Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 210727
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
327 AM EDT THU MAY 21 2015

.SYNOPSIS...
UNSETTLED WEATHER WILL CROSS THE AREA TODAY AS A COLD FRONT SLOWLY
PUSHES SOUTH AND EAST. DRIER CANADIAN HIGH PRESSURE WILL BUILD OVER
THE CAROLINAS AND NORTHEAST GEORGIA FRIDAY AND REMAIN THROUGH THE
WEEKEND. SOUTHERLY FLOW MOISTURE AROUND BERMUDA HIGH PRESSURE WILL
GRADUALLY RETURN EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 AM THU...LOW PRESSURE IS CURRENTLY CENTERED OVER THE SRN
APPALACHIANS...MOVING SLOWLY EWD ALONG A STALLED FRONTAL BOUNDARY.
THE BOUNDARY MARKS THE LEADING EDGE OF A DRY CONTINENTAL AIRMASS
SPRAWLING OVER THE MIDWEST AND MID-SOUTH. MUCH COOLER/DRIER AIR HAS
ALREADY WORKED INTO MIDDLE AND WEST TN ON ITS COLD SIDE. A FEW
SHOWERS OVER EAST TN CONTINUE TO MOVE EWD BEHIND THE LOW...BUT
ANALYZED CAPE VALUES ARE VERY SMALL IN THAT AREA WITH EVEN LESS OVER
THE MTNS. HOWEVER THE EXPECTATION OVER THE NEXT FEW HRS IS THAT
ENHANCED FORCING WILL COME TO THE MTNS AS MOISTURE INCREASES ON
STRENGTHENING UPSLOPE FLOW...AND TO MUCH OF THE PIEDMONT AS
WARM/MOIST ADVECTION OVER THE BOUNDARY TAPS INTO DEVELOPING
INSTABILITY WITHIN WEAK UPPER TROUGH. THE I-77 CORRIDOR HAS ALREADY
SEEN A SURGE IN SFC BASED CAPE AS DEWPTS RISE...AND INDEED SOME SCT
CELLS ARE FIRING UP ON RADAR IN THAT AREA. THOUGH THE UPGLIDE
APPEARS MOST ROBUST ALONG OUR NRN BORDER A BIT AFTER DAYBREAK...THE
HEAVIEST SHOWERS MIGHT BE THE ONES THAT FIRE IN THE MORE UNSTABLE
AIR SOUTH OF THE BOUNDARY BEFORE THEN. MOST MESO GUIDANCE SHOWS THE
ACTIVITY PROPAGATING EAST INTO CENTRAL NC AS THE MORNING PROGRESSES.

THE LOW WILL SLOWLY DEPART THE AREA OVER THE COURSE OF THE DAY...BUT
POPS WILL DIMINISH EAST OF THE MTNS. SUFFICIENT MOISTURE REMAINS
THERE ON THE UPSLOPE FLOW TO KEEP A POP THRU THIS EVENING. EAST OF
THE MTNS DOWNSLOPING AND DRYING IMPLIES CLEARING SKIES. MAX TEMPS
WILL BE MUCH COOLER IN THE MTNS...REACHING ONLY THE MID 70S IN THE
VALLEYS. THE PIEDMONT WILL REMAIN ABOVE NORMAL...MOSTLY MID
80S...BUT WITH LOWER HUMIDITY. A RATHER TIGHT PRESSURE GRADIENT
REMAINS ACRS THE CWFA INTO TONIGHT. THE ORIENTATION OF THE GRADIENT
AS WELL AS A SUBSIDENCE INVERSION NEAR THE TOP OF THE MTNS SUGGESTS
THAT A GAP WIND MAY HOWL IN MTN VALLEYS...PARTICULARLY THE FRENCH
BROAD...KEEPING ASHEVILLE GUSTY MUCH OF THE NIGHT TONIGHT. THIS
COULD ALSO BRING SOME BRISK GUSTS TO GREENVILLE AND SPARTANBURG AS
WELL. MINS WILL BE SLIGHTLY BELOW NORMAL.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
AS OF 245 AM EDT THU...A PROMINENT RIDGE AXIS OVER THE CENTRAL CONUS
ON FRIDAY WILL STEADILY MIGRATE EASTWARD AND BUILD OVER THE ERN
SEABOARD THROUGH THE WEEKEND. A SPRAWLING SFC HIGH CENTER WILL MOVE
OVER THE REGION UNDER THE RIDGE...WITH LOWER THICKNESSES ACROSS THE
REGION ON FRIDAY AND AGAIN ON SATURDAY WITH THE ARRIVAL OF A WEAKLY
REINFORCING BACK DOOR COLD FRONT. EXPECT NEAR CLIMO MINS BUT WITH
MAXES A COMFORTABLE CATEGORY OR SO BELOW CLIMO IN MOST AREAS FRI AND
SAT AFTERNOON.

THE SFC HIGH WILL MOVE OFF THE COAST ON SUNDAY...WITH A MODERATING
SRLY FLOW DEVELOPING INTO THE FORECAST AREA. MAX TEMPS WILL CLIMB
BACK TO NEAR OR SLIGHTLY ABOVE NORMAL. WEAK SE TO S UPSLOPE FLOW
COULD PRODUCE ISOLD SHRA IN THE EXTREME SRN MTNS...BUT CHANCES
APPEAR TOO SMALL TO INCLUDE FOR MOST LOCATIONS AT PRESENT.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
AS OF 245 AM EDT THU...THE RIDGE AXIS WILL MIGRATE FURTHER OFFSHORE
EARLY NEXT WEEK...WITH SRLY RETURN FLOW MOISTURE IMPROVING MONDAY
INTO TUESDAY. ANTICIPATE ISOLATED DIURNAL CONVECTIVE CHANCES
INCREASING OVER THE MTNS ON MON AFTN IN UPSLOPE AND WEAK
INSTABILITY. A SLOW AND STEADY UPTICK IN DEWPOINTS...MOISTURE...AND
INSTABILITY WILL OCCUR THROUGH TUE...WITH SCATTERED LATE DAY
SHRA/TSRA COVERAGE POSSIBLE IN THE MOUNTAINS. TEMPERATURES WILL
CONTINUE TO WARM...WITH PIEDMONT MAXES AROUND 90 IN ERN/SE SECTIONS
TUE AFTN.

A SHORTWAVE LIFTING E FROM THE PLAINS WILL SLOWLY START TO BREAK
DOWN THE RIDGE ON WED. THIS WILL ALLOW DEEPER MOISTURE TO MOVE INTO
THE SRN APPALACHIANS AND INCREASE CONVECTION TO MORE SOLID CHANCES.
VERY WARM CONDITIONS WILL CONTINUE THROUGH MID WEEK...WITH MAXES
AROUND 90 IN MANY AREAS EAST OF THE MTNS.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
AT KCLT...WEAK LOW PRESSURE WILL SLOWLY MOVE ALONG A STATIONARY
FRONTAL BOUNDARY NEAR THE NC-SC BORDER THIS MRNG. PATCHY MIDLEVEL
CLOUDS ALREADY HAVE DEVELOPED INVOF THE LOW...AND GOING TOWARD DAWN
THERE WILL LIKELY BE A LOWER STRATUS DECK DEVELOPING EAST AND NORTH
OF THE FIELD WHERE MOIST FLOW OVER THE BOUNDARY OCCURS. GUIDANCE HAS
HINTED AT MVFR CIGS AT KCLT ON SOME PAST RUNS BUT CONSENSUS IS NOW
VFR. THE SAME FLOW IS EXPECTED TO FIRE UP SOME SHRA/TSRA WHICH DO
STAND A CHANCE OF PASSING OVERHEAD. TEMPO THUS INCLUDED. WINDS WILL
VEER AROUND TO NW AS THE LOW DEPARTS...USHERING IN COLD ADVECTION
WHICH WILL GRADUALLY CLEAR SKIES. WINDS WILL STRENGTHEN AS THE DAY
GOES ON AND GUSTS ARE MOST LIKELY AFTER SUNSET.

ELSEWHERE...ISOLD TO SCT SHRA AND A FEW TSRA ARE EXPECTED TO PASS
THRU THE AREA THIS MRNG WITH SFC LOW MOVING ALONG STALLED
FRONT...WITH THE BEST COVERAGE EXPECTED OVER THE NC PIEDMONT A
LITTLE AFTER DAYBREAK. ACTIVITY COULD BE ASSOCIATED WITH BRIEF MVFR
CIG/VSBY. MOIST ISENTROPIC UPGLIDE OVER THE BOUNDARY WILL BRING SOME
LOW CLOUDS VERY NEAR KHKY MORE OR LESS IN THE SAME TIMEFRAME AS THE
BEST PRECIP CHANCES. VEERING FLOW IS EXPECTED IN THE WAKE OF THE
LOW...AND E OF THE MTNS DIMINISHING PRECIP CHANCES AND SKY COVER ARE
ANTICIPATED. FAIRLY ROBUST PRESSURE GRADIENT WILL REMAIN AS HIGH
PRESSURE MOVES IN FROM THE MID MISSISSIPPI VALLEY LATER TODAY. NWLY
COLD ADVECTIVE FLOW WILL STILL HAVE ENOUGH MOISTURE THAT SOME LOW
PRECIP CHANCES AND MVFR LEVEL CLOUD COVER WILL LINGER ON THE WRN
SLOPES OF THE NC MTNS...POSSIBLY DRIFTING OVER KAVL. NW WINDS AND
GUSTS WILL PICK UP THRU THIS EVENING. SETUP APPEARS FAVORABLE FOR A
GAP WIND TO KEEP KAVL/KGSP/KGMU REMARKABLY GUSTY MUCH OF TONIGHT.

OUTLOOK...DEEP HIGH PRESSURE WILL SETTLE OVER THE SOUTHEAST LATE
THIS WEEK AND REMAIN THROUGH TUESDAY. CONDITIONS SHOULD REMAIN
GENERALLY FAIR THROUGH THE PERIOD.

CONFIDENCE TABLE...

            07-13Z        13-19Z        19-01Z        01-06Z
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  85%
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_TABLES

&&

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

&&

$$
SYNOPSIS...WIMBERLEY
NEAR TERM...WIMBERLEY
SHORT TERM...HG
LONG TERM...HG
AVIATION...WIMBERLEY



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