Severe Thunderstorm Warning 313, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
435 PM EDT FRI AUG 23 2013

.SYNOPSIS...
A COLD FRONT WILL MOVE INTO THE REGION TONIGHT...TRIGGERING SHOWERS
AND THUNDERSTORMS BEFORE USHERING IN DRIER WEATHER FOR THE WEEKEND.
HIGH PRESSURE WILL BUILD BACK IN FOR THE FIRST PART OF THE
WEEK...BEGINNING A GRADUAL WARMING TREND. RETURNING SOUTHERLY FLOW
WILL GRADUALLY INCREASE MOISTURE ACROSS THE REGION...INCREASING
CHANCES FOR SHOWERS AND THUNDERSTORMS EACH AFTERNOON. A SERIES OF
COLD FRONTS WILL MOVE THROUGH THE REGION LATE IN THE WEEK ELEVATING
RAIN CHANCES FURTHER.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 430 PM...AREA OF CONVECTION IS SHIFTING TO THE WRN CWFA AND
DYING OFF EAST OF I-77. HAVE UPDATED AFTERNOON AND EVENING POP TO
REFLECT THESE TRENDS. NOW HAVE HIGHEST POP FOLLOWING THE TRACK OF
THE CURRENT OUTFLOW BOUNDARY AND SPREADING ACROSS THE UPSTATE INTO
NE GA. ALSO HAVE HIGH POP SPREADING SW ACROSS THE NC MTNS AS WELL.
POP SIGNIFICANTLY REDUCED OVER THE I-77 CORRIDOR. SVR STORMS REMAIN
POSSIBLE AS THE STORMS MOVE INTO AN AREA WITH SIGNIFICANTLY HIGHER
DCAPE VALUES. TEMPS FELL SIGNIFICANTLY WITH THE LINE OF TSRA AND
HAVE FOLLOWED THESE TRENDS AS WELL...ALTHOUGH NOT AS DRAMATICALLY.

AS OF 230 PM EDT FRIDAY...A LINE OF SHOWERS AND THUNDERSTORMS HAS
DEVELOPED OVER THE WRN NC FOOTHILLS AND PIEDMONT. THE LINE IS BEING
FORCED BY LLVL SFC CONVERGENCE AND DIFFERENTIAL HEATING RESULTING
FROM THE APPROACH OF AN H5 SHORT WAVE WHICH THE RAP CURRENTLY HAS
LOCATED OVER NE TN AND SW VA. THE DEEP LAYER SHEAR ISN/T
STRONG...BUT THE AIRMASS AHEAD OF THE LINE IS QUITE UNSTABLE AND IT
ALREADY HAS A WELL ESTABLISHED REAR INFLOW JET PER THE TERMINAL
DOPPLER RADAR AT CHARLOTTE. THE NAM AND GFS BOTH STRENGTHEN SFC
CONVERGENCE AHEAD OF THE LINE. THEREFORE IT SHOULD CONTINUE TO MOVE
TO THE SOUTHEAST AND AT LEAST MAINTAIN ITSELF IF NOT GET STRONGER.
BUT IT SHOULD ALSO BUILD TO THE SOUTHWEST...OR NEW STORMS MAY
ORIGINATE OVER THE SC MTNS...AS THE LLVL WINDS BACK ACROSS MOST OF
THE UPSTATE AND EVEN INTO NE GA OVER THE NEXT COUPLE HOURS. AT THIS
RATE MOST LOCATIONS OVER THE FOOTHILLS AND PIEDMONT SHOULD GET INTO
THE ACT OVER THE NEXT 4 TO 6 HOURS AND POPS HAVE BEEN RAISED TO
LIKELY TO CATEGORICAL FOR THE REST OF THE DAY. DCAPE VALUES ARE HIGH
OVER THE UPSTATE...BUT DROP OFF RAPIDLY INTO NORTH CAROLINA. SO AS
THE LINE MOVE SOUTHWARD...IT/S TENDENCY TO PRODUCE STRONG OUTFLOW
SHOULD INCREASE.

STORMS SHOULD DIMINISH FROM NORTH TO SOUTH THIS EVENING. I THINK
THERE WILL ENOUGH CONVECTIVE DEBRIS AND MIXING EAST OF THE MTNS TO
PREVENT FOG FROM FORMING AGAIN. OVER THE MOUNTAINS WINDS ARE
EXPECTED TO DECOUPLE OVERNIGHT AS THE LLVL GRADIENT WINDS WILL BE
ORIENTED OUT OF THE NE...ORTHOGONAL TO THE HIGHER NC MTN CHAINS.
THEREFORE...THE MTN VALLEYS SHOULD SEE FOG AND STRATUS ONCE AGAIN.

COLD AIR DAMMING DEVELOPS FOR SATURDAY. THE MODELS STILL HAVE
1000-2000 SBCAPE VALUES OVER THE SOUTHERN ZONES. I/VE KEPT LOW END
CHANCE POPS ALONG THE UPPER SAVANNAH RIVER VALLEY AND OVER THE
SOUTHWEST AND CENTRAL NC MTNS. TYPICALLY IN THESE SITUATIONS MOST OF
THE DEVELOPMENT IS OVER THE SW MTNS AND ALONG THE EASTERN ESCARPMENT
OF THE BLUE RIDGE. CLOUDS MAY DISSIPATE IN THE DRIER AIR OVER THE
PIEDMONT AND ALONG THE TN LINE...WITH GENERALLY MOSTLY CLOUDY SKIES
EXPECTED ELSEWHERE.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AT 230 PM EDT FRIDAY...A STRONG UPPER HIGH WILL BE CENTERED OVER MO
ON SATURDAY NIGHT....WHILE A POSITIVELY TILTED UPPER TROUGH WILL BE
JUST OFF THE EAST COAST. THIS TROUGH MOVES FARTHER OFF THE EAST
COAST ON SUNDAY...WHILE THE UPPER RIDGE REMAINS CENTERED OVER MO. ON
MONDAY THE UPPER RIDGE RETROGRESSES INTO KS.

A COLD FRONT TO OUR SOUTH WILL DRIFT FARTHER SOUTH ACROSS FL
SATURDAY NIGHT AND SUNDAY...WHILE DRIER AIR AND HIGH PRESSURE SPREAD
ACROSS THE CAROLINAS AND GA FROM THE NE. MODEL TIME HEIGHTS SHOW A
THINNING...LINGERING LAYER OF MOISTURE AT AROUND 850 MB BEHIND THE
FRONT. WITH JUST A WEAK EASTERLY UPSLOPE FLOW DEVELOPING AS WINDS
VEER IN THE LOW LEVELS...ONLY VERY SMALL POPS WILL BE CARRIED SUNDAY
EVENING AND LATE MONDAY. TEMPERATURES WILL RUN BELOW NORMAL THROUGH
THE PERIOD...WITH A SLIGHT WARMING TREND ON MONDAY AS HEIGHTS RISE
ALOFT WITH THE PROGRESSION OF THE ATLANTIC TROUGH.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 200 PM EDT FRIDAY...OVERALL A MUCH DRIER PATTERN FOR THE
EXTENDED THAN WHAT WE HAVE SEEN IN THE PAST FEW WEEKS. AN UPPER
RIDGE WILL BE FIRMLY ENTRENCHED OVER THE CENTRAL PLAINS BY MONDAY
NIGHT WHILE A SURFACE RIDGE WILL SHIFT SOUTHEASTWARD TOWARDS THE
ATLANTIC TO TAKE ON BERMUDA HIGH CHARACTERISTICS. THIS WILL SET UP A
WEAK SOUTHEASTERLY FLOW REGIME AT THE SURFACE...AND BY WEDNESDAY A
HIGH IN THE NORTHEAST WILL ALLOW A WEAK WEDGE TO BUILD IN OVER THE
APPALACHIANS AND ADVECT IN MODERATELY DRIER AIR. ANY CONVECTION WILL
FOLLOW A DIURNAL PATTERN...AND THEN WILL BE LIMITED MAINLY TO AREAS
OF UPSLOPE FLOW. AN EXPANDING SURFACE HIGH OVER THE GREAT LAKES WILL
PUSH MULTIPLE FRONTAL BOUNDARIES SOUTHWARD THROUGH THE CWA BY THE
END OF THE WEEK...INCREASING RAIN CHANCES ONCE AGAIN. RISING HEIGHTS
DUE TO THE UPPER LEVEL RIDGE WILL ALLOW HIGH TEMPERATURES TO
MODERATE BACK TO NORMAL LEVELS...IN THE MID TO HIGH 80S...FOR MOST
OF NEXT WEEK.

&&

.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT...THE LINE OF THUNDERSTORMS WEAKENED AND SPLIT THE AIRFIELD.
CHC FOR ADDITIONAL ACTIVITY NEAR THE AIRPORT IS LOW THIS EVENING...
SO WILL REMOVE MENTION...BUT WATCH FOR NEEDED AMD. WINDS SHUD STAY
LIGHT FROM THE NORTH INTO THE EVENING. IN FACT...SHOULD ONLY SEE SCT
LOW VFR CLOUDS UNLESS MORE CELLS DEVELOP. LATER TONIGHT AN MVFR
STRATO-CU DECK MAY MOVE IN AS THE TRUE SFC OLD FRONT ARRIVES. THE
RAP AND OUR LOCAL WRF ARW DO THIS AND I/VE ADDED A PERIOD OF MVFR
CIGS FROM 09-14 UTC TONIGHT AND TMRW. WINDS WILL VEER FROM NW TO NE
AS THE FRONT MOVES THROUGH.

ELSEWHERE...A LINE OF THUNDERSTORMS WILL DROP SOUTHEAST AND SHUD
AFFECT KGSP/KGMU THIS AFTERNOON AND POSSIBLY KAVL/KAND. KHKY LOOKS
TO BE OUT OF DANGER...BUT AN ADDITIONAL CELL COULD DEVELOP LATER.
WINDS WILL GO NORTH BEHIND THE GUST FRONT ASSOCIATED WITH THE LINE
OF STORMS. THEN LOW VFR CLEARS OUT UNTIL LATER TONIGHT. LATER
TONIGHT MVFR CIGS WILL DEVELOP OVER NC...BUT THEY MAY NOT MAKE IT
INTO THE UPSTATE. THEREFORE NO MVFR CIGS WERE CARRIED AT THE SOUTH
CAROLINA TAF SITES. AT KAVL THE WINDS SHOULD BE COME LIGHT LATE
TONIGHT AS THE FRONT IS MOVING IN FROM THE NE. THIS WILL SUPPORT
ANOTHER NIGHT WITH STRATUS AND FOG. WINDS WILL BECOME RATHER BRISK
OUT OF THE NORTHEAST AFTER SUNRISE. I WOULDN/T BE SURPRISED TO SEE
SOME GUSTS UP TO 20 KTS OVER THE UPSTATE AND AT KCLT.

OUTLOOK...A DRIER PATTERN IS EXPECTED AS HIGH PRESSURE GRADUALLY
BUILDS IN FROM THE NORTH OVER THE WEEKEND.

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-20Z
KCLT       HIGH 100%     HIGH 100%     HIGH  81%     HIGH  95%
KGSP       HIGH 100%     HIGH  91%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     MED   67%     LOW   56%     MED   67%
KHKY       HIGH 100%     HIGH  80%     LOW   52%     HIGH  95%
KGMU       HIGH 100%     HIGH  91%     HIGH  95%     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...VISIN
NEAR TERM...MCAVOY/RWH
SHORT TERM...JAT
LONG TERM...VISIN
AVIATION...MCAVOY/RWH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
229 AM EDT FRI AUG 23 2013

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-240630-
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-
229 AM EDT FRI AUG 23 2013

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

.DAY ONE...TODAY AND TONIGHT.

A COLD FRONT WILL PUSH INTO THE AREA FROM THE NORTH THIS AFTERNOON
INTO TONIGHT. SCATTERED THUNDERSTORMS ARE EXPECTED ALONG AND AHEAD
OF THE FRONT...WITH A FEW POSSIBLY PRODUCING LARGE HAIL AND
DAMAGING WIND GUSTS. ISOLATED FLASH FLOODING WILL BE POSSIBLE WITH
SOME OF THE HEAVIER DOWNPOURS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

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.

CDG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
134 PM EDT FRI AUG 23 2013

NCZ035-036-056-057-231815-
ALEXANDER-CATAWBA-IREDELL-ROWAN-
134 PM EDT FRI AUG 23 2013

...A STRONG THUNDERSTORM WILL AFFECT CENTRAL IREDELL...EASTERN
CATAWBA...NORTHWESTERN ROWAN AND SOUTHERN ALEXANDER COUNTIES THROUGH
215 PM EDT...

AT 132 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR SCOTTS...OR 8 MILES NORTHWEST OF
STATESVILLE...MOVING SOUTHEAST AT 10 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  LOOKOUT SHOALS LAKE...
  CLAREMONT...
  NEWTON...
  STATESVILLE...
  TROUTMAN...

WIND GUSTS UP TO 40 MPH...AND TORRENTIAL RAINFALL ARE EXPECTED WITH
THIS STORM.

FREQUENT LIGHTNING IS OCCURRING WITH THIS STORM. IF OUTDOORS...TRY TO
GET INDOORS OR INTO A HARD TOPPED VEHICLE. OTHERWISE...STAY AWAY FROM
OPEN AREAS AND ISOLATED HIGH OBJECTS SUCH AS TREES. WHEN INDOORS...
STAY AWAY FROM WINDOWS AND DOORS AND AVOID USING WIRED ELECTRONIC
DEVICES. TRY TO UNPLUG UNNECESSARY APPLIANCES BEFORE THE STORM
APPROACHES.

LAT...LON 3569 8061 3555 8101 3555 8115 3584 8132
      3587 8108 3594 8077

JPT

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
217 PM EDT FRI AUG 23 2013

NCZ036-056-057-069>072-231900-
CABARRUS-CATAWBA-GASTON-IREDELL-LINCOLN-MECKLENBURG-ROWAN-
217 PM EDT FRI AUG 23 2013

...A STRONG THUNDERSTORM WILL AFFECT EASTERN LINCOLN...NORTHEASTERN
GASTON...NORTHERN MECKLENBURG...NORTHWESTERN CABARRUS...SOUTHERN
CATAWBA...SOUTHERN IREDELL AND WESTERN ROWAN COUNTIES THROUGH 300 PM
EDT...

AT 216 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 3 MILES NORTHEAST OF TERRELL...OR 12 MILES SOUTH
OF STATESVILLE...MOVING SOUTHEAST AT 20 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  DENVER...
  LAKE NORMAN...
  MOORESVILLE...
  DAVIDSON...
  CORNELIUS...
  CHINA GROVE...

WIND GUSTS UP TO 40 MPH...AND TORRENTIAL RAINFALL ARE EXPECTED WITH
THIS STORM.

FREQUENT LIGHTNING IS OCCURRING WITH THIS STORM. IF OUTDOORS...TRY TO
GET INDOORS OR INTO A HARD TOPPED VEHICLE. OTHERWISE...STAY AWAY FROM
OPEN AREAS AND ISOLATED HIGH OBJECTS SUCH AS TREES. WHEN INDOORS...
STAY AWAY FROM WINDOWS AND DOORS AND AVOID USING WIRED ELECTRONIC
DEVICES. TRY TO UNPLUG UNNECESSARY APPLIANCES BEFORE THE STORM
APPROACHES.

LAT...LON 3546 8044 3530 8072 3526 8110 3566 8135
      3563 8108 3569 8081 3574 8061

JPT

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
442 PM EDT FRI AUG 23 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0439 PM     HAIL             MILL SPRING             35.30N 82.16W
08/23/2013  E0.75 INCH       POLK               NC   PUBLIC

            PEA TO PENNY HAIL REPORTED.

&&

07

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