Severe Thunderstorm Warning 30, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
156 AM EDT SUN APR 25 2010

.SYNOPSIS...
STRENGTHENING SOUTHERLY FLOW WILL PROMOTE WIDESPREAD SHOWERS AND
THUNDERSTORMS TONIGHT AND EARLY SUNDAY MORNING...BEFORE A COLD FRONT
MOVES OVER THE REGION SUNDAY AFTERNOON AND EVENING. HIGH PRESSURE
WILL THEN BUILD BACK OVER THE SOUTHEAST BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TODAY/...
ATMOSPHERE HAS BEEN SLOW TO DESTABILIZE ACROSS THE WRN CAROLINAS
THIS EVENING...AS FCST BY PREVIOUS MODEL RUNS. AS OF 02Z...WE STILL
LACK SURFACE-BASED INSTABILITY/BUOYANCY...SO CONVECTIVE CELLS MOVING
IN FROM N GA QUICKLY GIVE UP THEIR LIGHTNING AS THEY MOVE NE INTO
OUR AREA. RADAR TRENDS ALSO SHOW THE LEADING EDGE OF THE MID LEVEL
DRY AIR AS THE BACK EDGE OF THE MORE WIDESPREAD SHOWERS AND STORMS
OVER NW GA. PROSPECTS FOR INCREASED INSTABILITY STILL REMAIN GRIM...
BUT NOT READY TO COMPLETELY GIVE UP ON SVR POTENTIAL...OWING TO
STRONG SHEAR THAT WILL PERSIST OVERNIGHT. THE BEST COMBINATION OF
SHEAR AND INSTABILITY IS EXPECTED TO OCCUR FROM 06Z TO 12Z OR SO...
JUST NOT SURE GOING FORWARD IF IT WILL AMOUNT TO ENOUGH OF A THREAT
TO LEAD TO ANYTHING MORE THAN ISOLATED SEVERE. IN FACT...SPC HAS CUT
BACK ON THE EASTWARD EXTENT OF THE SLIGHT RISK. SO...SOME
ADJUSTMENTS ARE IN ORDER. AFTER 03Z...THE WIDESPREAD COVERAGE OF
CONVECTIVE STORMS SHOULD BE LIMITED TO THE AREA E OF THE MTNS....
WITH THE GRADIENT GRADUALLY SHIFTING EAST OVER THE NEXT SEVERAL
HOURS. THINK A LIKELY TO CHANCE POP WILL HANDLE THE COVERAGE OVER
THE MTNS. TEMPS SHOULD STAY NEARLY STEADY OVERNIGHT...SO ADJUSTMENTS
WERE MADE BASED ON RECENT OBS.

STORMS ARE LIKELY TO BE ONGOING ON SUNDAY MORNING. WITH THE FLOW
TURNING MORE WESTERLY...THEY SHOULD MOVE OUT OF THE FA FAIRLY
QUICKLY. HOWEVER...THE NAM MAINTAINS QUITE A BIT OF INSTABILITY OVER
THE REGION DURING THE DAY. IN FACT...THE STEEPEST LAPSE RATES OF
THIS WHOLE EVENT ARE TOMORROW AFTN. THE GFS DRIES THINGS OUT MUCH
MORE QUICKLY. HOWEVER...IT/S NOT ALWAYS EASY TO SCOUR OUT MOISTURE E
OF THE MTNS...AND I/VE MAINTAINED CHANCE POPS THROUGH THE DAY. WHILE
THE COVERAGE SHOULD BE SCT AT BEST...THE POTENTIAL CERTAINLY EXISTS
FOR MORE DISCRETE MULTICELL OR SUPERCELL STORMS TO DEVELOP.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...
AS OF 130 PM SATURDAY...THE FA WILL BE UNDER A BROAD L/WV ERN CONUS
TROF THRU THE SHORT TERM...WITH TWO PRIMARY S/WVS TRACKING ACRS THE
AREA...ONE SUNDAY NIGHT AND A SECOND ONE TUESDAY.

MODELS IN MUCH DISAGREEMENT ON TIMING AND AMPLITUDE OF BOTH
FEATURES...ESPECIALLY THE SECOND ONE...WHICH DIVES SE ACRS THE NRN
PLAINS STATES. UNDER THE FIRST TROF...A SFC LOW WILL CONTINUE TO
WEAKEN OVER THE UPPER OH VALLEY...AS A COASTAL LOW BECOMES THE
DOMINANT LOW. THE FA WILL BE UNDER A GENERALLY Q-VECTOR DIVERGENT
REGION...WITH LLVL CAA AND DRY AMS WORKING IN FROM THE WEST.
HOWEVER...WRAPAROUND MOISTURE WILL LINGER ALONG THE WESTERN SLOPES
OF THE APPALACHIANS THRU MONDAY. FCST SNDGS SHOW ENUF MOISTURE AND
LLVL CAPE FOR SHWRS...BUT MID LVL CAP TO PRECLUDE A MENTION OF
TSTMS. IN THE LEE OF THE TN BORDER COUNTIES...ISOLD SHWR ACTIVITY
LOOKS POSSIBLE AS S/WV ENHANCES LIFT. TEMPS STILL SLIGHTLY ABOVE
NORMAL SUNDAY NIGHT AND MONDAY.

AS A SECOND...MORE POTENT S/WV DIVES SEWD THRU THE AREA
TUESDAY...THERE LOOKS TO BE LTL IN THE WAY OF SFC REFLECTION...WITH
JUST A LEE TROF AND UPSLOPE ALONG TN BORDER BEING THE ONLY SOURCES
OF LLVL CONVERGENCE. GUIDANCE SEEMS TO AGREE ON SLIGHTLY HIGHER CHCS
THAN MONDAY...SO INCREASED POP TO HIGH-END CHC TN BORDER AND LOW-END
CHC TO THE EAST (STILL SLGT CHC IN SRN UPSTATE AND UPPER SAVANNAH
VALLEY. AGAIN...NOT GREAT MID LVL LAPSE RATES FOR TSTMS...SO KEPT
WORDING AS JUST SHWRS. TEMPS WILL BE ABOUT A CATEGORY COOLER THAN
MONDAYS READINGS UNDER NWLY CAA FLOW.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 130 PM SATURDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON WED
WITH THE 12Z GFS AND OLDER 00Z ECMWF REMAINING IN FAIRLY GOOD
AGREEMENT WITH THE LINGERING L/WV TROUGH ACROSS THE EASTERN CONUS.
THE NEWER GFS DEVELOPS AN ANTECEDENT S/WV DURING THE DAY ON WED AND
PUSHES THE ASSOCIATED VORT MAX SOUTH OF THE CWA. THIS FEATURE IS NOT
PRESENT ON EITHER THE ECMWF OR GEM MODEL. REGARDLESS...BASED ON ITS
POSITION I DOUBT IT WOULD HAVE MUCH IMPACT ON OUR SENSIBLE WX.
HEIGHTS RISE THRU THE REMAINDER OF THE PERIOD AS AN H5 RIDGE BUILDS
IN FROM THE WEST AND SFC HIGH PRESSURE DOMINATES THE SYNOPTIC
PATTERN THRU DAY 7. LINGERING NW FLOW MAY BE ABLE TO PRODUCE SOME
PRECIP OVER THE NC MOUNTAINS EARLY IN THE PERIOD...HOWEVER LATEST
GUIDANCE IS SHYING AWAY FROM THIS. I KEPT A CHANCE POP FOR THE FIRST
6 HRS OF THE MEDIUM RANGE AND THEN TAPERED OFF TO A DRY FCST AFTER
12Z WED. PATTERN IS PROGGED TO AMPLIFY FURTHER ON DAYS 6 AND 7 WITH
LIGHT WINDS AND CLIMBING TEMPS. BY DAY 7...MAX VALUES IN THE LOW TO
MID 80S ARE FCST.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
DYNAMIC SITUATION REMAINS EARLY THIS MORNING AS AREA OF SH/TSRA MOVE
OUT OF THE FOOTHILLS AND PIEDMONT...WITH ANOTHER LINE OF SH/TSRA TO
MOVE INTO THE MTNS AND WRN CWFA. THIS LINE WILL MOVE ACROSS AND OUT
OF THE AREA NEAR DAYBREAK. ALTHOUGH STORMS ARE EMBEDDED IN THIS
LINE...THERE IS STILL ENUF UNCERTAINTY...DUE TO STABLE ATMOS OVER
OUR AREA AND TIMING CONCERNS...TO KEEP ONLY CB MENTIONED IN TAFS.
LOW CLOUDS WILL CLEAR BEHIND THIS LINE...BUT MAY LINGER THRU NOON.
SLY WINDS AHEAD OF THE LINE BECOME SWLY AND GUSTY DURING THE
MORNING...WITH SPEEDS AND GUSTS INCREASING FOR THE AFTERNOON. WINDS
DIMINISH THIS EVENING WITH CLEARING SKIES.

AT KCLT...EXPECT PREVAILING MVFR WITH TEMPO IFR IN SHRA THRU
DAYBREAK. MVFR CIGS WITH GUSTY SSW WINDS DURING THE MORNING AND VFR
WITH STRONGER SW WINDS AND GUSTS FOR THE AFTERNOON. LIGHT SW WINDS
WITH CLEARING SKIES THIS EVENING.

ELSEWHERE...EXPECT PREVAILING MVFR WITH TEMPO IFR IN SHRA THRU
DAYBREAK. MVFR CIGS WITH GUSTY SW WINDS DURING THE MORNING AND VFR
WITH STRONGER SW WINDS AND GUSTS FOR THE AFTERNOON. LIGHT SW WINDS
WITH CLEARING SKIES THIS EVENING. KAVL WILL SEE WINDS BECOMING LIGHT
NWLY DURING THE EVENING.

OUTLOOK...SCT SHRA AND A FEW TSTMS ARE STILL POSSIBLE MON AND
TUE...MAINLY OVER THE MTNS...BUT RESTRICTIONS WILL BE MORE SPOTTY.
FAIR WEATHER IS THEN EXPECTED WED-FRI.

&&

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

&&

SYNOPSIS...JPT
NEAR TERM...MCAVOY/PM
SHORT TERM...ARK
LONG TERM...JPT
AVIATION...RWH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
138 AM EDT SUN APR 25 2010

GAZ010-017-018-026-028-029-NCZ048-051>053-058-059-062>065-SCZ001>006-
010-011-260545-
RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-MADISON-SWAIN-HAYWOOD-
BUNCOMBE-GRAHAM-NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-
HENDERSON-OCONEE MOUNTAINS-PICKENS MOUNTAINS-GREENVILLE MOUNTAINS-
GREATER OCONEE-GREATER PICKENS-GREATER GREENVILLE-ANDERSON-ABBEVILLE-
138 AM EDT SUN APR 25 2010

...TORNADO WATCH 102 IN EFFECT UNTIL 9 AM EDT THIS MORNING...

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

.DAY ONE...TONIGHT AND SUNDAY.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   TORNADO WATCH.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTERS ARE REQUESTED TO FORWARD ANY REPORTS OF LARGE
HAIL...DAMAGING WINDS...TORNADOES OR FLASH FLOODING TO OUR OFFICE.

NCZ033-035>037-049-050-056-057-068>072-082-501>510-SCZ007>009-
012>014-019-260545-
AVERY-ALEXANDER-IREDELL-DAVIE-YANCEY-MITCHELL-CATAWBA-ROWAN-
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-SPARTANBURG-CHEROKEE-
YORK-LAURENS-UNION SC-CHESTER-GREENWOOD-
138 AM EDT SUN APR 25 2010

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

.DAY ONE...TONIGHT AND SUNDAY.

WIND SHEAR AND INSTABILITY WILL INCREASE ACROSS THE REGION EARLY
THIS MORNING...BRINGING AN INCREASED RISK OF ISOLATED SEVERE
STORMS. ALTHOUGH THE BEST CHANCES FOR SEVERE THUNDERSTORMS PRIOR
TO DAYBREAK WILL EXIST WEST OF THE I-26 CORRIDOR...SCATTERED
STORMS WILL SPREAD INTO THE PIEDMONT AND FOOTHILLS OF NORTH
CAROLINA...AS WELL AS EASTERN PORTIONS OF THE UPSTATE BY SUNRISE.
THESE STORMS WILL BE CAPABLE OF PRODUCING LARGE HAIL...AREAS OF
DAMAGING WINDS...AND ISOLATED TORNADOES. THIS THREAT FOR SEVERE
STORMS WILL CONTINUE INTO THE AFTERNOON.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTERS ARE REQUESTED TO FORWARD ANY REPORTS OF LARGE
HAIL...DAMAGING WINDS...TORNADOES OR FLASH FLOODING TO OUR OFFICE.