Severe Thunderstorm Warning 263, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
516 PM EDT WED JUL 24 2013

.SYNOPSIS...
A COLD FRONT WILL MOVE ACROSS THE CAROLINAS...REACHING THE COAST
EARLY FRIDAY. HIGH PRESSURE WILL FILL IN BEHIND THE FRONT AND REMAIN
FOR MOST OF THE WEEKEND. ANOTHER FRONT WILL APPROACH THE AREA LATE
SUNDAY BRINGING YET ANOTHER INCREASE IN CHANCES FOR SHOWERS AND
THUNDERSTORMS THROUGH MONDAY. CONDITIONS WILL GRADUALLY IMPROVE
STARTING ON TUESDAY INTO MID WEEK...AS HIGH PRESSURE TAKES OVER
AGAIN.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 510 PM EDT...CONVECTION ISN/T ORGANIZING ALONG OUTFLOW BNDRYS
SO MUCH AS IT IS RANDOMLY DEVELOPING ACROSS THE WRN CAROLINAS AND NE
GA LATE THIS AFTN. THEREFORE I WENT WITH A MORE UNIFORM AREA OF
CHANCE POPS ACROSS THE FA THE NEXT FEW HOURS. LATER THIS EVENING
THE FLOW JUST ABOVE THE BNDRY LAYER WILL PICK UP TO AROUND 25-30
KTS FROM THE NE. THIS COULD HELP TO FOCUS CONVECTION A LITTLE
MORE...ESPECIALLY OVER THE NC PIEDMONT AND FOOTHILLS WHERE THE
INCREASING FLOW WILL HAPPEN THE SOONEST...AND THUS WITH THE MOST
RESIDUAL INSTABILITY.

AS OF 240 PM...LATEST RADAR IMAGES INDICATE A CLUSTER OF SHRA/TSRA
OVER THE SC/GA MTNS...DRIFTING SLOWLY SSE. RECENT SATELLITE IMAGES
INDICATE THAT FAIR WEATHER CU HAS DEVELOPED ACROSS THE CWA.
HOWEVER...TCU WAS DETECTED ACROSS MCDOWELL...BURKE...AND CALDWELL AT
OF 1830Z. 12Z 4KM WRF-NMM AND SPC SSEO SUPPORT TO FORMATION OF A
BROKEN LINE OF CONVECTION SHOULD ACROSS THE NC FOOTHILLS AND UPSTATE
MTNS BETWEEN 3 TO 4 PM. THE STORMS WILL LIKELY FORM A COOL POOL AND
INCREASE IN COVERAGE AND SPEED EASTWARD DURING THE HEAT OF THE
AFTERNOON. THE LINE SHOULD PUSH EAST OF I-85 AND THE CLT METRO
BETWEEN 22Z TO 23Z...EXITING THE CWA BY BETWEEN 1Z TO 3Z.

12Z OBSERVED SOUNDINGS FROM FFC AND GSO BOTH INDICATE CAPE VALUES
SLIGHTLY BELOW 1500 J/KG. THE LATEST MESOSCALE ANALYSIS INDICATES
CAPE VALUES AROUND 2000 J/KG. THE FREEZING LEVEL RANGED FROM 14.7
KFT/WBZ 10.6 KFT AT GSO TO 14.2 KFT/WBZ 12.5 KFT AT FFC. STORM
MOTIONS SHOULD CARRY STORMS SSE BETWEEN 10 TO 15 KTS. I WOULD EXPECT
THAT THE GREATEST THREAT FOR SVR THUNDERSTORMS WILL OCCUR ACROSS THE
FOOTHILLS AND PIEDMONT WITH BETTER ORGANIZED MULTI-CELL
STORMS...PRODUCING DAMAGING WINDS AND POSSIBLY LARGE HAIL. THE
PRELIMINARY 55 DBZ CORE HEIGHT FOR HAIL WILL BE 26.0 KFT. THE
CURRENT HWO WILL REMAIN.

THURSDAY...THE CWA WILL REMAIN ON THE WEST SIDE OF A DEVELOPING
COASTAL LOW. THE CIRCULATION AROUND THE LOW COMBINED WITH HIGH
PRESSURE ACROSS THE OHIO RIVER VALLEY WILL SUPPLY THE REGION WITH
LIGHT NORTH TO NORTHEAST FLOW. A MID LEVEL L/W TROF WILL REMAIN
OVERHEAD...WITH SEVERAL SMALL S/W. FORECAST SOUNDINGS INDICATE THAT
CAPE VALUES MAY AGAIN RANGE CLOSE TO 2000 J/KG. MTN SHRA AND TSRA
SHOULD FORM FROM MID DAY THROUGH THE EARLY AFTERNOON. SCT CONVECTION
WILL MOVE OFF OF THE MTNS AND DEVELOP ACROSS THE FOOTHILLS AND
PIEDMONT DURING THE HEAT OF THE AFTERNOON. CLOUD COVER WILL LIKELY
DEVELOP AS SCT TO BKN LOW BASED CU. THE COMBINATION OF THE CLOUD
COVER AND COOLER THICKNESSES SHOULD RESULT IN HIGH TEMPERATURES
AROUND 5 DEGREES COOLER THAN TODAY.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
AS OF 145 PM WEDNESDAY...A 500 MB SHEAR AXIS WILL BEGIN TO SHIFT
EAST...AS A SFC LOW RIDES NE INVOF THE MID ATLANTIC OFF SHORE WATERS
TOWARD CAPE COD BY FRIDAY NIGHT. WEAK HIGH PRES AND OVERALL
SUPPRESSED VERTICAL MOTIONS SHUD RESULT IN A QUIET NIGHT THURSDAY
NIGHT AND LIMITED CONVECTIVE CHCS ON FRIDAY. MODELS BRING SOME
MOISTURE FROM THE SOUTH...MAINLY ACRS THE WRN ZONES BY FRIDAY
AFTN...WITH 1500-2000 J/KG OF CAPE POSSIBLE AND A LIGHT SLY UPSLOPE
FLOW AT 850 MB. I WILL KEEP THE SLGT CHC POP ACRS THE PIEDMONT AND
CHC POP IN THE MTNS. TEMPS ARE FCST TO START OUT ON THE COOL SIDE
FRIDAY MORNING IN THE 50S MTNS AND 60S ACRS MOST OF THE
PIEDMONT...THEN REACHING ONLY THE 70S MTNS AND MID-UPR 80S PIEDMONT.

FRIDAY NIGHT AND SATURDAY...AN UPR LOW WILL CLOSE OFF AND DIG INTO
THE GREAT LAKES...WITH A MOIST AXIS SETTING UP ON THE EAST SIDE OF
THE CIRCULATION FROM THE GULF NE UP THE APPALACHIAN CHAIN. PWATS
WILL STAY MODEST WITHIN THE AXIS...GENERALLY 100-125% OF NORMAL.
INSTBY AND SHEAR WILL ALSO BE MODEST...SO WHILE POPS RAMP UP TO
HIGH-END CHC TO LIKELY BY SAT AFTN...THE HEAVY RAIN AND SEVERE
THREATS ARE NOT EXPECTED TO BE ELEVATED. TEMPS WILL BE NEAR NORMAL
FRI NIGHT...AND REMAIN BELOW NORMAL FOR HIGHS ON SATURDAY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 1245 PM WEDNESDAY...MODEL SOLNS BEGIN TO DIVERGE IN THE MEDIUM
RANGE...AS SHORTWAVE ENERGY WORKS TO EJECT AN UPR LVL VORTEX OUT OF
THE GREAT LAKES...LEAVING QUASI-ZONAL FLOW ACRS THE NRN TIER STATES
AND SUBTROPICAL RIDGE ACRS THE SOUTH. THE 12Z GFS IS ON THE
SLOWER/MORE AMPLIFIED SIDE OF THE GUIDANCE ENVELOPE WITH THE GREAT
LAKES LOW...AND PUSHES THE MOISTURE AXIS THRU THE AREA AND USHERS IN
DRY WX FOR MON AND TUE. THE ECMWF CONTINUES TO BE STRONGER WITH A
SHORTWAVE ROUNDING THE LONGWAVE TROF ACRS THE SOUTHEAST STATES
MON-TUE...AND RESULTS IN THE MOISTURE AXIS PIVOTING TO AN E-W
ORIENTATION ATOP THE CWFA. THIS SOLN IS MORE UNSETTLED THRU NEW DAY
7 (NEXT WED). THE WPC PREFERENCE WAS FOR AN ENS MEAN BLEND...WHICH
APPEARS MORE IN LINE WITH THE ECMWF (AT LEAST IN TERMS OF OUR
SENSIBLE WX). SO GOING WITH THE WPC...I HAVE A PRIMARILY DIURNAL
CYCLE OF HEFTY CHC POPS EACH DAY...HIGHEST ON SUNDAY WHEN THE
MOISTURE AXIS AND BEST UPPER SUPPORT WILL BE CENTERED OVER THE AREA.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...AT 1745Z...DEEP CONVECTION WAS BEGINNING TO DEVELOP OVER
THE EAST FACING SLOPES AND WITHIN A CU FIELD ACROSS THE MIDLANDS OF
SC. THE LATEST SATELLITE AND WEB CAMS INDICATED THAT A WEAK CU
FORMED ACROSS THE CLT METRO AREA. THE ENVIRONMENT FEATURES CAPES
AROUND 2000 J/KG WITH LITTLE TO NO LLVL CIN. BASED ON CONVECTION
ALLOWING MODELS...SATELLITE TRENDS...AND THE LATEST MESOSCALE
ANALYSIS...STORMS SHOULD CONTINUE TO DEVELOP ACROSS THE EAST FACING
MTNS SLOPES AND ADJACENT FOOTHILLS THROUGH 20Z. ONCE THE BAND FORMS
AND DEVELOPS A COOL POOL...CONVECTION SHOULD SWEEP TOWARD THE EAST.
THE PRIMARY PERIOD OF CONVECTION SHOULD OCCUR BETWEEN 22Z TO 01Z
OVER THE CLT TERMINAL. BY MID EVENING...THE BAND OF SHRA/TSRA SHOULD
PUSH EAST OF THE REGION AND GRADUALLY DISSIPATE. I WILL INDICATE
CLEARING CONDITIONS WITH LIGHT WINDS OVERNIGHT. HOWEVER...IF THE
AIRFIELD RECEIVES A DOWNPOUR LATER THIS AFTERNOON AND EVENING...MVFR
FOG COULD DEVELOP...I WILL LEAVE OUT OF THE TAF FOR NOW. BY
SUNRISE...WINDS SHOULD SHIFT FROM THE NE...ADVECTING GREATER
MOISTURE FROM THE NORTH. I WILL INDICATE LOWER CU BASES...BUT
REMAINING VFR.

ELSEWHERE...TRENDS REMAIN SIMILAR TO CLT. HOWEVER...KGSP/KGMU/KHKY/KAND
WILL STAND THE GREATEST CHC FOR SHRA/TSRA LATE THIS FROM 20Z TO
23Z...HIGHLIGHTED WITH A TEMPO. THE BULK OF THE CONVECTION SHOULD
DEVELOP SOUTH AND EAST OF KAVL...I WILL CARRY A VCTS. FORECAST
SOUNDINGS AND CONDENSATION PRESSURE DEFICITS FOR THE KAVL SUPPORT
THE MENTION OF DAWN FOG AND IFR STRATUS...HIGHLIGHTED WITH A TEMPO.
SHRA AND TSRA MAY DEVELOP A LITTLE EARLIER TOMORROW.

OUTLOOK...A COLD FRONT WILL GRADUALLY SETTLE SE OF THE TERMINAL
FORECAST AREA THU THROUGH FRI. LINGERING BOUNDARY LAYER MOISTURE MAY
PRODUCE ISOLATED TO SCATTERED DIURNAL THUNDERSTORMS AGAIN DURING THE
AFTN AND EVENING HOURS...ESPECIALLY IN AND NEAR THE MTNS. THE
FORECAST HAS LOW CONFIDENCE THROUGH THE WEEKEND...BUT A TREND TOWARD
MORE PRECIPITATION AND RESTRICTIONS LOOKS MOST LIKELY.

CONFIDENCE TABLE...

            21-03Z        03-09Z        09-15Z        15-21Z
KCLT       HIGH 100%     HIGH 100%     HIGH  82%     HIGH  95%
KGSP       HIGH 100%     HIGH 100%     HIGH  98%     HIGH 100%
KAVL       HIGH 100%     HIGH  91%     HIGH  83%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH  93%     HIGH  98%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     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...PAT
NEAR TERM...MCAVOY/NED
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...NED

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
236 AM EDT WED JUL 24 2013

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-250645-
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-
236 AM EDT WED JUL 24 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 DEVELOP ACROSS THE REGION THIS
AFTERNOON AND EVENING. SOME OF THESE STORMS ACROSS THE FOOTHILLS
AND PIEDMONT REGIONS COULD BE STRONG TO SEVERE WITH DAMAGING
WINDS...LARGE HAIL...AND CLOUD TO GROUND LIGHTNING BEING THE MAIN
THREATS.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

NONE.

CDG

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