Special Weather Statement, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
306 AM EDT TUE AUG 7 2012

.SYNOPSIS...
A STATIONARY FRONT WILL LINGER ACROSS THE REGION TODAY...THEN SLOWLY
DISSIPATE TONIGHT. A COLD FRONT WILL PUSH ACROSS THE AREA FROM THE
WEST TOWARD THE END OF THE WEEK. THEN HIGH PRESSURE WILL BUILD IN
BEHIND THE FRONT THIS WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 215 AM EDT TUESDAY...SHOWER ACTIVITY HAD BEEN WANING UNTIL A
COUPLE HOURS AGO WHEN MORE SHOWERS BEGAN TO SPROUT UP ALONG THE
ESCARPMENT AND OVER THE NC PIEDMONT. A COUPLE OF CLOUD TO GROUND
LIGHTNING STRIKES HAVE BEEN OBSERVED IN THE PAST FEW MINUTES WITHIN
THE TALLER CELLS...BUT OTHERWISE MOST LOCATIONS ARE JUST GETTING
LIGHT RAIN. IN LIGHT OF THE SHOWERS...I INCREASED POPS TO LIKELY
ALONG THE I-85 CORRIDOR WITH THUNDER CHANCES GOING UP AFTER ABOUT
14Z ONCE WE GET MORE UNSTABLE. OTHERWISE...TODAY WILL CLOUDY AND WET
WITH THE SFC FRONTAL BNDY REMAINING NEAR STATIONARY OVER THE REGION
AND MORE WEAK...S TO SWLY LOW LVL FLOW PERSISTING OVER THE CWFA. AS
WE MOVE INTO TONIGHT AND THE OVERNIGHT...THE MODELS INDICATE SOME
DEGREE OF DRYING FROM THE NW TO THE SE AS A CANADIAN SFC HIGH BEGINS
TO SPREAD DRIER AIR INTO THE REGION. THE NAM IS ABOUT 6 HRS FASTER
WITH THIS DRYING COMPARED TO THE OTHER MODELS...WITH THE NORTHERN
HALF OF THE CWFA DRY BY 00Z WED. THINK THIS IS TOO FAST SO I KEEP
HIGHER POPS THRU 6Z OR SO AND THEN TAPER THEM BACK TO SOLID/SLIGHT
CHANCE AFTER 6Z. MAIN CONCERN TODAY/TONIGHT WILL BE ONGOING FLOODING
THREAT...HOWEVER LATEST QPF GUIDANCE IS NOT APPROACHING FFG FOR OUR
AREA. STILL...SOME ISOLATED FLOODING IS CERTAINLY NOT OUT OF THE
QUESTION IF TRAINING OCCURS. WITH THE AMPLE CLOUD COVER TODAY...HIGH
TEMPS SHOULD STAY ABOUT 4 TO 6 DEGREES BELOW NORMAL FOR EARLY AUGUST
AND MIN TEMPS A FEW DEGREES ABOVE NORMAL.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
AS OF 215 AM TUESDAY...SHORTWAVE TROF SHUD SHIFT EAST ON
WEDNESDAY...TAKING THE DEEPER RH WITH IT. THE LLVLS WILL REMAIN
MOIST...AND FCST SNDGS SHOW MORE INSTBY WITH MID LVL DRY AIR AND
WARMER BL. SO SCATTERED SHWRS AND TSTMS ARE EXPECTED ACRS THE
AREA...AND A SHOTGUN 40-50 POP LOOKS GOOD. SEVERE THREAT LOOKS TO
RETURN TO MORE TYPICAL LEVELS FOR THIS TIME OF YEAR
(PULSE/MICROBURST VARIETY). THURSDAY LOOKS SIMILAR TO
WEDNESDAY...EXCEPT PERHAPS A LITTLE MORE DRYING OF THE LLVLS. A
MODEL BLEND BRINGS POPS DOWN TO CLIMO NORMALS (30-40 MTNS AND 20-30
PIEDMONT). SEVERE POTENTIAL ALSO SHUD BE SIMILAR TO WEDNESDAY. TEMPS
SHUD BE NEAR NORMAL BOTH DAYS.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 245 AM TUESDAY...GUIDANCE STILL IN GOOD AGREEMENT ON DIGGING A
DEEP UPR TROF OVER THE GREAT LAKES/OH VLY ON FRIDAY...PUSHING A COLD
FRONT THRU THE REGION. NO CHANGES WERE MADE TO THE MEDIUM RANGE WITH
THIS PACKAGE.

PREVIOUS DISCUSSION...
AS OF 155 PM MONDAY...THE GLOBAL MODELS ARE IN VERY GOOD AGREEMENT
IN PUSHING A COLD FRONT ASSOCIATED WITH AFOREMENTIONED STORM SYSTEM
ACROSS THE AREA FRIDAY/FRIDAY NIGHT. DESPITE THE PRESENCE OF VERY
MOIST PROFILES...THERE MAY BE ENOUGH DEEP LAYER SHEAR AND
INSTABILITY TO SUPPORT AN ORGANIZED SEVERE WEATHER THREAT ON FRIDAY.

BY EARLY SATURDAY...THE GFS AND ECMWF ARE SIMILAR IN STALLING THE
FRONTAL BOUNDARY JUST SOUTH AND EAST OF THE AREA...WITH MUCH DRIER
AIR SWEEPING INTO THE REGION IN THE WAKE OF STRONG UPPER TROUGH. WE
HAVE OPTED TO LINGER SOME TOKEN SLIGHT CHANCE POPS ACROSS MOST OF
THE AREA (LOW CHANCE IN THE SOUTHEAST ZONES) UNTIL CONFIDENCE
INCREASES IN THE POSITION OF THE FRONTAL ZONE FOR THE WEEKEND.
(ALTHOUGH A PERFECT PROG OF BOTH THE GFS AND ECMWF WOULD SUGGEST A
DRY AND ACTUALLY RATHER PLEASANT MID-AUGUST WEEKEND).

BY MONDAY...WITH THE UPPER TROUGH PROGRESSING QUICKLY EAST OF THE
AREA...AND ADDITIONAL HEIGHT FALLS OCCURRING TO OUR WEST...THE
MEDIUM RANGE MODELS SUGGEST QUICK MODIFICATION OF THE CONTINENTAL
AIR MASS OVER THE AREA WILL OCCUR. INSTABILITY MAY BE HIGH ENOUGH
MONDAY AFTERNOON TO ALLOW A RETURN OF TYPICAL DIURNAL CONVECTION...
SO CHANCE POPS HAVE BEEN INTRODUCED FORN DAY 7. TEMPERATURES SHOULD
GENERALLY HOVER AROUND CLIMO THROUGH THE PERIOD.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
AT KCLT...SOME LIGHT RAIN SHOWERS WILL LIKELY PERSIST OVER THE
AIRFIELD FOR THE NEXT FEW HOURS WITH MORE SHOWERS EXPECTED LATER
THIS MORNING. WITH THE VERY MOIST ATMOSPHERE REMAINING IN PLACE THRU
THE TAF PERIOD WE CAN EXPECT MORE SH AND THUNDERSTORMS TODAY AND
TONIGHT AS THE SFC FRONT REMAINS STALLED OVER THE AREA. I DROP THE
VISBY AND CIGS TO MVFR AT 10Z WITH VCSH AND THEN MAINTAIN MVFR CIGS
THRU THE AFTERNOON WITH PREVAILING -SHRA AND A PROB30 FOR TSRA WITH
IFR VISBY AT 2SM BETWEEN 21 AND 24Z AND ANOTHER PROB30 GROUP FROM
0100 TO 0400Z ON THE 8TH. WINDS WILL BE FAIRLY LIGHT AND WILL LIKELY
BOUNCE AROUND SOME THRU THE PERIOD...BUT THEY SHOULD BE MOSTLY FROM
THE SOUTH TO SWLY.

ELSEWHERE...SIMILAR TO KCLT WITH CIGS ALREADY DOWN BELOW VFR FOR
ALL THE SITES EXCEPT KGMU WHICH I EXPECT TO GO DOWN DURING THE NEXT
HOUR OR SO. ALL SITES WILL LIKELY SEE REDUCED VISBY BY 9Z OR SO AS
THE TEMP FALLS A FEW MORE DEGREES AND THEY REACH SATURATION AND I
EXPECT VISBY TO REBOUND BACK TO VFR BY 14 OR 15Z. SHOWERS AND
THUNDERSTORMS WILL AFFECT THE TAF SITES AGAIN TODAY/TONIGHT AS THE
UPPER SHORTWAVE SLOWLY CROSSES OVERHEAD AND THE SFC BOUNDARY REMAINS
STALLED OVER THE REGION. I THINK LOW TO MID LVLS WILL BEGIN TO DRY
OUT SOME FROM THE NW AFTER ROUGHLY 6Z TOMORROW WITH THE NAM12
ACTUALLY DRYING ABOUT 4 TO 6HRS FASTER THAN THE OTHER MODELS.

OUTLOOK...DEEP MOISTURE WILL REMAIN IN PLACE ACROSS THE REGION
THROUGH EARLY WED...WITH SOLID COVERAGE OF SHRA/TSRA AND ASSOCIATED
RESTRICTIONS. WEAK DRYING IS POSSIBLE WED/EARLY THU...BUT THEN
MOISTURE POOLS AGAIN AHEAD OF AN APPROACHING COLD THROUGH FRI.
EXPECT UNSETTLED WEATHER AND CONTINUOUSLY CHANGING FLIGHT CONDITIONS
FOR THE REMAINDER OF THE 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...ARK
NEAR TERM...JPT
SHORT TERM...ARK
LONG TERM...ARK/JDL
AVIATION...JPT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
417 PM EDT MON AUG 6 2012

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-072030-
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-
417 PM EDT MON AUG 6 2012

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

.DAY ONE...TONIGHT.

NUMEROUS SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP ACROSS
THE REGION THROUGH TONIGHT. THESE THUNDERSTORMS WILL PRODUCE
LOCALLY HEAVY RAINFALL. ISOLATED FLASH FLOODING COULD RESULT WHERE
THUNDERSTORMS REPEATEDLY AFFECT THE SAME LOCATION. IN ADDITION...
CLOUD TO GROUND LIGHTNING STRIKES AND BRIEF GUSTY WINDS MAY
ACCOMPANY SOME OF THE STORMS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

A STATIONARY FRONT WILL LINGER ACROSS THE AREA THROUGH WEDNESDAY
AS A WEAK TROPICAL LOW OVER THE GULF STATES LIFTS ABUNDANT
MOISTURE INTO THE REGION. NUMEROUS SHOWERS AND THUNDERSTORMS WILL
DEVELOP AGAIN ON TUESDAY. VERY HEAVY RAIN WILL ACCOMPANY SOME OF
THE SHOWERS AND STORMS...AND A FEW LOCATIONS MAY SEE ENOUGH
RAINFALL FOR LOCALIZED FLASH FLOODING TO DEVELOP.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTERS ARE REQUESTED TO FORWARD ANY REPORTS OF DAMAGING
WINDS OR FLASH FLOODING TO OUR OFFICE.

LANE

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
401 AM EDT TUE AUG 7 2012

SCZ001-002-004>006-010-070900-
ANDERSON-GREATER GREENVILLE-GREATER OCONEE-GREATER PICKENS-OCONEE
MOUNTAINS-PICKENS MOUNTAINS-
401 AM EDT TUE AUG 7 2012

...STRONG THUNDERSTORMS WILL AFFECT CENTRAL GREENVILLE...EASTERN
OCONEE...NORTHERN ANDERSON AND PICKENS COUNTIES THROUGH 500 AM EDT...

AT 357 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
SHOWERS AND THUNDERSTORMS PRODUCING VERY HEAVY RAIN ALONG A LINE
EXTENDING FROM 3 MILES NORTHEAST OF LAKE KEOWEE TO PIEDMONT...MOVING
NORTHEAST AT 15 MPH.

THESE STORMS WILL IMPACT LOCATIONS NEAR...
  NINE TIMES...
  PICKENS...
  WHITE HORSE ROAD AT I-85...
  ROCKY BOTTOM...
  HAYWOOD MALL...

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 3469 8316 3506 8287 3508 8284 3499 8254
      3498 8254 3498 8251 3490 8225 3453 8258

ARK