Severe Thunderstorm Warning 71, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
241 PM EDT SAT MAY 2 2009

.SYNOPSIS...
A COLD FRONT WILL REMAIN JUST TO THE WEST OF THE REGION THROUGH THE
WEEKEND. THE FRONT WILL MOVE THROUGH THE WESTERN CAROLINAS ON MONDAY
AND THEN DISSIPATE OVER CENTRAL GEORGIA AND THE MIDLANDS ON TUESDAY.

&&

.NEAR TERM /THROUGH SUNDAY/...
CURRENT RADAR SHOWS A WEAKENING AREA OF LIGHT/MODERATE RAIN SHOWERS
OVER THE MOUNTAINS...THE REMNANTS OF THE MCS THAT MOVED OUT OF TN.
TO THE S...LATEST LAPS ANALYSIS SHOWS THAT CAPES HAVE INCREASED INTO
THE 1000-1500J RANGE OVER THE WESTERN UPSTATE/NE GA THANKS TO LOW TO
MID 60 DEWPOINTS ADVECTING INTO THE AREA. SOME STRONGER SCATTERED
THUNDERSTORMS HAVE DEVELOPED OVER N GA IN THIS UNSTABLE AIRMASS AND
ARE  MOVING NE TOWARD THE FORECAST AREA. FOR THE REMAINDER OF THE
AFTERNOON INTO THE EARLY EVENING...EXPECT SCATTERED TO NUMEROUS
THUNDERSTORMS TO AFFECT NE GA...EASTWARD THROUGH THE SC UPSTATE AND
EVENTUALLY THE NC PIEDMONT BY EARLY EVENING AS REMNANT MCV TRACKS
EASTWARD. THE MOUNTAINS/FOOTHILLS SHOULD JUST EXPERIENCE SHOWERS IN
THE MORE STABLE AIRMASS. ALSO CANT RULE OUT A SEVERE STORM IN THE
HIGH BUOYANCY AIRMASS OVER THE PIEDMONT. EXPECT THUNDERSTORM ACTIVITY
TO WANE QUICKLY AFTER SUNSET DUE TO LOSS OF HEATING AND LOSS OF ANY
SYNOPTIC SCALE LIFT. HENCE...FOR THE OVERNIGHT ONLY WIDELY SCATTERED
SHOWERS AT BEST...EXCEPT MODELS INDICATE THAT THE WESTERN UPSLOPE
AREAS WILL SEE AN INCREASE IN COVERAGE OF SHOWERS LATE TONIGHT AS
LOW LEVEL WIND FIELDS INCREASE. HAVE RAISED POSP IN THAT AREA LATE
TONIGHT.

SUNDAY LOOKS TO BE A MOSTLY CLOUDY AND BREEZY DAY AS LOW PRESSURE
DEVELOPS TO THE NW ALONG THE STATIONARY FRONT. IN FACT...LAKE WIND
CONDITIONS ARE LIKELY ALL AREAS...WITH EVEN ADVISORY CRITERIA OVER
THE HIGHER ELEVATIONS IN THE MOUNTAINS. LOOKS LIKE IT WILL BE THE
MOUNTAINS/FOOTHILLS THAT WILL HAVE THE BEST CHANCE FOR
SHOWERS/THUNDERSTORMS ON SUN WHERE BEST FORCING SETS UP. GUIDANCE
SUGGESTS LIKELY POPS ACROSS THE FAR N TAPERING TO JUST SLIGHT CHANCE
SOUTHERN PIEDMONT COUNTIES. SUNDAY WILL BE A WARM DAY AND LEANED
TOWARD THE HIGHER MET NUMBERS.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
AS OF 240 PM SATURDAY...A COUPLE SHORT WAVES AFFECT THE REGION SUN
NGHT - TUE. THE FIRST WAVE WILL LIFT JUST A LITTLE TO THE NW OF THE
REGION SUN NIGHT. THERE CONTINUE TO BE TIMING AND PLACEMENT
DIFFERENCES WITH THIS SMALL WAVE IN THE MODELS...MAINLY RELATED TO
CONVECTIVE FEEDBACK. THE GFS IS FASTER THAN THE NAM AND THE EC IS
SLOWER THAN EITHER. REGARDLESS...BASED ON THE MODEL LLVL WIND
FIELDS...ISENTROPIC UPGLIDE WILL INCREASE OVERNIGHT AND SOME KIND OF
MCS IS LIKELY TO MOVE INTO THE MOUNTAINS DURING THE NIGHTTIME HOURS.
I HAVE LIKELY POPS OVER THE MTNS AND NC FOOTHILLS THROUGH THE
NIGHT...WHICH LINES UP WELL WITH THE NEIGHBORS. THE SEVERE THREAT
WILL BE LOW...BUT LOCALLY HEAVY RAIN IS POSSIBLE.

ON MON A TRAILING SHORT WAVE WILL MOVE THROUGH THE REGION.
AGAIN...THERE ARE TIMING DIFFERENCES...BUT THE MOST LIKELY TIME OF
ARRIVAL IS MONDAY EVENING. THIS IS A LARGER WAVE WHICH HAS EXCELLENT
ASSOCIATED UPPER DIVERGENCE. THIS WILL HAVE MORE OF AN EFFECT OF THE
SFC PATTERN...RESULTING IN GOOD LLVL CONVERGENCE OVER THE HEART OF
THE FA DURING THE AFTERNOON. LAYER RH/S WILL BE HIGH AND THE SHEAR
WEAK...SO ANY SEVERE WEATHER WILL BE QUITE ISOLATED...BUT THERE
SHOULD BE FAIRLY WIDESPREAD SHOWER AND THUNDERSTORM ACTIVITY AND I
HAVE LIKELY POPS ACROSS THE ENTIRE FA. IT/S HARD TO PINPOINT WHERE
THE MOST ACTIVITY WILL BE...BUT EYEBALLING THE NAM/GFS/EC SFC FRONTS
LOOKS TO PLACE THE BEST CONVERGENCE OVER THE EASTERN PART OF THE FA.

BY EARLY TUE THE PATTERN IS FLAT OR WEAKLY ANTICYCLONIC. THERE
SHOULD BE MUCH LESS ACTIVITY ON TUE WITH MILDER TEMPS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 140 PM SATURDAY...A BROAD...LOW AMPLITUDE LONG WAVE TROUGH
WILL PERSIST ACROSS THE CENTRAL PART OF THE COUNTRY FOR MOST OF THE
EXTENDED PART OF THE FORECAST...BEFORE SHIFTING EASTWARD BY NEXT
WEEKEND. THE EXTENDED RANGE MODELS HAVE BEEN CHANGING DAILY...WHICH
IS EXACTLY WHAT ONE WOULD EXPECT WITH A LOW AMPLITUDE FLOW...
ESPECIALLY THIS TIME OF YEAR. ITS HARD TO KNOW WHAT TO EXPECT 24
HOURS IN THE FUTURE...SO THIS IS CERTAINLY A LOW CONFIDENCE
EXTENDED FORECAST UNTIL THE PATTERN TAKES ON A LITTLE MORE AMPLITUDE.

THE GFS IMPLIES THAT THERE WILL BE WIDESPREAD CONVECTION ACROSS THE
REGION ON WED AS IT IS MORE PROGRESSIVE THAN THE OTHER MODELS IN
BRINGING ENERGY ACROSS THE ERN CONUS. IT/S INTERESTING TO NOTE THAT
ALL THE MEDIUM RANGE MODELS ARE INCREASING THE DEEP LAYER RIDGING
OVER THE SW STATES. IF THIS CONTINUES THEN THE GFS COULD VERY WELL
BE RIGHT...BUT THE 00 UTC EC AND 12 UTC CANADIAN KEEP THE TROUGH
MUCH FARTHER WEST AND HAVE ONLY A VERY WEAK WAVE SKIRTING THE REGION
ON WED. THEREFORE I WENT LOWER THAN HPC WITH WED POPS...CONFINING
CHANCE POPS TO THE MTNS. TEMPS LOOK AS THOUGH THEY WILL BE WELL
ABOVE NORMAL.

ON THU THE EC AND CANADIAN BRING A STRONGER SHORT WAVE TOWARD THE
REGION...THOUGH MOST OF THE ENERGY LIFTS TO THE NORTH AS THEY STILL
HAVE FAIRLY LOW HEIGHTS OVER THE PLAINS AND A STRONG RIDGE OFF THE
SE COAST. ONCE AGAIN THIS WOULD CONFINE THE BEST PCPN CHANCES TO THE
MTNS AND AREAS TO THE WEST. CONSIDERING HOW MUCH RAIN HAS FALLEN
OVER PARTS OF CENTRAL TN OF LATE...IT SEEMS THAT WE HAVE DEVELOPED A
PATTERN WITH THE RIDGE HERE IN THE SE KEEPING MOST OF THE PCPN TO
OUR WEST. THERE WILL BE EXCEPTIONS...BUT IT MAKES SENSE TO FOLLOW
THIS TREND UNTIL THERE IS A MAJOR PATTERN CHANCE.

CONFIDENCE IN THE FRI/SAT PERIOD REMAINS LOW. HOWEVER...WITH HEIGHTS
GRADUALLY RISING OVER THE SW...THE LOW AMPLITUDE LONG WAVE WILL
START TO SHIFT TO THE EAST. WITH LESS SRN STREAM ENERGY TO WORRY
ABOUT...THE MAIN CONCERN WILL BE MCS ACTIVITY DEVELOPING THE W TO NW
FLOW OVER THE REGION. TYPICALLY...ONCE AGAIN...THAT WILL KEEP THE
BEST PCPN CHANCES OVER THE MTNS...WHICH IS WHAT I HAVE. IT WILL
REMAIN WARMER THAN NORMAL THROUGH THE EXTENDED RANGE.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
AT KCLT...VFR CONDITIONS WILL BE THE GENERAL RULE FROM LATE THIS
AFTERNOON INTO EARLY TONIGHT WITH MID LEVEL CEILINGS LOWERING TO
AROUND 4000 FT BY 22Z. THE BEST CHANCE FOR THUNDERSTORM ACTIVITY IN
THE VICINITY OF THE AIRPORT WILL BE IN THE 21Z-01Z RANGE. IF A STORM
CROSSES THE TERMINAL SOME BRIEF MVFR CEILINGS/VSBY ARE LIKELY.
THUNDERSTORM CHANCES DROP OFF QUICKLY SHORTLY AFTER SUNSET AND ONLY
MID LEVEL CEILINGS SHOULD BE THE RULE FOR MOST OF THE NIGHT. SOME OF
THE GUIDANCE IS NOW SUGGESTING THAT A PERIOD OF MVFR/IFR CONDITIONS
ARE POSSIBLE AROUND SUNRISE ON SUNDAY. I CAN CERTAINLY SEE A
SCENARIO OF SOME THIN STRATUS AROUND 1000 FT...IN THE 11Z-13Z
TIMEFRAME...BUT FOR NOW WILL JUST GO WITH A SCT010. WINDS SHOULD
CONTINUE TO FAVOR SW EXCEPT VARIABLE AROUND THUDNERSTORMS THIS
AFTERNOON/EVENING. SW WINDS WILL INCREASE ON SUNDAY WITH GUSTS TO
AROUND 25 KTS BY MIDDAY.

ELSEWHERE OUTSIDE THE MOUNTAINS...ESSENTIALLY THE SAME SITUATION AS
FOR KCLT. HOWEVER...THIS AFTERNOONS THUNDERSTORMS WILL AFFECT THE
SC TERMINALS BY 20Z WITH KAND HAVING THE BEST CHANCE TO BE IMPACTED.
HAVE INTRODUCED A TEMPO FOR THUNDER THERE. ALL AIRPORTS COULD SEE A
BRIEF PERIOD OF MVFR CONDITIONS THIS AFTERNOON IN A THUNDERSTORM. AT
KAVL/KHKY...TEMPO RAIN SHOWERS ALONG WITH MVFR CEILINGS UNTIL ABOUT
21Z. SOME STRATUS MAY AFFECT ALL TAF SITES AROUND SR ON SUNDAY. HAVE
GONE WITH SCT-BKN WITH CEILINGS AROUND 1000 FT. WINDS WLL BECOME
GUSTY OUT OF THE SW ON SUNDAY BY 16Z.

OUTLOOK...MORNING FOG/STRATUS WILL BE POSSIBLE AGAIN EARLY ON
MONDAY. ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS IS EXPECTED ON
MONDAY AS A FRONT MOVES THROUGH THE REGION. SHRA AND TSRA WILL
RESULT IN PERIODS OF RESTRICTIONS. THERE MAY BE A LULL IN
SHOWER/THUNDERSTORM ACTIVITY ON TUE...BUT MORE UNSETTLED WEATHER IS
ANTICIPATED BY MIDWEEK.

&&

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

&&

SYNOPSIS...MCAVOY
NEAR TERM...LG
SHORT TERM...MCAVOY
LONG TERM...MCAVOY
AVIATION...LG

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
352 PM EDT SAT MAY 2 2009

GAZ010-017-NCZ033-048>053-058-059-062>065-501-503-505-507-509-
SCZ001>003-032000-
RABUN-HABERSHAM-AVERY-MADISON-YANCEY-MITCHELL-SWAIN-HAYWOOD-BUNCOMBE-
GRAHAM-NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-
HENDERSON-CALDWELL MOUNTAINS-BURKE MOUNTAINS-MCDOWELL MOUNTAINS-
RUTHERFORD MOUNTAINS-POLK MOUNTAINS-OCONEE MOUNTAINS-
PICKENS MOUNTAINS-GREENVILLE MOUNTAINS-
352 PM EDT SAT MAY 2 2009

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

NUMEROUS SHOWERS AND A FEW THUNDERSTORMS WILL AFFECT THE MOUNTAINS
OF THE WESTERN CAROLINAS AND NORTHEAST GEORGIA THIS EVENING. THE
ATMOSPHERE OVER THE MOUNTAINS IS FAIRLY STABLE...SO THE ONLY
THREAT FROM THUNDERSTORMS WILL BE BRIEF...HEAVY RAIN AND A LITTLE
CLOUD TO GROUND LIGHTNING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

SEVERAL PERIODS OF SHOWER AND THUNDERSTORM ACTIVITY ARE EXPECTED
ACROSS THE MOUNTAINS SUNDAY AND MONDAY. A FEW OF THE STORMS MAY
BECOME SEVERE PRODUCING DAMAGING WINDS AND LARGE HAIL...THOUGH THE
GREATER THREAT WILL BE HEAVY RAIN. WHILE CONDITIONS ARE STILL
FAIRLY DRY AND STREAM LEVELS LOW...ISOLATED FLASH FLOODING MAY
BEGIN TO DEVELOP AS THUNDERSTORMS REPEATEDLY AFFECT THE SAME AREAS.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTERS ARE REQUESTED TO FORWARD ANY REPORTS OF LARGE
HAIL...DAMAGING WINDS...TORNADOES OR FLASH FLOODING TO OUR OFFICE.

GAZ018-026-028-029-NCZ035>037-056-057-068>072-082-502-504-506-508-
510-SCZ004>014-019-032000-
STEPHENS-FRANKLIN-HART-ELBERT-ALEXANDER-IREDELL-DAVIE-CATAWBA-ROWAN-
CLEVELAND-LINCOLN-GASTON-MECKLENBURG-CABARRUS-UNION NC-
GREATER CALDWELL-GREATER BURKE-EASTERN MCDOWELL-GREATER RUTHERFORD-
EASTERN POLK-GREATER OCONEE-GREATER PICKENS-GREATER GREENVILLE-
SPARTANBURG-CHEROKEE-YORK-ANDERSON-ABBEVILLE-LAURENS-UNION SC-
CHESTER-GREENWOOD-
352 PM EDT SAT MAY 2 2009

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

SCATTERED THUNDERSTORM WILL AFFECT THE FOOTHILLS AND PIEDMONT OF
THE WESTERN CAROLINAS AND NORTHEAST GEORGIA THIS EVENING. THE
ATMOSPHERE OVER THE REGION IS VERY UNSTABLE THIS EVENING...AND
MANY OF THE STORMS WILL PRODUCE DAMAGING WINDS AND HAIL UP THE
SIZE OF QUARTERS. THE SEVERE THREAT WILL DIMINISH AFTER SUNSET.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL AFFECT THE
REGION SUNDAY AND MONDAY. A FEW SEVERE STORMS ARE POSSIBLE DURING
THE AFTERNOON HOURS SUNDAY AND MONDAY. LOCALLY HEAVY RAIN IS
LIKELY WITH THE STORMS...THOUGH THE DRY GROUND AND LOW STREAM
LEVELS SHOULD LIMIT THE THREAT OF ANY FLASH FLOODING.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTERS ARE REQUESTED TO FORWARD ANY REPORTS OF LARGE
HAIL...DAMAGING WINDS...TORNADOES OR FLASH FLOODING TO OUR OFFICE.

MCAVOY

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
435 PM EDT SAT MAY 02 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0411 PM     HAIL             HODGES                  34.29N 82.25W
05/02/2009  E0.75 INCH       GREENWOOD          SC   PUBLIC

&&

LG

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