Severe Thunderstorm Warning 365, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
757 PM EDT THU AUG 20 2009

.SYNOPSIS...
AN UPPER LEVEL LOW PRESSURE SYSTEM AND ITS ASSOCIATED SURFACE COLD
FRONT WILL MOVE TOWARD THE REGION FROM THE NORTHWEST ON FRIDAY. THE
FRONT SHOULD MOVE THROUGH EARLY SATURDAY. GRADUAL DRYING IS THEN
EXPECTED SUNDAY THROUGH MONDAY AS WEAK HIGH PRESSURE BUILDS OVER THE
REGION. MOISTURE WILL SLOWLY RETURN THROUGH THE MIDDLE OF NEXT WEEK
UNDER THE RIDGE.

&&

.NEAR TERM /THROUGH FRIDAY/...
IMPULSES WITHIN THE DEEP AND MOIST SW FLOW WILL CONTINUE TO TRIGGER
DEEP CONVECTION INTO THIS EVENING. POCKETS OF MODERATE INSTABILITY
WILL SUPPORT A FEW STRONG STORMS...BUT HIGH FREEZING LVLS/WET BULB
ZERO HEIGHTS WILL LIMIT THE MAIN THREAT TO LOCALLY HEAVY RAIN AS
SNDGS INDICATE PWATS AROUND 2 INCHES. DEEP MOISTURE BAND LINGERS
INTO THE OVERNIGHT...ESPECIALLY ACRS THE WESTERN CWFA. BUT...
QUESTIONABLE AMOUNTS OF DEEP FORCING LEADS TO UNCERTAINTY WITH
RESPECT TO NOCTURNAL PCPN CHANCES. WILL ON JUST A SHOTGUN CHANCE FOR
THE BALANCE OF THE CWFA WITH HIGHER POP ACRS THE WESTERN MTNS AND
WILL FAVOR HPC QPF...GENERALLY ON LIGHT SIDE. OTHERWISE...EXPECTING
SOME DEGREE OF LOWER CLOUD REDEVELOPMENT...PATCHY MAINLY VALLEY/LOW
SPOT BR...AND ANOTHER MUGGY NIGHT. AFOREMENTIONED DEEP RH BAND WILL
CONTINUE TO BE A FACTOR FOR FRIDAY/S FCST...AS IT SLOWLY SAGS SE
ACRS THE CWFA. SENSIBLE WX FCST WILL GENERALLY BE CLOSE TO
PERSISTENCE...SHOWER AND TSTM CVRG INCREASING TO NUMEROUS CVRG BY
THE AFTERNOON.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
AS OF 230 PM THURSDAY...A REINFORCING UPPER WAVE IS EXPECTED TO
ROUND THE MAIN LOW PRES SYSTEM OVER ERN CANADA FRI NIGHT INTO
SAT...DIGGING INTO THE OH VALLEY. RECENT ECM RUNS HAVE FEATURED A
DEEP CUTOFF LOW FORMING FROM THIS WAVE SE OF THE OH VALLEY...BUT
THIS APPEARS TO BE AN OUTLIER...SO A CONSENSUS OF NAM/GFS AND
ENSEMBLES WILL BE FEATURED WITH THE TIMING OF THE UPPER TROUGH.
LINGERING CHANCE TO LIKELY FRI EVENING POPS WILL BE NEEDED AS THE
DEEPER PRE/FRONTAL MOISTURE BAND TRAVERSES THE AREA. THE ASSOCIATED
TRAILING SFC COLD FRONT WILL FINALLY PUSH INTO THE REGION BY
DAYBREAK SAT AND WORK SLOWLY E OF THE FORECAST AREA THROUGH SAT
NIGHT. THE BEST FORCING AHEAD OF THE TROUGH APPEARS TO COME TOGETHER
LATE SAT WITH DECENT RIGHT ENTRANCE REGION JET DIVERGENCE COMBINING
WITH THE DEEP LAYER DPVA. HOWEVER...DRYING WILL ONSET QUICKLY FROM
SW WITH FROPA...AND THIS WILL COMBINE WITH A WESTERLY 850 MB
DOWNSLOPE FLOW TO LIMIT POPS AND DIMINISH THEM FROM W TO E SAT
THROUGH SAT NIGHT.

THE LONGWAVE TROUGH AXIS SHOULD SLIP EAST OF THE AREA ON
SUNDAY...BUT WITH A LINGERING UPPER LEVEL WEAKNESS ALONG THE SRN
APPALACHIANS THROUGH SUN NIGHT. DRYING WILL CONTINUE THROUGH
SUNDAY...BUT STEEPENING LAPSE RATES UNDER THE TROUGH AXIS COULD LEAD
TO ISOLATED MTN CONVECTION DURING PEAK HEATING. TEMPERATURES WILL BE
A BLEND OF MOS GUIDANCE THROUGHOUT.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 230 PM THURSDAY...A WEAK TROUGH OR SHEAR AXIS WILL PERSIST
ALONG THE APPALACHIANS MON THROUGH WED. LOW LEVEL FLOW WILL ACQUIRE
AN EASTERLY UPSLOPE COMPONENT EARLY MON...LIKELY KEEPING OR
REINFORCING LINGERING BOUNDARY LAYER MOISTURE ACROSS THE REGION. LOW
LEVEL FLOW WILL STEADILY VEER SE ON TUE THEN SOUTHERLY ON WED...WITH
UPSLOPE SHIFTING ACCORDINGLY. WILL FEATURE DIURNAL...MAINLY
MTN...SLIGHT CHC POPS MON THROUGH WED. UPPER HEIGHTS WILL BRIEFLY
RISE LATE WED...BEFORE ANOTHER SHORTWAVE APPROACHES FROM THE NW ON
THU. THE GFS FEATURES LOWER HEIGHTS ACROSS THE E THAN THE OTHER
MODELS/ENSEMBLES FOR THU. LEANING AWAY FROM THE OPERATIONAL
GFS...WILL JUST KEEP ISOLATED DIURNAL TSTM CHANCES GOING IN THE
FORECAST AS A BACKDOOR COLD FRONT SHOULD STAY NORTH OF THE AREA THU.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
SCATTERED TO NUMEROUS MTN SHRA/TSRA AND SCT FOOTHILLS SHRA/TSRA WILL
REMAIN THROUGH THE REMAINDER OF THE EVENING. COVERAGE SHOULD
DECREASE SIGNIFICANTLY AROUND MIDNIGHT...HOWEVER...THE MTNS MAY
CONTINUE TO OBSERVE CLUSTERS OF SHRA/TSRA OVERNIGHT. MOS AND
PERSISTENCE SUPPORTS A MENTION OF STRATUS ACROSS THE WESTERN
CAROLINAS DURING THE PRE DAWN HOURS. LOW CLOUDS WILL LIKELY MIX TO
VFR BETWEEN 13-14Z. WESTERN CAROLINA SHRA AND TSRA WILL REDEVELOP BY
MID DAY TOMORROW WITH AN APPROACHING COLD FRONT. CHCS APPEAR HIGH
ENOUGH TO MENTION VCSH AND CB IN THE SKY GROUP WITHIN EACH TAF.

AT KCLT...AT 2350Z...RECENT TCLT TDWR IMAGES INDICATED SEVERAL
OUTFLOW BOUNDARIES DRIFTING AROUND THE METRO AREA. THESE BOUNDARIES
COULD RESULT IN PERIODS OF GUSTY CONDITIONS...BUT DIRECTIONS SHOULD
FAVOR THE SOUTH. MOS AND PERSISTENCE SUPPORTS A MENTION OF STRATUS
AND LIGHT FOG ACROSS THE TERMINAL DURING THE PRE DAWN HOURS. LOW
CLOUDS WILL LIKELY MIX TO VFR BETWEEN 13-14Z. SHRA AND TSRA WILL
REDEVELOP BY MID DAY TOMORROW WITH AN APPROACHING COLD FRONT. CHCS
APPEAR HIGH ENOUGH TO MENTION VCSH AND CB IN THE SKY GROUP.

OUTLOOK...CIG/VSBY RESTRICTIONS EXPECTED AGAIN FRIDAY NIGHT. A COLD
FRONT PUSHES THRU THE AREA EARLY SATURDAY...USHERING IN DRIER AIR.

&&

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

&&

SYNOPSIS...JPT
NEAR TERM...CSH
SHORT TERM...HG
LONG TERM...HG
AVIATION...NED

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
341 PM EDT THU AUG 20 2009

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-211945-
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-
341 PM EDT THU AUG 20 2009

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 SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP ACROSS
THE WESTERN CAROLINAS AND NORTHEAST GEORGIA THROUGH TONIGHT. ONE
OR TWO OF THE THUNDERSTORMS COULD PRODUCE DAMAGING WIND
GUSTS...HOWEVER...THE MAIN THREAT FROM THE THUNDERSTORMS WILL BE
TORRENTIAL DOWNPOURS. THE AIR MASS ACROSS THE REGION IS RICH IN
TROPICAL MOISTURE WHICH SHOULD ALLOW SOME OF THE STORMS TO BE
EFFICIENT RAIN PRODUCERS. THIS COULD RESULT IN LOCALIZED FLOODING
WHERE SHOWERS PERSIST...ESPECIALLY TONIGHT.

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

NUMEROUS THUNDERSTORMS ARE EXPECTED ACROSS THE AREA AGAIN ON FRIDAY.
HEAVY RAINFALL FROM THE THUNDERSTORMS COULD PRODUCE LOCALIZED
FLOODING IN A FEW AREAS. AN ISOLATED SEVERE THUNDERSTORM COULD
PRODUCE DAMAGING WIND GUSTS.

.SPOTTER INFORMATION STATEMENT...

NONE.

HG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
514 PM EDT THU AUG 20 2009

NCZ082-202145-
UNION-
514 PM EDT THU AUG 20 2009

...A STRONG THUNDERSTORM WILL AFFECT SOUTHWESTERN UNION COUNTY
THROUGH 545 PM EDT...

AT 513 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 6 MILES SOUTH OF WAXHAW...OR 9 MILES NORTHEAST OF
LANCASTER...MOVING NORTHEAST AT 15 MPH.

* OTHER LOCATIONS AFFECTED INCLUDE BUT ARE NOT LIMITED TO MINERAL
  SPRINGS...WAXHAW...TRINITY AND MONROE.

HEAVY RAIN...LIGHTNING...SMALL HAIL...AND WIND GUSTS OF 30 TO 40 MPH
ARE EXPECTED WITH THIS STORM.

RB

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
536 PM EDT THU AUG 20 2009

NCZ082-202200-
UNION-
536 PM EDT THU AUG 20 2009

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN UNION COUNTY
THROUGH 600 PM EDT...

AT 533 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 6 MILES NORTH OF MARSHVILLE...OR 12 MILES
NORTHEAST OF MONROE...MOVING NORTHEAST AT 15 MPH.

* OTHER LOCATIONS AFFECTED INCLUDE BUT ARE NOT LIMITED TO NEW SALEM
AND OLIVE BRANCH.

SMALL HAIL...AND WIND GUSTS OF 30 TO 40 MPH ARE EXPECTED WITH THIS
STORM.

RB

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
548 PM EDT THU AUG 20 2009

NCZ082-202245-
UNION-
548 PM EDT THU AUG 20 2009

...A STRONG THUNDERSTORM WILL AFFECT WESTERN UNION COUNTY THROUGH 645
PM EDT...

AT 547 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 4 MILES SOUTHEAST OF WAXHAW...OR 11 MILES
NORTHEAST OF LANCASTER...MOVING NORTHEAST AT 15 MPH.

* OTHER LOCATIONS AFFECTED INCLUDE BUT ARE NOT LIMITED TO MINERAL
  SPRINGS...WAXHAW AND MONROE.

HEAVY RAIN...FREQUENT LIGHTNING...SMALL HAIL...AND WIND GUSTS OF 30
TO 40 MPH ARE EXPECTED WITH THIS STORM.

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

INTENSE LIGHTNING IS OCCURRING WITH THIS STORM. IF OUTDOORS...STAY
AWAY FROM ISOLATED HIGH OBJECTS SUCH AS TREES. MOVE INDOORS IF
POSSIBLE. WHEN INDOORS...STAY AWAY FROM WINDOWS AND DOORS AND AVOID
USING TELEPHONES UNLESS IT IS AN EMERGENCY. TRY TO UNPLUG UNNECESSARY
ELECTRICAL APPLIANCES BEFORE THE THUNDERSTORM APPROACHES.

RB

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
648 PM EDT THU AUG 20 2009

NCZ072-202330-
CABARRUS-
648 PM EDT THU AUG 20 2009

...A STRONG THUNDERSTORM WILL AFFECT EASTERN CABARRUS COUNTY THROUGH
730 PM EDT...

AT 645 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 3 MILES SOUTH OF MIDLAND...OR 14 MILES NORTH OF
MONROE...MOVING NORTHEAST AT 20 MPH.

* OTHER LOCATIONS AFFECTED INCLUDE BUT ARE NOT LIMITED TO MOUNT
  PLEASANT AND MIDLAND.

HEAVY RAIN...LIGHTNING...SMALL HAIL...AND WIND GUSTS OF 30 TO 40 MPH
ARE EXPECTED WITH THIS STORM.

RB

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
726 PM EDT THU AUG 20 2009

GAZ017-210000-
HABERSHAM-
726 PM EDT THU AUG 20 2009

...A STRONG THUNDERSTORM WILL AFFECT HABERSHAM COUNTY THROUGH 800 PM
EDT...

AT 724 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 5 MILES NORTHWEST OF ALTO...OR 10 MILES SOUTHWEST
OF CLARKESVILLE...MOVING EAST AT 15 MPH.

* OTHER LOCATIONS AFFECTED INCLUDE BUT ARE NOT LIMITED TO
  TURNERVILLE...MOUNT AIRY...HOLLYWOOD...DEMOREST...CORNELIA...
  CLARKESVILLE AND BALDWIN.

HEAVY RAIN...FREQUENT LIGHTNING...SMALL HAIL...AND WIND GUSTS OF 30
TO 40 MPH ARE EXPECTED WITH THIS STORM.

INTENSE LIGHTNING IS OCCURRING WITH THIS STORM. IF OUTDOORS...STAY
AWAY FROM ISOLATED HIGH OBJECTS SUCH AS TREES. MOVE INDOORS IF
POSSIBLE. WHEN INDOORS...STAY AWAY FROM WINDOWS AND DOORS AND AVOID
USING TELEPHONES UNLESS IT IS AN EMERGENCY. TRY TO UNPLUG UNNECESSARY
ELECTRICAL APPLIANCES BEFORE THE THUNDERSTORM APPROACHES.

RB

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
858 PM EDT THU AUG 20 2009

SCZ001-002-005-210130-
GREATER PICKENS-OCONEE MOUNTAINS-PICKENS MOUNTAINS-
858 PM EDT THU AUG 20 2009

...A STRONG THUNDERSTORM WILL AFFECT EASTERN OCONEE AND PICKENS
COUNTIES THROUGH 930 PM EDT...

AT 858 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR LAKE KEOWEE...OR 9 MILES NORTHEAST OF
WALHALLA...MOVING NORTHEAST AT 25 MPH.

* OTHER LOCATIONS AFFECTED INCLUDE BUT ARE NOT LIMITED TO LAKE
  KEOWEE...SIX MILE...SALEM...ROCKY BOTTOM...PICKENS AND NINE TIMES.

HEAVY RAIN...LIGHTNING...SMALL HAIL...AND WIND GUSTS OF 30 TO 40 MPH
ARE EXPECTED WITH THIS STORM.

RB