Area Forecast Discussion
Issued by NWS Greer, SC

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016
FXUS62 KGSP 021852
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
252 PM EDT MON MAY 2 2016

.SYNOPSIS...
A WARM AND HUMID AIRMASS WILL PERSIST AHEAD OF A COLD FRONT
APPROACHING FROM THE NORTHWEST THROUGH TONIGHT. THIS FRONT WILL
SLOWLY CROSS THE AREA ON TUESDAY. ANOTHER COLD FRONT WILL CROSS THE
REGION ON THURSDAY AND BRING A COOLER AND DRIER AIR MASS FROM CANADA
THAT SHOULD PERSIST INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 150 PM...AS EXPECTED...THE REGION IS SEEING CONVECTION POPPING
UP ON RADAR IMAGERY...AS SBCAPE HAS INCREASED TO 1500-2500 J/KG AND
CONVECTIVE TEMPS HAVE BEEN MADE. FORCING IS STILL SUBTLE
OVERALL...BUT WILL INCREASE AS THE AFTN AND EVENING PROGRESSES. THE
RAP SHOWS 0-6 KM BULK SHEAR AROUND 20-30 KTS...WITH 30-40 KTS ALONG
THE I-40 CORRIDOR. IN THAT AREA...THE SHEAR AND INSTBY WILL COMBINE
FOR A BETTER SEVERE STORM THREAT...WITH SUPERCELL-LIKE STORMS
POSSIBLE. SO A SEVERE THUNDERSTORM WATCH WILL BE ISSUED FROM
BUNCOMBE COUNTY NORTH AND EAST UNTIL 10 PM THIS EVENING. TO THE
SOUTH...GIVEN THE STRONG INSTBY...EXPECT AT LEAST A FEW SEVERE
STORMS WILL BE POSSIBLE THIS AS WELL.

THIS EVENING...GUIDANCE IN GOOD AGREEMENT THAT A COLD FRONT WILL
PUSH INTO THE NC MTNS FROM THE WEST...WHILE AN AREA OF DECENT UPPER
DIVERGENCE WILL SET UP WITHIN A RIGHT ENTRANCE REGION OF A JET
STREAK. FORECAST SOUNDINGS SHOW LINGERING ELCAPE OF 800-1500 J/KG
WITH IMPROVING SHEAR. CAMS AREA ALSO IN GOOD AGREEMENT ON A MAXIMUM
OF CONVECTIVE COVERAGE THIS EVENING. SO POPS ARE MAXIMIZED IN THE
LIKELY TO CATEGORICAL RANGE FROM 0-6Z...THEN START TO TAPER OFF FROM
WEST TO EAST THRU DAYBREAK. LOW TEMPS WILL BE ABOUT 10 DEGREES ABOVE
NORMAL.

TUESDAY...THE ENTRANCE REGION OF THE UPPER JET WILL SHIFT EAST...BUT
PERIODS OF MID-UPPER LEVEL DPVA WILL CONTINUE AS A POSITIVELY TILTED
TROUGH MAKES LITTLE PROGRESS EAST ACROSS THE MID MS VALLEY. A SFC
COLD FRONT WILL STALL ALONG THE BLUE RIDGE IN THE MORNING...AND
LIKELY BE A FOCUS FOR ANOTHER ROUND OF AFTN SHOWERS AND
THUNDERSTORMS...MAINLY ALONG AND EAST OF I-85. BULK SHEAR LOOKS
BETTER THAN MONDAY...BUT THE BETTER CAPE WILL BE TO THE EAST AS DRY
AIR STARTS TO WORK IN FROM THE WEST. A DAY 2 MARGINAL SEVERE RISK IS
JUST TO OUR EAST. TEMPS WILL BE ABOUT 5-10 DEG ABOVE NORMAL UNDER
PARTLY CLOUDY SKIES.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
AS OF 230 PM EDT MONDAY...AN EASTERN CONUS TROUGH WILL DEEPEN FROM THE
GREAT LAKES TO THE SOUTHERN APPALACHIANS THROUGH WEDNESDAY...WHILE A
DEPARTING SURFACE COLD FRONT SETTLES SOUTHEAST OF THE REGION. A LEAD
SHORTWAVE WILL CROSS THE MOUNTAINS TUESDAY NIGHT AHEAD OF THE MAIN
TROUGH...BUT LIKELY WITH LIMITED MOISTURE AND PRECIPITATION. THE
CLOSED UPPER LOW CENTER WILL THEN CROSS WESTERN NORTH CAROLINA WED
NIGHT THROUGH THURSDAY AND STEEPER LAPSE RATES UNDER THIS SYSTEM
SHOULD PROVIDE FOR BETTER SHOWER COVERAGE OVER THE HIGH
TERRAIN...WITH LESSER CHANCES EAST OF THE MOUNTAINS IN DRIER AIR AND
LOW LEVEL DOWNSLOPE FLOW.

MOST OF THE MOISTURE IN THE DEEP LAYER NW FLOW UNDER THE PASSING
TROUGH WILL BE CONFINED TO THE MOUNTAINS...ESPECIALLY NEAR THE TN
BORDER. 850 MB TEMPERATURES MAY BOTTOM OUT NEAR FREEZING BY 12Z ON
THURSDAY...BUT MODEL PROFILES OVER THE HIGH MOUNTAIN HAVE A SURFACE
WARM LAYER TO KEEP MINS IN THE MID 30S WITH MAINLY RAIN.
OTHERWISE...BREEZY TO WINDY CONDITIONS OVER THE MOUNTAINS WILL BE
THE BIGGEST IMPACT ON THURSDAY. MINS WILL BE A CATEGORY BELOW
CLIMO...WITH THU AFTERNOON MAXES 10 TO 15 DEGREES BELOW CLIMO IN THE
COOLER AIRMASS.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 240 PM EDT MONDAY...THE PASSING UPPER LEVEL TROUGH AXIS WILL
DEPART THE EASTERN SEABOARD ON FRIDAY. HEIGHTS WILL THEN BUILD FROM
THE WEST OVER THE WEEKEND WITH SPRAWLING SURFACE HIGH PRESSURE FROM
THE LOWER MS RIVER VALLEY TO THE SOUTHERN APPALACHIANS. THIS WILL
KEEP THE WEATHER DRY THROUGH THE WEEKEND. A BACKDOOR BOUNDARY WILL
SETTLE JUST NORTH OF THE AREA ON SUNDAY...HOWEVER ANY PRECIPITATION
WITH THIS FEATURE SHOULD REMAIN JUST NORTH OF OUR FORECAST
AREA...WITH THE BOUNDARY LIFTING BACK NORTHWARD THROUGH MONDAY.
ISOLATED CONVECTION ALONG THE BLUE RIDGE COULD RETURN AS EARLY AS
MONDAY AFTERNOON IN THE WARM SECTOR. TEMPERATURES WILL QUICKLY
RECOVER TO WELL ABOVE CLIMO SUNDAY THROUGH MONDAY.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
AT KCLT...THUNDERSTORM ACTIVITY IS BEGINNING TO PICK UP RAPIDLY THIS
AFTN...WITH NUMEROUS SHOWERS AND STORMS EXPECTED BY LATE AFTN. GIVEN
THE SHOTGUN APPEARANCE ON RADAR...TIMING WHEN CELLS WILL IMPACT
STILL TOO UNCERTAIN...SO WILL GO WITH FOUR HOUR TEMPO FROM 18-22Z.
THE INSTBY IS FAIRLY ROBUST...SO GUSTY WINDS AND/OR HAIL THREAT WILL
EXIST WITH THE AFTN ACTIVITY. LATER THIS EVENING...STORMS FROM THE
WEST ARE EXPECT TO CROSS THE AREA...AS MOISTURE AND FORCING SHOULD
SUPPORT CONVECTION WELL PASSED SUNSET. WILL CONTINUE THE PREVAILING
TSRA WITH LOWERING CIGS TO MVFR. CONVECTION SHOULD BEGIN TO TAPER
OFF IN THE 6-9Z TIME FRAME. LOW CLOUDS WILL BEGIN TO LIFT LATE
TUESDAY MORNING. WINDS WILL FAVOR A SW DIRECTION THRU THE
PERIOD...WITH A FEW LOW-END GUSTS POSSIBLE THIS AFTN...BUT MAINLY
GUSTS WILL BE WITH CONVECTION.

ELSEWHERE...SIMILAR TO KCLT ABOVE. HAVE VCTS AND/OR TEMPO FOR TSRA
THIS AFTN...AS RADAR ECHOES ARE BLOSSOMING QUICKLY. MORE STORMS WILL
ENTER THE AREA FROM THE WEST THIS EVENING...WITH MOISTURE AND
FORCING SUPPORTING CONVECTION WELL PAST SUNSET. PREVAILING TSRA AND
PROB30 FOR TS THRU MOST OF THE NIGHT. CONVECTION SHOULD TAPER OFF
FROM WEST TO EAST DURING THE PRE-DAWN HOURS. WINDS WILL FAVOR A S TO
SW DIRECTION THRU THE PERIOD...EXCEPT SWITCHING TO NW AROUND 6Z AT
KAVL AS A FRONT PUSHES IN FROM THE WEST. THE FRONT IS EXPECTED TO
GET HUNG UP ALONG THE BLUE RIDGE THRU 18Z TUESDAY. AS FOR FOG AND/OR
STRATUS...GUIDANCE IS MIXED...BUT I EXPECT THAT IF WE GET WIDESPREAD
RAIN OVERNIGHT AND SOME CLEARING OF MID CLOUDS AND PRECIP ENDS
BEFORE DAYBREAK...MAY SEE MORE IFR OR LOWER RESTRICTIONS. WILL GO
WITH MVFR FOR NOW. CIGS WILL BEGIN TO LIFT LATE TUESDAY MORNING.

OUTLOOK...AFTN SHRA/TSRA EXPECT AGAIN TUESDAY...BUT MOSTLY EAST OF
THE MTNS. DRY AIR WILL WORK IN FROM THE WEST TUESDAY NIGHT THRU
WEDNESDAY. A STRONG UPPER LOW WILL SWING THRU THE AREA WED NIGHT
THRU THU...AND WILL BRING SHRA AND TSRA MAINLY TO THE MTNS.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH  98%     HIGH  86%     HIGH  80%
KGSP       HIGH 100%     HIGH  91%     MED   71%     HIGH  83%
KAVL       HIGH 100%     HIGH  80%     MED   75%     HIGH  81%
KHKY       HIGH 100%     HIGH  91%     HIGH  85%     HIGH  80%
KGMU       HIGH 100%     HIGH  89%     MED   70%     HIGH  84%
KAND       HIGH 100%     HIGH  87%     MED   62%     HIGH  86%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

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

&&

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



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