Flash Flood and Damaging Wind in North Carolina, September 8, 2012

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1216 PM EDT SAT SEP 8 2012

.SYNOPSIS...
A STRONG COLD FRONT WILL CROSS THE CAROLINAS AND NORTHEAST GEORGIA
THROUGH TONIGHT...PUSHING EAST OF THE AREA BY DAYBREAK SUNDAY. DRY
HIGH PRESSURE WILL BUILD IN FROM THE NORTH SUNDAY AND REMAIN IN
PLACE THROUGH THE END OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
S TO SWLY WINDS PICK UP AHEAD OF A STRONG COLD FRONT MOVING TOWARD
THE AREA FROM THE WEST. SIGNIFICANT MID LEVEL FORCING EXPECTED AS A
STRONG SHORT WAVE MOVES IN WITH THE FRONT. GOOD UPPER DIVERGENCE
MOVES IN AS WELL WITH THE RIGHT ENTRANCE REGION OF THE UPPER JET.
LOW LEVEL CONVERGENCE SHUD BE QUITE STRONG AS WELL. THE QUESTION
WILL BE HOW THE CONVECTION DEVELOPS AND MOVES ACROSS THE AREA WITH
THE SYSTEM. THE SRN END OF THE LINE OF CONVECTION HAS WEAKENED AND
BECOME SCT THIS MORNING AS IT MOVES ACROSS MIDDLE TN. THE NRN END OF
THE LINE REMAINS STRONG AND BKN. THE NAM IS THE SLOWEST BRINGING
THIS LINE TO THE MTNS...BUT EVEN THE FASTEST GUIDANCE ONLY BRINGS
SCT POP TO THE WRN MTNS BY DAYBREAK. THE MESOSCALE GUIDANCE AGREES
WITH THIS AS WELL. THE SYNOPTIC GUIDANCE HOLDS THE BEST PRECIP
COVERAGE OVER THE MTNS DURING THE MORNING AS THE CONVECTION STALLS
WHEN IT THIS THE MTNS. THE CONVECTION THEN SPEEDS UP AND MOVES INTO
THE NC PIEDMONT DURING THE AFTERNOON. THE NAM/GFS BOTH SKIP THE
PRECIP OVER MUCH OF THE UPSTATE THEN REFORM CONVECTION SOUTH OF
I-85. THE WRF-ARW HAS THIS AS WELL...WHILE THE WRF-NMM HINTS AT THIS
BUT DOES HAVE SCT CONVECTION MOVING ACROSS THE UPSTATE. THE SREF
KEEPS THE LINE MORE BKN. ALL THE GUIDANCE SUGGESTS THE LINE WILL
REMAIN BKN AS IT MOVES ACROSS NC. H85 WINDS REMAIN SW THRU THE
DAY...SO IT SEEMS LIKE AT LEAST SOME CONVECTION WILL MOVE THRU.
THEREFORE...HAVE POP BECOMING CATEGORICAL OVER THE MTNS AND LIKELY
ELSEWHERE. CONVECTION INCREASES IN INTENSITY DURING THE AFTERNOON AS
IT MOVES INTO THE NC PIEDMONT AND THE SRN/ERN UPSTATE. MODERATE
INSTABILITY DEVELOPS WITH DECENT SHEAR. THEREFORE...A SQUALL LINE
WITH DAMAGING WIND PRODUCING STORMS COULD MOVE ACROSS THAT AREA.

THE FRONT MOVES EAST OF THE AREA THIS EVENING TAKING THE CONVECTION
WITH IT. THAT SAID...MOISTURE AND WEAK FORCING LINGER BEHIND THE
FRONT DURING THE EVENING...SO SCT SHRA COULD LINGER THRU MIDNIGHT.
AT THE VERY LEAST...CLOUDS WILL LINGER THRU THAT TIME BEFORE DRIER
AIR WORKS IN ENDING THE CLOUDS AND PRECIP THREAT. LOWS WILL BE NEAR
NORMAL.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
AS OF NOON SATURDAY...HIGH PRESSURE WILL BRING SUNNY AND MILD
WEATHER TO THE REGION MONDAY AND TUESDAY. DEWPOINTS WILL MIX INTO
THE U40S TO L50S DURING THE DAY WHICH WILL FEEL GREAT AFTER THE
RECENT SPELL OF VERY MUGGY CONDITIONS. TEMPERATURES WILL RUN 1 TO 2
CATEGORIES BELOW NORMAL. FOR AGENCIES INTERESTED IN CONTROLLED
BURNS...THE HUMIDITY VALUES ARE GENERALLY EXPECTED TO RUN BETWEEN 30
AND 40 PERCENT IN THE AFTERNOON HOURS. I DON/T SEE STRONG DOWNSLOPE
FLOW OR ANYTHING THAT SHOULD CAUSE THE DEWPOINTS TO VERIFY
APPRECIABLY LOWER...WHICH MEANS BURNING CONDITIONS WILL GENERALLY BE
GOOD WITH AFTERNOON MIXING HEIGHTS UP AROUND 6 TO 7 KFT. THE ONLY
CONCERN WILL BE VERY LIGHT WINDS EACH DAY AS THE BNDRY LAYER FLOW
WILL BE UNDER 5KTS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 1200 PM SATURDAY...THE LATEST MEDIUM RANGE MODELS CONTINUE TO
INDICATE THAT BROAD UPPER LEVEL RIDGE OF HIGH PRESSURE WILL REMAIN
ANCHORED OVER THE EASTERN CONUS THROUGH LATE IN THE WEEK. WITH
PERSISTENT N/NE FLOW AND STRONG CAPPING INVERSION ALOFT...WILL
FORECAST DRY THROUGH FRIDAY. TEMPERATURES WILL REMAIN 2-3
DEGREES BELOW NORMAL WITH AFTERNOON HIGHS IN THE LOW 80S OVER THE
PIEDMONT AND 70S FOOTHILLS/MOUNTAINS.

SATURDAY INTO SUNDAY MORNING...BOTH THE LATEST GFS AND THE ECMWF ARE
IN FAIRLY GOOD AGREEMENT ON A POSITIVELY TILTED UPPER TROUGH OVER
THE NORTHERN PLAINS FRIDAY PROGRESSING EASTWARD ACROSS THE OHIO
VALLEY ON LATE SATURDAY...BUT STILL KEEPS AN ASSOCIATED COLD FRONT
TO OUR WEST THRU THE PERIOD. WITH INCREASING MOISTURE AND DIURNAL
INSTABILITY AHEAD OF THE APPROACHING COLD FRONT...I MENTIONED SLIGHT
CHANCE FOR AFTERNOON SHOWERS AND THUNDERSTORMS ACROSS OUR CWA ON
SATURDAY. TEMPERATURES WILL MODERATE TO NEAR NORMAL.

&&

.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...STILL SOME IFR CIGS SHOWN AT SITES JUST TO THE SOUTH AND
WEST. SATELLITE TRENDS INDICATE THESE ARE IMPROVING. KEPT SOME SCT
PATCHES OF STRATUS IN THROUGH THE MORNING AND TRIED TO INDICATE
DEVELOPING CUMULUS BY EARLY AFTERNOON. COLD FRONT MOVES IN LATER AND
TIMING FROM PREVIOUS FCST PACKAGE SEEMS REASONABLE. TSRA CHC
INCREASES BY MID AFTERNOON WITH A LINE OF STORMS MOVING THRU LATE
AFTERNOON...THEN SCT TSRA MOVE ACROSS WITH THE ACTUAL FRONT. LATEST
GUIDANCE STILL FAVORS VFR CONDITIONS SUNDAY MORNING.

ELSEWHERE...SIMILAR CONDITIONS TO KCLT. GUIDANCE HAS BEST POP FOR
THE NC SITES WITH SOME GUIDANCE SUGGESTING STORMS SKIP OVER THE SC
SITES AND REFORM EAST AND SOUTH. HAVE GONE WITH VCTS AND PROB30 FOR
NOW...BUT THIS COULD BE OVERDONE FOR THE SC SITES. OTHERWISE...MVFR
OR IFR CIGS WITH MVFR OR IFR VSBY COULD FORM BY DAYBREAK. EXPECT
SIMILAR TRENDS TO WINDS...WITH FROPA AND WIND SHIFT OCCURRING
EARLIER THAN KCLT. LINGERING LOW VFR CIGS POSSIBLE POST FROPA.

OUTLOOK...DRY AUTUMNAL HIGH PRES WILL DOMINATE THE WEATHER OVER THE
REGION SUNDAY THROUGH LATE 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...JOH
NEAR TERM...RWH
SHORT TERM...MCAVOY
LONG TERM...JOH
AVIATION...JW/RWH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1255 PM EDT SAT SEP 8 2012

GAZ010-017-018-026-028-029-NCZ035>037-056-057-068>072-082-501>510-
SCZ001>014-019-091700-
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-
1255 PM EDT SAT SEP 8 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 FOOTHILLS AND
PIEDMONT OF THE WESTERN CAROLINAS AND NORTHEAST GEORGIA THIS
AFTERNOON AND EVENING AS A COLD FRONT MOVES OUT OF THE MOUNTAINS.
WITH A VERY UNSTABLE AIRMASS IN PLACE AND INCREASING SHEAR...SOME
OF THE THUNDERSTORMS ARE LIKELY TO BECOME SEVERE...PRODUCING
DAMAGING STRAIGHT LINE WINDS AND A FEW INSTANCES OF LARGE HAIL.

THE STORMS WILL BECOME MORE ORGANIZED AS THEY MOVE TO THE EAST.
THEREFORE...THE GREATEST SEVERE THREAT WILL BE ACROSS THE PIEDMONT
OF THE CAROLINAS...ESPECIALLY ALONG THE I-77 URBAN CORRIDOR AND
THE UPSTATE EAST OF GREENVILLE. THERE IS EVEN A THREAT OF A
BRIEF...ISOLATED TORNADO OVER THE WESTERN NORTH CAROLINA PIEDMONT
THIS AFTERNOON AND EARLY EVENING.

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

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

DISPATCHERS PLEASE FORWARD THIS INFORMATION ON TO EMERGENCY
MANAGERS AND OTHER COUNTY OFFICIALS. SKYWARN SPOTTERS ARE
REQUESTED TO FORWARD ANY REPORTS OF LARGE HAIL...DAMAGING
WINDS...TORNADOES OR FLASH FLOODING TO OUR OFFICE.

NCZ033-048>053-058-059-062>065-091700-
AVERY-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-GRAHAM-
NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-HENDERSON-
1255 PM EDT SAT SEP 8 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...SUNDAY THROUGH FRIDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

NONE.

MCAVOY

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1247 PM EDT SAT SEP 8 2012

NCZ068-502-504>508-081730-
CLEVELAND-EASTERN MCDOWELL-GREATER BURKE-GREATER CALDWELL-GREATER
RUTHERFORD-MCDOWELL MOUNTAINS-RUTHERFORD MOUNTAINS-
1247 PM EDT SAT SEP 8 2012

...STRONG THUNDERSTORMS WILL AFFECT BURKE...NORTHERN RUTHERFORD...
NORTHWESTERN CLEVELAND...SOUTHEASTERN CALDWELL AND SOUTHEASTERN
MCDOWELL COUNTIES THROUGH 130 PM EDT...

AT 1243 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM NEBO TO LAKE LURE...
MOVING EAST AT 40 MPH.

THESE STORMS WILL IMPACT LOCATIONS NEAR...
  GLENWOOD...
  THERMAL CITY...
  MORGANTON...
  GAMEWELL...
  HUDSON...
  CONNELLY SPRINGS...

SMALL HAIL...WIND GUSTS OF 40 TO 50 MPH AND TORRENTIAL RAIN 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 3589 8133 3545 8160 3539 8212 3541 8215
      3540 8227 3579 8190 3594 8134

JOH

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
105 PM EDT SAT SEP 8 2012

SCZ019-081745-
GREENWOOD-
105 PM EDT SAT SEP 8 2012

...A STRONG THUNDERSTORM WILL AFFECT SOUTHERN GREENWOOD COUNTY
THROUGH 145 PM EDT...

AT 1259 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 5 MILES NORTHWEST OF CALLISON...OR 11 MILES SOUTH
OF GREENWOOD...MOVING EAST AT 20 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  CALLISON...
  NINETY SIX...

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

LAT...LON 3401 8224 3400 8227 3408 8230 3413 8226
      3423 8197 3420 8192 3414 8187 3397 8199
      3397 8205 3398 8205 3398 8216 3397 8219

JOH

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
120 PM EDT SAT SEP 8 2012

NCZ068-508>510-SCZ003-007-081800-
CLEVELAND-EASTERN POLK-GREATER RUTHERFORD-GREENVILLE MOUNTAINS-POLK
MOUNTAINS-SPARTANBURG-
120 PM EDT SAT SEP 8 2012

...STRONG THUNDERSTORMS WILL AFFECT NORTHEASTERN GREENVILLE...
NORTHWESTERN CLEVELAND...NORTHWESTERN SPARTANBURG...POLK AND SOUTHERN
RUTHERFORD COUNTIES THROUGH 200 PM EDT...

AT 116 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 5 MILES SOUTHEAST OF
LAKE LURE TO NORTH SALUDA RESERVOIR...MOVING EAST AT 35 MPH.

THESE STORMS WILL IMPACT LOCATIONS NEAR...
  COLUMBUS...
  TRYON...
  LANDRUM...
  RUTHERFORDTON...
  SPINDALE...
  BOSTIC...

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

LAT...LON 3548 8153 3518 8175 3519 8187 3516 8186
      3509 8252 3520 8242 3521 8239 3518 8237
      3519 8236 3523 8235 3524 8236 3528 8235
      3540 8224

JOH