Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 030206
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1006 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/...
0210 UTC UPDATE...ONLY MINOR ADJOURNMENTS WERE MADE TO OVERNIGHT LOW
TEMPERATURES AND DEW POINTS. WINDS WERE UPDATED TO INCLUDE THE
LATEST ADJMAV DATA...PRESERVING GUSTS AT HIGHER ELEVATIONS
OVERNIGHT. POPS WERE ONCE AGAIN ADJUSTED UP EAST OF THE BLUE RIDGE
PER RADAR TRENDS.

0100 UTC UPDATE...POPS WERE RAISED IN THE WEST BASED ON RADAR TRENDS.

2315 UTC UPDATE...SKY COVER WAS ADJUSTED ONCE AGAIN PER SATELLITE
IMAGERY. WINDS WERE UPDATED TO INCLUDE THE LATEST NAM DATA...
PRESERVING GUSTS AT HIGHER ELEVATIONS OVERNIGHT. POPS WERE UPDATED
PER RADAR TRENDS.

2100 UTC UPDATE...SKY COVER WAS UPDATED PER VISIBLE SATELLITE
IMAGERY. POPS AND QPF WERE RAISED IN THE PIEDMONT PER RADAR TRENDS.

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 /02Z TUESDAY THROUGH SATURDAY/...
AT KCLT...THUNDERSTORM CHANCES PERSIST THIS EVENING...AND POSSIBLY
INTO THE OVERNIGHT. WINDS WILL FAVOR THE SSW...WITH GUSTS
DIMINISHING OVERNIGHT...EXCEPT IN WHEN THUNDERSTORMS ARE IN THE
AREA. WINDS WILL INCREASE AGAIN ON TUESDAY AHEAD OF A FRONT...WITH
THUNDER CHANCES INCREASING AS WELL. GUIDANCE VARIES GREATLY ON
OVERNIGHT CEILINGS...AND FOR NOW HAVE FAVORED A BLENDS THAT LOWERS
CIGS TO IFR AROUND DAWN. GUIDANCE FAVORS VFR VISIBILITY
OVERNIGHT...FALLING TO PERHAPS 6SM BEFORE DAWN.


ELSEWHERE...THUNDERSTORMS WILL BE POSSIBLE THIS EVENING AHEAD OF A
FRONT...DECREASING SOMEWHAT AFTER MIDNIGHT. WINDS WILL FAVOR THE SSW
AHEAD OF A COLD FRONT...VEERING NW AT KAVL BEFORE DAWN. GUSTS WILL
DIMINISH THIS EVENING...EXCEPT IN THE VICINITY OF THUNDERSTORMS.
GUIDANCE VARIED CONSIDERABLY ON OVERNIGHT CEILINGS...WITH A BLEND
FAVORING LOW VFR IN THE FOOTHILLS...AND MVFR AT KAVL. VSBY
RESTRICTIONS ARE FAVORED BEFORE DAWN EVERYWHERE BUT KGSP AND
KGMU...WITH IFR AT KHKY...AND MVFR AT KAVL AND KAND. WINDS WILL
INCREASE AHEAD OF THE FRONT ON TUESDAY.

OUTLOOK...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...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       HIGH  96%     MED   73%     HIGH  91%     HIGH 100%
KGSP       HIGH  95%     HIGH  92%     HIGH 100%     HIGH  90%
KAVL       HIGH  97%     MED   79%     HIGH  82%     HIGH 100%
KHKY       MED   77%     HIGH  86%     HIGH 100%     HIGH 100%
KGMU       HIGH  93%     HIGH  92%     HIGH  90%     HIGH  90%
KAND       HIGH  98%     HIGH  96%     MED   77%     HIGH  90%

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/JAT
SHORT TERM...HG
LONG TERM...HG
AVIATION...JAT



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