Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 210612
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
212 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 TODAY/...
AS OF 200 AM THU...LOW PRESSURE IS CURRENTLY CENTERED OVER THE SRN
APPALACHIANS...MOVING SLOWLY EWD ALONG A STALLED FRONTAL BOUNDARY AT
THE LEADING EDGE OF A DRY CONTINENTAL AIRMASS SPRAWLING OVER THE
MIDWEST AND MID-SOUTH. COLD AND DRY ADVECTION IS NOTED OVER MUCH OF
MIDDLE AND WEST TN. 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 IS THAT
BY DAYBREAK 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 ELEVATED INSTABILITY WITHIN WEAK UPPER TROUGH. CHANCES
CONTINUE TO LOOK BEST OVER THE NC MTNS AND AREAS ALONG/NORTH OF I-40
JUST AFTER DAYBREAK WHEN THE UPGLIDE LOOKS MOST ROBUST.

AS OF 245 PM WED...SURFACE FLOW VEERS SHARPLY WEST/NORTHWEST THU
MRNG AS HIGH PRESSURE SLIDES IN. INCREASED PRESSURE GRADIENT ALONG
WITH MIXING OF ENHANCED LOW LEVEL WINDS WILL LIKELY PROMOTE SOME
GUSTS EARLY ON IN THE DAY...AMONGST CLEARING SKIES.  TEMPERATURES
THROUGH THE PERIOD WILL COOL SLIGHTLY BEHIND THE COLD FRONTAL
PASSAGE...HOWEVER SHOULD REMAIN ABOVE NORMAL.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
AS OF 215 PM WED...THE SHORT RANGE SHAPES UP TO BE FAIRLY QUIET. A
SHORT WAVE WILL PASS BY WELL TO THE N ON THURSDAY EVENING...WHICH
SHOULD PUSH THE UPPER TROF AXIS ACROSS THE WESTERN CAROLINAS/NE
GEORGIA OVERNIGHT. SOME RESIDUAL MOISTURE MAY GET FORCED UP THE W
SIDE OF THE MTNS BY THE NW FLOW...BUT THAT SHOULD NOT AMOUNT TO MUCH
MORE THAN A SMALL CHANCE OF SHOWERS THAT WOULD TAPER OFF BY
MIDNIGHT. FROM THAT POINT ONWARD...THE UPPER PATTERN EVOLVES SLOWLY
WITH A RIDGE AXIS TO THE WEST THROUGH THE END OF SATURDAY. THAT
SHOULD TAKE SURFACE HIGH PRESSURE SLOWLY PAST TO THE NORTH ON FRIDAY
AND SATURDAY...PERHAPS REACHING THE MID ATLANTIC COAST BY SUNSET
SATURDAY. MOISTURE RETURN IS NOT EXPECTED AS THE UPPER RIDGE AXIS
REMAINS WELL TO THE WEST. THUS...EXPECT DRY WEATHER AND NORMAL TEMPS
FOR BOTH FRIDAY AND SATURDAY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 205 PM EDT WED...A STRONG ULVL RIDGE WILL CONTINUE TO BUILD
ACROSS THE ERN CONUS SAT NIGHT WITH THE AXIS MOVING OF THE EAST
COAST BY LATE MONDAY. THE GFS H5 Z ENS MEAN AGREES WELL WITH THE OP
MODEL PROGRESSIONS AND VERY LITTLE MEMBER SPREAD IS SEEN ACROSS THE
SE/RN STATES THROUGH MOST OF THE PERIOD. IN THE LOWER LEVELS...A
STRENGTHENING BERMUDA HIGH WILL MAINTAIN A RIDGE ACROSS THE
CAROLINAS SUN/MON BEFORE BREAKING DOWN TUE/WED AS A UPPER S/W AND
COLD FRONT APPROACHES FROM THE WEST.

THERE ISN/T MUCH CHANGE IN THE SENSIBLE WX FCST FROM THE PREVIOUS
PACKAGE. THE BEST GOM MOISTURE FLUX WILL BE MAXIMIZED WEST OF THE
CWFA INTO MON...BEFORE ADDED ATL MOISTURE BEGINS TO ADVECT FROM THE
SE. MODEL SOUNDINGS SHOW A PERSISTENT MLVL SUBS INVERSION INTO MON
AS WELL...SO ANY CONVEC ACTIVITY SHOULD REMAIN RELEGATED ACROSS THE
HIGHER TERRAIN AND SHUNTED WITH DEEPER SHOWERS DEVELOPING MON
AFTERNOON IN LOCALIZED MECH LIFT...POSSIBLY PRODUCING A FEW TSTMS.
POPS REMAIN SLIGHT TO LOW END CHANCE THROUGH MON...WITH AN INCREASE
TO MID RANGE MTN POPS TUE/WED AS THE SUBS PATTERN WEAKENS IN A
DIURNALLY DESTABILIZING ATMOS. TEMPS WEREN/T CHANGED MUCH...STILL
EXPECT A MODEST INCREASE EACH AFTERNOON WITH MAXES ARND 10 DEGREES
ABOVE NORMAL BY WED.

&&

.AVIATION /06Z 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...

            06-12Z        12-18Z        18-24Z        00-06Z
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  86%
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...CDG/WIMBERLEY
SHORT TERM...PM
LONG TERM...SBK
AVIATION...WIMBERLEY



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