Special Weather Statement, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
351 PM EDT THU SEP 6 2012

.SYNOPSIS...
SLIGHTLY DRIER AIR WILL PREVAIL ACROSS OUR REGION ON FRIDAY UNDER
WEAK HIGH PRESSURE. A STRONG COLD FRONT WILL MOVE ACROSS THE
AREA SATURDAY AND SATURDAY NIGHT WITH DRY AIR OVERSPREADING THE
REGION ON SUNDAY. DRY HIGH PRESSURE WILL SETTLE OVER THE REGION FOR
MUCH OF NEXT WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
430 PM EDT UPDATE...THE BIGGEST CHANGE FOR THE UPDATE INCLUDED
ADDING A NUMEROUS -SHRA/TS AREA ACROSS THE EASTERN UPSTATE AND INTO
THE NC PIEDMONT AROUND KCLT...PER THE LATEST 88D TRENDS AND SFC
CONVERGENCE FIELDS. THERE COULD BE SOME TRAINING HYDRO ISSUES LATER
ON...DEPENDIN ON TRANSLATION OF THE UPPER TROF EASTWARD. SKY COVER
WAS ADJUSTED USING THE LATEST VSBL LOOP AND INTERPOLATED HR/LY
THROUGH THE EVENING. MINOR CHANGES WERE MADE TO TEMPS/TDS...MAINLY
ACROSS THE EASTERN PIEDMONT WHERE CONVECTIVE CLOUD COVER HAS KEPT
HR/LY VALUES LOWER THAN FORECASTED.

THE 16 UTC RAP AND WATER VAPOR IMAGERY CONTINUE TO INDICATE A WELL
DEFINED SHORT WAVE TROF SLOWLY PROGRESSING ACROSS THE NC MTNS. AHEAD
OF THE TROUGH...A STOUT AREA OF PVA EXITS OVER THE FOOTHILLS AND
WESTERN PIEDMONT. THE WAVE WILL CONTINUE TO SLOWLY TRANSLATE TO THE
ESE OVER THE NEXT SEVERAL HOURS. DEWPOINTS ARE QUITE HIGH OVER THE
WESTERN CAROLINAS AND NE GA...AND NOW THAT TEMPS HAVE WARMED INTO
THE L-M80S...SBCAPE VALUES HAVE RISEN TO 2000 J/KG OR HIGH IN MANY
AREAS. THIS HAS RESULTED IN THE DEVELOPMENT OF SHRA/TSTMS OVER THE
ERN UPSTATE AND SRN NC PIEDMONT. THE ACTIVITY SHOULD INCREASE IN
COVERAGE OVER THE NEXT COUPLE HOURS...THEN MOVE EAST OF THE REGION
BY EARLY EVENING. THE LATEST SPC MESOANALYSIS SHOWS A DCAPE MINIMUM
ACROSS THE REGION. FREEZING LEVELS ARE ALSO OVER 15KFT.
THEREFORE...NEITHER DAMAGING WINDS OR NOR HAIL WILL BE MUCH OF A
THREAT WITH STORMS THIS AFTN. THE STORMS SHOULD NOT BECOME VERY
ORGANIZED AND 30 TO 40 PERCENT COVERAGE...MAINLY OVER THE ERN
ZONES...STILL LOOKS REASONABLE. THE EXCEPTION TO THIS COULD BE THE
SRN NC PIEDMONT WHERE THE WAVE IS ALSO RESULTING IS INCREASED LLVL
CONVERGENCE.

LATE TONIGHT WIDESPREAD DENSE VALLEY FOG IS EXPECTED OVER THE NC
MTNS. WITH THE MID-LEVELS DRY OUT...FOR SHOULD ALSO BE A LITTLE MORE
WIDESPREAD ACROSS THE FOOTHILLS AND PIEDMONT...PARTICULARLY ALONG
THE LARGER RIVER VALLEYS.

SLIGHTLY DRIER AIR WILL WORK INTO THE REGION TOMORROW. A SHORT WAVE
RIDGE WILL ALSO SLOWLY TRANSLATE ACROSS THE FA. WITH MUCH DRIER AIR
ALOFT AND WARM H7 TEMPS CONVECTION WILL HAVE DIFFICULTLY DEVELOPING
TOMORROW AND I HAVE A DRY FORECAST FOR THE FOOTHILLS AND PIEDMONT.
ISOLATED STORMS ARE POSSIBLE OVER THE MTNS...PARTICULARLY OVER THE
HIGHER ELEVATIONS. WITH DRIER AIR AND LIGHT DOWNSLOPE
FLOW...TEMPERATURES WILL RISE INTO THE L90S ACROSS MUCH OF FOOTHILLS
AND PIEDMONT.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
COLD FROPA AND ASSOCIATED PRECIPITATION ARE THE BIG CONCERN FOR
FRIDAY NIGHT AND SATURDAY. 850MB WINDS WERE STRONGER ON 00Z NAM THAN
ON 06Z GFS...WHICH LED THE NAM TO PRODUCE STRONGER THETA-E ADVECTION
AND MOISTURE TRANSPORT AHEAD OF THE FRONT. 12Z NAM HAS WEAKER WINDS
MORE IN LINE WITH THE GFS AND ITS MOISTURE FIELDS REFLECT THE WEAKER
ADVECTION. DECENT AGREEMENT BETWEEN MODELS IN TIMING OF
FROPA...WHICH APPEARS TO OCCUR BETWEEN 12Z AND 18Z. PRECIPITABLE
WATER VALUES INCREASE AS THE FRONT ENTERS THE PIEDMONT...BUT THE
VALUES OVER THE MOUNTAINS ARE MORE EXTREME WITH RESPECT TO
CLIMATOLOGY. IF THE DYNAMICS ALONG THE FRONT WERE MORE IMPRESSIVE I
WOULD BE INCLINED TO GO WITH HIGHER QPF...BUT KEPT IT IN CHECK FOR
NOW.

WITH THE FRONT MOVING THROUGH EARLY IN THE DAY...INSTABILITY WILL BE
LIMITED...BUT FORECAST SOUNDINGS INDICATE ENOUGH CAPE TO WARRANT A
THUNDER MENTION. HOWEVER THE BETTER CHANCES FOR THUNDER WILL BE OVER
THE SC PIEDMONT ZONES DURING THE AFTERNOON AS THAT AREA WILL HAVE
MORE TIME TO DESTABILIZE.

COLD ADVECTION AND SUBSIDENCE SET IN QUICKLY BEHIND THE FRONT AND
MODELS AGREE PRECIP SHOULD END BY LATE SATURDAY EVENING. COULD SEE
SOME STRONG GAP WINDS IN THE MOUNTAIN VALLEYS OVERNIGHT SATURDAY
NIGHT GIVEN STRONG WINDS IN 1000-3000 FT LAYER AND WEAK INVERSION
PROFILE EXPECTED WITH PARTLY CLOUDY SKIES STILL IN PLACE.

SUNDAY LOOKS TO BE REFRESHINGLY COOLER AND LESS HUMID
WITH HIGHS IN THE MID 70S OVER THE MOUNTAINS TO THE LOWER 80S OVER
THE PIEDMONT. ONE ITEM OF NOTE IS THAT THE 00Z EC DEVELOPS THE
TROUGH INTO A CUTOFF UPPER LOW OVER THE NORTHEAST CONUS...WITH A
WEAK LOBE OF VORTICITY REACHING THE MOUNTAINS LATE SUNDAY. HOWEVER
THE MODEL DOES NOT PRODUCE ANY PRECIP AND THE WHOLE TROUGH IS LONG
GONE ON THE GFS AT THIS TIME ANYWAY...SO STILL FEEL PRETTY CONFIDENT
WITH DRY FORECAST SUNDAY.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 200 PM EDT THURSDAY...BY 00Z MONDAY ALL MODELS ARE INDICATING
THAT DRY AIR WILL BE WELL ESTABLISHED AS THE AXIS OF THE UPPER
TROUGH WILL BE OVER OUR AREA AND MOVING EAST.  COOLER CANADIAN HIGH
PRESSURE WILL BE MOVING FROM THE MISSISSIPPI VALLEY SUNDAY EVENING
TO BE POSITIONED OVER WEST VIRGINIA BY AROUND 00Z TUESDAY. HIGH
PRESSURE WILL SLOWLY SLIDE OFF THE EAST COAST IN MID WEEK AS THE
NEXT COLD FRONT APPROACHES FROM THE NORTHWEST.  HPC HAS THE FRONT
OVER THE OHIO RIVER THURSDAY MORNING AS THAT POSITION MORE CLOSELY
FOLLOWS THE ECMWF WHICH HAS A MUCH MORE SHALLOW TROUGH CROSSING THE
GREAT LAKES AND HAS VERY LITTLE MOISTURE.  THE GFS IS MUCH SLOWER
WITH A SHARPER UPPER TROUGH AND DEEPER MOISTURE.  THEREFORE...ONLY
INCREASING THE CLOUDS A BIT OVER THE MOUNTAINS AT THE END OF THE
CURRENT FORECAST WHICH AT THIS POINT IS THURSDAY NIGHT.

TEMPERATURES WILL BE A FEW DEGREES BELOW NORMAL DURING THE FIRST
HALF OF THE WEEK AND WARMING TO JUST BELOW NORMAL BY THURSDAY.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
AT KCLT...SCT SHRA ARE BEGINNING TO DEVELOP OVER THE UPSTATE AND WRN
NC PIEDMONT ALONG A LINE FROM ABOUT 20 MILES NW OF THE AIRFIELD TO
40 MILES TO IT/S SOUTHWEST. WITH AN UNSTABLE ATMOSPHERE AND A WELL
DEFINED UPPER TROUGH APPROACHING...THE SHRA SHOULD GROW INTO TSTMS
AND MOVE INTO THE VCNTY OF THE AIRFIELD BY 19 UTC. THE CONVECTION
SHOULD LAST 3 TO 4 HOURS BEFORE MOVING EAST OF THE REGION BY 22-23
UTC. WINDS WILL BE OUT OF THE SW THIS AFTN AND WILL BE LIGHT
OVERNIGHT. AREAS OF MVFR FOG ARE LIKELY LATER TONIGHT. IN
FACT...DENSE FOG IS A GOOD BET IN PARTS OF THE WESTERN
PIEDMONT...BUT THIS WON/T BE INCLUDED AT KCLT AS THE AIRFIELD
TYPICALLY IS ONE OF THE LAST PLACES TO FOG UP.

ELSEWHERE...SCT SHRA WERE BEGINNING TO DEVELOP ACROSS THE REGION AT
ISSUANCE TIME. COVERAGE AND INTENSITY SHOULD INCREASE OVER THE NEXT
COUPLE HOURS AS AN UPPER LEVEL TROUGH CROSSES THE REGION.
HOWEVER...THE CONVECTION WILL BE SCT ENOUGH THAT ONLY VCTS WILL BE
CARRIED AT THE UPSTATE AND FOOTHILL TAF SITES. OF COURSE TEMPO OR
PREVAILING WILL BE ADDED TO ANY SITES THAT LOOK TO BE IMMEDIATELY
THREATENED. ONCE THE TROUGH PASSES...THERE SHOULD BE LESS MID AND
HIGH LEVEL CLOUDS OVERNIGHT. THIS WILL FAVOR THE DEVELOPMENT OF
DENSE VALLEY FOG IN THE NC MTNS...AS WELL AS SOME OF THE NON-MTN
RIVER VALLEYS. LIFR FOG HAS BEEN CARRIED AT KAND AND KHKY WITH
PREVAILING VLIFR AT KAVL.

OUTLOOK...BRIEF DRYING FROM THE WEST IS EXPECTED INTO FRIDAY. A COLD
FRONT WILL APPROACH THE REGION FROM THE NORTHWEST ON SATURDAY AND
MOVE EAST OF THE AREA ON SUNDAY. A LINE OF THUNDERSTORMS IS POSSIBLE
WITH THE FRONT ON SATURDAY. DRY AUTUMNAL HIGH PRES WILL DOMINATE THE
AREA EARLY NEXT WEEK.

AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE
PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE
CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)...

WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM

&&

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

&&

SYNOPSIS...DEO
NEAR TERM...MCAVOY/SBK
SHORT TERM...JW
LONG TERM...DEO
AVIATION...MCAVOY

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
239 PM EDT THU SEP 6 2012

GAZ010-017-018-026-028-029-NCZ035>037-056-057-068>072-082-501>510-
SCZ001>014-019-071845-
RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-ALEXANDER-IREDELL-
DAVIE-CATAWBA-ROWAN-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-
239 PM EDT THU SEP 6 2012

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

SCATTERED THUNDERSTORMS WILL AFFECT MUCH OF THE PIEDMONT AND
FOOTHILLS OF THE WESTERN CAROLINAS AND NORTHEAST GEORGIA INTO THE
EARLY EVENING HOURS. THE MAIN THREAT FROM THUNDERSTORMS THE REST
OF THE DAY WILL BE LOCALLY HEAVY RAIN AND FREQUENT CLOUD TO GROUND
LIGHTNING. HIGHLY LOCALIZED URBAN FLOODING IS POSSIBLE IF THE
STORMS REPEATEDLY AFFECT THE SAME LOCATION.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

NONE.

NCZ033-048>053-058-059-062>065-071845-
AVERY-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-GRAHAM-
NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-HENDERSON-
239 PM EDT THU SEP 6 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN NORTH CAROLINA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

NONE.

MCAVOY

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
524 PM EDT THU SEP 6 2012

SCZ007-008-062215-
CHEROKEE-SPARTANBURG-
524 PM EDT THU SEP 6 2012

...STRONG THUNDERSTORMS WILL AFFECT CHEROKEE AND NORTHERN SPARTANBURG
COUNTIES THROUGH 615 PM EDT...

AT 519 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 4 MILES WEST OF
BLACKSBURG TO FINGERVILLE...MOVING SOUTH AT 10 MPH.

THESE STORMS WILL IMPACT LOCATIONS NEAR...
  LAKE BOWEN...
  BLACKSBURG...
  MAYO...
  GAFFNEY...
  BOILING SPRINGS SC...
  COWPENS...

SMALL HAIL...WIND GUSTS OF 40 TO 50 MPH AND TORRENTIAL RAIN ARE
EXPECTED WITH THESE STORMS.

LAT...LON 3519 8217 3517 8151 3517 8149 3505 8144
      3503 8149 3498 8148 3494 8149 3493 8148
      3493 8205

07