Severe Thunderstorm Warning 270, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
537 PM EDT THU JUL 25 2013

.SYNOPSIS...
PRECIPITATION CHANCES WILL REMAIN IN THE FORECAST THROUGH THE
WEEKEND AS A SERIES OF UPPER LEVEL DISTURBANCES AND A COLD FRONT
PASS THROUGH.  CONDITIONS LOOK TO IMPROVE SLIGHTLY FOR THE START OF
NEXT WEEK AS SURFACE HIGH PRESSURE BUILDS WHILE REDUCING CHANCES FOR
PRECIPITATION.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 530 PM EDT THURSDAY...THOUGH ISOLATED...SOME STRONG STORMS ARE
DEVELOPING ALONG THE BLUE RIDGE. THE FLOW HAS BACKED TO THE SE JUST
EAST OF THE MTNS AND THE RESULTANT MOISTURE CONVERGENCE SHOULD
CONTINUE TO SUPPORT ISOLATED STRONG TO SEVERE STORMS FOR A FEW MORE
HOURS. THE MOIST INTENSE CONVECTION SHOULD GENERALLY DROP TO THE
SOUTH...FOLLOWING THE BEST INFLOW AND RICHEST LLVL DEWPOINTS.

PREVIOUS DISCUSSION...
ALTHOUGH STRATOCU FIELD HAS BECOME INCREASINGLY EXTENSIVE AND
CELLULAR OVER THE PIEDMONT DURING THE PAST HOUR OR TWO...THE CU IS
GENERALLY FLAT/UNINSPIRED. MEANWHILE...RIDGE TOP CU REMAINS SOMEWHAT
AGITATED NEAR THE BLUE RIDGE...BUT THE FIRST CELL HAS YET TO POP.
IN LIGHT OF 1500-2000 J/KG SBCAPE...WE WILL CONTINUE TO ADVERTISE
LOW (NEAR THE BLUE RIDGE) OR SLIGHT (EVERYWHERE ELSE) CHANCE POPS
ACROSS THE AREA. IN LIGHT OF A GENERALLY UNFAVORABLE SYNOPTIC
PATTERN...AND RELATIVELY LOW CAPE VALUES FOR MID-SUMMER... ANY
CONVECTION THAT DOES DEVELOP SHOULD DISSIPATE BY LATE EVENING. MIN
TEMPS SHOULD BE VERY CLOSE TO CLIMO.

FOR FRIDAY...THE UPPER AIR PATTERN ACROSS MUCH OF THE EASTERN CONUS
WILL BE MARKED BY FALLING HEIGHTS...AS A FAIRLY SIGNIFICANT TROUGH
APPROACHES FROM THE MISS VALLEY. THE RESULT SHOULD BE AN ENVIRONMENT
A LITTLE LESS HOSTILE TO CONVECTION. FORECAST SOUNDINGS ALSO APPEAR
A BIT MORE UNSTABLE ACROSS THE AREA FRIDAY AFTERNOON...ESP ACROSS
THE WESTERN HALF OF THE AREA...AND A LIGHT E/SE UPSLOPE FLOW COULD
ACT TO FOCUS CONVECTION NEAR THE BLUE RIDGE. THE RESULT SHOULD BE
POPS INCREASING A LITTLE ABOVE CLIMO (30-40 PERCENT ACROSS MUCH OF
THE AREA) BY THE END OF THE DAY.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 215 PM THURSDAY...THE SHORT TERM STILL LOOKS TO BE QUITE
ACTIVE AS MODELS REMAIN IN GOOD AGREEMENT WITH REGARD TO
BROAD UPPER TROF PATTERN PERSISTING THROUGH THE SHORT TERM PERIOD
WITH A SERIES OF VORT MAXES PASSING THROUGH THE REGION.

WITH UPSLOPE FLOW AND AND THE APPROACH OF A SHORT WAVE FROM THE
WEST...FRIDAY NIGHT WILL SHOW A NON-DIURNAL POP TREND AS EXPECT THAT
SCT TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL CONTINE THROUGHOUT
THE NIGHT. ON SAT...LOOKS LIKE NUMEROUS SHOWERS/STORMS WILL AFFECT
THE WESTERN CAROLINAS AND NE GA AS THE UPPER SHORT WAVE TRAVERSES
THE AREA. THE 12Z NAM IS ESPECIALLY BULLISH WITH QPF AS IT DEVELOPS
A CONVECTIVE COMPLEX AND MOVES ACROSS NE GA AND THE UPSTATE.

A WEAK COLD FRONT IS FORECAST TO SLIP ACROSS THE MOUNTAINS SAT
NIGHT...BUT MODELS THEN KEEP IT STATIONARY ALONG THE LEE OF THE
MOUNTAINS ON SUNDAY. THIS SHOULD SERVE AS A TRIGGER FOR ADDITIONAL
SCT TO NUMEROUS SHOWERS/STORMS ON SUNDAY...MOST NUMEROUS ACROSS
EASTERN SECTIONS.

USED A MODEL CONSENSUS FOR MOST GRID FIELDS. MAX TEMPS ARE FORECAST
TO BE ABOUT A CATEGORY BELOW AVERAGE.

AS THE UPPER TROUGH MOVES

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 200 PM THURSDAY...GENERALLY ZONAL FLOW ALOFT IS FORECAST BY
THE MEDIUM RANGE MODELS FOR MON INTO TUE AS THE UPPER TROUGH MOVES
EAST...AND THEN TRANSITION TO THE NW AS A LARGE UPPER HIGH BUILDS
OVER TX. SURFACE HIGH PRESSURE IS FORECAST TO BUILD OVER THE AREA ON
MONDAY IN THE WAKE OF THE WEAK FRONTAL PASSAGE ON SUNDAY. THE 12Z
GFS SHOWS NO QPF RESPONSE ON MONDAY INTO MIDDAY TUE...SO WILL LEAN
TOWARD A DRYER SOLUTION FOR  MON/TUE...BUT RAMP UP POPS INTO THE
CHANCE CATEGORY BY LATE IN THE DAY TUE AS THE FRONT TO THE SOUTH
RETURNS AS A WARM FRONT. FROM THERE...IT APPEARS THAT THE WEATHER
WILL BECOME QUITE UNSETTLED AGAIN BY MIDWEEK AS DEEP MOISTURE
SPREADS ACROSS THE REGION...COMBINED WITH WEAKLY DIFLUENT FLOW ALOFT
AND PASSING UPPER IMPULSES. HENCE....WILL HAVE SOLID CHANCE POPS
FROM TUE NIGHT THROUGH THU...BUT SHOW A DIURNAL MAXIMUM OF POPS
DURING THE DAY. USED A COMBINATION OF WPC AND MODEL CONSENSUS GRIDS
FOR MOST OF THE FIELDS...EXCEPT THE BEFORE MENTIONED MON PERIOD WITH
LOWER POPS PER GFS. MAX TEMPS ARE FORECAST TO REMAIN A CATEGORY OR
SO BELOW SEASONAL AVERAGES...THOUGH WARMING SOME BY LATE WEEK.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
AT KCLT AND ELSEWHERE...EXTENSIVE MVFR/LOW VFR STRATOCU AND CUMULUS
CONTINUE TO AFFECT MUCH OF THE PIEDMONT. A BRIEF PERIOD OF CIG
RESTRICTIONS WILL BE POSSIBLE EARLY IN THE PERIOD...ESP AT KCLT...
BUT CONTINUED HEATING SHOULD ALLOW CLOUD BASES TO LIFT WELL INTO THE
VFR CATEGORY BY LATE AFTERNOON. OTHERWISE...ISOLATED CONVECTION IS
EXPECTED TO DEVELOP ACROSS THE AREA LATE THIS AFTERNOON AND
EVENING...BUT CURRENT EXPECTATIONS ARE THAT COVERAGE SHOULD REMAIN
SPARSE ENOUGH TO PRECLUDE A MENTION OF CONVECTION IN THE TAFS...
EXCEPT AT KAVL...WHERE COVERAGE IS EXPECTED TO BE A LITTLE GREATER
OVER THE HIGH TERRAIN.

A DEVELOPING LOW LEVEL E/SE FLOW AND PERSISTENT LOW LEVEL MOISTURE
IS EXPECTED TO RESULT IN EXPANSION OF LOW CLOUDS ACROSS THE AREA
LATE TONIGHT AND EARLY FRIDAY (ESP NEAR THE BLUE RIDGE). HOW LOW AND
HOW WIDESPREAD THIS CLOUD COVER WILL BE REMAINS OPEN FOR DEBATE. FOR
NOW...HAVE GENERALLY OPTED TO INTRODUCE MVFR CIGS AT MOST TERMINALS
AFTER 06Z...BUT CIGS COULD CERTAINLY BE LOWER...ESP NEAR THE BLUE
RIDGE.

OUTLOOK...DEEPER MOISTURE WILL INCREASE INTO THE WEEKEND AHEAD OF AN
APPROACHING COLD FRONT...WITH RESTRICTIONS BECOMING MORE LIKELY
ALONG WITH INCREASING SHRA/TSRA CHANCES. BRIEF DRYING IS POSSIBLE ON
MONDAY WITH HIGH PRES FOLLOWING FROPA.

CONFIDENCE TABLE...

            21-03Z        03-09Z        09-15Z        15-21Z
KCLT       HIGH  92%     HIGH  85%     HIGH  94%     MED   73%
KGSP       HIGH 100%     MED   71%     MED   65%     HIGH  80%
KAVL       HIGH  92%     LOW   44%     MED   62%     HIGH  80%
KHKY       HIGH  85%     LOW   52%     LOW   42%     MED   73%
KGMU       HIGH 100%     MED   72%     MED   67%     HIGH  80%
KAND       HIGH 100%     HIGH 100%     LOW   54%     MED   70%

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...DEO
NEAR TERM...JDL/MCAVOY
SHORT TERM...LG
LONG TERM...LG
AVIATION...JDL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
328 PM EDT THU JUL 25 2013

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-261930-
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-
328 PM EDT THU JUL 25 2013

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

ISOLATED TO SCATTERED THUNDERSTORMS WILL REDEVELOP ACROSS THE
EASTERN SLOPES OF THE HIGH TERRAIN AND FOOTHILLS THIS
AFTERNOON..THEN MOVE INTO THE FOOTHILLS AND PIEDMONT LATE THIS
AFTERNOON AND THIS EVENING. AN ISOLATED SEVERE STORM COULD OCCUR
AND PRODUCE DAMAGING WINDS AND LARGE HAIL.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

NONE.

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