Special Weather Statement, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
435 PM EDT THU APR 5 2012

.SYNOPSIS...
AN UPPER LOW WILL MERGE WITH THE DEPARTING TROUGH AS IT MOVES OFF
THE EAST COAST ON FRIDAY. COOL AND DRY HIGH PRESSURE WILL THEN BUILD
OVER OUR REGION INTO SATURDAY AND WEAKEN.  AN UPPER TROUGH IS
FORECAST TO SET UP OVER THE EAST NEXT WEEK WHICH COULD LEAD TO
COOLER THAN NORMAL TEMPERATURES.

&&

.NEAR TERM /THROUGH FRIDAY/...
AT 430 PM EDT... STRONGEST CONVECTIVE STORMS MOVING SLOWLY
NORTHEAST FROM SOUTHERN NC MOUNTAINS SOUTHEAST INTO SC PIEDMONT.
STORMS WILL CONTINUE THAT MOTION IN THE NEAR TERM... BUT MORE
STABLE AIR JUST TO THE EAST WILL LIKELY PREVENT EXPANSION OF
DAMAGING WIND AND HAIL INTO OUR EASTERN ZONES. RAIN WILL GRADUALLY
SPREAD INTO THAT AREA... HOWEVER. RAIN WILL PERSIST WESTERN
PORTION OF NC PIEDMONT... FOOTHILLS... AND ALONG BLUE RIDGE
ESCARPMENT. WILL MONITOR THAT AREA FOR POSSIBILITY OF EXCESSIVE
RAINFALL LATER AS PERSISTENT EAST/WEST AREA OF PRECIPITATION
DEVELOPS JUST NORTH OF SURFACE LOW. DRIER AIR MOVING INTO
SOUTHWESTERN ZONES WILL RESULT IN DIMINISHING SHOWER CHANCE FOR A
WHILE... BUT BAND OF CONVECTIVE RAINFALL ASSOCIATED WITH UPPER
LEVEL SYSTEM WILL SWING INTO AREA LATER THIS EVENING OR EARLY
TONIGHT.

PREVIOUS DISCUSSION...
CONVECTION DEVELOPED NEARLY ON SCHEDULE...BUT MAYBE A TAD EARLIER
THAN EXPECTED. WATCH ALREADY IN PLACE ACROSS MOST OF THE WRN CWFA
LOOKS WELL PLACED. STRONG INSOLATION OCCURRED IN THIS AREA WITH
POOLING DEW POINTS ALONG THE STALLED FRONT. THIS LEAD TO MODERATE
INSTABILITY ACROSS THIS AREA AS EXPECTED. VERY HIGH DCAPE VALUES AND
WET BULB ZERO LEVELS ARE IN PLACE AS WELL DUE TO THE VERY DRY MID
LEVELS SEEN ON THE 12Z FFC RAOB. THE WATCH INCLUDES MUCH OF THE CLT
METRO AREA EVEN THO THEY ARE NORTH OF THE FRONT. THE SFC BASED AND
MIXED LAYER CAPE IS LOW OVER THAT AREA...BUT MODERATE MUCAPE IS
ANALYZED DUE TO STEEP LAPSE RATES. THEY ARE ALSO ON THE EDGE OF THE
HIGHER DCAPE VALUES AS WELL. THE CONVECTION DEVELOPING OVER THE MTNS
AND FOOTHILLS SHUD SLIDE EAST ACROSS THE PIEDMONT EVEN WITH LESS
THAN IDEAL CONDITIONS. EXPECT WIDESPREAD TSRA TO DEVELOP AND TREK
EASTWARD OVER NE GA AND THE UPSTATE AS WELL THIS AFTERNOON AND EARLY
EVENING.

THE PRECIP SHUD BECOME LESS DEEPLY CONVECTIVE LATE THIS EVENING AND
OVERNIGHT AS INSTABILITY WEAKENS AHEAD OF THE APPROACHING UPPER LOW.
HAVE KEPT THE CHARACTER OF PRECIP AS SHRA FOR SIMPLICITY ALTHOUGH IT
MAY BE MORE STRATIFORM...ESPECIALLY ACROSS THE NORTHERN CWFA.
FORCING WILL BE QUITE STRONG AS QG COUPLET MOVES ACROSS THE AREA
AHEAD OF THE UPPER LOW. THIS WILL BE COMBINED WITH GOOD LOW LEVEL
CONVERGENCE AS A SFC LOW FORMS ALONG THE FRONT AND AN H85 LOW MOVES
IN AS WELL. UPPER DIVERGENCE INCREASES AHEAD OF A JET MAX MOVING IN
AHEAD OF THE UPPER LOW. ALL THIS SHOULD COMBINE WITH DEEP MOISTURE
FOR A PERIOD OF WIDESPREAD SHRA OR RA LATE THIS EVENING OR
OVERNIGHT. THE PRECIP BEGINS TO DIMINISH FROM NORTH TO SOUTH AND
WEST TO EAST AS THE FORCING MOVES OUT OF THE AREA. CANNOT RULE OUT
LOCALLY HEAVY RAINFALL...ESPECIALLY OVER AREAS WHERE TSRA MOVE THRU
THIS AFTERNOON AND RAINFALL LINGERS THRU THE EVENING.

ANY LINGERING PRECIP QUICKLY TAPERS OFF FRI MORNING AS THE SYSTEM
MOVES EAST OF THE AREA. CLOUDS WILL SCATTER OUT FOR MOST AREAS
DURING THE AFTERNOON....BUT COULD LINGER ACROSS THE BLUE RIDGE THRU
THE DAY IN WEAK UPSLOPE FLOW. HIGHS WILL BE QUITE A BIT COOLER AS
THICKNESSES FALL IN THE COOLER AND DRIER AIR MASS MOVING IN...ENDING
UP AS MUCH AS 5 DEGREES BELOW NORMAL.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 2 PM EDT THURSDAY...THE SHORT TERM FCST PICKS UP AT 00Z ON
SATURDAY WITH THE STEEP UPPER RIDGE AXIS OVER THE CENTRAL CONUS AND
A BROAD UPPER TROF LINGERING OVER NEW ENGLAND. AS THE UPPER RIDGE
DRIFTS TOWARDS THE CAROLINAS IT WILL DEAMPLIFY SO THAT BY THE END OF
THE PERIOD LATE SUNDAY WE ARE UNDER NEARLY ZONAL NWLY H5 FLOW.

ON SATURDAY...DRY AND COOL HIGH PRESSURE CENTERED OVER THE GREAT
LAKES WILL BRING US THE COOLEST TEMPERATURES WE HAVE HAD IN A WHILE.
LOWS EARLY SATURDAY MORNING WILL LIKELY DROP DOWN INTO THE MID TO
UPPER 30S ACROSS MUCH OF WESTERN NC WITH LOWER 30S IN SOME OF THE
NORTHERN MOUNTAINS. WINDS WILL ALSO BE LIGHT...SO THERE IS GOOD
POTENTIAL FOR PATCHY FROST. RH VALUES DROP BELOW 30% FOR ABOUT 4 TO
6 HOURS DURING THE AFTERNOON/EARLY EVENING PERIOD...HOWEVER WEAKER
WINDS SHOULD SUPPRESS FIRE DANGER POTENTIAL. ON SUNDAY...SOME SORT OF
WEAK BNDY WILL MOVE THRU THE CWFA DURING THE AFTERNOON...BUT THIS
WILL HAVE LITTLE IMPACT ON THE SENSIBLE WX. TEMPS WILL WARM BACK
INTO THE LOW TO MID 70S AS THICKNESSES INCREASE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 2 PM THURSDAY...NO MAJOR CHANGES WERE MADE TO THE MEDIUM RANGE
FCST WITH THINGS STAYING IN LINE WITH HPC GUIDANCE. REFER TO
PREVIOUS DISCUSSION BELOW.

PREVIOUS DISCUSSION...
AS OF 130 AM THURSDAY...ON SUNDAY THE WEAK UPPER RIDGE WILL BE
BREAKING DOWN.  WITH PLENTY OF SUNSHINE AND THICKNESS VALUES ON THE
WARM SIDE...EXPECT HIGHS IN THE 70S ACROSS THE FORECAST AREA.
STARTING THE WEEK...EXPECT AN UPPER TROUGH TO DEVELOP OVER THE
EAST.  BOTH THE GFS AND ECMWF HAVE A CLOSED OFF LOW OVER THE GREAT
LAKES AT 12Z MONDAY AS IT SLIDES EAST OR SOUTHEAST.  THE ECMWF HAS A
DEEPER TROUGH AS WE PROGRESS INTO THE MID WEEK.  LOOKS LIKE THE BEST
CONSENSUS OF SHOWERS OVER THE NC MOUNTAINS WILL BE TUESDAY
AFTERNOON.  A GOOD PRESSURE GRADIENT DEVELOPS MONDAY AFTERNOON AND
GRADUALLY DECREASES ON TUESDAY AND I HAVE INCREASED THE WIND IN THIS
PERIOD AS THIS GRADIENT CERTAINLY SUPPORTS IT.  THE ECMWF HAS AN
UPPER CLOSED OFF LOW OVER THE CAROLINAS AND VIRGINIA WEDNESDAY NIGHT
AS THE GFS HAS THE TROUGH TRYING TO PULL OFF THE EAST COAST BY THAT
TIME.  TEMPERATURES SHOULD BE NEAR NORMAL ON MONDAY...BUT AS THE
TROFINESS SETS UP FOR DAYS 6 AND 7 THE TEMPERATURES WILL LIKELY BE A
FEW DEGREES BELOW NORMAL BY THAT TIME.  LOWS IN THE 30S FOR THE NC
MOUNTAINS IN MID WEEK.

&&

.AVIATION /21Z THURSDAY THROUGH TUESDAY/...
AT KCLT...NE WINDS...OCNL DUE E...WILL CONTINUE THRU THE PERIOD AS
THE AIR FIELD REMAINS NORTH OF THE SFC FNT. CONVECTION LOOKS MORE
LIKELY EVEN WITH THE COOLER DRIER AIR IN PLACE AS ELEVATED
INSTABILITY REMAINS QUITE HIGH. DID NOT INCLUDE IN THE TAF ATTM...
BUT WILL LIKELY NEED TO AMD AS CELLS DEVELOP AND MOVE TOWARD THE
SITE. BEST CHC WILL BE LATE AFTERNOON. AS THE SCENARIO TRANSITIONS
TO MORE OF A RAIN EVENT THIS EVENING...VSBY AND CIGS WILL BEGIN TO
LOWER...POSSIBLY TO IFR. VSBY IMPROVES TOWARD DAYBREAK AS RAIN MOVES
OUT...BUT AT LEAST MVFR CIGS WILL CONTINUE THRU NOON BEFORE CLOUDS
BEGIN TO SCATTER OUT AND LIFT. WINDS COULD BE GUSTY AT ANY TIME...
BUT MOST LIKELY FROM DAYBREAK THRU NOON WHEN BEST MIXING OCCURS.

ELSEWHERE...KHKY WILL BE SIMILAR TO KCLT THRU THE PERIOD. THE WRN
SITES HAVE CONVECTION NEARBY OR ONGOING...SO TS ALREADY IN TAFS.
THAT SAID...A SIMILAR TREND WILL DEVELOP AS THE FRONT SAGS SOUTHWARD
THIS EVENING AND SCENARIO TRANSITIONS TO MORE OF A RAIN EVENT. MVFR
VSBY AND CIGS...POSSIBLY IFR CIGS...EXPECTED OVERNIGHT AS WELL WITH
ONLY SLOWLY IMPROVING CONDITIONS FRI MORN. WINDS BECOME NE WITH TIME
AND DEVELOP GUSTS TOWARD MORNING.

OUTLOOK...A DRY HIGH PRESSURE SYSTEM WILL BUILD IN BY FRI AFTERNOON
AND DOMINATE THE WEATHER THROUGH THE WEEKEND.

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...JPT
NEAR TERM...LGL/RWH
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...LGL/RWH

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
337 PM EDT THU APR 5 2012

GAZ010-017-018-026-028-029-NCZ048-051>053-058-059-062>065-068-070-
071-082-507>510-SCZ001>014-019-061945-
RABUN-HABERSHAM-STEPHENS-FRANKLIN-HART-ELBERT-MADISON-SWAIN-HAYWOOD-
BUNCOMBE-GRAHAM-NORTHERN JACKSON-MACON-SOUTHERN JACKSON-TRANSYLVANIA-
HENDERSON-CLEVELAND-GASTON-MECKLENBURG-UNION NC-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-
337 PM EDT THU APR 5 2012

...SEVERE THUNDERSTORM WATCH 146 IN EFFECT UNTIL 9 PM EDT THIS
EVENING...

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   SEVERE THUNDERSTORM WATCH.

A COLD FRONT WILL STALL OVER THE UPSTATE OF SOUTH CAROLINA AND THE
NORTH CAROLINA MOUNTAINS THIS AFTERNOON. WIDESPREAD SHOWER AND
THUNDERSTORM ACTIVITY WILL DEVELOP ALONG THE FRONT. SOME OF THESE
THUNDERSTORMS ARE EXPECTED TO BECOME SEVERE AND PRODUCE DAMAGING
WINDS AND LARGE HAIL. AN ISOLATED TORNADO IS POSSIBLE...ESPECIALLY
IN THE VICINITY OF THE FRONT. AREAS THAT STAND THE BEST CHANCE OF
SEEING SEVERE STORMS WILL GENERALLY BE ALONG AND SOUTH AND WEST OF
A LINE FROM ASHEVILLE TO SPARTANBURG AND CHESTER.

THUNDERSTORMS MAY REPEATEDLY AFFECT THE SAME LOCATIONS TODAY. IF
THIS OCCURS...LOCALIZED VERY HEAVY RAIN IS POSSIBLE WHICH COULD
CAUSE FLASH FLOODING. URBAN AREAS WILL BE PARTICULARLY
SUSCEPTIBLE TO FLASH FLOODING THROUGH THE EVENING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

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

NCZ033-035>037-049-050-056-057-069-072-501>506-061945-
AVERY-ALEXANDER-IREDELL-DAVIE-YANCEY-MITCHELL-CATAWBA-ROWAN-LINCOLN-
CABARRUS-CALDWELL MOUNTAINS-GREATER CALDWELL-BURKE MOUNTAINS-
GREATER BURKE-MCDOWELL MOUNTAINS-EASTERN MCDOWELL-
337 PM EDT THU APR 5 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PIEDMONT NORTH CAROLINA AND
WESTERN NORTH CAROLINA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

A COLD FRONT WILL STALL JUST SOUTH OF THE REGION THIS AFTERNOON.
A FEW THUNDERSTORMS WILL FORM NORTH OF THE FRONT...PARTICULARLY
ACROSS THE MOUNTAINS AND FOOTHILLS. LOCALLY HEAVY RAIN AND CLOUD
TO GROUND LIGHTNING WILL BE THE MAIN THREAT FROM THUNDERSTORMS
THROUGH THE EVENING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

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

JPT

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