Severe Thunderstorm Warning 409, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
247 PM EDT SUN AUG 31 2008

.SYNOPSIS...
A WEAK COLD FRONT ACROSS THE WESTERN CAROLINAS WILL BECOME
STATIONARY ACROSS THE SOUTHERN UPSTATE TONIGHT. HIGH PRESSURE WILL
THEN BUILD INTO THE REGION ON MONDAY AND SHOULD PUSH THE FRONT SOUTH
OF THE AREA. DRY AND SEASONABLE CONDITIONS WILL REMAIN FROM TUESDAY
THROUGH THURSDAY. TROPICAL CYCLONE HANNA COULD AFFECT THE
SOUTHEASTERN UNITED STATES FRIDAY THROUGH THE WEEKEND.

&&

.NEAR TERM /THROUGH MONDAY/...
OVER THE NEXT 24 HOURS...A LARGE UPPER ANTICYCLONE WILL CONTINUE TO
BUILD OVER THE GREAT LAKES AND OH VALLEY...WHICH WILL SUPPORT A
SURFACE HIGH MOVING SLOWLY OVER THE LOWER GREAT LAKES/SRN ONTARIO.
THIS SHOULD DRIVE A BACK DOOR COLD FRONT FROM THE MID ATLANTIC DOWN
ACROSS THE CAROLINAS TONIGHT AND MONDAY MORNING. LOW LEVEL MOISTURE
AHEAD AND POOLED ALONG THIS BOUNDARY SHOULD FUEL ISOLATED TO
SCATTERED DEEP CONVECTION FOR THE REST OF THE DAY AND INTO THE
OVERNIGHT HOURS...SIMILAR TO THE PREVIOUS FEW DAYS. A DEVELOPING
EASTERLY FLOW SHOULD PUSH THE CLOUDS AND ANY CONVECTIVE PRECIP
GRADUALLY OFF TO THE SOUTHWEST EARLY MONDAY MORNING. THIS WILL DROP
TEMPS DOWN A CATEGORY TOWARD CLIMO ON MONDAY AS THE HIGH BUILDS IN
FROM THE NORTH IN THE AFTERNOON.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 215 PM EDT SUNDAY...AS DEEP LAYER HIGH PRESSURE DRIFTS SOUTH
ACROSS THE MID-ATLANTIC AND INTO THE SOUTHEAST DURING MID0-WEEK...
DRIER AIR WILL FILTER INTO THE CWFA...BRINGING AN END TO THE CHANCES
FOR DIURNAL CONVECTION FOR AT LEAST A COUPLE OF DAYS. WITH THE DRIER
AIR IN PLACE...LOW TEMPS WILL AVERAGE A CATEGORY OR TWO BELOW NORMAL
THROUGH THE PERIOD. HOWEVER...DAYTIME HIGHS SHOULD BE AROUND
NORMAL...MAYBE EVEN A FEW DEGREES ABOVE CLIMO ON WEDNESDAY...AS
HEIGHTS RISE UNDERNEATH THE BUILDING RIDGE.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 230 PM SUNDAY...ANOTHER DRY AND PLEASANT DAY ON HAND THU WITH
MID/ATLANTIC HIGH RETREATING NORTH A BIT BUT STILL DOMINATING THE
CAROLINA REGION. CROSS SECTIONS SHOW A DEEP SUBSIDENCE DRY LAYER
OVERHEAD AND WILL EXPECT SOME MIXING TO KEEP RH LEVELS FAIRLY LOW
FOR THIS TIME OF YEAR. HIGHS SHOULD HAVE NO PROBLEM REACHING NORMAL
LEVELS IN GOOD SUBSIDENCE...HOWEVER WILL EXPECT INCREASING CI
THROUGH THE LATE AFTERNOON IN ADVANCE OF HANNA. THE 12Z GFS
CONTINUES WELL NORTH AND FAST WITH THE HANNA TRACK THAN THE HPC
OFFICIAL TRACK AND THE REGIONAL TROPICAL MODELS...SO WILL SIDE WITH
THE SLOWER AND MORE SOUTHERN RUN OF THE 00Z ECMWF FOR LATTER
EXTENDED PERIOD GUIDANCE.

IN ESSENCE...THE GFS SOUNDINGS WERE CONSIDERED BUT ADJUSTED AHEAD IN
TIME BY ABOUT 12 HOURS AND WEST ABOUT 100 MILES. THIS SCENARIO
INCREASES CLOUD COVER SIGNIFICANTLY THROUGH 12Z FRI AND BRINGS
PRECIP BANDS TO THE EASTERN ZONES AND UPSLOPE REGIONS BY 18Z FRI.
SOUNDINGS INDICATE PW VALUES OVER 2 INCHES OVER KGSP...EVEN ON THE
EASTERN MOST GFS. HEAVY RAIN IS CERTAINLY PROBABLE WITH THESE
TROPICAL BANDS BUT THE SYSTEM AS WHOLE LOOKS TO MOVE OUT OF THE FA
FAIRLY QUICKLY BY SAT AFTERNOON. STILL THE POTENTIAL FOR FLOODING
WILL BE A REAL CONCERN. SOUNDINGS ALSO INDICATE A 12 HOUR WINDOW
LATE FRI WITH A 50 KT H9 JET PASSING OVERHEAD...SO HIGH GUSTY WINDS
SHOULD BE IN THE OFFING THROUGH FRI NIGHT. ITS TOO EARLY TO DEPICT
THESE WINDS IN THE GRID GRAPHICS...HOWEVER THE AFM AND PFM PRODUCTS
WILL ADVERTISE GUST POTENTIALS.

BOTH THE ECMWF AND THE GFS PULL THE REMNANTS OF HANNA NORTH WITH
BROAD OHIO VALLEY TROF AND BOTH BUILD IN STRONG BERMUDA HIGH
PRESSURE IN BY SAT EVENING. THE 40 POPS WERE CONTINUED FOR SAT...BUT
SAT NIGHT THROUGH THE REMAINDER OF THE EXT PERIOD WILL SEE ONLY ISOL
CHANCES WITH SOUTHWESTERLY MOIST FLOW RETURNING THROUGH SUN. WITH
ALL THE CLOUD COVER ANTICIPATED...MAX TEMPS SHOULD BE ABOUT 5
DEGREES BELOW NORMAL FRI THROUGH SUN. MINS ARE EXPECTED A DEGREE OR
TWO ABOVE NORMAL.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
A PERSISTENT FORECAST FOR THE NEXT 24 HOURS. SITES WILL BE IN AND
OUT OF A LOW END VFR CEILING FOR THE AFTERNOON WITH CLOUD BASES IN
THE 4K TO 5K FOOT RANGE. ISOLATED TO SCATTERED SHOWERS AND A FEW
THUNDERSTORMS WILL POP UP...BUT THIS WILL NOT BE INDICATED IN THE
TAFS AT THIS TIME. UNLIKE LAST NIGHT...THOUGH...DEVELOPING EASTERLY
FLOW IN THE FACE OF A BACK DOOR COLD FRONT DROPPING DOWN FROM THE
MID ATLANTIC COAST WILL KEEP A LOW LEVEL CLOUD CEILING ACROSS THE
REGION AND PROBABLY PREVENT FOG FROM DEVELOPING TO THE POINT WHERE
IT WOULD REDUCE VISIBILITY MUCH LOWER THAN 5 OR 6 MILES. AT THIS
POINT...TERMINALS WILL BE KEPT VFR WITH THE EXCEPTION OF KAVL.
EXPECT AT LEAST ISOLATED SHOWERS THROUGH MONDAY MORNING AS THE FRONT
PUSHES THROUGH...BUT NOT ENOUGH TO MENTION IN THE TAFS. DRIER AIR
WILL FILTER IN FROM THE NE ON MONDAY MORNING WHICH SHOULD SCATTER
OUT THE LOW CLOUDS BY AFTERNOON.

OUTLOOK...VFR CONDITIONS WITH DRYING UNDER BUILDING HIGH PRESSURE IS
EXPECTED THROUGH THE WEEK.

&&

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

&&

SYNOPSIS...SBK
NEAR TERM...PM
SHORT TERM...JDL
LONG TERM...SBK
AVIATION...PM

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
456 AM EDT SUN AUG 31 2008

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-010900-
RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-AVERY-ALEXANDER-
IREDELL-DAVIE-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-CATAWBA-
ROWAN-GRAHAM-NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-
HENDERSON-CLEVELAND-LINCOLN-GASTON-MECKLENBURG-CABARRUS-UNION NC-
CALDWELL MOUNTAINS-GREATER CALDWELL-BURKE MOUNTAINS-GREATER BURKE-
MCDOWELL MOUNTAINS-EASTERN MCDOWELL-RUTHERFORD MOUNTAINS-
GREATER RUTHERFORD-POLK MOUNTAINS-EASTERN POLK-OCONEE MOUNTAINS-
PICKENS MOUNTAINS-GREENVILLE MOUNTAINS-GREATER OCONEE-
GREATER PICKENS-GREATER GREENVILLE-SPARTANBURG-CHEROKEE-YORK-
ANDERSON-ABBEVILLE-LAURENS-UNION SC-CHESTER-GREENWOOD-
456 AM EDT SUN AUG 31 2008

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

.DAY ONE...TODAY AND TONIGHT.

SCATTERED TO ISOLATED THUNDERSTORMS ARE FORECAST TO DEVELOP ACROSS
THE WESTERN CAROLINAS AND NORTHEAST GEORGIA THIS AFTERNOON AND EARLY
THIS EVENING. A FEW OF THESE STORMS MAY PRODUCE STRONG TO DAMAGING
WIND GUSTS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.