Severe Thunderstorm Warning 90, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
153 PM EDT THU JUN 13 2013

.SYNOPSIS...
A COLD FRONT WILL CROSS THE AREA LATE THIS AFTERNOON THROUGH THE
EVENING. DRY HIGH PRESSURE WILL BUILD IN FROM THE NORTH BEHIND THE
FRONT FRIDAY...AND SETTLE ACROSS THE REGION THROUGH THE WEEKEND. THE
NEXT COLD FRONT WILL APPROACH FROM THE NORTHWEST EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1010 AM EDT THURSDAY...THE INGREDIENTS LOOK TO BE COMING
TOGETHER FOR A GOOD CHANCE OF SEVERE WEATHER ACROSS THE FORECAST
AREA THIS AFTERNOON. THE 12 UTC GSO SOUNDING HAS STEEP MID-LEVEL
LAPSE RATES...BUT QUITE A BIT OF VERY WARM DRY AIR IN THE LOW
LEVELS. IN FACT...THE SOUNDING HAD A 1430 METER 1000-850 MB
THICKNESS...WHICH YIELDS A MAX TEMP OF 101 DEGREES USING A VENERABLE
OLD MAX TEMP TECHNIQUE WE HAVE. CURRENT TEMPERATURE READINGS ARE
RUNNING 5 TO 7 DEGREES ABOVE WHAT WAS PROJECTED...AND I/VE RAISED
MAX TEMPS 3 TO 5 DEGREES ACROSS THE FORECAST AREA THIS AFTERNOON.
EVEN THIS MAY NOT BE ENOUGH AND SOME LOCATIONS WILL EASILY MAKE THE
UPPER 90S OVER THE PIEDMONT. DEWPOINTS SHOULD MIX OUT A
LITTLE...ESPECIALLY OVER THE NC FOOTHILLS AND PIEDMONT AND THE NRN
UPSTATE. THEY WILL MIX OUT LESS FARTHER TO THE WEST WHERE LLVL
MOISTURE IS DEEPER...PER THE OHX SOUNDING. SUB-CLOUD DEWPOINT
DEPRESSIONS WILL RUN 30 TO 35 DEGREES BY MID AFTERNOON WHICH WILL
STRONGLY SUPPORT DAMAGING OUTFLOW WINDS.

CONVECTION IS CURRENTLY ORGANIZING ALONG THE SFC FRONT OVER THE
KY/IN LINE. IT/S STILL A BIT TRICKY AS TO WHETHER THAT CONVECTION
WILL DEVELOP INTO A SEVERE MCS AND SWEEP INTO THE MTNS AROUND 3
PM...OR IF THE CLOUDY CONDITIONS OVER MOST OF KY WILL CAUSE THE LINE
TO STRUGGLE UNTIL THE OUTFLOW MOVES ACROSS THE MTNS. IF THE LATTER
HAPPENS...WE MAY NOT SEE A WELL-ORGANIZED MCS UNTIL THE CONVECTION
GETS OUT INTO THE FOOTHILLS AND PIEDMONT IN THE MID TO LATE AFTN
HOURS. WE/LL KNOW BETTER IN A COUPLE HOURS AS THE LINE DEVELOPS OVER
KY AND TN.

AS OF DAYBREAK...STILL WAITING FOR SIGNS OF UPSTREAM MCS
DEVELOPMENT. HAVE PUSHED BACK THE ONSET OF THE PRECIP REACHING THE
NC MTNS UNTIL A BIT LATER IN THE MORNING.

FOR TODAY...BEEN LOOKING AT A POTENTIAL WIND DAMAGE PRODUCING SQUALL
LINE EVENT IN THE MODEL GUIDANCE FOR THE LAST SEVERAL DAYS. STILL
THINK THERE IS EXCELLENT POTENTIAL IN SPITE OF THE LACK OF RESPONSE
IN THE OPERATIONAL GFS. THE MODELS SHOW A DECENT SHORT WAVE MOVING
ACROSS THE CUMBERLAND PLATEAU DURING THE MIDDLE PART OF THE
DAY...OVER THE TOP OF WHERE AN OLD MCS OUTFLOW BOUNDARY WILL LIKELY
BE LINGERING. THIS SHOULD TRIGGER THE DEVELOPMENT OF A NEW LINEAR
MCS THAT WILL PROPAGATE EASTWARD WITH THE UPPER WAVE. THE DPVA AND
UPPER DIVERGENCE WILL ARRIVE DURING PEAK HEATING. NOT SURE WHY THE
MCS WOULD NOT BE MAINTAINED ACROSS THE MTNS AND E OF THE BLUE RIDGE
WHERE BUOYANCY SHOULD BE GREATER THAN 2000 J/KG. ALTHO THERE MIGHT
BE SOME LOSS OF ORGANIZATION OVER THE MTNS...THINK ANY REDEVELOPMENT
WILL TAKE PLACE MUCH CLOSER TO THE BLUE RIDGE THAN WHAT THE GFS
INDICATES. THE MCS WOULD THEN PROGRESS EASTWARD AND WOULD EXIT THE
FCST AREA BEFORE SUNSET. THE PRIMARY THREAT APPEARS TO BE WIND
DAMAGE. ASSUMING WE GET A DECENT COLD POOL THAT FORMS AND DRIVES THE
MCS EASTWARD...WE COULD SEE SEVERAL SWATHS OF WIND DAMAGE. THIS WILL
BE HIGHLIGHTED IN THE HWO. THE FCST REFLECTS MORE CONFIDENCE THAN
THE GUIDANCE WOULD INDICATE...THUS THE LIKELY POP. THINK THE
MAJORITY OF THE DAY WILL BE HOT AND HUMID WITH NO SHOWER ACTIVITY...
BUT THAT IT IS LIKELY THAT MOST PLACES WILL SEE THE PASSAGE OF A
LINE OF SHOWERS AND THUNDERSTORMS MAINLY DURING THE AFTERNOON...SO
IT WILL STORM FOR AN HOUR OR TWO AND THEN DRY OUT BY EARLY EVENING.

FOR TONIGHT...EXPECT A QUIET NIGHT WITH TEMPS COOLING OFF IN THE
EVENING IN THE WAKE OF THE AFTERNOON CONVECTION...AND WITH HIGH
PRESSURE BUILDING IN FROM THE NW.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
AS OF 245 AM THURSDAY...THE SHORT TERM SHUD BE QUIET AND
SEASONABLE...AS CONTINENTAL AIR MASS FILTERS IN FROM THE NORTH UNDER
CONFLUENT NWLY FLOW ALOFT. I INHERITED A DRY FCST FOR THIS
WEEKEND...AND THAT STILL LOOKS GOOD. MAY SEE A RETURN OF A FEW ISOLD
SHWRS/TSTMS IN THE NC MTNS SUNDAY AFTN...AS HIGH PRES SETTLES OVR
THE NORTH ATLANTIC...WHICH BRINGS A MOIST RETURN FLOW TO THE AREA.
HIGHS WILL BE GENERALLY IN THE LWR-MID 80S IN THE PIEDMONT AND MTN
VLYS WITH LOWS IN THE 50S MTNS AND 60S PIEDMONT.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
AS OF 245 AM THURSDAY...UPR FLOW BRIEFLY FLATTENS INTO A QUASI-ZONAL
PATTERN SUNDAY NIGHT INTO MONDAY...ALLOWING A WEAK FRONTAL BNDRY TO
SAG SOUTH INTO THE AREA. GUIDANCE IN GOOD AGREEMENT ON UNSETTLED WX
RETURNING TO THE AREA MONDAY AND TUESDAY...AS UPR LVL SHORTWAVE
ENERGY CROSSES THE AREA. AN UPR RIDGE WILL AMPLIFY AGAIN ACRS THE
SRN PLAINS/MS VLY MIDWEEK...WHICH WILL PUT THE CWFA BACK INTO A NWLY
FLOW REGIME...AND PROBABLY DRIER WX. TEMPS LOOK TO BE NEAR OR
SLIGHTLY ABOVE NORMAL THRU THE MEDIUM RANGE.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AT KCLT...TIMING THE CONVECTION DEVELOPING OVER ERN TN AT THIS TIME
BRINGS IT ACROSS THE AIRFIELD BETWEEN 20-21 UTC. CONSIDERING THE
SHEAR AND INSTABILITY CHARACTERISTICS OF THE AIRMASS THIS
AFTERNOON...THE STORMS WILL PUT OUT STRONG OUTFLOW BOUNDARIES AND
THEY SHOULD MOVE RAPIDLY TO THE EAST AS THEY EVOLVE. THEREFORE I
THINK THAT TIMING WILL WORK WELL. I DIDN/T ADD GUSTS TO THE TEMPO
GROUP YET...BUT I PROBABLY WILL ONCE I CHAT A LITTLE MORE WITH THE
CWSU AS THERE IS A GOOD CHANCE OF AT LEAST A 40KT GUST WITH THE
LINE...POSSIBLY HIGHER. OTHERWISE WINDS WILL BE GUSTY OUT OF THE
SOUTHWEST AHEAD OF THE LINE...WITH WINDS VEERING AROUND TO WEST AND
THEN NORTHWEST BEHIND THE LINE DURING THE COURSE OF THE EVENING.
GUSTS UP TO 18 KTS OR SO WILL BE POSSIBLE AFTER SUNRISE TOMORROW AS
WE START TO MIX BEHIND A COLD FRONT.

ELSEWHERE...CONDITIONS ELSEWHERE WILL BE THE SAME AS AT KCLT AS A
SQUALL LINE SWEEPS OUT OF THE MOUNTAINS IN A FEW HOUR/S TIME.

OUTLOOK...HIGH PRESSURE WILL BUILD IN THU NITE AND PRODUCE GENERALLY
QUIET WEATHER AND VFR CONDITIONS THROUGH THE WEEKEND.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH  91%     HIGH  96%     HIGH 100%
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...ARK
NEAR TERM...MCAVOY
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...MCAVOY

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
156 PM EDT THU JUN 13 2013

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-141800-
RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-AVERY-ALEXANDER-
IREDELL-DAVIE-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-CATAWBA-
ROWAN-GRAHAM-NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-
HENDERSON-CLEVELAND-LINCOLN-GASTON-MECKLENBURG-CABARRUS-UNION NC-
CALDWELL MOUNTAINS-GREATER CALDWELL-BURKE MOUNTAINS-GREATER BURKE-
MCDOWELL MOUNTAINS-EASTERN MCDOWELL-RUTHERFORD MOUNTAINS-
GREATER RUTHERFORD-POLK MOUNTAINS-EASTERN POLK-OCONEE MOUNTAINS-
PICKENS MOUNTAINS-GREENVILLE MOUNTAINS-GREATER OCONEE-
GREATER PICKENS-GREATER GREENVILLE-SPARTANBURG-CHEROKEE-YORK-
ANDERSON-ABBEVILLE-LAURENS-UNION SC-CHESTER-GREENWOOD-
156 PM EDT THU JUN 13 2013

...SEVERE THUNDERSTORM WATCH 307 IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST GEORGIA...PIEDMONT
NORTH CAROLINA...WESTERN NORTH CAROLINA AND UPSTATE SOUTH CAROLINA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   SEVERE THUNDERSTORM WATCH.

A LINE OF THUNDERSTORMS MOVING ACROSS EASTERN TENNESSEE WILL DIVE
TO THE SOUTHEAST THIS AFTERNOON AND MOVE ACROSS THE MOUNTAINS OF
THE CAROLINAS BETWEEN 2 AND 5 PM. THE LINE WILL THEN CROSS THE
REMAINDER OF THE FOOTHILLS AND PIEDMONT DURING THE LATE AFTERNOON
AND EARLY EVENING HOURS. THE ATMOSPHERE OVER THE REGION WILL BE
VERY UNSTABLE THIS AFTERNOON AND THESE STORMS WILL BE CAPABLE OF
PRODUCING LARGE SWATHS OF DAMAGING DOWNBURST WINDS.
ISOLATED...BRIEF TORNADOES ARE ALSO POSSIBLE...ESPECIALLY OVER THE
NORTH CAROLINA FOOTHILLS AND PIEDMONT. A FEW OF THE STORMS WILL
ALSO PRODUCE LARGE HAIL...THOUGH DAMAGING STRAIGHT-LINE WINDS
WILL BE THE MOST SIGNIFICANT THREAT. SEVERE STORMS SHOULD EXIT THE
REGION BY AROUND SUNSET.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTERS ARE REQUESTED TO FORWARD ANY REPORTS OF LARGE
HAIL...DAMAGING WINDS...TORNADOES OR FLASH FLOODING TO OUR OFFICE.
DISPATCHERS...PLEASE FORWARD THIS INFORMATION ON TO EMERGENCY
MANAGERS.

MCAVOY

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
149 PM EDT THU JUN 13 2013

NCZ033-048>053-058-059-131900-
AVERY-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-GRAHAM-
NORTHERN JACKSON-
INCLUDING THE CITIES OF...NEWLAND...SPRUCE PINE...CHEROKEE...
BRYSON CITY...WAYNESVILLE...ASHEVILLE...SYLVA
149 PM EDT THU JUN 13 2013

...INTENSIFYING THUNDERSTORMS APPROACHING WESTERN NORTH CAROLINA...

AT 145 PM EDT...NATIONAL WEATHER SERVICE RADAR INDICATED STRONG TO
SEVERE THUNDERSTORMS ACROSS THE TENNESSEE VALLEY. THESE
THUNDERSTORMS SHOULD CONTINUE TO STRENGTHEN AS THEY APPROACH THE
FAR WESTERN MOUNTAINS AFTER 2 PM. THE THREAT FOR DAMAGING STRAIGHT
LINE WINDS WILL INCREASE...WHILE ISOLATED LARGE HAIL CAN ALSO BE
EXPECTED. A SEVERE THUNDERSTORM WATCH IS IN EFFECT UNTIL 8 PM.

STAY TUNED TO NOAA WEATHER RADIO OR LOCAL MEDIA OUTLETS...AS
WARNINGS WILL LIKELY BE ISSUED FOR PORTIONS OF THE AREA BY 230 PM.

LANE