Severe Thunderstorm Warning 425, NWS Greenville-Spartanburg, SC

914 
WWUS52 KGSP 181758
SVSGSP

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
158 PM EDT WED JUL 18 2012

NCC199-181807-
/O.CAN.KGSP.SV.W.0425.000000T0000Z-120718T1830Z/
YANCEY NC-
158 PM EDT WED JUL 18 2012

...THE SEVERE THUNDERSTORM WARNING FOR CENTRAL YANCEY COUNTY IS
CANCELLED...

THE STORM WHICH PROMPTED THE WARNING HAS WEAKENED BELOW SEVERE
LEVELS.  HOWEVER HEAVY RAIN IS STILL POSSIBLE WITH THIS THUNDERSTORM.

LAT...LON 3593 8218 3573 8224 3577 8234 3580 8234
      3582 8236 3582 8237 3582 8241 3586 8242
      3590 8245 3600 8239
TIME...MOT...LOC 1757Z 296DEG 13KT 3583 8221

$$
LGL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
114 PM EDT WED JUL 18 2012

.SYNOPSIS...
HIGH PRESSURE WILL WEAKEN AND SHIFT SOUTH OVER THE NEXT FEW DAYS.
THIS WILL ALLOW A FRONTAL BOUNDARY OVER THE OHIO VALLEY TO DROP
SOUTH...INTO THE CAROLINAS LATE FRIDAY. THE FRONT WILL REMAIN
OVER OR JUST SOUTH OF THE REGION THROUGH THE WEEKEND AND DISSIPATE
ON MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
1730 UTC UPDATE...SKY AND POPS HAVE BEEN UPDATED PER SATELLITE
IMAGERY AND RADAR TRENDS...WITH A DECREASE IN BOTH IN THE LEE OF THE
MOUNTAINS...AND AN INCREASE OVER THE MOUNTAINS. QPF WAS ADJUSTED
ACCORDINGLY. WINDS WERE UPDATED WITH A BLEND OF 12Z NAM AND 12Z
ADJMAV.

AT 1000 AM EDT WEDNESDAY...AN UPPER RIDGE ALOFT WAS CENTERED OVER
THE OZARK MTS THIS MORNING...WHILE A CLOSED UPPER LOW WAS LOCATED
OVER S GA...AND A LOW AMPLITUDE UPPER TROUGH EXTENDED FROM EASTERN
CANADA TO THE NORTHEAST USA.SURFACE ANALYSIS PLACED A COLD FRONT
ACROSS THE NORTHERN TIER OF STATES...AND A LEE TROUGH ALONG THE
EASTERN SEABOARD. THE MODELS SHOW THE UPPER LOW DRIFTING SLOWLY NW
UP THE SAVANNA RIVER VALLEY TODAY...LENDING ADDITIONAL SUPPORT FOR
CONVECTION IN AN AIR MASS THAT WILL BE MOIST AND UNSTABLE. IN THIS
SCENARIO...CONVECTION MAY START EARLIER IN THE PIEDMONT THAN IN
PREVIOUS DAYS...AS AN IMPULSE ROUNDS THE RETROGRADING UPPER LOW.
DIFFERENTIAL HEATING IN THE MOUNTAINS IS EXPECTED TO START
CONVECTION BY EARLY AFTERNOON. BOTH DAMAGING WINDS AND HAIL WILL BE
POSSIBLE. MAXIMUM TEMPERATURES WILL BE SLIGHTLY ABOVE NORMAL...AND
WITH DEW POINTS SLIGHTLY ABOVE NORMAL...THE HEAT INDEX WILL APPROACH
100 DEGREES IN THE PIEDMONT...WHICH IS STILL BELOW THE ADVISORY
CRITERIA OF 105 DEGREES.

TONIGHT...CONVECTION SHOULD FADE DURING THE MID TO LATE EVENING
HOURS. DEBRIS CLOUDS AND HIGH CLOUD INCREASING FROM THE WEST SHOULD
KEEP SKY COVER PARTLY TO MOSTLY CLOUDY. A BLEND OF MOS SUPPORTS MIN
TEMPERATURES IN THE MID 60S ACROSS THE MTNS TO L70S EAST.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 245 AM WEDNESDAY...LIKELY POPS CONTINUE TO LOOK GOOD ACROSS
THE MOUNTAINS AND FOOTHILLS WITH HIGH CHANCE POPS OVER THE PIEDMONT
FOR THURSDAY. A WEAK SRN STREAM TROUGH WILL BE ORIENTED N TO S
ACROSS THE SRN APPALACHIANS WITH HIGH PW/S AND HIGH DEEP LAYER RH/S
WITHIN THE TROUGH. A SERIES A WEAK H5 CONVECTIVE INDUCED SHORT WAVES
WILL BE EMBEDDED WITHIN THE TROUGH. THE GFS AND ECMWF BOTH HAVE
QUITE A BIT OF PCPN OVER THE REGION IN THE AFTN AND EVENING HOURS.
CONVECTION SHOULD END THURSDAY EVENING AS THERE WILL BE A LIGHT
DOWNSLOPE FLOW AND A TENDENCY FOR NVA TO DEVELOP AS THE SRN STREAM
TROUGH BEGINS TO KICK TO THE EAST IN ADVANCE OF A STRONGER NRN
STREAM TROUGH.

THE NRN STREAM THROUGH WILL PUSH A COLD FRONT IN THE NRN PART OF THE
FA BY LATE IN THE DAY ON FRIDAY. ONCE AGAIN...WHTH MODERATE
INSTABILITY...ABOUT 20 KTS OF DEEP LAYER SHEAR AND ABOVE NORMAL
PW/S...THERE SHOULD BE NUMEROUS SHOWERS AND TSTMS ACROSS THE REGION.
PW/S WILL BE NORTH OF 2 INCHES BOTH THURSDAY AND FRIDAY. THERE WILL
ALMOST CERTAINLY BE LOCALIZED AREAS OF EXCESSIVE RAINFALL AND A FEW
INSTANCES OF FLASH FLOODING. HOWEVER...THE FORCING IS NOT STRONG
ENOUGH TO NAIL DOWN AN AREA OR PERIOD OF TIME THAT WOULD WARRANT A
FLASH FLOOD WATCH. THE GENERALLY W TO SW ORIENTED DEEP LAYER SHEAR
WILL ALSO HOPEFULLY LIMIT ANCHORING OR TRAINING CELLS DURING THE
THU/FRI TIME FRAME THOUGH THE MAGNITUDE OF THE SHEAR IS SO WEAK THAT
MIGHT NOT BE OF MUCH HELP.

CONVECTION COULD LAST WELL INTO FRIDAY NIGHT AS THE SFC COLD FRONT
WILL BE DROPPING ACROSS THE REGION AND POPS ONLY GRADUALLY TAPER OFF
INTO THE LATE NIGHT HOURS.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 1245 PM WEDNESDAY...THE LATEST GUIDANCE KEEPS A STATIONARY
FRONT OVER THE AREA SUNDAY. THE FRONT BEGINS TO WASH OUT MONDAY AS
THE BERMUDA HIGH POKES BACK INTO THE REGION FROM THE EAST.
HOWEVER...A SHEAR AXIS AND A BAND OF DEEP MOISTURE WILL REMAIN OVER
THE AREA MONDAY IN THE WEAKNESS BETWEEN THE BERMUDA HIGH AND THE
STRONG RIDGE OVER THE CENTRAL CONUS. THE RIDGE AND THE BERMUDA HIGH
MERGE TUESDAY AS A TROF MOVES OFF SHORE OF NEW ENGLAND...BUT THE
DEEP MOISTURE AND A LEE TROF REMAIN OVER MUCH OF THE SERN US. THE
CENTER OF THE RIDGE IS PUSHED SOUTH INTO THE GULF WEDNESDAY...BUT
RIDGE AXIS REMAINS OVER OUR AREA...AS ANOTHER TROF DROPS FROM CANADA
INTO THE NRN PLAINS. THIS HELPS PUSH A BACK DOOR COLD FRONT TOWARD
THE AREA DURING THE DAY.

ALTHOUGH A GOOD CHANCE OF CONVECTION AGAIN ON SUNDAY...GUIDANCE
DIFFERS ON BETTER CHANCES FOR ONE AREA OR ANOTHER. THEREFORE...HAVE
GONE WITH CHC POP FOR NOW. OTHERWISE...MAINLY DIURNAL CHC POP MON
THRU WED WITH THE MOISTURE AND WEAK FORCING IN PLACE. ABOVE NORMAL
LOWS AND BELOW NORMAL HIGHS AGAIN SUNDAY...THEN THE HEAT BUILDS WITH
THE RIDGE. HIGHS RISING INTO THE MID 90S BY WED WITH LOW TO MID 70S
EACH MORNING.

&&

.AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...SCATTERED CONVECTION IS EXPECTED THIS AFTERNOON. BASED THE
SLOWER THAN ANTICIPATED DEVELOPMENT...CONFIDENCE IS A LOWER FOR A
RESTRICTION...AND NONE WILL BE CARRIED AT THIS TIME. TS WITH A LOW
VFR CIG WILL BE CARRIED. LIGHT SW WINDS WILL PERSIST. A CONSENSUS OF
GUIDANCE DOES NOT SUPPORT DAYBREAK FOG ON THURSDAY. ALTHOUGH THE
CHANCE OF PRECIPITATION WILL INCREASE ON THURSDAY MORNING AS A FRONT
APPROACHES FORM THE NORTH...CHANCES ARE STILL TOO LOW MENTION A
RESTRICTION.

ELSEWHERE...CONVECTION WILL DEVELOP THIS AFTERNOON...WITH THE BEST
COVERAGE IN THE MOUNTAINS. A TEMPO FOR THUNDERSTORM BASED MVFR
RESTRICTIONS WILL BE CARRIED AT KAVL...WHILE FOOTHILLS SITES GET TS
AND A LOW VFR CIG WITH CB. LIGHT WINDS WILL REMAIN FROM THE SW TO
WSW...EXCEPT AT KAVL WHERE THEY WILL CHANNEL UP THE VALLEY FORM THE
NW. AT THIS TIME GUIDANCE PLACES FOG IN THE MOUNTAIN VALLEYS SW OF
KAVL. BASED ON THE TRENDS FROM THIS MORNING...FOG WILL BE CARRIED AT
KAVL AND KAND AS WELL. CHANCES FOR CONVECTION INCREASE ON THURSDAY
AS A FRONT APPROACHES FROM THE NORTH...BUT CONFIDENCE IS TOO LOW TO
CARRY A RESTRICTION.

OUTLOOK...SCATTERED THUNDERSTORMS WILL CONTINUE LATE
THURSDAY...ESPECIALLY OVER THE NC MOUNTAINS. A WEAK COLD FRONT WILL
REACH THE AREA ON FRIDAY...REMAINING INTO THE WEEKEND...AND
INCREASING THE CHANCE OF THUNDER...LOW CIGS...AND FOG.

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...MCAVOY
NEAR TERM...JAT/NED
SHORT TERM...MCAVOY
LONG TERM...MCAVOY
AVIATION...JAT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
533 AM EDT WED JUL 18 2012

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-190945-
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-
533 AM EDT WED JUL 18 2012

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

.DAY ONE...TODAY AND TONIGHT.

SCATTERED TO NUMEROUS SLOW MOVING THUNDERSTORMS WILL DEVELOP OVER
THE REGION AGAIN TODAY. A FEW OF THE THUNDERSTORMS WILL PRODUCE
SMALL AREAS OF WIND DAMAGE AND HAIL UP TO THE SIZE OF QUARTERS.
LOCALLY VERY HEAVY RAINFALL IS ALSO POSSIBLE WITH THE STRONGER
STORMS AND FLOODING OF POOR DRAINAGE AREAS MAY DEVELOP. MANY OF
THE STORMS WILL PRODUCE FREQUENT CLOUD TO GROUND LIGHTING THIS
AFTERNOON.

THE EFFECTS OF HEAVY RAIN AND SATURATED SOILS WILL ENHANCE THE
THREAT OF TREES FALLING.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

NONE.

14

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
109 PM EDT WED JUL 18 2012

NCZ033-048>053-058-059-062>065-501>505-181745-
AVERY-BUNCOMBE-BURKE MOUNTAINS-CALDWELL MOUNTAINS-GRAHAM-GREATER
BURKE-GREATER CALDWELL-HAYWOOD-HENDERSON-MACON-MADISON-MCDOWELL
MOUNTAINS-MITCHELL-NORTHERN JACKSON-SOUTHERN
JACKSON-SWAIN-TRANSYLVANIA-YANCEY-
109 PM EDT WED JUL 18 2012

...THUNDERSTORMS ARE DEVELOPING OVER THE MOUNTAINS AND FOOTHILLS OF
NORTH CAROLINA...

AT 100 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
SCATTERED THUNDERSTORMS WERE DEVELOPING OVER THE MOUNTAINS AND
FOOTHILLS
OF NORTH CAROLINA. PEA SIZE HAIL WAS REPORTED NEAR CANTON JUST
BEFORE 1:00 PM. ADDITIONAL OCCURRENCES OF SMALL HAIL... ALONG WITH
GUSTY WINDS... ARE EXPECTED DURING THE AFTERNOON.

THE THUNDERSTORMS WILL ALSO PRODUCE LIGHTNING AND LOCALLY HEAVY. THE
THUNDERSTORMS WILL MOVE VERY SLOWLY... HIGH WATER LEVELS ARE
POSSIBLE IN POOR DRAINAGE AREAS.

LAT...LON 3546 8397 3557 8374 3557 8349 3577 8315
      3578 8299 3594 8291 3593 8281 3607 8264
      3596 8256 3617 8222 3611 8208 3629 8192
      3612 8181 3612 8171 3591 8159 3499 8346
      3516 8374 3525 8371 3522 8392 3528 8404

LGL