Severe Thunderstorm Warning 2, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
904 PM EDT MON APR 12 2004

.UPDATE...
ORIENTATION AND STRENGTH OF WEDGE HAS CHANGED LITTLE SINCE
MID-AFTERNOON WITH KGSP VWP STILL INDICATING A NE WIND IN THE LOWEST
GATE. 18Z ETA AND GFS BOTH TOO LOW WITH PROGGED PRESSURE FALLS AT
00Z AND THE ETA IN FACT WAS WAY TOO AGGRESSIVE WITH SFC BASED
INSTABILITY WHICH WAS PROGGED TO BE WEST OF CLT BY NOW. 18Z GFS WAS
ACTUALLY CLOSER TO REALITY AS PER 00Z MSAS LI PLOT. LIFTING PARCELS
FROM ABOVE SFC LAYER DOES YIELD SOME POSITIVE CAPE AND NEGATIVE
SHOWALTER INDEX VALUES AND THIS IS APPARENT WITH CURRENT 88D SHOWING
TSTM NEAR NE GA.

FEEL 18Z GFS HANDLING OF SHOWALTER INDEX FIELD PRETTY GOOD INTO THE
OVERNIGHT AND WILL HAVE THUNDER MENTION...WHETHER IT REMAINS ELEVATED
OR NOT...ABOUT HALF WAY NORTH INTO THE NC MTNS AND EXTENDING FURTHER
WEST...PAST I-77 IN THE PIEDMONT. PROBABLY WILL SEE LITTLE CHANGE IN
WEDGE ORIENTATION THIS EVENING...BUT INCREASING DEEP FORCING OUT
AHEAD OF APRCHG VORT SHOULD BE ABLE BEGIN PINCHING WEDGE OFF
OVERNIGHT. TO WHAT DEGREE WEDGE EROSION OCCURS BY DAYBREAK IS QUITE
DEBATABLE...BUT WILL GO SLOWER THAT WHAT 18Z ETA IS OFFERING.

AS FAR AS PCPN CVRG FOR THE OVERNIGHT...THE LARGE SCALE PATTERN WOULD
DEFINITELY FAVOR AN INCREASE IN SHOWERS AND SOME THUNDER...AND POP
GRIDS WILL TREND TO THIS DIRECTION INTO TUESDAY MORNING. WILL
CONTINUE WILL CATEGORICAL CVRG IN THE WEST AS QPF MAX SLIDES NWD
INTO THIS AREA. LITTLE CHANGE TO CURRENT SPC DAY 1 SLIGHT RISK
WITH LATEST UPDATE AND PLAN ON REFRESHING CURRENT SPS TO ADDRESS
POSSIBLE SVR THREAT FOR THE OVERNIGHT HOURS.
&&

.PREV DISCUSSION...
THE WEDGE REMAINS IN PLACE OVER THE CWA WITH WARM FRONT TO THE SOUTH
RUNNING FROM ILM TO AGS.  OVERRUNNING PRECIP REMAINS THE FORECAST
ISSUE TODAY.  THE PROBLEM IS THAT TEMPERATURES ARE PARTICULARLY
UNSTABLE ALOFT AND AS THE FRONT DRIFTS NORTHWARD...WE MOVE INTO A
REGIME THAT COULD PRODUCE SEVERE THUNDERSTORMS SOUTH OF I85.

TEMPERATURES REMAIN IN THE 40S TO LOW 50S IN OUR AREA BUT 60S AND
70S FROM CAE SOUTHWARD.  WITH SFC DWPNTS IN THE 60S AND 70S IN
SOUTH OF FRONT WILL PROVIDE AMPLE MOISTURE FOR TSTMS DVLPMNT.  SPC
KEEPS US IN THEIR OUTLOOK THROUGH TUESDAY. MIN TEMPERATURES WILL BE
SOMEWHAT CONFUSING AS I EXPECT SLOW WARMING THROUGH THE NIGHT.

SOME CONCERN ABOUT HOW FAST TO SCOUR OUT THE WEDGE.  WE NORMALLY HAVE
A TENDENCY TO WARM THINGS UP TO QUICKLY.  BUT IT IS LATE ENOUGH IN
THE YEAR...AND THE COLD AIR IS SHALLOW ENOUGH TO EXPECT THINGS TO
WARM UP STARTING TUESDAY.

ETA REMAINS MODEL OF CHOICE IN THE SHORT TERM.

WRAPAROUND FLOW BEHIND LOW IS EXPECTED TO CAUSE PROBLEMS IN THE
MOUNTAINS LATE TUESDAY AND WEDNESDAY.  FCST SOUNDINGS INDICATED RAIN
AND SNOW MIX...ENDING WITH JUST SNOW WEDNESDAY MORNING.  SOUNDINGS
INDICATE SNOW DOWN TO 3300 FEET BEFORE ENDING.  I DONT EXPECT MUCH
OF AN ACCUMULATION EXCEPT ON HIGHEST TERRAIN.  AFTER THAT THINGS
CLEAR UP AND WE GET BACK INTO A SPRINGTIME REGIME AGAIN.

NEXT SURGE NEXT MONDAY WITH GFS SOUNDINGS PRETTY IMPRESSIVE FOR
THUNDERSTORMS MONDAY AFTERNOON THEN WITH APPROACHING FRONT.  KEEPING
POPS IN SILENT SLIGHT CHANCE RANGE UNTIL IT GETS CLOSER.
&&

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

CSH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
607 AM EDT MON APR 12 2004

GAZ010-017-018-026-028-029-NCZ033>037-048>059-062>072-082-SCZ001>014-
019-121207-
ABBEVILLE SC-ALEXANDER NC-ANDERSON SC-AVERY NC-BUNCOMBE NC-BURKE NC-
CABARRUS NC-CALDWELL NC-CATAWBA NC-CHEROKEE SC-CHESTER SC-
CLEVELAND NC-DAVIE NC-ELBERT GA-FRANKLIN GA-GASTON NC-GRAHAM NC-
GREATER GREENVILLE SC-GREATER OCONEE SC-GREATER PICKENS SC-
GREENVILLE MOUNTAINS SC-GREENWOOD SC-HABERSHAM GA-HART GA-HAYWOOD NC-
HENDERSON NC-IREDELL NC-LAURENS SC-LINCOLN NC-MACON NC-MADISON NC-
MCDOWELL NC-MECKLENBURG NC-MITCHELL NC-NORTHERN JACKSON NC-
OCONEE MOUNTAINS SC-PICKENS MOUNTAINS SC-POLK NC-RABUN GA-ROWAN NC-
RUTHERFORD NC-SOUTHERN JACKSON NC-SPARTANBURG SC-STEPHENS GA-
SWAIN NC-TRANSYLVANIA NC-UNION SC-UNION NC-YANCEY NC-YORK SC-
607 AM EDT MON APR 12 2004

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

.DAY ONE...

LOW PRESSURE OVER THE DEEP SOUTH WILL APPROACH THE SOUTHERN
APPALACHIANS TODAY. AS THE LOW APPROACHES...SHOWERS AND
THUNDERSTORMS WILL INCREASE ALONG AND NORTH OF A WARM FRONT. THIS
WILL RESULT IN WAVES OF SHOWERS AND THUNDERSTORMS PERSISTING OVER
THE REGION TODAY AND THIS EVENING. SOME OF THE THUNDERSTORMS ALONG
AND SOUTH OF INTERSTATE 85 MAY BECOME SEVERE ALONG WITH HEAVY RAIN.
PLEASE SEE THE LATEST SEVERE WEATHER OUTLOOK (CAESPSGSP) FOR
ADDITIONAL DETAILS.

.DAYS TWO THROUGH SEVEN...

LOW PRESSURE WILL MOVE OVER EASTERN TENNESSEE TONIGHT AND WILL
SLOWLY MOVE NORTHEAST TO CENTRAL VIRGINIA BY WEDNESDAY MORNING. AS
THE LOW MOVES NORTH OF THE WESTERN CAROLINAS...A COLD FRONT WILL
SWEEP ACROSS THE REGION TUESDAY. SHOWERS AND THUNDERSTORMS WILL
DEVELOP ALONG THE FRONT...ESPECIALLY OVER THE NORTH CAROLINA
PIEDMONT. THESE THUNDERSTORMS WILL LIKELY DEVELOP HEAVY RAINFALL AND
MAY ALSO BECOME SEVERE. PLEASE SEE THE LATEST SEVERE WEATHER OUTLOOK
(CAESPSGSP) FOR ADDITIONAL DETAILS.

WEDNESDAY MORNING...COLD AIR WILL BUILD OVER THE MOUNTAINS AS A
MID-LEVEL AREA OF LOW PRESSURE MOVES EAST. NORTHWEST WINDS IN
COMBINATION WILL ATMOSPHERIC LIFT WILL GENERATE SHOWERS MAINLY OVER
THE TENNESSEE BORDER COUNTIES OF NORTH CAROLINA OVERNIGHT.
TEMPERATURES WILL FALL INTO THE 20S AND 30S DEPENDING ON
ELEVATION...RESULTING IN A MIXTURE OF RAIN AND SNOW IN THE
VALLEYS TO SNOW ON THE PEAKS. SOME MEASURABLE SNOWFALL MAY OCCUR
OVER 3000 FEET ELEVATION.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED TODAY AND TONIGHT.

NED

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
925 PM EDT MON APR 12 2004

GAZ010-017-018-026-028-029-NCZ033>037-048>059-062>072-082-SCZ001>014-
019-130800-
ABBEVILLE SC-ALEXANDER NC-ANDERSON SC-AVERY NC-BUNCOMBE NC-BURKE NC-
CABARRUS NC-CALDWELL NC-CATAWBA NC-CHEROKEE SC-CHESTER SC-
CLEVELAND NC-DAVIE NC-ELBERT GA-FRANKLIN GA-GASTON NC-GRAHAM NC-
GREATER GREENVILLE SC-GREATER OCONEE SC-GREATER PICKENS SC-
GREENVILLE MOUNTAINS SC-GREENWOOD SC-HABERSHAM GA-HART GA-HAYWOOD NC-
HENDERSON NC-IREDELL NC-LAURENS SC-LINCOLN NC-MACON NC-MADISON NC-
MCDOWELL NC-MECKLENBURG NC-MITCHELL NC-NORTHERN JACKSON NC-
OCONEE MOUNTAINS SC-PICKENS MOUNTAINS SC-POLK NC-RABUN GA-ROWAN NC-
RUTHERFORD NC-SOUTHERN JACKSON NC-SPARTANBURG SC-STEPHENS GA-
SWAIN NC-TRANSYLVANIA NC-UNION SC-UNION NC-YANCEY NC-YORK SC-
925 PM EDT MON APR 12 2004

...A FEW SEVERE THUNDERSTORMS AND SOME HEAVY RAIN POSSIBLE OVERNIGHT
ACROSS PORTIONS OF THE WESTERN CAROLINAS AND NORTHEAST GEORGIA...

A STRONG UPPER LEVEL AREA OF LOW PRESSURE WILL TRACK NORTHEAST INTO
THE SOUTHERN APPALACHIANS BY TUESDAY MORNING WITH AN ASSOCIATED AREA
OF SURFACE LOW PRESSURE MOVING INTO EAST TENNESSEE. THIS SHOULD ALLOW
A WARM FRONT TO RETURN NORTH INTO SOUTHWEST NORTH CAROLINA AND THE
WESTERN UPSTATE BY DAYBREAK.

WIDESPREAD THUNDERSTORMS OCCURRING IN GEORGIA AND ALABAMA WILL
CONTINUE TO MOVE NORTHEAST INTO THE REGION OVERNIGHT AND ASSOCIATED
RAINFALL COULD BE HEAVY ACROSS THE MOUNTAINS AND ADJACENT FOOTHILLS
LATER TONIGHT.

AN INCREASE IN WIND SPEEDS THROUGHOUT THE ATMOSPHERE WILL ACCOMPANY
THE AFORMENTIONED UPPER LOW...AND IN CONCERT WITH AN INCREASE IN
THUNDERSTORMS...COULD RESULT IN A FEW SEVERE STORMS...ESPECIALLY
LATE TONIGHT AS THE WARM FRONT LIFTS INTO THE AREA. THE GREATEST
UNCERTAINTY WITH THIS FORECAST IS HOW QUICKLY...AND HOW FAR NORTH
UNSTABLE AIR CAN MOVE INTO THE WESTERN CAROLINAS. AT THIS POINT
THE GREATEST THREAT FOR ANY SEVERE WEATHER WILL BE ACROSS SOUTHWEST
NORTH CAROLINA...NORTHEAST GEORGIA AND THE WESTERN UPSTATE LATE
TONIGHT.

FOR ADDITIONAL WEATHER INFORMATION...CHECK OUR WEB SITE AT
WWW.ERH.NOAA.GOV/GSP