Special Weather Statement, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
803 PM EDT FRI AUG 3 2012

.SYNOPSIS...
CIRCULATION AROUND HIGH PRESSURE CENTERED OVER THE WESTERN ATLANTIC
WILL KEEP THE SOUTHERN APPALACHIAN REGION WARM AND HUMID THROUGH THE
WEEKEND. A COLD FRONT IS EXPECTED TO SLOWLY SWEEP ACROSS THE WESTERN
CAROLINAS AND NORTHEAST GEORGIA EARLY NEXT WEEK...POSSIBLY BECOMING
STATIONARY AND LINGERING INTO LATE IN THE WORK WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
0000 UTC UPDATE...POPS WERE LOWERED IN THE CENTRAL NC MOUNTAINS
WHERE A GAP ION COVERAGE HAS APPEARED. QPF WAS LOWERED IN THE SC
FOOTHILLS...AND RAISED IN THE CHARLOTTE AREA.

PREVIOUS DISCUSSION...CONVECTION HAS BEGUN TO DEVELOP OVER THE
SOUTHWEST AND CENTRAL NC MTNS. LAYER RH VALUES ARE THE HIGHEST IN
THIS PART OF THE FORECAST AREA...AND IT/S CLOSET TO THE APPROACHING
SHORTWAVE TROUGH WHICH CURRENTLY EXTENDS FROM CENTRAL KY TO ERN TN.
THE FEATURE ITSELF IS QUITE WEAK AND THE EFFECTIVE BULK SHEAR ACROSS
THE REGION IS WELL UNDER 20 KTS. THEREFORE DIFFERENTIAL HEATING AND
LLVL MASS CONVERGENCE SHOULD BE THE MAIN DRIVERS FOR CONVECTION THIS
EVENING. THE LATEST HI-RES NUMERICAL MODEL RUNS ARE MORE VARIED THAN
WHAT I SAW THIS MORNING. THE WRF-ARW AND THE HRRR BOTH DEVELOP
CONVECTION OVER PARTS OF THE FA...BUT IT/S NOT LOOKING AS ORGANIZED
AS EARLIER. THE 12 UTC 4KM SPC WRF ON THE OTHER HAND HAS A LARGE
AREA OF CONVECTION OVER THE WESTERN UPSTATE AND NE GA THIS EVENING.
THE 12 UTC NAM HAS STRONG LLVL CONVERGENCE THIS EVENING AND ALSO
DEVELOPS INTENSE SLOW MOVING CONVECTION OVER THE UPSTATE.
OVERALL...THE IDEA OF LIKELY POPS SLOWLY SPREADING FROM WEST TO EAST
ACROSS THE FA THE REST OF THE AFN AND EVENING STILL LOOKS GOOD.
DCAPE VALUES ARE WELL OVER 1000 J/KG ACROSS THE UPSTATE AND NE
GA...AND PULSE SEVERE STORMS ARE A GOOD BET AGAIN THIS EVENING.
PULSE SEVERE WON/T BE LIKELY OVER THE NC MTNS AND FOOTHILLS...BUT
EVEN THOUGH CURRENT DCAPE VALUES AREN/T THAT GREAT...I STILL SUSPECT
WE/LL SEE A FEW SEVERE STORMS ALONG THE I-77 URBAN CORRIDOR. VERY
HEAVY RAIN IS ALSO POSSIBLE IS SPOTS AND ISOLATED FLASH FLOODING IS
POSSIBLE. LATER TONIGHT WIDESPREAD LOW CLOUDS SHOULD DEVELOP ACROSS
MOST OF THE FA.

ON SATURDAY THE UPPER TROUGH WEAKENS QUICKLY AS THE ATLANTIC RIDGE
STARTS TO BUILD BACK INTO THE REGION. THE WEAKENING OF THE TROUGH IS
A LITTLE FASTER THAN WHAT WE/D BEEN EXPECTING. LAYER RH/S WILL
REMAIN HIGH AND EVEN WITH VERY WEAK FORCING...THERE SHOULD BE PLENTY
OF CONVECTION OVER THE HIGH TERRAIN AND A LITTLE LESS OUT ACROSS THE
FOOTHILLS AND PIEDMONT. THE SEVERE AND FLOODING RISK DON/T LOOK AS
GREAT TOMORROW. INTERESTINGLY...THE STRONGEST FORCING OF THE DAY
COULD COME IN THE FORM OF THE SEA-BREEZE FRONT WHICH THE NAM BRINGS
INTO THE SE ZONES EARLY IN THE EVENING.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 145 PM EDT...EXPECT SOME ONGOING SCATTERED CONVECTION SATURDAY
EVENING TO WANE RATHER QUICKLY AS SUBTROPICAL RIDGE BUILDS WESTWARD
INTO THE AREA SAT NIGHT. HENCE...THE SAT OVERNIGHT THROUGH SUNDAY
MORNING IS EXPECTED TO BE TRANQUIL. ON SUNDAY AFTERNOON...UPSLOPE
FLOW AND THE APPROACH OF A WEAK COLD FRONT FROM THE NW SHOULD
TRIGGER SCATTERED TO NUMEROUS SHOWERS/THUNDERSTORMS ACROSS THE
MOUNTAINS. ONLY ISOLATED TO WIDELY SCATTERED ACTIVITY IS EXPECTED
ELSEWHERE. THE MODELS BRING THE FRONTAL BOUNDARY INTO THE MOUNTAINS
SUNDAY NIGHT WHICH NECESSITATES MAINTAINING AT LEAST SCATTERED POPS
THERE. ON MONDAY...THE FRONT IS FORECAST TO LAY OUT ACROSS THE
WESTERN CAROLINAS INTO NE GA WHICH SHOULD BE A FOCAL POINT FOR
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS. MAXIMUM
TEMPERATURES ARE EXPECTED TO BE NEAR CLIMO WITH MIN TEMPERATURES
ABOUT A CATEGORY ABOVE AVERAGE.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 1 PM EDT FRIDAY...THE MEDIUM RANGE IS EXPECTED TO FEATURE
SOME DEGREE OF BROAD UPPER TROFFING OVER THE EASTERN U.S. WITH
PERHAPS SOME AMPLIFICATION IN THE TROUGH TOWARD THE END OF THE
PERIOD. THE PERSISTENT TROUGH AND THE PRESENCE OF THE FRONT WILL
CONTINUE TO TRIGGER SHOWERS AND THUNDERSTORMS THROUGH TUE...WITH AN
UPTICK DURING THE FAVORED AFTERNOON AND EVENING TIME PERIOD. THERE
IS SOME DIVERGENCE IN THE GUIDANCE IN REGARD TO HOW FAR SOUTH THE
AFOREMENTIONED FRONT GOES. THE ECM CAMP TAKES THE FRONTAL BOUNDARY
JUST SOUTH OF THE AREA ON WED AND BRINGS SOMEWHAT DRYER INTO THE
REGION FOR WED INTO THU. THIS WOULD PRODUCE A DECREASE IN
SHOWER/THUNDERSTORM ACTIVITY FOR WED INTO THU. ON THE OTHER HAND...
THE GFS HANGS UP THE BOUNDARY OVER THE AREA THROUGH THE PERIOD WITH
A CONTINUATION OF ENHANCED SHOWER AND THUDNERSTORM ACTIVITY THROUGH
THE END OF THE WEEK. HPC SIDED WITH THE ECM FRONTAL POSITION. WE
GENERALLY STAYED CLOSE TO HPC GUIDANCE WITH HIGHER THAN CLIMO POPS
FOR TUE AND THEN SOMEWHAT LOWER THAN CLIMO...ESPECIALLY ACROSS THE
MOUNTAINS FOR WED. BASICALLY CLIMO POPS RETURN FOR THE END OF THE
WEEK. USED A BLEND OF HPC/GMOS FOR TEMPS WHICH ESSENTIALLY IS CLOSE
TO CLIMO.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...CONVECTIVE ACTIVITY IS EXPECTED TO CONTINUE NEAR THE FIELD
FOR SEVERAL HOURS THIS EVENING AS A MID LEVEL SYSTEM CROSSES THE
EAST COAST...POSSIBLY ACCOMPANIED BY MVFR CIG AND VSBY. OTHERWISE...
LOW VFR CIGS ARE EXPECTED UNTIL EARLY MORNING...WHEN GUIDANCE
SUGGEST IFR CIGS IN A MOIST BOUNDARY LAYER. GUIDANCE CIG HEIGHTS
WERE RAISED ABOUT 500 FEET FOR CONTINUITY WITH CIGS FROM THIS
MORNING...AS CONFIDENCE IS LIMITED IN THE LOW END IFR MODEL CIG.
THIS LEAVES KCLT WITH A LOW END MVFR CIG AROUND DAYBREAK. MODEL VSBY
WAS MVFR...BUT THE MODELS HAVE BEEN TOO LOW WITH VSBY...AND VFR WILL
BE CARRIED FOR NOW. CONVECTIVE CHANCES FOR SATURDAY AFTERNOON ARE
HIGH ENOUGH TO CARRY A PROB30. SOUTHERLY WINDS WILL PREVAIL.

ELSEWHERE...MOUNTAIN CONVECTION IS EXPECTED TO DEVELOP ACROSS THE
MOUNTAINS AND INTO THE FOOTHILLS THIS EVENING...AND MVFR CIG AND
VSBY RESTRICTIONS WILL BE POSSIBLE. AFTERWORDS...LOW VFR CIGS CAN BE
EXPECTED INTERMITTENTLY UNTIL SEVERAL HOURS BEFORE DAWN. AT THAT
POINT MODEL GUIDANCE IS QUITE DIRE WITH CIG HEIGHTS...BUT WITH LOW
CONFIDENCE IS SUCH LOW CIGS...A GENERAL IFR WILL BE CARRIED...EXCEPT
VFR AT KAND. GUIDANCE FAVORS MVFR VSBY EAST OF THE MOUNTAINS...AND
LIFR IN THE MOUNTAIN. BASED ON TRENDS FROM YESTERDAY AND LIMITED
CONFIDENCE...IFR WILL BE CARRIED IN THE MOUNTAINS...MVFR ALONG
INTERSTATE 40...AND VFR TO THE SOUTH. SATURDAY AFTERNOON CONVECTIVE
CHANCES WARRANT PROB30 AT ALL LOCATIONS. WINDS WILL GENERALLY BE
FROM THE S OR SE.

OUTLOOK...ISO/SCT AFTN-EVE TSTMS ACROSS THE AREA EACH DAY. MTN VLYS
WILL SEE BEST CHANCE OF MORNING LOW CLOUDS/FOG.

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...NED
NEAR TERM...JAT/MCAVOY
SHORT TERM...LG
LONG TERM...LG
AVIATION...JAT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
247 PM EDT FRI AUG 3 2012

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-041900-
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-
247 PM EDT FRI AUG 3 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.

NUMEROUS THUNDERSTORMS WILL DEVELOP ACROSS THE MOUNTAINS AND
FOOTHILLS THIS AFTERNOON AND SLOWLY MOVE EASTWARD INTO THE EVENING
HOURS. SOME OF THE STORMS ARE EXPECTED TO BECOME SEVERE WITH SMALL
AREAS OF DAMAGING WIND AND HAIL UP TO THE SIZE OF QUARTERS
POSSIBLE. THE BEST CHANCE FOR WIND DAMAGE WILL BE OVER THE
UPSTATE...NORTHEAST GEORGIA AND THE SOUTHERN PIEDMONT OF NORTH
CAROLINA.

THUNDERSTORMS THIS EVENING WILL ALSO BE SLOW MOVING...AND A FEW
LOCATIONS WILL SEE SEVERAL INCHES OF RAIN IN A SHORT PERIOD OF
TIME. ISOLATED FLASH FLOODING IS POSSIBLE...PARTICULARLY IF HEAVY
RAIN AFFECTS URBAN AREAS OR A LOCATION THAT HAS SEEN HEAVY RAIN
IN RECENT DAYS. IN ADDITION...NEARLY CONTINUOUS CLOUD TO GROUND
LIGHTING WILL ACCOMPANY THE STRONGER STORMS THIS EVENING.

.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 OR FLASH FLOODING TO OUR OFFICE.

MCAVOY

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
339 PM EDT FRI AUG 3 2012

NCZ048-052-053-032030-
BUNCOMBE-HAYWOOD-MADISON-
339 PM EDT FRI AUG 3 2012

...STRONG THUNDERSTORMS WILL AFFECT MADISON...NORTHEASTERN HAYWOOD
AND NORTHWESTERN BUNCOMBE COUNTIES THROUGH 430 PM EDT...

AT 336 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 3 MILES NORTHWEST OF
SPRING CREEK TO 3 MILES NORTH OF CANTON...MOVING NORTHEAST AT 15 MPH.

THESE STORMS WILL IMPACT LOCATIONS NEAR...
  HOT SPRINGS...
  LEICESTER...
  LEICESTER...
  MARSHALL...
  WEAVERVILLE...

SMALL HAIL...AND WIND GUSTS UP TO 40 MPH ARE EXPECTED WITH THESE
STORMS.

HEAVY RAINS MAY FLOOD AREAS WITH POOR DRAINAGE...SUCH AS DITCHES AND
UNDERPASSES. AVOID THESE AREAS AND DO NOT CROSS FLOODED ROADS. WATER
LEVELS OF SMALL STREAMS AND RIVERS MAY ALSO RISE RAPIDLY. SEEK HIGHER
GROUND IF THREATENED BY FLOOD WATERS.

LAT...LON 3604 8259 3597 8260 3597 8257 3570 8255
      3553 8294 3580 8297 3584 8292 3591 8291
      3594 8284 3593 8281 3596 8279 3605 8261

KRENTZ

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
857 PM EDT FRI AUG 3 2012

NCZ069>071-040145-
GASTON-LINCOLN-MECKLENBURG-
857 PM EDT FRI AUG 3 2012

...A STRONG THUNDERSTORM WILL AFFECT EASTERN LINCOLN...NORTHEASTERN
GASTON AND NORTHWESTERN MECKLENBURG COUNTIES THROUGH 945 PM EDT...

AT 854 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR STANLEY...OR 9 MILES NORTHEAST OF
GASTONIA...MOVING NORTH AT 5 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  MOUNTAIN ISLAND LAKE...
  IRON STATION...
  LOWESVILLE...

SMALL HAIL...AND WIND GUSTS UP TO 40 MPH ARE EXPECTED WITH THIS
STORM.

LAT...LON 3555 8113 3546 8084 3523 8099 3529 8120

KRENTZ