Severe Thunderstorm Warning 115, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
711 PM EDT TUE APR 25 2006

.SHORT TERM /REST OF TONIGHT/...
WILL UPDATE FORECAST PRODUCTS FOR SEVERE THUNDERSTORM WATCH 251
UNTIL 06Z.

&&

.PREV DISCUSSION...
 /ISSUED 237 PM EDT TUE APR 25 2006/

SHORT TERM /TONIGHT THROUGH FRIDAY/...
PRESENTLY CU FIELD IS BEGINNING TO SHOW SOME DEVELOPMENT ACROSS THE
NORTHERN PART OF THE UPSTATE IN AN AREA OF -5 LI/S ON THE GOES
SOUNDER DATA. THIS IS ALSO AN AREA WHERE WE HAVE A DIFFERENTIAL
HEATING BOUNDARY. SBCAPES IN THIS AREA AVERAGE BETWEEN 1000-1500 AND
WE SHOULD BEGIN TO SEE SOME THUNDERSTORMS POP BEFORE LONG. WHILE
MID LEVEL LAPSE RATES ARE NOT GREAT...WE DO HAVE A DEEP MIXED
LAYER TODAY AND DAMAGING WIND POTENTIAL THROUGH SUB-CLOUD LAYER
DAPE IS RATHER HIGH.

SO FAR NOTHING HAS DEVELOPED UPSTREAM THAT WOULD THREATEN US. MOST
OF THE STORMS INSTEAD HAVE INITIATED ON THE SOUTHERN PART OF THE
OUTFLOW BOUNDARY FROM THE MCS THAT EARLIER WENT THROUGH AR. THE
MESOSCALE CONVECTIVE VORTEX SPAWNED BY THIS SYSTEM TOOK OFF TO THE
NORTHEAST AND IS CURRENTLY DRIVING CONVECTION OVER CENTRAL KY.
SO...PRESENTLY...THERE IS NOTHING TO OUR WEST WHICH WOULD MOVE INTO
THE FORECAST AREA LATER IN THE AFTERNOON OR EVENING. I CERTAINLY
EXPECT THIS TO CHANGE...BUT AT PRESENT I DON/T HAVE A REAL GOOD FEEL
FOR WHEN OR WHERE EXACTLY CONVECTION WILL INITIATE.

WHILE CONVECTIVE THREAT SHOULD DIMINISH AFTER MIDNIGHT PER THE
LIMITED INSTABILITY ON THE MODELS AND THE LACK OF ANY KIND OF STRONG
LOW LEVEL JET OR WARM ADVECTION...I WILL KEEP CONVECTION IN THE
FORECAST TO ACCOUNT FOR CONVERGENCE ON THE SURFACE FRONT AS IT DROPS
INTO THE AREA. THE FRONT ITSELF WILL DROP INTO THE REGION VIA CAD
PROCESSES...THOUGH IT IS SLOWER ON THE LATEST NAM WHICH IS MUCH MORE
IN LINE WITH THE GFS. THIS RESULTS IN QUITE A BIT OF INSTABILITY AND
STRONG CONVERGENCE IN THE SOUTHWEST PART OF THE CWFA TOMORROW
AFTERNOON. IN FACT...0-6KM SHEAR WILL BE NEARLY 60KTS...THOUGH LOW
LEVEL FLOW WILL BE WEAK. EXPECT THAT WE MAY SEE SOME STRONG STORMS
ALONG THE LEADING EDGE OF THE FRONT BEGINNING A LITTLE AFTER NOON.

THE GFS APPEARS TO BE OVER-DONE WITH PCPN IN THE COLD AIR NORTH OF
THE FRONT WEDNESDAY AFTERNOON AND EVENING. IT APPEARS TO BE
SUFFERING FROM QUITE A BIT OF CONVECTIVE FEEDBACK. PER
COLLABORATION...ALL OF THE NEIGHBORING OFFICES HAVE DECIDED TO GO
CLOSER TO THE NAM. THEREFORE I WENT WITH POPS CONSIDERABLY LOWER
THAN THE MAV ON WEDNESDAY ACROSS THE FORECAST AREA IN THE MORE
STATICALLY STABLE AIR NORTH OF THE FRONT.

THE NAM AND GFS CONTINUE TO SHOW DIFFERENCES WITH THE STRENGTH OF
UPPER LEVEL AND SURFACE SYSTEMS CROSSING THE AREA WEDNESDAY NIGHT.
THE CONSENSUS OPINION OF FOLLOWING THE WEAKER NAM SOLUTION WILL
CONTINUE TO BE FOLLOWED...ENDING PRECIPITATION EARLIER WEDNESDAY
EVENING IN THE WAKE OF A SURFACE WAVE...AND DRYING THE AREA OUT
EARLIER ON THURSDAY AS SURFACE FLOW BACKS AND GAINS A DOWNSLOPE
COMPONENT. WEAK DOWNSLOPE FLOW CONTINUES THROUGH THURSDAY NIGHT. A
BACK DOOR COLD FRONT MOVES SOUTH OUT OF VIRGINIA FRIDAY...BUT WITH
MARGINAL MOISTURE. POPS WITH THIS SYSTEM WILL BE DELAYED UNTIL
EXTENDED FORECAST...WHEN THE BOUNDARY ENTERS OUR AREA.

TEMPERATURES WILL BE BELOW NORMAL UNDER CLOUD COVER AND IN
NORTHEAST FLOW THURSDAY...MODERATING SOMEWHAT FRIDAY AS IN
DOWNSLOPE WARMING.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A VERY AMPLIFIED UPPER LEVEL PATTERN IS EXPECTED DURING MEDIUM RANGE
FORECAST...WITH A MEAN LONGWAVE OVER EASTERN NORTH AMERICA. A SLOW
MOVING CLOSED UPPER LOW UPSTREAM...AND AN ASSOCIATED SURFACE
SYSTEM...WILL KEEP OUR AREA ON THE SOUTHERN FRINGE OF EAST COAST
RIDGE AS A SURFACE WAVE CRAWLS ACROSS THE SOUTHEAST FROM SATURDAY
THROUGH MONDAY. WITH AN EXPECTED MOISTURE INFLUX ALONG THE EDGE OF
THE RIDGE...CHANCE POPS WILL BE INCLUDED IN THE FORECAST...
DECREASING WITH TIME AS UNCERTAINTY CREEPS INTO THE FORECAST
SOLUTION. THERE SHOULD BE ENOUGH INSTABILITY ALONG THE SOUTHERN
PERIPHERY OF THE SURFACE RIDGE...EVEN IF ALOFT...TO INCLUDE THUNDER
IN THE FORECAST.

THE DIURNAL TEMPERATURE RANGE WILL BE LIMITED BY CLOUDS AND MOISTURE
OVER THE WEEKEND IN ADVANCE OF THE APPROACHING SURFACE WAVE...WITH
WARMING MONDAY AS THE WARM FRONT MOVES NORTH OF OUR AREA...AND MORE
WARMING TUESDAY IN DOWNSLOPE FLOW BEHIND THE WAVE.

AVIATION...
PRIMARY CONCERN WITH THIS SET OF TAFS IS WHAT TO DO WITH CONVECTIVE
TREAT THE NEXT 24 HOURS AND THE TIMING OF LOW CLOUDS ASSOCIATED WITH
COLD AIR DAMMING ON WED. AT THIS TIME I HAVE NOT INCLUDED ANYTHING
OTHER THAN /CB/ GROUPS IN ANY OF THE TAFS. SINCE THERE IS NOT ANY
ONGOING UPSTREAM CONVECTION...IT IS ALL BUT IMPOSSIBLE TO TIME
THUNDERSTORMS WELL ENOUGH TO INCLUDE ANY TEMPO GROUPS.
HOWEVER...THERE ALMOST CERTAINLY WILL BE CONVECTION SOME TIME LATER
TODAY OR THIS EVENING AT KAVL AND KHKY. ONLY THING TO DO IS WATCH
THE TRENDS AND AMEND WITH STORMS LOOK TO BE A COUPLE HOURS OUT. AS
FOR THE TIMING OF THE LOW CLOUDS...WILL USE A BLEND OF THE MAV/MET
MOS. THIS MEANS THAT WINDS WILL GRADUALLY SHIFT FROM SOUTHWEST TO
NORTHEAST BY DAWN. WINDS SHOULD BECOME FAIRLY LIGHT AT MOST TAF
SITES A FEW HOURS AFTER SUNSET...THEN INCREASE WITH BACK DOOR FRONT
BETWEEN 10-13 UTC

&&

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

SHORT TERM...HG

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
533 AM EDT TUE APR 25 2006

GAZ010-017-018-026-028-029-NCZ033>037-048>059-062>072-082-
SCZ001>014-019-260945-
RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-AVERY-CALDWELL-
ALEXANDER-IREDELL-DAVIE-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-
BUNCOMBE-MCDOWELL-BURKE-CATAWBA-ROWAN-GRAHAM-NORTHERN JACKSON-
MACON-SOUTHERN JACKSON-TRANSYLVANIA-HENDERSON-POLK-RUTHERFORD-
CLEVELAND-LINCOLN-GASTON-MECKLENBURG-CABARRUS-UNION NC-
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 TUE APR 25 2006

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

.DAY ONE...TODAY AND TONIGHT
SCATTERED THUNDERSTORMS ARE EXPECTED OVER THE MOUNTAINS AND
FOOTHILLS THIS AFTERNOON. ISOLATED THUNDERSTORMS ARE FORECAST
ELSEWHERE ACROSS THE WESTERN CAROLINAS AND NORTHEAST GEORGIA LATE
THIS AFTERNOON. A COLD FRONT WILL BRING ADDITIONAL THUNDERSTORMS
TO THE MOUNTAINS THIS EVENING. THE STORMS SHOULD GRADUALLY WEAKEN
TO AREAS OF RAIN AND DRIZZLE AFTER MIDNIGHT. THIS AFTERNOON AND
EVENING...THE ATMOSPHERE MAY SUPPORT A FEW SEVERE THUNDERSTORMS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY
SHOWERS AND THUNDERSTORMS ARE FORECAST FOR THIS WEEKEND.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE NEEDED ACROSS THE MOUNTAINS AND
FOOTHILLS LATE THIS AFTERNOON AND EVENING.

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
531 PM EDT TUE APR 25 2006

NCZ034>037-055>057-252230-
ALEXANDER-BURKE NC-CALDWELL-CATAWBA-DAVIE-IREDELL-ROWAN-
INCLUDING THE CITIES OF...HICKORY...MOCKSVILLE...MORGANTON...
SALISBURY...STATESVILLE
531 PM EDT TUE APR 25 2006

...STRONG THUNDERSTORMS TO AFFECT THE INTERSTATE 40 CORRIDOR
THROUGH THE EARLY EVENING HOURS...

AT 531 PM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SERIES OF STRONG THUNDERSTORMS FROM HICKORY TO JUST WEST OF
MORGANTON...MOVING EAST AT 30 MPH. THESE THUNDERSTORMS WILL AFFECT
LOCATIONS ALONG THE INTERSTATE 40 CORRIDOR THROUGH 7 PM.
PEA SIZE HAIL...FREQUENT LIGHTNING...AND BRIEFLY HEAVY RAIN WILL BE
POSSIBLE WITH ANY THUNDERSTORM.

HG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
617 PM EDT TUE APR 25 2006

NCZ053-054-065-067-252302-
BUNCOMBE-HENDERSON-MCDOWELL-RUTHERFORD-
INCLUDING THE CITIES OF...ASHEVILLE...HENDERSONVILLE...MARION...
RUTHERFORDTON
617 PM EDT TUE APR 25 2006

...STRONG THUNDERSTORMS TO MOVE INTO MCDOWELL COUNTY...

AT 610 PM...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM OVER THE SOUTHEAST CORNER OF BUNCOMBE COUNTY...
NORTHEAST OF BAT CAVE.  THIS STORM WILL MOVE OVER SOUTHERN MCDOWELL
COUNTY AND COULD BRUSH THE NORTHWEST CORNER OF RUTHERFORD COUNTY
NORTH OF LAKE LURE.  THE STORM WAS MOVING EAST AT 30 MPH. THE STORM
WILL REACH THE SUGAR HILL AREA IN MCDOWELL COUNTY AROUND 630 PM.
PEA SIZE HAIL...FREQUENT LIGHTNING...AND BRIEFLY HEAVY RAIN WILL BE
POSSIBLE WITH ANY THUNDERSTORM.

DEO