Special Weather Statement, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
113 PM EDT SAT MAR 31 2012

.SYNOPSIS...
A SERIES OF UPPER LEVEL DISTURBANCES AHEAD OF A COLD FRONT WILL MOVE
ACROSS THE CAROLINAS...REACHING THE COAST ON SUNDAY. DRIER AIR WILL
THEN MOVE IN AND REMAIN IN PLACE THROUGH THE MIDDLE OF THE WEEK WHEN
ANOTHER NORTHERN GULF WEATHER DISTURBANCE ENTERS THE PICTURE.

&&

.NEAR TERM /THROUGH TONIGHT/...
1730 UTC UPDATE...CLOUDS HAVE BEEN UPDATED FROM SATELLITE
IMAGERY...AND POPS REDUCED EARLY THIS AFTERNOON DUE TO LESS LOW
CLOUD COVER. A COLD FRONT MOVING SE ACROSS THE TN VALLEY WILL
SUPPORT THE DEVELOPMENT OF SCATTERED CONVECTION AS INSTABILITY
INCREASES WITH HEATING THIS AFTERNOON. POPS WILL INITIALLY FAVOR
THE MOUNTAINS...AND LATER THE PIEDMONT. CAPE AND SHEAR ARE NOT
OVERLY IMPRESSIVE...BUT MAY BE ENOUGH TO SUPPORT A FEW SEVERE
THUNDERSTORMS. WINDS WERE UPDATED WITH A BLEND OF 06S ADJMAV AND 12Z
NAM...RESULTING IN WESTERLY FLOW IN NE GA AND UPSTATE SC...AND NW
FLOW IN NC.

1400 UTC UPDATE...AN UPPER RIDGE WAS LOCATED OVER THE FRONT RANGE OF
THE ROCKIES THIS MORNING...WHILE AND UPPER TROUGH WAS OVER THE
EASTERN PART OF THE NATION. SEVERAL SHORTWAVE TROUGHS WERE MOVING
THROUGH THE BASED OF THIS TROUGH...ON OVER E TN...AND ANOTHER IN THE
MID MS RIVER VALLEY. PRECIPITATION ASSOCIATED WITH THE FIRST
SHORTWAVE WILL EXIT THE INTERSTATE 77 CORRIDOR THIS MORNING...
FOLLOWED BY PARTIAL DRYING BELOW 850 MB. MODEL TIME HEIGHT SHOW
MOISTURE REMAINING AT 850 MB AS A COLD FRONT NOW IN THE TN VALLEY
ARRIVES THIS AFTERNOON. A WESTERLY LOW LEVEL DOWNSLOPE FLOW IN THE
WAKE OF THE FIRST SYSTEM WILL LIMIT PRECIPITATION WITH THE FRONT.
INSTABILITY AND SPEED SHEAR...THOUGH NOT TREMENDOUS...WILL BE
SUFFICIENT TO ALLOW SCATTERED THUNDERSTORMS TO ORGANIZE ALONG THE
FRONT...AND A FEW SEVERE THUNDERSTORMS WITH LARGE HAIL AND DAMAGING
WIND WILL BE POSSIBLE. ISOLATED TO SCATTERED SHOWERS WILL REMAIN
ALONG THE TN BORDER THIS AFTERNOON BEHIND THE FRONT IN MOIST NW
UPSLOPE FLOW. WINDS WERE UPDATED WITH A BLEND OR 06Z ADJMANV AND
NAM. MAXIMUM TEMPERATURES WILL BE NEAR MID MAY VALUES IN DOWNSLOPE
FLOW.

1140 UTC UPDATE...POPS HAVE BEEN INCREASE JUST WEST OF THE
INTERSTATE 77 CORRIDOR BASED ON RADAR TRENDS SHOWING A SLOWER
EASTWARD MOVEMENT OF PRECIPITATION. QPF WAS RAISED A BIT JUST SOUTH
OF KCLT.

THE LLVL FLOW OVER THE REGION IS STARTING TO VEER PER THE VAD WIND
PROFILES AT KFFC AND KGSP. THIS IS IN RESPONSE TO A SHORTWAVE
MOVING ACROSS NE GA ATTM. AN AREA OF LIGHT TO MODERATE RAIN WITH A
FEW HEAVIER SHOWERS HAS ANCHORED ITSELF TO THE SRN ESCARPMENT OF THE
BLUE RIDGE...BUT AS THE WAVE IS PASSING...THE RAIN IS FINALLY
STARTING TO KICK OUT TO THE EAST. ACTUALLY...MOST OF THE FA HAS SEEN
RAIN OVERNIGHT...BUT THIS BATCH WILL BE A LITTLE HEAVIER AS IT MAKES
IT/S WAY UP I-85 OVER THE NEXT 3 TO 5 HOURS.

BY 12 UTC MOST OF THE FA WILL BE UNDER WEAK NVA BEHIND THE WAVE.
WEST TO WEST NORTHWESTERLY DOWNSLOPE FLOW WILL HELP TO LIFT
WIDESPREAD LOW STRATUS...AND THE SUN SHOULD BEGIN TO PEAK OUT BY
LATE MORNING OR NOON. ANOTHER UPSTREAM SHORT WAVE WILL ACROSS THE
REGION FROM 00-03 UTC THIS EVENING. THE FEATURE SHOWS UP QUITE WELL
ON THE WATER VAPOR IMAGERY THIS MORNING...AND IT/S EVEN SUPPORTING A
FEW SHRA OVER CENTRAL MISSOURI ATTM.

THE NAM BACKS THE FLOW ACROSS THE GREAT VALLEY OF ERN TN AND ACROSS
THE WESTERN PIEDMONT OF THE CAROLINAS AND NE GA BY LATE AFTN AHEAD
OF THE WAVE. STEEPENING LAPSE RATES AND POOLING LLVL DEWPOINTS WILL
YIELD A MODERATELY UNSTABLE ATMOSPHERE...AND SCT AFTN AND EVENING
TSTMS ARE EXPECTED ACROSS THE MTNS...ESPECIALLY NEAR THE TN LINE AS
WELL AS OUT ACROSS THE PIEDMONT AND EASTERN FOOTHILLS. THE
IMMEDIATE LEE OF THE MOUNTAINS MAY BE A LITTLE TOO STABLE FOR TSTMS
ON ACCOUNT OF THE DOWNSLOPE DRYING EARLIER IN THE DAY. I HOPE I
DIDN/T GET TOO CUTE CARVING OUT A SMALL AREA OF NON POPS IN THE
LEE...BUT THIS DOES MATCH THE NAM/S SFC CAPE FIELD. A FEW OF THE
STORMS COULD HAVE BOTH LARGE HAIL AND DAMAGING WINDS AS THE
MID-LEVELS OF THE ATMOSPHERE WILL DRY OUT MODESTLY THIS AFTN.

SCT CONVECTION SHOULD CLEAR THE SE ZONES BY MID-EVENING. DRIER BNDRY
LAYER AIR ENTERS THE FA...THOUGH THE NAM SOUNDINGS STILL HAVE A
SUSPICIOUS LOOKING AMOUNT OF LLVL MOISTURE. HOWEVER...THE SREF PROBS
OF LOW CIGS AND VSBYS ARE QUITE LOW AND THE NAM SFC CONDENSATION
PRESSURE DEFICITS ARE FAIRLY HIGH...RANGING FROM 10 TO 30 MB. THEY
ARE LOWER OVER THE MTNS HOWEVER...AND I HAVE ADDED DENSE VALLEY FOG
TO THESE AREAS.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 230 AM SATURDAY...THE LATEST MODELS CONTINUE TO INDICATE THAT
DRY SURFACE HIGH BUILDS INTO THE REGION AS BROAD UPPER RIDGE
AMPLIFIES OVER THE CENTRAL CONUS ON SUNDAY. THEREFORE...MOSTLY DRY
CONDITIONS CAN BE EXPECTED ACROSS OUR CWA WITH DAYTIME HIGHS
REACHING IN THE LOW 80S OVER THE PIEDMONT. MONDAY...AN UPPER LOW
TROUGH OVER THE GREAT LAKES MOVES SE ACROSS THE NEW ENGLAND COAST BY
12Z MON AND THIS WILL PUSH A WEAK COLD FRONT INTO OUR FORECAST AREA.
DRY NW DOWNSLOPE WINDS WILL DEVELOP OVER THE PIEDMONT IN THE WAKE OF
THE FRONT AND THIS WILL HELP DAYTIME HIGHS WARMING INTO THE UPPER
80S. GENERALLY MOSTLY DRY CONDITIONS ARE EXPECTED BUT DUE TO
INCREASING INSTABILITY...CANNOT RULE OUT A FEW THUNDERSTORMS
DEVELOPING OVER THE REGION DURING THE AFTERNOON WITH BETTER CHANCE
OVER THE NC MOUNTAINS. SO POPS HAVE BEEN ADJUSTED ACCORDINGLY.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
AS OF 330 AM FRIDAY...BOTH THE LATEST ECMWF AND THE GFS HAVE TRENDED
MUCH SLOWER AGAIN WITH THE UPPER LOW PRESSURE AND AN ASSOCIATED COLD
FRONT TRANSLATING EAST ACROSS THE REGION DURING THE END OF THE
MEDIUM RANGE FORECAST PERIOD.

TUESDAY INTO WEDNESDAY...MODELS INDICATE THAT A SERIES OF UPPER
DISTURBANCES WILL MOVE THROUGH THE REGION AHEAD OF AN APPROACHING
LOW FROM THE WEST. THE COMBINATION OF DIURNAL INSTABILITY AND UPPER
FORCING MAY SUPPORT FOR THE DEVELOPMENT OF THUNDERSTORMS. SO I HAVE
KEPT POPS IN THE 30S MAINLY IN THE AFTERNOON HOURS EACH DAY.

THURSDAY AND FRIDAY...AN UPPER LOW OVER THE TX/OK PANHANDLE ON
WEDNESDAY IS PROGGED TO MOVE EAST ACROSS THE MISSISSIPPI VALLEYS
THURSDAY AND CROSSES OUR FORECAST AREA BETWEEN 12Z AND 18Z FRI. THE
ECMWF IS SLOWER AND KEEPS THE PRECIP OVER THE REGION THROUGH FRI
NIGHT WHILE THE GFS IS A BIT FASTER WITH THE SYSTEM EXITING OUR
FORECAST AREA BY EARLY FRIDAY. DUE TO THE UNCERTAINTY...LOW END
CHANCE POPS WERE MENTIONED THROUGH FRI MORNING. TEMPERATURES WILL
REMAIN WELL ABOVE NORMALS FOR TUE/WED AND DROPPING BACK TO NEAR
NORMALS BY THURSDAY.

&&

.AVIATION /17Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...LOW CLOUDS SHOULD DIMINISH THIS AFTERNOON WITH DRYING IN A
WESTERLY FLOW. ANOTHER ROUND OF LOW CLOUDS ARE EXPECTED WITH A FRONT
MOVING IN FROM THE WEST LATE THIS AFTERNOON...BUT WITHOUT
RESTRICTIONS. CONVECTIVE CHANCES ALONG THE FRONT ARE TOO LOW TO
MENTION MORE THAN CB. GUIDANCE LIKES VERY LOW CLOUD HEIGHTS AND FOG
AROUND DAYBREAK SUNDAY...BUT CLOUDS AMOUNT IS EXPECTED TO BE
INSUFFICIENT FOR A CIG. IFR VSBY IN FOG LOOKS MORE PROBABLE. VFR
RETURNS BY MID SUNDAY MORNING.WINDS VEER FROM WNW TODAY...TO NE LATE
TONIGHT.

ELSEWHERE...A BAND OF SCATTERED LOW CLOUDS IS EXPECTED WILL SWEEP
SOUTHEAST ACROSS THE AREA WITH A COLD FRONT THIS AFTERNOON.
THUNDERSTORMS ALONG THIS FRONT WILL BE TOO SCATTERED TO MENTION
ANYTHING MORE THAN CB.WESTERLY WINDS WILL VEER TO NW TONIGHT AND NE
ON ENE SUNDAY MORNING. THE LOW END OF GUIDANCE CONSENSUS SUPPORTS
VERY LOW CLOUDS AND FOG TOWARD DAYBREAK SUNDAY...WITH MVFR VSBY...
EXCEPT LIFR AT KHKY. CLOUD COVER IS NOT EXPECTED TO BE GREAT ENOUGH
FOR CIGS HOWEVER. VFR RETURNS BY MID SUNDAY MORNING.

OUTLOOK...DRY WEATHER IS EXPECTED SUNDAY NIGHT AND MONDAY. ANOTHER
SYSTEM WILL SPREAD SHRA AND TSTMS INTO THE REGION TUE AND WED. IT
LOOKS AS THOUGH THE SYSTEM WILL HAVE PLENTY OF MOISTURE AND
RESTRICTIVE CIGS AND VSBYS ARE POSSIBLE...ESPECIALLY AT NIGHT.

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...JOH
NEAR TERM...JAT/MCAVOY
SHORT TERM...JOH
LONG TERM...JOH
AVIATION...JAT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
602 AM EDT SAT MAR 31 2012

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-011015-
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-
602 AM EDT SAT MAR 31 2012

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

.DAY ONE...TODAY AND TONIGHT.

AN UPPER LOW WILL CROSS THE REGION THIS AFTERNOON...TRIGGERING
SCATTERED SHOWERS AND THUNDERSTORMS. A FEW OF THE THUNDERSTORMS
MAY BE SEVERE...PRODUCING HAIL TO THE SIZE OF QUARTERS AND
DAMAGING STRAIGHT LINE WINDS. THE BEST CHANCE OF A SEVERE STORM
WILL BE OVER THE NORTH CAROLINA MOUNTAINS...AS WELL AS ACROSS THE
PIEDMONT OF NORTH AND SOUTH CAROLINA AND NORTHEAST GEORGIA.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

NONE.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
149 PM EDT SAT MAR 31 2012

NCZ037-057-311830-
DAVIE-ROWAN-
149 PM EDT SAT MAR 31 2012

...A STRONG THUNDERSTORM WILL AFFECT CENTRAL ROWAN AND DAVIE COUNTIES
THROUGH 230 PM EDT...

AT 144 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 4 MILES WEST OF FARMINGTON...OR 8 MILES NORTH OF
MOCKSVILLE...MOVING SOUTHEAST AT 25 MPH.

* OTHER LOCATIONS AFFECTED INCLUDE BUT ARE NOT LIMITED TO SPENCER...
  SHEFFIELD...MOCKSVILLE...FORK CHURCH...FARMINGTON...COOLEEMEE AND
  ADVANCE.

SMALL HAIL...AND WIND GUSTS OF 30 TO 40 MPH ARE EXPECTED WITH THIS
STORM.

LAT...LON 3568 8033 3561 8043 3595 8071 3603 8070
      3606 8065 3606 8051 3592 8036 3588 8037
      3588 8041 3585 8038 3582 8046 3579 8047
      3577 8045 3574 8045 3573 8034 3570 8032

07