Severe Thunderstorm Warning 129, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
229 PM EDT THU MAY 28 2009

.SYNOPSIS...
A COLD FRONT WILL MOVE ACROSS THE FORECAST AREA ON FRIDAY AS WEAK
HIGH PRESSURE BUILDS IN FOR THE WEEKEND. THIS HIGH WILL THEN SHIFT
EASTWARD OVER THE ATLANTIC ON MONDAY...AND WILL REMAIN THERE THROUGH
THE MIDDLE OF THE WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
AN UPPER TROUGH AXIS WILL PROGRESS FROM THE LOWER MS RIVER VALLEY TO
THE SOUTHERN APPALACHIANS BY FRIDAY AFTERNOON. AN ASSOCIATED COLD
FRONT WILL MOVE FROM THE GULF STATE THIS AFTERNOON...TO THE
MOUNTAINS BY FRIDAY MORNING...THEN EAST OF OUR AREA BY LATE
AFTERNOON. CONVECTIVE ACTIVITY FROM THIS AFTERNOON WILL LINGER
INTO EARLY EVENING...WITH A GRADUAL DIMINISHING TREND LATE THIS
EVENING AND OVERNIGHT. A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED
FOR THE NC MOUNTAINS AND FOOTHILLS FOR THIS AFTERNOON...WHERE
INSTABILITY APPEARS TO BE MAXIMIZED AT THIS TIME.

INSTABILITY ALONG OF AND AHEAD OF THE FRONT WILL SUPPORT SCATTERED
CONVECTION AGAIN ON FRIDAY...WITH THE BEST SUPPORT SHIFTING FROM THE
MOUNTAINS IN THE MORNING...TO THE PIEDMONT IN THE AFTERNOON.

MINIMUM TEMPERATURES TONIGHT WILL ABOVE NORMAL IN ELEVATED MOISTURE
IN THE WARM SECTOR. DOWNSLOPE FLOW BEHIND THE FRONT FRIDAY WILL
OFFSET NADY HEIGHT FALLS OR COLD ADVECTION...KEEPING MAXIMUM
TEMPERATURES JUST A FEW DEGREES BELOW FULL SUMMERTIME NORMALS.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH MONDAY/...
AS OF 205 PM THURSDAY...A SHORT WAVE WILL MOVE EAST OF THE REGION
FRIDAY NIGHT...FOLLOWED BY WEAK HIGH PRESSURE AND LOWER DEWPOINTS.
WHILE THERE IS A LITTLE DEWPOINT RECOVERY LATE IN THE DAY OVER THE
FOOTHILLS...BUFKIT SOUNDINGS ON BOTH THE NAM AND GFS LOOK STABLE
ENOUGH FOR ME TO KEEP PCPN OUT OF THE FORECAST FOR THE DAY. WITH
SUNNY SKIES AND A LIGHT DOWNSLOPE FLOW...TEMPS SHOULD RISE WELL INTO
THE 80S OVER THE FOOTHILLS AND PIEDMONT. A FEW SHRA MAY MAKE A RUN
AT THE NRN MTNS LATE SAT NGHT AHEAD OF ANOTHER WEAK FRONT...BUT WITH
WEAK OVERALL SYNOPTIC FORCING...AND THE FRONT COMING THROUGH DURING
THE MINIMUM PERIOD OF INSTABILITY...COVERAGE SHOULD BE VERY LIMITED.

ON SUNDAY THE SFC BNDRY WILL WORK SE ACROSS THE FA. THE NAM DRIES
OUT MOST OF THE FA BY LATE SUN AFTN...WITH THE BEST SFC CONVERGENCE
DEVELOPING DOWN OVER THE MIDLANDS. THE GFS IS A LITTLE
SLOWER...THOUGH THE AXIS OF IT/S HIGHEST CAPES ARE ALSO OUTSIDE OF
THE FA. OVERALL...IT LOOKS LIKE ANOTHER DRY DAY AND I/VE KEPT POPS
UNDER 20 PERCENT EVERYWHERE. HIGHS WILL AGAIN RISE WELL INTO THE 80S
FOR PRETTY MUCH THE SAME REASONS I LISTED FOR SATURDAY.

&&

.LONG TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 130 PM THURSDAY...THE MEDIUM RANGE TAKES ON A VERY SUMMER LIKE
LOOK WITH THE BELT OF UPPER LEVEL WESTERLIES DISPLACED WELL TO THE
NORTH AND A SUBTROPICAL SURFACE HIGH OFF TO THE EAST. PRECIP CHANCES
WILL BE PRIMARILY DIURNALLY DRIVEN WITH AN INCREASING TREND THROUGH
THE END OF THE PERIOD AS A FRONTAL BOUNDARY TRIES TO SAG IN FROM THE
NORTH. EXPECT ISOLATED TO SCATTERED CONVECTION EACH AFTERNOON AND
EVENING IN A MODERATELY UNSTABLE AIRMASS. MAIN THREAT THROUGH THE
PERIOD WILL BE LOCALLY HEAVY RAINFALL WITHIN THUNDERSTORMS AS WEAK
FLOW THROUGH THE ATMOSPHERIC COLUMN WILL GREATLY LIMIT STORM
MOVEMENT. TEMPERATURES WILL RUN ABOUT 4 TO 5 DEGREES ABOVE CLIMO
WITH HIGHS EACH AFTERNOON IN THE LOW 80S IN THE MOUNTAINS...MID TO
UPPER 80S EVERYWHERE ELSE.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL SPREAD EAST
FROM THE MOUNTAINS INTO THE FOOTHILLS AND PIEDMONT THIS
AFTERNOON...WARRANTING CUMULONIMBUS AND VCTS IN THE TAFS...AND
TEMPORARY THUNDER AT KAVL. CONVECTION WANES THIS EVENING. GUIDANCE
HAS CEILING RESTRICTIONS LATE TONIGHT...WITH A BLEND SUPPORTING IFR
IN THE FOOTHILLS...AND MVFR AT KAVL AND KHKY...THE SAME PLACES WHERE
GUIDANCE SUPPORTS MVFR VISIBILITY. BY MORNING WINDS COME UP FROM THE
WEST AND CONDITIONS IMPROVE TO VFR.

AT KCLT...SHOWERS DEVELOPING TO THE EAST WILL DRIFT FARTHER EAST.
EVENTUALLY CONVECTION NOW REACHING THE BLUE RIDGE WILL REACH THE
PIEDMONT...AND CUMULONIMBUS WILL BE CARRIED IN THE TAF. AFTER
CONVECTION DIMINISHES THIS EVENING...MAV GUIDANCE LOWERS CEILINGS
DRAMATICALLY. FOR NOW A TEMPORARY LOW MVFR CEILING WILL BE CARRIED
AROUND DAWN. WINDS COME UP FROM THE WEST BY MID MORNING...WITH THE
CEILING BECOMING VFR.

OUTLOOK...THUNDERSTORMS COULD REDEVELOP ON FRIDAY AFTERNOON AS A
COLD FRONT MOVES ACROSS THE REGION. AFTER A DRY SATURDAY...ISOLATED
AFTERNOON THUNDERSTORMS ARE POSSIBLE ACROSS THE MOUNTAINS ON
SUNDAY...WITH MORNING MVFR FOG AND STRATUS RESTRICTIONS BECOMING
MORE LIKELY WITH TIME.

&&

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

&&

SYNOPSIS...BSH
NEAR TERM...JAT
SHORT TERM...MCAVOY
LONG TERM...BSH
AVIATION...JAT

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