Severe Thunderstorm Warning 284, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
248 PM EDT SAT AUG 23 2014

.SYNOPSIS...
A BACK DOOR COLD FRONT WILL PUSH INTO THE AREA FROM THE NORTHEAST
THIS EVENING AND TONIGHT...USHERING IN COOLER TEMPERATURES STARTING
SUNDAY. DRY AND COOLER CONDITIONS WILL CONTINUE THROUGH MID NEXT
WEEK AS A WEDGE OF SURFACE HIGH PERSISTS ACROSS THE REGION.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 245 PM EDT...DEEP LAYER NW FLOW PERSISTS THIS AFTN BETWEEN A
STRONG HIGH PRES RIDGE OVER THE CENTRAL CONUS AND LOW PRESSURE
OFFSHORE OF NEW ENGLAND. AN MCV SLIDING SWD EAST OF THE RIDGE IS
PASSING THROUGH ERN TN THIS AFTN AND MAY JUST BRUSH THE EXTREME SRN
APPALACHIANS THROUGH LATE AFTN. MOST OF THE FORCING THROUGH THE
EVENING HOURS SHOULD FOCUS ALONG THE APPROACHING BACKDOOR COLD FRONT
WHERE LOW LEVEL CONVERGENCE WILL BE STRONGEST. ALTHOUGH COVERAGE MAY
END UP BEING A BIT BETTER ALONG THE IMMEDIATE FRONTAL ZONE...850 TO
500 MB LAPSE RATES WILL BE GREATEST OVER THE UPPER SAVANNAH RIVER
REGION LATE THIS AFTN AND THIS EVENING...AND THAT IS WHERE
CONVECTION MIGHT BECOME STRONGEST. THE SFC FRONT WILL CONTINUE TO
WORK THROUGH THE REGION FROM NE TO SW OVERNIGHT. BEHIND THE
BOUNDARY...EASTERLY UPSLOPE FLOW SHOULD TRIGGER CONVECTION IN SW VA
WHICH WILL THEN LIKELY SLIDE SWD ALONG THE ERN ESCARPMENT OF THE
MOUNTAINS OVERNIGHT INTO SUNDAY MORNING. THAT IS WHERE THE GREATEST
POTENTIAL FOR LOCALLY HEAVY RAINFALL WILL BE...BUT HEAVY RAIN AND
LOCALIZED HYDRO PROBLEMS COULD DEVELOP IN ANY LOCATIONS EXPERIENCING
TRAINING. EXPECT VERY WARM MINS GIVEN THAT ALL THE THICKNESS FALLS
ARE WELL NE OF THE FRONT AND WILL TAKE UNTIL SUNDAY TO ARRIVE...AND
LOW CLOUDS WILL FILL IN BEHIND THE FRONT TO KEEP TEMPS WARM.

THE DEEP AND STRONG RIDGE AXIS STRETCHING FROM THE MOUTH OF THE MS
RIVER TO THE GREAT LAKES WILL THEN BUILD EWD TOWARD THE APPALACHIANS
THROUGH SUNDAY. AT THE SFC...HIGH PRES WILL STEADILY NOSE INTO THE
REGION AS THE FRONTAL BOUNDARY SETTLES JUST SW OF THE AREA. DEEP
MOIST EASTERLY FLOW WILL KEEP CONSIDERABLE CLOUDS ACROSS THE REGION
ON SUNDAY AND SPAWN AT LEAST SCATTERED SHOWER COVERAGE. WEAK
THUNDERSTORMS WILL BE POSSIBLE AS WELL NEAR THE ESCARPMENT AND IN
ELEVATED INSTABILITY IN SW SECTIONS. IN ADDITION...THE DEEPER
MOISTURE POOL WILL GET SHUNTED TOWARD SRN SECTIONS OF THE FORECAST
AREA BY LATE SUNDAY TO PUSH THE GREATER HEAVY RAINFALL THREAT THERE.
MAXES SHOULD RUN AT LEAST ONE TO TWO CATEGORIES BELOW CLIMO.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 230 PM SATURDAY...THE BACK DOOR COLD FRONT WILL CONTINUE TO
EDGE FURTHER WEST...OUT OF OUR FORECAST AREA (FA) SUNDAY NIGHT. WE
GO WITH THE IDEA THAT THE PERSISTENT CLOUD COVER...FROM 1000-850 MB
MOISTURE...WILL ONLY THIN SLIGHTLY IN OUR EASTER SECTIONS LATE
SUNDAY NIGHT. THIS IS SHOWN NICELY ON THE PLAN VIEW OF MOST SHORT
TERM MODEL GUIDE AND BUFKIT DATA. MEANWHILE...SCATTERED SHOWERS WILL
HOLD INTO THE EVENING OVER PARTS OF OUR WESTERN FA...WHILE ELEVATED
INSTABILITY COULD STILL YIELD A RUMBLE OF THUNDER.

A CONTINUED SLOW EROSION OF THE LOWER CLOUDS SHOULD BE NOTED FROM
THE EAST ON MONDAY... ALTHOUGH ENOUGH MOISTURE IN THE SOUTHWEST
PORTION OF THE NC MOUNTAINS COULD YIELD A STRAY SHOWER OR
THUNDERSTORM FROM MIDDAY ON MONDAY INTO THE VERY EARLY EVENING.

THIS ALL STEMS FROM THE RE-ALIGNMENT OF THE UPPER TROF OFF THE EAST
COAST...WHICH WILL BE MOVING SLOWLY EAST...AND THE TEMPORARY
RETROGRESSION OF THE UPPER HIGH PRESSURE SYSTEM BACK TO THE
MISSISSIPPI VALLEY.

HOWEVER...ONCE THE TROF TO THE EAST EASES FURTHER OUT INTO THE
ATLANTIC...THE UPPER LEVEL RIDGE OF HIGH PRESSURE WILL BUILD BACK
TOWARD OUR FA MONDAY NIGHT AND TUESDAY. THEREFORE...WE HAVE A DRY
FORECAST IN THE CARDS DURING THOSE PERIODS WITH OVERALL SUBSIDENCE
SETTLING IN.

IN THE TEMPERATURE DEPARTMENT...WE HAVE READINGS SLIGHTLY HIGHER ON
TUESDAY COMPARED TO MONDAY...WITH LESS CLOUDINESS. HOWEVER NOT EVEN
CLOSE TO THOSE VALUES WE HAVE RECENTLY EXPERIENCED.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 230 PM EDT SATURDAY...TUESDAY NIGHT AND WEDNESDAY...THE LATEST
GLOBAL MODELS CONTINUE TO INDICATE THAT A COOL AIR WEDGE OF SURFACE
HIGH WILL PERSIST UNDERNEATH AN UPPER RIDGE OF H5 HIGH. THIS WILL
YIELD DRY CONDITIONS WITH SLIGHTLY BELOW NORMAL TEMPS. THURSDAY THRU
SATURDAY...THE UPPER RIDGING WILL BEGIN TO WEAKEN BY LATE THUR AS AN
UPPER TROUGH APPROACHES FROM THE CENTRAL STATES. THE NEW 12Z GFS IS
ABOUT 24HRS FASTER THAN THE OLD ECMWF BRINGING THE TROUGH AND AN
ASSOCIATED COLD FRONT TO OUR FORECAST AREA LATE FRI/EARLY SAT WHILE
THE ECMWF KEEPS STRONGER UPPER RIDGING UNTIL IT WEAKENS BY SAT
NIGHT. MEANWHILE...BOTH MODELS SUGGEST THAT A TROPICAL LOW OVER THE
BAHAMAS WILL TRACK N/NNW TOWARD OFF THE SE COASTS THROUGH THUR/FRI
BUT THEN PULLS NE AWAY BY FRI IN RESPONSE TO AN APPROACHING TROUGH.
IT APPEARS THAT THIS TROPICAL FEATURE WILL NOT DIRECTLY AFFECT OUR
WEATHER AT THIS TIME THOUGH THERE IS STILL SOME DEGREE OF
UNCERTAINTY IN REGARDS TO THE TRACK. USING MODEL BLEND
SOLUTIONS...HAVE MENTIONED SLIGHT CHANCE TO LOW END CHANCE POPS THU
THRU SAT. TEMPERATURES WILL START OUT 2-5 DEGREES BELOW NORMAL
WED...WITH A GRADUAL MODERATING TREND EXPECTED THRU DAY 7.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
AT KCLT...CONVECTIVE COVERAGE SHOULD FILL IN ALONG THE APPROACHING
BACK DOOR COLD FRONT THROUGH THE EVENING HOURS. THIS IS CURRENTLY
HANDLED WITH TEMPO TSRA 22Z TO 02Z...BUT NEARBY SHOWERS AND ISOLD
TSRA COULD BE AN ISSUE IN THE DEEP MOISTURE THROUGH MUCH OF THE
NIGHT. NE WINDS WILL PICK UP WITH FROPA AND A LOWER CLOUD DECK WILL
ARRIVE FROM THE NE BY 08Z. THE GUIDANCE IS SPLIT...BUT THERE IS A
TREND TOWARD IFR ON BOTH THE MAV AND MET WHILE THE LAMP REMAINS
MVFR. HAVE LOWERED THE MVFR CIGS FORECAST FOR THE OVERNIGHT
HOURS...BUT IFR REMAINS A POSSIBILITY. EXPECT ONLY SLOW RECOVERY
THROUGH MVFR SUNDAY MORNING WITH SHOWERS REMAINING IN THE
VICINITY...ALONG WITH PERSISTENT NE FLOW.

ELSEWHERE...CONVECTION IS FILLING IN MAINLY IN THE MOST UNSTABLE
AREAS OF THE SRN ESCARPMENT...AND STEERING FLOW MAY TAKE THESE CELLS
TOWARD THE UPSTATE TAF SITES THROUGH 20Z. A VCTS IS CURRENTLY
FEATURED...BUT A TEMPO TSRA COULD BE ADDED THERE IN THE NEAR FUTURE.
OTHERWISE...COVERAGE IS EXPECTED TO EXPAND ALONG THE APPROACHING
BACK DOOR COLD FRONT. THIS SHOULD YIELD THE BEST THUNDER CHANCES
THROUGHOUT DURING THE EVENING HOURS. EXPECT VFR CIGS THIS EVENING TO
GIVE WAY TO LOWER MVFR CIGS OVERNIGHT WITH FROPA FROM NE TO
SW...WITH IFR LIKELY AT KHKY BEFORE DAYBREAK. KHKY TO KAVL MAY SEE
THE BEST CHANCE OF CONTINUED SHOWERS IN EASTERLY UPSLOPE THROUGH
SUNDAY MORNING. CIGS WILL BE VERY SLOW TO RECOVER THROUGH SUNDAY
MORNING WITH THE PERSISTENT MOIST EASTERLY FLOW...WITH NOTHING
HIGHER THAN MVFR TO LOWER END VFR BY 18Z THROUGHOUT.

OUTLOOK...DRYING ON CONTINUED NE FLOW IS EXPECTED MONDAY THROUGH
TUESDAY. DIURNAL THUNDERSTORMS MAY RETURN TO THE MTNS MID WEEK.
MORNING LOW CLOUDS AND FOG WILL BE POSSIBLE...ESPECIALLY IN THE MTN
VALLEYS.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH  94%     HIGH  94%     HIGH  98%
KGSP       HIGH 100%     HIGH 100%     HIGH  87%     HIGH 100%
KAVL       HIGH 100%     HIGH  95%     HIGH  81%     HIGH  87%
KHKY       HIGH 100%     HIGH  90%     HIGH  84%     HIGH  89%
KGMU       HIGH 100%     HIGH 100%     HIGH  91%     HIGH  95%
KAND       HIGH 100%     HIGH 100%     HIGH  97%     HIGH  92%

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...JOH
NEAR TERM...HG
SHORT TERM...TS
LONG TERM...JOH
AVIATION...HG

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
639 AM EDT SAT AUG 23 2014

GAZ010-017-018-026-028-029-NCZ033-035>037-049-050-053-056-057-
062>065-068>072-082-501>510-SCZ001>014-019-241045-
RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-AVERY-ALEXANDER-
IREDELL-DAVIE-YANCEY-MITCHELL-BUNCOMBE-CATAWBA-ROWAN-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-
639 AM EDT SAT AUG 23 2014

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

.DAY ONE...TODAY AND TONIGHT.

SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THE WESTERN CAROLINAS
AND NORTHEAST GEORGIA THIS AFTERNOON AND WILL LINGER INTO TONIGHT.
COVERAGE IS EXPECTED TO BE THE GREATEST ACROSS THE NORTH CAROLINA
FOOTHILLS AND PIEDMONT AS A BACKDOOR COLD FRONT ARRIVES THIS
EVENING. THESE STORMS WILL PRODUCE FREQUENT CLOUD TO GROUND
LIGHTNING WITH HEAVY DOWNPOURS. A FEW STORMS COULD PRODUCE
DAMAGING WINDS OR LARGE HAIL. ISOLATED FLASH FLOODING MAY OCCUR
ACROSS URBAN AREAS AND AREAS NEAR THE ESCARPMENT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

..SUNDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..MONDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..TUESDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..WEDNESDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..THURSDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..FRIDAY...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.

NCZ048-051-052-058-059-241045-
MADISON-SWAIN-HAYWOOD-GRAHAM-NORTHERN JACKSON-
639 AM EDT SAT AUG 23 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN NORTH CAROLINA.

.DAY ONE...TODAY AND TONIGHT.

SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THE WESTERN NORTH
CAROLINA MOUNTAINS THIS AFTERNOON AND WILL LINGER INTO TONIGHT.
THESE STORMS WILL PRODUCE FREQUENT CLOUD TO GROUND LIGHTNING WITH
HEAVY DOWNPOURS. A FEW STORMS COULD PRODUCE DAMAGING WINDS OR
LARGE HAIL.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

..SUNDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..MONDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..TUESDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..WEDNESDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..THURSDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..FRIDAY...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.

NED

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
212 PM EDT SAT AUG 23 2014

NCZ064-SCZ001-002-005-231900-
GREATER PICKENS-OCONEE MOUNTAINS-PICKENS MOUNTAINS-TRANSYLVANIA-
212 PM EDT SAT AUG 23 2014

...A STRONG THUNDERSTORM WILL AFFECT NORTHWESTERN PICKENS...
NORTHEASTERN OCONEE AND SOUTHWESTERN TRANSYLVANIA COUNTIES THROUGH
300 PM EDT...

AT 211 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR LAKE JOCASSEE...OR 17 MILES NORTHWEST OF
PICKENS...MOVING SOUTH AT 10 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  LAKE JOCASSEE...
  DEVILS FORK STATE PARK...
  KEOWEE TOXAWAY STATE PARK...
  SALEM...

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

LAT...LON 3503 8301 3505 8305 3507 8305 3510 8302
      3513 8286 3482 8273 3479 8289 3481 8290
      3478 8294 3476 8302 3502 8307

HG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
220 PM EDT SAT AUG 23 2014

SCZ001-004-231900-
GREATER OCONEE-OCONEE MOUNTAINS-
220 PM EDT SAT AUG 23 2014

...A STRONG THUNDERSTORM WILL AFFECT OCONEE COUNTY THROUGH 300 PM
EDT...

AT 220 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR WALHALLA...MOVING SOUTH AT 10 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  WESTMINSTER...

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

LAT...LON 3456 8312 3456 8314 3458 8316 3459 8315
      3459 8317 3461 8316 3461 8320 3484 8323
      3488 8301 3458 8289 3454 8311

HG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
256 PM EDT SAT AUG 23 2014

NCZ509-510-SCZ003-007-231945-
EASTERN POLK-GREENVILLE MOUNTAINS-POLK MOUNTAINS-SPARTANBURG-
256 PM EDT SAT AUG 23 2014

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN GREENVILLE...
SOUTHWESTERN POLK AND NORTHWESTERN SPARTANBURG COUNTIES THROUGH 345
PM EDT...

AT 253 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR COLUMBUS...MOVING SOUTH AT 15 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  TRYON...
  LANDRUM...

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

PLEASE REPORT DAMAGING WINDS...HAIL...OR FLOODING TO THE NATIONAL
WEATHER SERVICE GREENVILLE SPARTANBURG BY CALLING TOLL FREE...1...
800...2 6 7...8 1 0 1...OR BY POSTING ON OUR FACEBOOK PAGE...OR TWEET
IT USING HASHTAG NWSGSP. YOUR MESSAGE SHOULD DESCRIBE THE EVENT AND
SPECIFIC LOCATION WHERE IT OCCURRED.

LAT...LON 3506 8205 3506 8222 3506 8223 3506 8236
      3530 8234 3531 8231 3533 8211

CDG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
305 PM EDT SAT AUG 23 2014

SCZ006-231945-
GREATER GREENVILLE-
305 PM EDT SAT AUG 23 2014

...A STRONG THUNDERSTORM WILL AFFECT CENTRAL GREENVILLE COUNTY
THROUGH 345 PM EDT...

AT 303 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR CHERRYDALE POINT...OR NEAR DOWNTOWN
GREENVILLE...MOVING SOUTH AT 15 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  HAYWOOD MALL...
  I-85 AT PELHAM ROAD...
  SHOPS AT GREENRIDGE...
  I-85 AT AUGUSTA RD...
  DONALDSON CENTER...
  SIMPSONVILLE...

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

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 3475 8246 3477 8245 3483 8249 3486 8248
      3490 8250 3497 8250 3500 8228 3491 8222
      3486 8223 3478 8215 3474 8217 3468 8246

CDG