Damaging Winds in South Carolina, July 22, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
815 PM EDT MON JUL 22 2013

.SYNOPSIS...
A BROAD UPPER TROUGH ATOP THE EASTERN UNITED STATES WILL PREVAIL
THROUGH THE REMAINDER OF THE WEEK. A SERIES OF UPPER LEVEL
WAVES...AND A COLD FRONT...WILL PASS THROUGH THE REGION DURING THE
FIRST PART OF THE WEEK KEEPING CHANCES FOR SHOWERS AND THUNDERSTORMS
ELEVATED.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
AS OF 755 PM EDT...ANOTHER WAVE OF SHOWERS IS MOVING ACROSS THE
WESTERN CWFA AND IS PRODUCING A FEW CG LIGHTNING STRIKES...BUT ONLY
A HANDFUL OVER THE PAST HOUR OR SO. ADDITIONAL CONVECTIVE ACTIVITY
WILL LIKELY BE ABLE TO SUSTAIN ITSELF THRU THE LATE EVENING AS SFC
BASED CAPE REMAINS FAVORABLE. THE SVR POTENTIAL REMAINS LOW FOR
THESE STORMS WITH THE MAIN CONCERN BEING ADDITIONAL FLASH FLOODING
OVER ALREADY SATURATED AREAS. THINGS ARE EXPECTED TO QUITE DOWN
AFTER MIDNIGHT AND SOUNDINGS BECOME LESS FAVORABLE AND WE LOSE SOME
OF OUR UPPER LVL SUPPORT.

PREVIOUS DISCUSSION...
AT 230 PM EDT... SCATTERED THUNDERSTORMS DEVELOPING OVER HIGHER
TERRAIN IN ADVANCE OF APPROACHING TROUGH ALOFT AND WARMING BOUNDARY
LAYER WILL BE THE MAIN FEATURE OF THE CWA WEATHER DURING THE REST OF
THE AFTERNOON AND THIS EVENING. VERTICAL WIND PROFILES SUGGEST THAT
CELL MOVEMENT TOWARD THE EAST AND NORTHEAST WILL DIMINISH LIKELIHOOD
OF PRECIPITATION REMAINING OVER A LOCATION TOO LONG. HEAVY RAIN WILL
OCCUR... BUT SHOULD BE CONFINED TO SMALL AREAS. NONETHELESS... WILL
HAVE TO MONITOR CONVECTIVE EVOLUTION AND SURFACE FEATURES TO ENSURE
THAT PERSISTENT HEAVY RAINFALL DOES NOT DEVELOP ALONG BOUNDARIES NOT
YET IDENTIFIABLE. CONVECTION ALLOWING MODELS DID A REASONABLY GOOD
JOB OF INDICATING STORMS WOULD DEVELOP AND WE WILL FOLLOW THE TREND
INDICATED BY THE MODELS WHICH SIGNAL CONTINUED WEAKENING OF EASTWARD
MOVING MCS THAT TRAVELED ACROSS TENNESSEE EARLIER IN THE DAY. TROUGH
WILL CROSS THE CWA TONIGHT RESULTING IN CONTINUED POPS FOR
CONVECTIVE STORMS BUT POPS DECREASING LATE TONIGHT AS MOST FAVORABLE
FORCING MOVES INTO FAR EASTERN PART OF CWA. AFTER 12Z TUESDAY... THE
500 MB TROUGH WILL BE EXITING THE AREA FOLLOWED BY ANTICYCLONIC
DIFFERENTIAL VORTICITY ADVECTION FOR MUCH OF THE DAY. THE AIRMASS
WILL BE DRIER ABUT PLAN TO CARRY POPS. NUMBERS WILL BE QUITE A BIT
LOWER THAN THE POPS OF THE PAST SEVERAL DAYS. MOST FAVORABLE
LOCATION FOR AFTERNOON SHOWERS AND THUNDERSTORMS WILL BE OVER THE
MOUNTAINS AND FOOTHILLS. NO MAJOR CHANGES IN TEMPERATURE ARE
EXPECTED. OVERNIGHT LOWS WILL BE IN THE UPPER 60S AND LOWER 70S WITH
LOWER AND MIDDLE 60S IN MOUNTAIN VALLEYS. DAYTIME HIGHS ON MONDAY
WILL BE BETWEEN 85 AND 90 OUTSIDE THE MOUNTAINS AND IN THE LOWER AND
MID 80S IN MOUNTAIN VALLEYS.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 130 PM MONDAY...A LONG WAVE TROF AXIS WILL MOVE LITTLE THRU
THE SHORT TERM...EXTENDING SOUTH FROM THE ERN GREAT LAKES THRU THE
CWFA. A SERIES OF SHORTWAVES WILL DIVE SE INTO THE AXIS...AMPLIFYING
THE LONGWAVE AND BRINGING SOME BETTER MID-UPR FLOW AND MID LVL LAPSE
RATES. MEANWHILE...LLVL FLOW WILL REMAIN LARGELY OUT OF THE
WEST...WITH PWATS CLOSER TO SEASONAL NORMS IN THE 100-125% OF NORMAL
RANGE. A WEAK FRONT WILL SAG SOUTH INTO THE AREA BY EARLY
WEDNESDAY...WITH BOTH THE NAM AND GFS AGREEING ON GOOD CONVERGENCE
ALONG THE BNDRY WED AFTN ACRS THE I-85 CORRIDOR. ONE OF THE UPR
SHORTWAVES WILL BE CROSSING THE AREA DURING PEAK HEATING...SO I
EXPECT AT LEAST SOLID CHC POPS FOR THE SRN HALF OF THE CWFA WED
AFTN. A LITTLE MORE FLOW WITH AN AMPLIFYING LONGWAVE SHUD RESULT IN
A LITTLE BIT OF SHEAR AND DECENT STORM MOTIONS. HOWEVER...THE MEAN
FLOW WILL BE NEARLY PARALLEL TO THE BNDRY...SO TRAINING STORMS MAY
BE A THREAT. MAX TEMPS WILL BE NEAR NORMAL.

WEDNESDAY NIGHT AND THURSDAY...A SECOND...MORE POTENT...SHORTWAVE
WILL DIVE INTO THE LONGWAVE TROF...WITH MORE SIGINIFICANT
AMPLIFICATION DEPICTED IN THE GUIDANCE. THERE IS DISAGREEMENT ON THE
EXACT POSITION OF THE TROF AXIS AT THAT POINT...AND ALSO ON WHERE
ANY SFC WAVE/REFLECTION DEVELOPS ALONG A STALLED BNDRY ACRS THE
COASTAL PLAIN. THE 12Z GFS HAS COME IN MORE IN LINE WITH WESTERN AND
WETTER 00Z ECMWF...WHILE THE 12Z NAM IS FURTHER EAST WITH THE
AXIS...AND DRIER FOR THE CWFA. THE 12Z CMC HAS COME IN MUCH FURTHER
WEST...AND IS WETTER FOR THURSDAY AS WELL. SINCE THIS IS MY FIRST
SHIFT IN A FEW DAYS...I HAVE OPTED TO MAKE LITTLE CHANGE TO
THURSDAY/S FCST...WHICH IS FOR A CHC POP ACRS THE AREA. THE GUIDANCE
SHOWS POSSIBLE WEDGE DEVELOPING ON THURSDAY AS WELL...AS A MODEST
SFC HIGH BLDS ACRS THE OH VLY AND NRN MID ATLANTIC...PUSHING SOME
NELY BL FLOW EAST OF THE APPALACHIANS. SO BELOW NORMAL TEMPS ARE
EXPECTED THURSDAY.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 1240 PM EDT MONDAY...WITH WEAK SFC RIDGING IN SUBTLE DAMMING
ORIENTATION ON FRIDAY...WILL LOWER MAX TEMPS A FEW DEGREES FROM THE
GOING FCST. AT THIS POINT...WILL MAINTAIN INHERITED SMALL CHANCE
POP...BUT WITHIN THE DEVELOPING WEAK LLVL UPGLIDE...WE MAY HAVE TO
RAMP POPS UPWARD AS THE WEEK WEARS ON. SOLID CHANCE POP WILL BE
MAINTAINED FOR SATURDAY WITH THE 22/12 UTC OP GFS INCREASING THE
WAA DOWNSTREAM OF FORCING MAXIMA...NOW PROGGED TO ROTATE THRU
THE BASE OF THE L/WV TROUGH. DEEP CONVECTIVE CVRG COULD BECOME
NUMEROUS LATER IN THE WEEKEND WITH A LAYER RH MAXIMA AND FRONTAL
ZONE PROGGED TO SAG SE ACRS THE CWFA SATURDAY NIGHT INTO SUNDAY.
IT REMAINS TO BE SEEN HOW FAR SE SLIGHTLY DRIER POST FRONTAL AIRMASS
WORKS INTO THE SE CONUS BY THE END OF THE PERIOD.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AT KCLT...I EXPECT VFR CONDITIONS TO PREVAIL THRU THE TAF PERIOD
WITH SOME BRIEF MVFR VISBY POSSIBLE FROM ROUGHLY 11 TO 13Z IN THE
MORNING. SFC WINDS MAY REMAIN TOO HIGH TO ALLOW ANY
RESTRICTIONS...SO MY CONFIDENCE WRT LOWER VISBY IS FAIRLY LOW.
OTHERWISE...WINDS WILL REMAIN FAIRLY STEADY OUT OF THE SW AND THEN W
THRU THE DAY AND INTO THE EVENING. CIGS ARE EXPECTED TO GO FROM BKN
TO SCT AS WE MOVE INTO THE AFTERNOON HOURS AND REMAIN AROUND THE 4K
FT LEVEL. THERE IS A CHANCE FOR MORE TSRA TOMORROW...HOWEVER THE
CHANCES ARE BELOW 30% AT THIS TIME SO I DECIDED NOT TO CARRY ANY
MENTION FOR THE TIME BEING.

ELSEWHERE...EXPECT VFR CONDITIONS TO PREVAIL THRU THE TAF PERIOD
WITH SOME BRIEF MVFR VISBY POSSIBLE AT EACH SITE FROM ROUGHLY 10 TO
13Z. KAVL COULD SEE LOWER IFR VISBY IN THE 10 TO 13Z TIME FRAME IF
SFC WINDS REMAIN WEAK ENOUGH. AS WITH KCLT...MY CONFIDENCE WRT LOWER
VISBY IS NOT VERY HIGH BECAUSE OF THE POSSIBILITY OF PERSISTENT 5+KT
WINDS. OTHERWISE...WINDS WILL REMAIN FAIRLY STEADY OUT OF THE SW AND
THEN W THRU THE DAY AND INTO THE EVENING WITH KAVL SEEING MORE OF A
NWLY COMPONENT BY EARLY AFTERNOON. CIGS ARE EXPECTED TO GO FROM BKN
TO SCT AS WE MOVE INTO THE AFTERNOON HOURS AND REMAIN AROUND THE 4K
FT LEVEL WITH KAVL EXPECTED TO SEE CIGS ABOUT 1000 TO 1500FT LOWER.
THERE IS A CHANCE FOR MORE TSRA TOMORROW...HOWEVER THE CHANCES ARE
BELOW 30% FOR KGSP...KGMU...AND KAND AND THEREFORE I DID NOT CARRY
ANY MENTION FOR THE TIME BEING. I DID INCLUDE A PROB30 FOR BOTH KAVL
AND KHKY FOR TSRA AND MVFR VISBY IN THE LATE AFTERNOON/EARLY EVENING
HOURS SINCE THEY HAVE FCST POPS IN THE 30 TO 35% RANGE.

OUTLOOK... SHOWERS AND THUNDERSTORMS WILL LIKELY ACCOMPANY A COLD
FRONTAL PASSAGE WEDNESDAY BUT BECOME LESS NUMEROUS DURING THE MIDDLE
OF THE WEEK AS HIGH PRESSURE EXTENDS SOUTHWARD FROM THE GREAT LAKES.
DURING THE LATTER PART OF THE WEEK SCATTERED AFTERNOON AND EVENING
THUNDERSTORMS WILL BE MOST NUMEROUS OVER THE MOUNTAINS. MORNING
VISIBILITY RESTRICTIONS DUE TO FOG ARE POSSIBLE EACH DAY.

CONFIDENCE TABLE...

            00-06Z        06-12Z        12-18Z        18-24Z
KCLT       HIGH 100%     HIGH  92%     HIGH  98%     HIGH 100%
KGSP       HIGH  97%     HIGH  90%     HIGH  95%     HIGH 100%
KAVL       LOW   59%     MED   77%     MED   79%     HIGH 100%
KHKY       HIGH 100%     HIGH  87%     HIGH  95%     HIGH 100%
KGMU       MED   69%     HIGH  87%     HIGH  95%     HIGH 100%
KAND       MED   72%     HIGH  80%     HIGH  96%     HIGH 100%

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...CSH
NEAR TERM...JPT
SHORT TERM...ARK
LONG TERM...CSH
AVIATION...JPT

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
302 AM EDT MON JUL 22 2013

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-230715-
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-
302 AM EDT MON JUL 22 2013

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

.DAY ONE...TODAY AND TONIGHT.

SHOWERS AND THUNDERSTORMS WILL REDEVELOP ACROSS THE REGION THIS
AFTERNOON AND INTO THE EVENING HOURS. SOME THUNDERSTORMS COULD BE
SEVERE WITH DAMAGING WINDS...CLOUD TO GROUND LIGHTNING...AND
HEAVY RAINFALL BEING THE MAIN THREATS. DUE TO RECENT HEAVY
RAINFALL...ANY LOCATIONS THAT RECEIVE MULTIPLE WAVES OF
THUNDERSTORMS WILL HAVE AN ELEVATED RISK OF FLASH FLOODING.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

NONE.

CDG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
402 PM EDT MON JUL 22 2013

SCZ008-009-222030-
CHEROKEE-YORK-
402 PM EDT MON JUL 22 2013

...A STRONG THUNDERSTORM WILL AFFECT CHEROKEE AND NORTHWESTERN YORK
COUNTIES THROUGH 430 PM EDT...

AT 359 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM NEAR GAFFNEY...MOVING EAST AT 25 MPH.

THIS STORM WILL IMPACT LOCATIONS NEAR...
  BLACKSBURG...

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

THE COMBINATION OF GUSTY WINDS AND WET SOIL CONDITIONS MAY CAUSE A
FEW TREES AND POWER LINES TO FALL. SEEK SHELTER INSIDER AN INTERIOR
ROOM.

LAT...LON 3491 8172 3515 8174 3518 8155 3516 8132
      3491 8131

WIMBERLEY

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