Special Weather Statement, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
813 PM EDT MON APR 30 2012

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL STRENGTHEN AND CONTROL THE WEATHER
THROUGH THE WEEK. SMALL AREAS OF UPPER LEVEL ENERGY WILL PROVIDE
SOME SHOWERS AND STORMS OVER THE MOUNTAINS AND MORE ISOLATED
ACTIVITY IN THE FOOTHILLS AND PIEDMONT LATE IN THE DAY.  A COLD
FRONT IS EXPECTED TO MOVE FROM NORTH TO SOUTH INTO THE AREA NEXT
WEEKEND.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 805 PM EDT...GRIDS ARE IN GOOD SHAPE. STRONG TO SEVERE STORMS
HAVE REMAINED CONFINED TO THE CENTRAL AND NRN NC MTNS AND THE NW
FOOTHILLS...EXACTLY AS WAS IN THE FORECAST.

PREVIOUS DISCUSSION...
AS OF 200 PM... 12Z NAM...LOCAL WRF AND THE 12Z GFS INDICATE THAT
CONVECTIVE INITIATION WILL OCCUR OVER THE NORTHERN MOUNTAINS IN THE
19Z-21Z TIMEFRAME...WITH CONVECTION THEN MOVING EAST THROUGH THE NC
FOOTHILLS INTO THE NORTHERN PIEDMONT. ADDITIONAL DEVELOPMENT THEN IS
FORECAST ESSENTIALLY THROUGH THE LEE TROUGH AROUND 00Z WITH STORMS
ACROSS THE NORTHERN UPSTATE INTO NE GA. CONVECTIVE ACTIVITY SHOULD
THEN WANE BY 06Z OR SO. CURRENT POP FIELD LOOKS GOOD IN REGARD TO
THIS SCENARIO.

SBCAPES ALREADY HAVE INCREASED INTO THE 1500-2000J/KG RANGE.
HOWEVER...IT LOOKS LIKE THERE IS SUFFICIENT CIN TO CAP CONVECTIVE
INITIATION UNTIL ABOUT 20Z IN THE NORTHERN MOUNTAINS. WITH BULK
SHEAR AROUND 30KT...THIS MY BE ENOUGH TO SUSTAIN UPDRAFTS AND ALLOW
CONVECTION TO SPREAD OUT OVER THE FOOTHILLS. ALSO...DCAPE OVER THE
MOUNTAINS IS AROUND 1000J...SO A FEW SEVERE STORMS ARE POSSIBLE WITH
LARGE HAIL AND DAMAGING WINDS.

ALL INDICATIONS ARE THAT THE STORMS WILL DISSIPATE BY 06Z...SO
IT SHOULD BE QUIET LATE TONIGHT WITH JUST DOME DEBRIS CLOUDINESS AND
PATCHY FOG. SOME STRATUS MAY MAKE A RUN AT THE EASTERN AND SOUTHERN
PERIPHERY OF THE CWA AROUND SUNRISE.

ON TUE...EXPECT A FEW SHOWERS TO BEGIN CROPPING UP IN THE MOUNTAINS
TUE MORNING WITH UPSLOPE FLOW AND AN APPROACHING VORT. SCATTERED
SHOWERS AND STORMS ARE THEN EXPECTED TO DEVELOP ACROSS THE NC
FOOTHILLS/PIEDMONT AS A WEAK FRONTAL BOUNDARY DROPS INTO THE AREA
DURING THE AFTERNOON. A FEW STORMS COULD MOVE OUT INTO NE GA AND THE
SC FOOTHILLS/PIEDMONT LATE IN THE DAY. CONDITIONAL INSTABILITY WILL
ONCE AGAIN BE ON THE ORDER OF 1500J/KG SO CAN'T RULE OUT A FEW
SEVERE STORMS OVER WESTERN NC WHERE WIND SHEAR IS THE GREATEST.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
AS OF 140 PM MONDAY...SHORT RANGE MODELS INDICATE THAT THE CENTER OF
H5 RIDGE WILL BUILD OVER THE SAVANNAH RIVER BASIN WEDNESDAY AND
THURSDAY. SKY COVER WILL REMAIN LIMITED TO PARTLY CLOUDY CONDITIONS
THROUGH THE PERIOD...ESPECIALLY OVER THE MTNS AND ADJACENT
FOOTHILLS. THE RIDGE WILL SUPPLY THE REGION WITH VERY WARM LLVL
THICKNESSES AND H85 TEMPS BETWEEN 16C TO 18C. USING A BLEND OF MOS
GUIDANCE...FORECAST LOW TEMPS ARE FORECAST TO RANGE FROM THE L50S
ACROSS THE MTN VALLEYS TO L60S EAST...OR AROUND 10 DEGREES ABOVE
NORMAL. THIS WILL SET THE STAGE FOR RECORD TO NEAR RECORD HIGH
TEMPERATURES EACH DAY. HERE ARE THE RECORDS FOR WEDNESDAY AND
THURSDAY FOR KGSP...KCLT...AND KAVL:

KGSP

MAY 2ND  90F IN 1959 FORECAST 90F
MAY 3RD  91F IN 1959 FORECAST 90F

KCLT

MAY 2ND  91F IN 1959 FORECAST 88F
MAY 3RD  94F IN 1902 FORECAST 91F

KAVL

MAY 2ND  88F IN 1935 FORECAST 85F
MAY 3RD  85F IN 1965 FORECAST 86F

WEDNESDAY AND THURSDAY...THE ENVIRONMENT WILL CHANGE LITTLE FROM DAY
TO DAY. FORECAST SOUNDINGS FEATURE A WEAK INVERSION AROUND H8 WITH
CIN VALUES RANGING BETWEEN 30 TO 60 J/KG. WIND FIELDS SHOULD RESULT
IN ONLY WEAK SHEAR...ESPECIALLY ON THURSDAY. THE STORM MODE SHOULD
REMAIN AS PULSE STORMS. GIVEN THE LINGERING INVERSION...LACK OF A
TRIGGER...AND SLOW STORM MOTIONS WILL FAVOR SCHC POPS EAST OF THE
MTNS...WITH CHC POPS ACROSS THE RIDGES.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 145 PM MONDAY...THE MEDIUM RANGE MODELS HAVE BEEN RATHER
CHANGEABLE.  MOST RECENT HPC WORD SAYS BLENDING ECMWF AND GEFS
ENSEMBLES ARE THE BEST WAY TO GO.  WHEN COMPARING THE OPERATIONAL
GFS AND ECMWF START THE MEDIUM RANGE IN A MODERATE 500MB RIDGE
THURSDAY NIGHT. BOTH SHOW THURSDAY EVENING CONVECTION FROM THE
VIRGINIAS TO EASTERN NC. THIS TREND DIMINISHES FOR LATE FRIDAY AS
THE RIDGE FLATTENS.  GOING INTO THE WEEKEND...THESE TWO MODELS
DIVERGE IN SOLUTIONS.  THE RIDGE REBUILDS OVER THE SE ON THE ECMWF
FOR SATURDAY WHILE RIDGE RETROGRADES TO TEXAS ON THE GFS WITH TROF
FORMING OVER EAST. THE LATEST 12Z GFS BRINGS THE COLD FRONT ACROSS
OUR AREA EARLY SUNDAY WHILE THE PREVIOUS RUN WAITED UNTIL LATE
MONDAY.  THE MOST RECENT ECMWF HAD A WEAK FRONT CROSSING OUR REGION
MONDAY NIGHT. OF COURSE...WITH THIS BEING A WEEK AWAY WE WILL HAVE
SLIGHT POPS IN FORECAST THROUGH THE GENERAL TIME UNTIL WE CAN NAIL
DOWN A MORE DEFINITE TIME FOR FRONTAL PASSAGE.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
AT KCLT...INTENSE TSTMS SHOULD REMAIN CONFINED TO THE NC MTNS AND
WRN FOOTHILLS THIS EVENING. WINDS WILL GENERALLY BE OUT OF THE
SOUTH. STRATUS IS EXPECTED TO DEVELOP OVER THE MIDLANDS AND INTO
CENTRAL NC LATE TONIGHT. THE BACK EDGE OF THE LOW CLOUDS WILL BE
QUITE CLOSE TO THE AIRFIELD. I/VE PUT FEW006 IN THE TAF FOR A FEW
HOURS AROUND SUNRISE. THE RUC BUFKIT REALLY IMPLIES THE LOW CIGS
WILL MAKE IT...BUT THE NAM IS MORE IFFY. TMRW AFTN A FEW TSTMS MAY
APPROACH THE AIRFIELD FROM THE NW LATE IN THE DAY.

ELSEWHERE...STRATUS IS EXPECTED TO DEVELOP EAST OF THE REGION
OVERNIGHT...BUT SHOULD STAY SEVERAL MILES EAST OF ALL THE UPSTATE
TAF SITES. MID LEVEL CLOUDS SHOULD KEEP SKIES CLOUDY ENOUGH TO
PREVENT WIDESPREAD VALLEY FOG IN THE NC MTNS. A STRENGTHENING LLVL
JET SHOULD KEEP THE WINDS UP ENUF IN THE FOOTHILLS AND PIEDMONT TO
PREVENT ANYTHING BUT PATCHY MVFR FOG AS WELL. WINDS WILL GENERALLY
BE OUT OF SOUTH TONIGHT...VEERING TO SW ON TUESDAY. SCT TSTMS WILL
DEVELOP OVER THE MTNS TUE...BUT COVERAGE IS NOT GREAT ENUF TO
INCLUDE IN THE TAF.

OUTLOOK...SCT TSTMS WILL DEVELOP OVER THE MTNS WED-FRI. A MOST
AIRMASS WILL ALLOW AREAS OF FOG AND STRATUS TO FORM IN SPOTS THROUGH
THE END OF THE WEEK AS WELL.

AN EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLE SHOWING THE
PERCENTAGE OF GUIDANCE MEMBERS AGREEING WITH THE SCHEDULED ISSUANCE
CATEGORY IS AVAILABLE AT FOLLOWING LINK (USE LOWER CASE)...

WWW.WEATHER.GOV/GSP/AVIATION/TABLES.HTM

&&

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

&&

SYNOPSIS...DEO
NEAR TERM...MCAVOY
SHORT TERM...NED
LONG TERM...DEO
AVIATION...MCAVOY

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
812 PM EDT MON APR 30 2012

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

0757 PM     HAIL             2 WNW WEAVERVILLE       35.71N 82.59W
04/30/2012  E1.25 INCH       BUNCOMBE           NC   PUBLIC

            OBSERVED OFF OF NEW STOCK RD.

&&

CSH

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