Flash Flood and Damaging Wind in North Carolina, August 22, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
525 PM EDT SAT AUG 22 2015

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO BUILD IN FROM THE NORTH...THOUGH SOME
MOISTURE WILL ALLOW SCATTERED SHOWERS AND THUNDERSTORMS TO LINGER
THROUGH THE WEEKEND. ANOTHER COLD FRONT WILL CROSS THE REGION ON
MONDAY...WITH A MUCH DRIER PERIOD STARTING ON TUESDAY. ISOLATED
AFTERNOON SHOWERS AND THUNDERSTORMS WILL RETURN BY THE END OF NEXT
WEEK.

&&

.NEAR TERM /THROUGH SUNDAY/...
AS OF 510 PM SATURDAY...ONLY A FEW WIDELY SCATTERED LIGHT RAIN
SHOWERS ACROSS THE AREA AT THIS TIME.  ACTIVITY HAS BEEN BELOW THAT
FORECAST BY HIGHER RES MODELS...PROBABLY DUE TO DIFFICULTY IN
PRECISELY RESOLVING WEAK SHORTWAVE RESPONSIBLE FOR LIMITED
ACTIVITY.  AS WEAK WAVE OVER SOUTHERN STATES CONTINUES TO PROGRESS
EASTWARD...SHOWER OR THUNDERSTORM ACTIVITY WILL STILL BE POSSIBLE
LATER THIS EVENING AND TONIGHT...BUT HAVE DECREASED THE PROBABILITY
FOR THE NEXT 6 HOURS FOLLOWING RADAR TRENDS.

AS OF 235 PM...CONVECTION REMAINS MOST NUMEROUS NEAR THE FAR SRN
BORDER OF THE CWFA. HOWEVER...CONVECTION SLOWLY DEVELOPING ACROSS
THE WRN CWFA. EXPECT THIS TO INCREASE TO SCT COVERAGE THRU THE
AFTERNOON AND LINGER INTO THE EVENING AS A SHORT WAVE MOVES IN FROM
THE WEST. CANNOT RULE OUT AN ISOLATED SVR STORM OR ISOLATED FLOODING
THIS AFTERNOON. ISOLATED SHOWERS WILL LINGER THRU THE NITE ACROSS
THE AREA AS THE VERY MOIST AND UNSTABLE AIR MASS AND WEAK FORCING
REMAINS. LOWS WILL BE ABOVE NORMAL.

ALL GUIDANCE INDICATES AT LEAST SCT CONVECTION DEVELOPS ACROSS THE
CWFA SUNDAY. HOWEVER...THEY DIFFER ON WHETHER IT IS MORE OF A
DIURNAL TREND...OR A BKN LINE OF CONVECTION FORMING OVER THE MTNS
AND MOVING EAST ACROSS THE CWFA. HAVE OPTED TO GO WITH THE DIURNAL
TREND OF SOLID CHC POP...BUT DID START THE TREND EARLIER THAN
NORMAL...LIKE WHAT OCCURRED SATURDAY MORNING. AN ISOLATED SVR STORM
OR EXCESSIVE RAINFALL AREA AGAIN POSSIBLE. HIGHS WILL BE NEAR NORMAL.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AT 230 PM EDT SATURDAY...ON SUNDAY EVENING AN UPPER RIDGE WILL BE
OVER THE WESTERN USA AND AN UPPER TROUGH WILL BE OVER THE EASTERN
USA. AS A STRONG CLOSED UPPER LOW MOVES ACROSS SOUTHERN ONTARIO...
THE UPPER PATTERN WILL AMPLIFY INTO MONDAY AND TUESDAY...WITH LITTLE
PROGRESSION. WEAK SHORTWAVE ENERGY ROUNDING THE TROUGH WILL CROSS
OUR AREA SUNDAY NIGHT...BUT THE BULK OF UPPER LEVEL VORTICITY WILL
REMAIN NEAR THE CLOSED LOW BETWEEN THE GREAT LAKES AND HUDSON BAY.

AT THE SURFACE...A COLD FRONT WILL APPROACH THE SOUTHERN
APPALACHIANS FROM THE NW ON SUNDAY NIGHT...SLOWLY CROSSING OUR AREA
ON MONDAY. THIS BOUNDARY WILL BE LARGELY MOISTURE STARVED...AS
INITIALLY LIMITED GULF INFLOW BECOMES ALMOST NON EXISTENT. MOVEMENT OF
THE FRONT OUR OF OUR PIEDMONT ZONES WILL BE QUITE SLOW ON MONDAY
NIGHT...AND SOME MODEST INCREASE IN MOISTURE ALONG THE BOUNDARY IS
POSSIBLE AS IT INTERACTS WITH WEAK ATLANTIC INFLOW. THE FRONT CRAWLS
EAST OF OUR AREA ON TUESDAY. ONLY MINIMAL POPS AND PRECIPITATION
WILL BE CARRIED WITH THE PASSAGE OF THIS BOUNDARY. TEMPERATURES WILL
FALL FROM SLIGHTLY ABOVE NORMAL TO NEAR NORMAL.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 230 PM SATURDAY...THE MEDIUM RANGE BEGINS AMID HEIGHT FALLS
ALONG THE EASTERN HALF OF THE CONUS WHILE A RIDGE CONTINUES TO
AMPLIFY OVER THE WEST. ON TUESDAY NIGHT...THE CWA WILL BE SITUATED
UNDER THE BASE OF THE AMPLIFIED UPPER LEVEL TROUGH WITH A SURFACE
HIGH BUILDING IN FROM THE CENTRAL PLAINS. THOUGH THE UPPER PATTERN
WILL NOT BE PARTICULARLY PROGRESSIVE...MAJOR MODELS ARE IN GOOD
AGREEMENT THAT THE SURFACE FRONT WILL MADE A RATHER CLEAN PASSAGE
THROUGH THE AREA BY WEDNESDAY. A NORTH/NORTHWESTERLY FLOW REGIME
WILL BE ESTABLISHED AT THE SURFACE...DRYING PROFILES SIGNIFICANTLY
AND LIMITING POPS TO NEAR NOTHING FOR THE MAJORITY OF THE FORECAST
AREA TUESDAY AND WEDNESDAY. DESPITE A FEW WEAK VORT MAXES ROUNDING
THE BASE OF THE TROUGH...UPPER LEVEL WARMING WILL HELP TO LIMIT
INSTABILITY EVERYWHERE EXCEPT THE FAR EASTERN PARTS OF THE
PIEDMONT...SO THE ONLY POPS CARRIED BEFORE FRIDAY ARE SLIGHT CHANCE
AGAINST OUR BORDER WITH COLUMBIA'S CWA. BY FRIDAY...SURFACE WINDS
WILL VEER TO THE SOUTHEAST AND GRADUALLY INCREASE MOISTURE AS WELL
AS PROVIDE A WEAK UPSLOPE COMPONENT TO THE FLOW. AS A
RESULT...SLIGHT CHANCE TO LOW-END CHANCE POPS MAKE A RETURN OVER THE
HIGHER TERRAIN DURING PEAK DIURNAL HEATING ON FRIDAY AND SATURDAY.
BOTH MIN AND MAX TEMPS WILL RUN VERY CLOSE TO CLIMO THROUGH THE
ENTIRE PERIOD.

&&

.AVIATION /22Z SATURDAY THROUGH THURSDAY/...
AT KCLT...VFR CONDITIONS EXPECTED THROUGH THE PERIOD...WITH BKN TO
OCCASIONALLY SCT VFR STRATOCU. CANT ENTIRELY RULE OUT CIGS LOWERING
TO MVFR LATE TONIGHT OR EARLY SUNDAY...BUT CONFIDENCE IS LOW.
CONVECTION MAY MAKE A RUN AT THE AIRFIELD FROM THE WEST...BUT EXPECT
CHANCE TO INCREASE OVERNIGHT AND CONTINUE INTO SUNDAY. HOWEVER...CHC
IS TOO LOW AND UNCERTAINTY TOO HIGH TO INCLUDE IN THE TAF ATTM.
LIGHT SELY WIND EARLY THIS AFTERNOON WILL RETURN TO LIGHT NE THIS
AFTERNOON AND CONTINUE OVERNIGHT. WINDS VEER BACK TO SLY WITH MIXING
SUNDAY MORNING.

ELSEWHERE...SIMILAR CONDITIONS TO KCLT...EXCEPT SOME LINGERING MVFR
CIGS EARLY THIS AFTERNOON. ALSO...ALL BUT KHKY HAS A BETTER CHC OF
CONVECTION...SO VCSH THEN VCTS ADDED. KAVL SHUD FALL TO AT LEAST
MVFR OVERNIGHT...WITH MVFR DEVELOPING AT KAND. CANNOT RULE OUT MVFR
AT KGSP/KGMU. EXPECT EARLY ONSET OF CONVECTION AGAIN SUNDAY...BUT
CHC AND TIMING TOO UNCERTAIN TO INCLUDE IN TAF ATTM. ELY WIND
BECOMES NELY OVERNIGHT...THEN SLY WITH MIXING SUNDAY. KAVL HAS SLY
WIND BECOMING CALM...THEN NLY SUNDAY.

OUTLOOK...DIURNAL CONVECTIVE CHANCES AND POTENTIAL FOR MORNING
FOG/STRATUS...ESP IN THE MTN VALLEYS WILL PERSIST INTO MONDAY. A
COLD FRONT IS EXPECTED TO BRING DRIER AIR INTO THE AREA BY TUE...
LIKELY BRINGING AN END TO CONVECTIVE AND MORNING RESTRICTION CHANCES
FOR AT LEAST A COUPLE OF DAYS.

CONFIDENCE TABLE...

            21-03Z        03-09Z        09-15Z        15-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH  94%     HIGH 100%     HIGH  84%     HIGH 100%
KAVL       HIGH  92%     HIGH 100%     HIGH  94%     HIGH  82%
KHKY       HIGH 100%     HIGH 100%     HIGH  98%     HIGH  97%
KGMU       HIGH  98%     HIGH 100%     HIGH  94%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     MED   69%     HIGH  95%

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

&&

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

&&

SYNOPSIS...LEV
NEAR TERM...RWH/WJM
SHORT TERM...JAT
LONG TERM...ARK/LEV
AVIATION...RWH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
328 PM EDT SAT AUG 22 2015

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-231930-
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-
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-CHESTER-GREENWOOD-
328 PM EDT SAT AUG 22 2015

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THUNDERSTORMS ARE IN THE FORECAST THROUGH TONIGHT. THE MAIN
THREAT WILL BE CLOUD TO GROUND LIGHTNING...BUT LOCALLY HEAVY RAIN
IS ALSO POSSIBLE WITH ANY SLOW MOVING STORMS.

.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...

NONE.

07

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
703 PM EDT SAT AUG 22 2015

NCZ053-222330-
BUNCOMBE NC-
703 PM EDT SAT AUG 22 2015

...THUNDERSTORM WITH TORRENTIAL RAINFALL WILL IMPACT PORTIONS OF
CENTRAL BUNCOMBE COUNTY UNTIL 730 PM EDT...

AT 703 PM EDT...DOPPLER RADAR WAS TRACKING A THUNDERSTORM WITH
TORRENTIAL RAINFALL 5 MILES NORTH OF DOWNTOWN ASHEVILLE...OR NEAR
WEAVERVILLE...MOVING EAST AT 5 MPH.

PEA SIZE HAIL AND WIND GUSTS UP TO 40 MPH WILL BE POSSIBLE WITH THIS
STORM.

LOCATIONS IMPACTED INCLUDE...
DOWNTOWN ASHEVILLE...WOODFIN...SWANNANOA...WEAVERVILLE...B.R.
PARKWAY-EAST ASHEVILLE TO CRAGGY GARDENS...NORTH ASHEVILLE...WARREN
WILSON COLLEGE...UNC ASHEVILLE...EAST ASHEVILLE AND WEST ASHEVILLE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

GUSTY WINDS CAN BLOW DOWN TREES THAT ARE DEAD...OR THAT HAVE WEAKENED
ROOT SYSTEMS. OUTDOOR FURNITURE AND SIMILAR ITEMS CAN BE TOSSED
AROUND IF NOT ANCHORED. SEEK SHELTER INDOORS.

TORRENTIAL RAINFALL 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 3559 8237 3559 8267 3574 8264 3576 8239
TIME...MOT...LOC 2303Z 259DEG 6KT 3567 8252

NED