RESULTING IN LIGHT
NORTHWEST FLOW. PROVIDED THE LIGHT DOWNSLOPE FLOW...HIGH
TEMPERATURES ARE FORECAST TO RANGE FROM THE 91 TO 94 EAST OF THE
MTNS...WITH UPPER 80S WITHIN THE MTN VALLEYS. FORECAST SOUNDINGS
INDICATE A DEEP INVERTED-V PROFILE...AND MILD TEMPS AROUND
H7...YIELDING WEAK CAPE ACROSS THE REGION. I WILL FORECAST CHC POPS
ACROSS THE RIDGES WITH SCHC POPS EAST.

ON FRIDAY...THE H5 RIDGE WILL BUILD ACROSS THE GREAT LAKES REGION
WITH A BROAD WEAKNESS ACROSS THE SOUTHEAST CONUS. A 1025+MB HIGH IS
FORECAST TO DEVELOP ACROSS THE NEW ENGLAND STATES...RIDGING
SOUTHWEST ACROSS THE ATLANTIC STATES. A BACK DOOR COLD FRONT IS
EXPECTED TO REACH THE PIEDMONT AND FOOTHILLS DURING THE DAYLIGHT
HOURS. THE COMBINATION OF WIDESPREAD WEAK INSTABILITY AND A SFC
BOUNDARY SHOULD TRIGGER SCT SHRA AND TSRA...ESPECIALLY NEAR THE EAST
FACING SLOPES. HIGH TEMPERATURES SHOULD RANGE 3 TO 4 DEGREES BELOW
THURSDAY/S VALUES.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 325 AM WEDNESDAY...THE MEDIUM RANGE MODELS INDICATE THAT THE
COLD AIR DAMMING PATTERN WILL DEVELOP AND PERSISTS THIS WEEKEND. IN
FACT...THE GFS INDICATES THAT PIEDMONT WINDS WILL STRENGTHEN TO
MARGINALLY GUSTY NE WINDS AFTER SUNRISE SATURDAY AND SUNDAY. THE NE
WINDS...BKN SKY COVER...SCT SHRA/TSRA...SHOULD PROVIDE COOLER
TEMPERATURES ON SATURDAY. THE 2M TEMPS FROM THE ECMWF AND GFS HAVE
HIGH TEMPERATURES IN THE LOW 80S ON SAT. I WILL MAINTAIN COOL HIGH
FOR SAT...GENERALLY 1 TO 2 DEGREES WARMER THAN THE RAW MODEL VALUES.
ON SUNDAY...NE WINDS APPEAR AS STRONG AS SAT...BUT CLOUD COVER
APPEARS A DEGREE THINNER. HIGH TEMPS WILL REMAIN BELOW NORMAL...BUT
LIKELY 1 TO 2 DEGREES WARMER THAN SAT. ON MONDAY...THE SFC HIGH
CENTER SHIFTS OVER THE WESTERN ATLANTIC...RESULTING IN WEAKER WINDS
ACROSS THE REGION. I WILL LIMIT CHC POPS TO THE MTNS AND FOOTHILLS.
HIGHS TEMPS MAY RANGE WITHIN A COUPLE OF DEGREES OF NORMAL ON MON.
ON TUESDAY...MID LEVEL RIDGE WILL BUILD ACROSS THE DEEP SOUTH OVER
THE SOUTHEAST CONUS...WITH A BROAD SFC HIGH ACROSS THE SOUTHERN
APPALACHIAN REGION. FORECAST SOUNDINGS INDICATE WEAK LAPSE RATES
WITHIN THE MID LEVELS...YIELDING WEAK VALUES OF INSTABILITY. I WILL
INDICATES DIURNAL SCHC TO CHC POPS...WITH COVERAGE FAVORING THE
MTNS. HIGHS SHOULD RANGE VERY CLOSE TO NORMAL.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT AND ELSEWHERE...SFC HIGH PRESSURE WILL REMAIN IN CONTROL
TODAY...BUT A WEAK SHORTWAVE WILL DRIFT FROM THE SRN APPALACHIANS TO
THE MID-ATLANTIC COAST. THIS ENHANCES POPS IN THE AFTN...BUT STILL
KEEPS CHANCES LOW ENOUGH TO OMIT AT THE TAF SITES. A SIMILARLY WEAK
FRONTAL BOUNDARY WILL ADVANCE SWD ACRS THE AREA TONIGHT BEHIND THE
TROUGH. WINDS WILL PREVAIL SWLY IN THE PIEDMONT BUT NW AT KAVL AND
KHKY...VEERING TO N THIS EVENING IF NOT GOING CALM TONIGHT. DRIER
AIR ARRIVING IN THE WAKE OF THE FRONT IS EXPECTED TO PRECLUDE
RESTRICTIONS AT DAYBREAK THU.

OUTLOOK...A PATTERN OF DIURNAL ISOLATED/WIDELY SCT SHOWERS
AND THUNDERSTORMS IS EXPECTED TO CONTINUE THRU THE END OF THE
WORK WEEK. BY THE WEEKEND...A MOIST EASTERLY FLOW IS EXPECTED TO
DEVELOP...BRINGING BETTER CHANCES FOR SHOWERS AND RESTRICTIONS. LOW
CLOUDS AND FOG WILL BE POSSIBLE EACH NIGHT IN THE MOUNTAIN VALLEYS.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  91%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     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

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...NED
NEAR TERM...TDP/WIMBERLEY
SHORT TERM...NED
LONG TERM...NED
AVIATION...TDP/WIMBERLEY



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