Severe Thunderstorm Warning 308, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
249 PM EDT SUN JUN 11 2006

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...

TONIGHT AND MONDAY...
CONVECTION DEVELOPING RAPIDLY AT MID AFTERNOON OVER THE HIGHER
TERRAIN OF NORTH CAROLINA. CORES ARE GROWING TALL QUICKLY.
ELSEWHERE...SATELLITE IMAGERY THE LAST HOUR OR TWO HAS SHOWN A
RAPID PROLIFERATION OF CUMULUS...EXCEPT FOR ACROSS OUR EASTERN
SECTIONS WHICH REMAIN CLEAR AND WHERE SURFACE AIR HAS BEEN A
LITTLE DRIER. FORECAST REASONING REALLY HAS NOT CHANGED MUCH FROM
THE PREVIOUS PACKAGE. SHORTWAVE ENERGY APPROACHING FROM THE
NORTHWEST SHOULD ALLOW FURTHER CONVECTIVE DEVELOPMENT THROUGH THE
EVENING. AT SOME POINT THIS EVENING...FRONTAL ZONE TO OUR NORTH
SHOULD ALSO BEGIN TO SAG SOUTHWARD...ASSISTING IN MOISTURE
CONVERGENCE. WE WILL FEATURE HIGHEST CHANCES OF RAIN...INTO THE
LIKELY CATEGORY...FOR THE WESTERN HALF OF OUR MOUNTAINS THROUGH
THE MORNING RUSH HOUR...AND TIER POPS DOWN TO SLIGHT CHANCE
THROUGH OVERNIGHT IN THE FAR SOUTHERN UPSTATE AND NORTHEAST
GEORGIA.

BY MONDAY MORNING...FRONT SHOULD BE APPROACHING THE SOUTH
CAROLINA/GEORGIA BORDER. WE WILL BRING SOLID CHANCES OF CONVECTION
INTO THE SOUTHERN CWFA...BUT KEEP HIGHEST CHANCES IN THE NORTH
CAROLINA PIEDMONT. FRONT EXPECTED SOUTH OF CWFA BY LATE IN THE DAY.
FORECAST SOUNDINGS UNSTABLE AGAIN...ESPECIALLY IN THE SOUTH...AND
FOR A RATHER LONG PERIOD OF TIME.

TEMPERATURES NOT LIKELY TO DROP TOO LOW OVERNIGHT...WILL FEATURE A
MILD NIGHT WITH MINS IN THE 70S ACROSS THE SOUTHERN MOST CWFA AND
THROUGH THE 60S IN THE NORTH. CLOUDS AND PRECIPITATION SHOULD KEEP
MAXES DOWN MONDAY...80S/LOWER 90S STILL IN THE SOUTH AND WITH MAXES
70S AND 80S FOR THE NORTH CAROLINA PORTION OF THE FORECAST AREA.

MONDAY NIGHT THROUGH WEDNESDAY NIGHT...
FORECAST FOR THE MONDAY NIGHT THROUGH WED NIGHT PERIOD IS
COMPLICATED BY THE TRACK THE TROPICAL CYCLONE CURRENTLY IN THE
SOUTHERN GULF OF MEXICO. THE OFFICIAL TRACK TAKES IT ACROSS CENTRAL
FL TUE MORNING. BY WED MORNING...THE CENTER IS PROJECTED TO BE A
COUPLE HUNDRED MILES EAST OF CHARLESTON. THE WRF AND NAM KEEP THE
CIRCULATION MUCH FARTHER WEST. IN FACT...I/VE HAD TO DISCARD BOTH
MODELS THIS PACKAGE DO TO THEIR EXTREME DIFFERENCES FROM THE
FORECAST TRACK. THIS LEAVES THE GFS WHICH IS FASTER THAN THE
OFFICIAL TRACK. IN FACT...THE OPERATIONAL RUN SHEARS THE SYSTEM TO
THE EXTENT THAT IS IS DIFFICULT TO IDENTIFY BEYOND TODAY.

THE EFFECT OF ALL THIS ON OUR SENSIBLE WEATHER WILL BE FOR A DRIER
FORECAST THAN IS IMPLIED BY THE NAM...AND MUCH DRIER THAN THE WRF.

I WILL MAINTAIN LOW CHANCE POPS IN THE SE ZONES MONDAY EVENING. A
COLD FRONT SHOULD MOVE THROUGH THE REGION BY MIDNIGHT AND DRY US
OUT.

TUE LOOKS DRY AND A LITTLE COOLER WITH APPRECIABLY LOWER SFC
DEWPOINTS AND 1000-850 MB THICKNESSES ON THE GFS. BY WED THE 500 MB
TROUGH WILL BE NEARLY DIRECTLY OVERHEAD...AND THE GFS BRINGS A SHORT
WAVE ACROSS THE REGION IN THE AFTERNOON. HOWEVER...THE MODEL
SOUNDINGS ARE QUITE INHIBITED...AND WILL ONLY CARRY A SLIGHT CHANCE
POP IN THE EASTERN ZONES.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
NCEP CHOOSE TO FOLLOW THE 00 UTC OPERATIONAL GFS FOR THE EXTENDED
RANGE. THIS PUTS THE FORECAST AREA ON THE BACK SIDE OF GRADUALLY
FILLING LONG WAVE TROUGH THU AND FRI. THE EASTWARD EXTENSION OF A
STRONG AND DEEP RIDGE OVER THE SRN PLANS WILL PUSH INTO THE REGION
NEXT WEEKEND. THIS CERTAINLY DOESN/T BODE WELL FOR MUCH NEEDED
RAINFALL. THERE ARE SOME LOW CHANCE POPS IN THE GRIDS FOR DAY
7...BUT IF THE PATTERN EVOLVES CONSISTENT WITH THE GFS...THE LATTER
PERIODS WILL ALMOST CERTAINLY VERIFY WARMER AND DRIER THAN WHAT WE
HAVE NOW.

&&

.AVIATION...
CHALLENGES FOR THE 18Z TAF SET REVOLVED AROUND CONVECTIVE POTENTIAL
AT ANY OF OUR SITES. EACH SITE SEEMS FAIR GAME FOR CONVECTION THE
NEXT 24 HOURS OR SO...DESPITE RELATIVELY LOW STATISICAL GUIDANCE
NUMBERS. KGSP 88-D SHOWS CONVECTION ALREADY ORGANIZING AT HIGHER
ELEVATIONS NEAR THE TENNESSEE BORDER WE START THE TAF PERIOD WITH A
VCSH AT KAVL...AND INCLUDE POSSIBLE THUNDER THERE 18 TO 21Z. FOR
NOW...KEPT KHKY AT VCSH THROUGH THE AFTERNOON BUT THAT TAF SITE
DEFINITELY A TARGET FOR AMENDMENT IN NEXT COUPLE OF HOURS AS
CONVECTIVE TRENDS MAKE THEMSELVES KNOWN. FORTUNATELY...WITH SUCH
DRIER AIR IN PLACE IN THE LOWER LEVELS...CEILINGS SHOULD REMAIN VFR
THROUGH THE BEGINNING OF THE OUTLOOK PERIOD...ALTHOUGH VISIBILITY
COULD BE LOWERED TO MVFR AT ANY OF THE TAF SITES DURING HEAVY
DOWNPOURS.

GREATEST CONVECTIVE COVERAGE SHOULD OCCUR THIS EVENING...AND THAT IS
WHEN WE TARGET ALL OUR TAF SITES FOR CONVECTION. KAVL GETS A
CATEGORICAL FOR RAIN SHOWERS THIS EVENING WITH TEMPO FOR THUNDER
FROM 01Z TO 04Z...THEN AGAIN IN THE PREDAWN WITH FRONT SAGGING SOUTH
AND BEST SHORTWAVE ENERGY PASSING. KHKY IS ALSO TARGETED FOR THE
PREDAWN HOURS...WITH KCLT INDICATED FOR THUNDER FROM 07Z THROUGH
11Z...AND AGAIN FROM 12Z TO 15Z IN TEMPO GROUPS.

THE UPSTATE TAF SITES WERE NOT INCLUDED IN A THUNDER CHANCE UNTIL
THE OUTLOOK PERIOD...AND VERY NEAR THE END OF THE OUTLOOK AT THAT.
TEMPO FOR MVFR VISIBILITY RESTRICTIONS INCLUDED AT KGSP/KGMU FROM
15Z TO 18Z ON MONDAY...AND FROM 16Z TO 18Z AT KAND.

&&

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

SHORT TERM...MCAVOY/SAB
LONG TERM...MCAVOY
AVIATION...SAB