Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 020928
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
528 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 500 AM...SEEING HINTS SOME FOG IS FORMING IN THE MTN
VALLEYS...BUT AS EXPECTED IT GENERALLY IS INTERMITTENT. HOWEVER
AROUND DAWN MORE SIGNIFICANT PERIODS OF RESTRICTED VISIBILITY
ARE POSSIBLE.

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 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
CAM GUIDANCE SOURCES SHOWING SOME SPREAD W.R.T. THE COVERAGE AND
WITH BUFKIT PROFILES QUESTIONABLE...I DID NOT GO ANY HIGHER THAN A
SCT MENTION. WEAK SHEAR BUT RELATIVELY DRY MID-UPPER LEVELS WOULD
SUGGEST THE PRIMARY IMPACTS WILL BE GUSTY WINDS.

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 /10Z WEDNESDAY THROUGH SUNDAY/...
09Z KCLT UPDATE...FEELING NO MORE CONFIDENT AS TO CONVECTIVE
CHANCES THIS AFTN...AND WITH CHANCE REMAINING BELOW 30 PERCENT A
MENTION STILL DOES NOT APPEAR TO BE NEEDED.

AT KCLT AND ELSEWHERE...VFR IS LIKELY TO PREVAIL THRU THE
PERIOD EXCEPT NEAR DAYBREAK TODAY IN THE MTN VALLEYS...WITH FOG
SUPPORTED MAINLY BY PERSISTENCE UNDER INFLUENCE OF UNCHANGED
PATTERN...GUIDANCE HAVING NOT VERIFIED WELL RECENTLY. COULD SEE
SOME FOG OR LOW STRATUS ROLL OFF THE LAKES IN UPSTATE SC AS
WELL...AFFECTING KAND...THOUGH CONFIDENCE TOO LOW TO MENTION
RESTRICTIONS THERE. IFR VSBY MENTIONED AT KAVL ONLY. 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 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 IF
NOT GOING CALM TONIGHT.

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...

            09-15Z        15-21Z        21-03Z        03-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       LOW   56%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH  91%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  91%     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...WIMBERLEY
SHORT TERM...NED
LONG TERM...NED
AVIATION...WIMBERLEY


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