Severe Thunderstorm Warning 242, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
709 PM EDT WED JUN 27 2007

.SYNOPSIS...
THE SOUTHEAST WILL REMAIN UNDER THE INFLUENCE OF A SUBTROPICAL HIGH
PRESSURE SYSTEM THROUGH THURSDAY...BEFORE A COLD FRONT APPROACHES
THE FORECAST AREA FROM THE NORTH LATE FRIDAY. THIS FRONT WILL
THEN MOVE SLOWLY SOUTH ACROSS THE REGION THROUGH SUNDAY MORNING
AS HIGH PRESSURE COVERS MUCH OF THE EASTERN SEABOARD BY EARLY NEXT
WEEK.

&&

.NEAR TERM /THROUGH THURSDAY/...
THE CENTER OF 590DM RIDGE WILL REMAIN OVER THE CWA TONIGHT AND
THURSDAY. THE FORECAST CONCERNS ARE CENTERED ON THE DIURNAL TIMING
AND STRENGTH OF AIR MASS TSRA. OVER THE NEXT 3-5 HRS...EXPECT SCT
PULSE TSRA TO CONTINUE MAINLY IN THE SOUTHERN FOOTHILLS AND THE
INTERSTATE 40 CORRDIOR IN THE LEE OF THE NC MTNS. STM MOTIONS WILL
REMAIN 10KTS OR LESS...GENERALLY DRIFTING TO THE NORTHEAST. THE
ENVIRONMENT MAY ALLOW A FEW OF THE STORMS TO REACH SEVERE LEVELS.
HOWEVER...DUE TO SLOW STM MOTIONS AND K-INDEX VALUES 35-40...ISO
EXCESSIVE RAIN IS POSSIBLE. AREAS OF MTN VALLEY FOG SHOULD DEVELOP
LATE TONIGHT.

A BLEND OF THE GFS AND NAM WAS USED FOR THURS. H5 HEIGHTS WILL
SLOWLY FALL DURING THE DAY AND A SMALL S/W COULD AUGMENT THE HIGH
TERRAIN LIFT LATE THURS AFTERNOON. OVERALL...I ANTICIPATE THAT THE
TIMING AND COVERAGE OF CONVECTION WILL CLOSELY FOLLOW TODAY/S
TRENDS. I WILL PAINT SCT SHRA/TSRA STARTING AROUND 16Z.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
THE CONTINUATION OF THE EXPECTED HEIGHT FALLS ACRS THE EASTERN CONUS
REMAINS ON TRACK FOR FRIDAY WITH THE FLOW ATOP THE CWFA EVEN SLATED
TO BECOME SLIGHTLY CYCLONICALLY CURVED BY FRIDAY NIGHT. THE BETTER
FRONTAL ZONE MOISTURE WILL ALSO BEGIN TO IMPINGE UPON THE CWFA AT
THIS JUNCTURE. NUMEROUS SHOWERS AND TSTMS ARE EXPECTED FRI
AFT/EVE...ESPECIALLY ACRS NC WHERE LARGER SCALE LIFT WILL BE
GREATER. GRANTED...WHERE THE ATMOSPHERE SHOULD BECOME MODERATELY
UNSTABLE...SOUTH OF FRONTAL ZONE...THE INCREASE IN MID-LVL FLOW IS
STILL MODEST...PERHAPS WEAK ENOUGH TO KEEP SVR STORMS ISOLATED...BUT
MULTI-CELL DEVELOPMENT REMAINS POSSIBLE ALONG WITH DAMAGING WIND
GUSTS. CWFA IS EXPECTED TO REMAIN UNDER THE INFLUENCE OF SLOWLY
SOUTHWARD PRESSING FRONTAL ZONE SATURDAY WITH 27/12 UTC OP GFS
AND 27/09 UTC SREF IN GOOD AGREEMENT AS FAR AS MASS FIELDS ARE
CONCERNED...PROGGED SCATTERED TO NUMEROUS SHOWERS AND TSTMS...
ESPECIALLY ACRS MY EASTERN ZONES WHERE LIFT SHOULD BE MAXIMIZED.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
OVERALL...VERY FEW NOTABLE CHANGES WERE MADE TO THE EXTENDED
FORECAST. THE PERIOD BEGINS WITH A COLD FRONT LOCATED JUST TO THE
SOUTH OF THE FA. WITH THAT IN MIND...I KEEP SLIGHT CHANCE POPS
AROUND THROUGH 12Z SUN. FROM SUN AFTERNOON ONWARD...UPPER TROUGH
AXIS SHIFTS OFF THE EAST COAST WITH SURFACE HIGH RIDGING DOWN THE
EAST SIDE OF THE APPS. A DRY FORECAST IS IN PLACE THROUGH TUES
MORNING...WITH SLIGHT CHANCE POPS TUES AFTERNOON ACROSS THE
MOUNTAINS AS SWRLY FLOW RETURNS OUT AHEAD OF LOW PRESSURE DEVELOPING
OVER UPPER MIDWEST. EASTERN TROUGH REASSERTS ITSELF BY WEDNESDAY AS
A SHORTWAVE DIVES ACROSS THE GREAT LAKES. AT LEAST SLIGHT CHANCE
POPS EVERYWHERE WED AFTERNOON THROUGH THURS MORNING AS COLD FRONT
APPROACHES FROM THE NORTH. TEMPS WARM THROUGHOUT THE EXTENDED AS
SWRLY FLOW DEVELOPS BY MID WEEK WITH LOWER 90S ACROSS THE NC PIEDMONT
AND THE UPSTATE.

&&

.AVIATION /23Z WEDNESDAY THROUGH MONDAY/...
CONVECTION IS DIMINISHING EVERYWHERE BUT THE INTERSTATE 40
CORRIDOR...AND THE ONLY TAF SITE THAT MAY HAVE THUNDERSTORM ISSUES
THIS EVENING WOULD BE KHKY. SATELLITE IMAGERY SHOWS CUMULUS FIELDS
IN DECLINE OVER SC TAF SITES...AND THE SAME IS EXPECTED AT KCLT WITH
THE LOSS OF HEATING. KHKY MAY BE SLOW TO LOSE LOW CLOUDS WITH
CONVECTION CONTINUING LONGER IN THE VICINITY. ANOTHER NIGHT OF FOG
IS EXPECTED WITH THE AIR MASS ONLY GETTING MORE MOIST. KAVL IS
EXPECTED TO GET DOWN TO LOW MVFR VISIBILITY AT A MINIMUM...AS COOL
AIR POOLS IN THE VALLEY. HEAVY RAINS THIS AFTERNOON SHOULD ALLOW
KHKY TO REACH IFR VISIBILITY. EVEN KCLT HAS SOME LIGHT RAIN...AND
UPPER END MVFR VISIBILITY IS EXPECTED THERE. CEILING PROBLEMS ARE
NOT EXPECTED UNLESS KAVL OR KHKY WERE TO GO EVEN LOWER WITH
VISIBILITY.

THURSDAY SHOULD BE MUCH LIKE TODAY...WITH SCATTERED AFTERNOON
CONVECTION BEGINNING AT MIDDAY NEAR THE BLUE RIDGE AND SPREADING
EAST. AT THIS POINT ONLY THUNDER IN THE VICINITY WILL BE CARRIED AT
KAVL FOR THURSDAY AFTERNOON...WITH SCATTERED CUMULUS CARRIED AT ALL
SITES. LOW LEVEL WINDS VEER IN THE AFTERNOON...INTRODUCING A
SLIGHT DOWNSLOPE COMPONENT IN THE LEE OF THE MOUNTAINS...AND IF THIS
TREND WERE TO INCREASE...AFTERNOON CONVECTION WOULD BE MORE LIMITED
THAN CURRENTLY EXPECTED.

AVIATION OUTLOOK...SCATTERED AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS AND EARLY MORNING FOG WILL CONTINUE THROUGH THE END OF
THE WEEK. A BACK DOOR COLD FRONT WILL APPROACH LATE FRIDAY AND
FRIDAY NIGHT. WIDESPREAD SHOWERS AND THUNDERSTORMS MAY DEVELOP ALONG
AND AHEAD OF THE FRONT ACROSS THE WESTERN CAROLINAS. HIGH PRESSURE
BUILDING IN FROM THE NORTH WILL PRODUCE VFR WEATHER SUNDAY INTO
MONDAY.

&&

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

&&

SYNOPSIS...BSH
NEAR TERM...NED
SHORT TERM...CSH
LONG TERM...BSH
AVIATION...JAT