Special Weather Statement, NWS Greenville-Spartanburg, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
710 PM EDT SUN MAY 1 2016

.SYNOPSIS...
A COLD FRONT WILL APPROACH FROM THE WEST AN KEEP A WARM AND HUMID
AIR MASS ACROSS THE SOUTHEAST REGION THROUGH MONDAY. THIS FRONT WILL
SLOWLY PUSH EAST OF THE AREA ON TUESDAY. ANOTHER COLD FRONT WILL
CROSS THE AREA ON THURSDAY AND BRING COOLER CANADIAN AIR PERSISTING
INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH MONDAY/...
2315 UTC UPDATE: POPS WERE ADJUSTED PER RADAR TRENDS. SKY COVER WAS
UPDATED FROM THE LATEST SATELLITE IMAGERY. WINDS WERE UPDATED TO
INCORPORATE THE LATEST NAM DATA.

2030 UTC UPDATE: POPS WERE RAISED IN THE UPPER SAVANNAH RIVER
VALLEY, AND IN PARTS OF WESTERN NC, PER RADAR TRENDS.

COVERAGE OF CONVECTION WILL GRADUALLY INCREASE AS WILL INSTABILITY
THROUGH THE REMAINDER OF THE AFTERNOON. WILL CONTINUE TO ADVERTISE
LIKELY POPS ALONG THE ESCARPMENT BY EARLY EVENING. SBCAPE REMAINS
RATHER MUTED ACROSS THE FORECAST AREA THIS AFTERNOON...ESP ACROSS
THE NW NC PIEDMONT...WHERE LOW CLOUDS HAVE PERSISTED NORTH OF
INCREASINGLY DIFFUSE CAD BOUNDARY. NEVERTHELESS...ENOUGH SUN IS
PEEKING THROUGH THE CU AND STRATOCU THAT ONE COULD EXPECT THE
ATMOSPHERE TO FURTHER DESTABILIZE...WITH SBCAPE LIKELY REACHING 2000
J/KG ACROSS ROUGHLY THE SW HALF OF THE FORECAST AREA BY LATE
AFTERNOON. BULK SHEAR REMAINS MARGINALLY STRONG...THUS A COUPLE OF
ISOLATED SEVERE STORMS WILL REMAIN POSSIBLE...WITH LARGE HAIL AND
DAMAGING WINDS BEING THE PRIMARY THREATS.

THE SHORT TERM MODELS ARE GENERALLY IN GOOD AGREEMENT THAT A WEAK
MID-LEVEL SHORT WAVE TROUGH WILL APPROACH THE AREA FROM THE
SOUTHWEST THIS EVENING. THIS IS MOST LIKELY A RESULT OF GRID-SCALE
CONVECTIVE FEEDBACK...AS IT HAS ITS ORIGINS WITHIN AN AREA OF
CONVECTIVE PRECIP WITHIN THE MODEL(S) ENVIRONMENT. HOWEVER...
SOMETIMES SUCH THINGS ARE /REAL/. IT IS INTERESTING THAT SOME OF THE
LATEST MESOSCALE/CONVECTION-ALLOWING MODELS ARE LIKING THE IDEA OF
SOME VIGOROUS-LOOKING CONVECTION DEVELOPING OVER THE UPSTATE AND
NORTHEAST GA BY LATE EVENING. I/M NOT QUITE PREPARED TO JUMP ON THIS
YET...BUT SOLID CHANCE POPS WILL BE ADVERTISED ACROSS THE WESTERN
HALF OF THE AREA THROUGH THE EVENING HOURS...WITH POPS GRADUALLY
TAPERING DOWN OVERNIGHT.

LITTLE CHANGE IN THE WEATHER REGIME IS EXPECTED FOR MONDAY...AS DEEP
SW FLOW REMAINS IN PLACE...SUPPORTING ABOVE NORMAL TEMPS/LOW LEVEL
MOISTURE...AND DECENT AFTERNOON INSTABILITY...WHILE FORECAST
SOUNDINGS INDICATE PERSISTENT MODERATE LEVELS OF SHEAR. WITH THE
COLD FRONT EXPECTED TO REMAIN OFF TO OUR WEST THROUGH THE DAY
(ALBEIT JUST TO OUR WEST BY THE END OF THE DAY)...IT APPEARS THAT
TERRAIN EFFECTS WILL ONCE AGAIN BE THE PRIMARY IMPETUS FOR
INITIATION OF CONVECTION OVER OUR AREA. WILL ONCE AGAIN ADVERTISE
LIKELY POPS ALONG THE BLUE RIDGE BY MID-AFTERNOON...EXPANDING THOSE
TO THE REMAINDER OF THE MTNS BY THE END OF THE PERIOD...TO ACCOUNT
FOR ACTIVITY ORIGINATING FROM THE FRONT TO POSSIBLY MOVE INTO THE
FORECAST AREA. CHANCE POPS SHOULD SUFFICE ACROSS THE REMAINDER OF
THE AREA. ANOTHER DAY WITH A MARGINAL CONVECTIVE THREAT APPEARS
LIKELY.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 130 PM EDT SUNDAY...THE BROAD MODEL CONSENSUS DOES NOT LEAD TO
MUCH CHANGE TO THE GOING THINKING WITH RESPECT TO THE EXPECTED
SENSIBLE WEATHER FOR TUESDAY.  UPPER LEVEL HEIGHTS ATOP THE SE CONUS
WILL CONTINUE THEIR STEADY LOWERING AND A BROAD WSW FLOW THROUGH A
DEEP LAYER REMAINS. DESPITE THE LACK OF ANY LARGER SCALE FORCING...
SCATTERED DIURNAL ENHANCED TSTMS ARE STILL PROBABLE. THE UPPER
PATTERN CONTINUES TO AMPLIFY ON WEDNESDAY BUT THE LOWER LEVEL
BAROCLINIC ZONE IS PROGGED TO TRANSLATE DOWNSTREAM OF THE CWFA
LEAVING US IN A RELATIVE LULL. ENERGY DUMBBELLING AROUND DEEPENING
UPPER LOW MAY RESULT IN MTN SHOWERS BY WED NITE.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 140 PM SUNDAY...GOOD CONFIDENCE IS HAD IN THE EXT RANGE FCST
AS THE OP MODELS ARE SHOWING GOOD AGREEMENT WITH THE ULVL PATTERN
AND THE SENSIBLE WX RESPONSE. THE GEFS MEMBERS ARE SHOWING LITTLE
SPREAD OVER THE ERN CONUS UNTIL LATE FRIDAY...MAINLY DUE TO DEEPNESS
DIFS WITH THE UPPER LOW.

THE PATTERN STILL SUGGESTS A DEVELOPING OMEGA BLOCK WITH THE ERN LOW
DEEPENING AND DROPPING SE OFF THE ATL COAST INTO THE SAT TIME
FRAME...THEN QUICKLY RISING HEIGHTS THROUGH THE REMAINDER OF THE
PERIOD. A COLD FRONT WILL BRING A SHOT OF LLVL MOISTURE TO THE FAR
WRN MTNS EARLY THU...WHICH WILL QUICKLY WANE AFTER SUNRISE. NOT
EXPECTING MUCH QPF RESPONSE FROM THIS FEATURE. THINGS WILL REMAIN
RATHER DRY AFTER THAT AS DEEP NW FLOW ENGULFS THE REGION AND A
REINFORCING SHOT OF LOW THETA/E AIR MIXES IN. THERE ARE SOME
DIFFERENCES FRI BTW THE OP MODELS WITH AN EMBEDDED S/W CREATING
SHOWERS ACROSS THE NRN ZONES...BUT GIVEN THE LARGE SCALE PATTERN AM
NOT ANTICIPATING MUCH MEASURABLE PRECIP WITH THIS SITUATION EITHER.
THE ATMOS WILL REMAIN RATHER STABLE THROUGH THE PERIOD...SO NO
THUNDER WILL BE INCLUDED IN THE GRIDS. OVERALL...THE PERIOD LOOKS TO
PRETTY NICE FOR EARLY MAY WITH MOSTLY DRY CONDS...MID/UPPER LEVEL
CLOUDS AND PLEASANT TEMPS. BELOW NORMAL HIGHS BY A CAT OR SO ARE
EXPECTED THU THRU SAT...THEN ABOVE NORMAL TEMPS PROBABLE BY SUN AS
UPPER RIDGE AXIS NEARS AND DEEP SUBS INCREASES.

&&

.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE...THUNDER MAY PERSIST WELL INTO THE
EVENING...WITH SOME MODELS EVEN SUGGESTING AN INCREASE AROUND
MIDNIGHT. GUIDANCE HAD VARIED ON DAYBREAK VSBY RESTRICTIONS, BUT THE
BEST BET APPEARS TO BE AT MOUNTAIN AND FOOTHILL SITES, WITH VFR AT
KCLT. CEILING ARE EXPECTED TO FALL TO MVFR BY DAWN AT SC SITES AND
BRIEFLY IFR AT KCLT. BLENDED GUIDANCE SUPPORTS LOW VFR DAYBREAK CIGS
AT KAVL AND KHKY, BUT SCATTERED LOW DECK CLOUDS WILL BE CARRIED AS WELL.
IMPROVEMENT TO VFR IS EXPECTED AFTER DAWN. THUNDER CHANCES, THOUGH
NEVER ZERO, WILL INCREASE AGAIN WITH HEATING AFTER DAWN, ESPECIALLY
IN THE MOUNTAINS. WINDS WILL GENERALLY FAVOR THE SSW.

OUTLOOK...UNSETTLED WEATHER/OCCASIONAL CONVECTION/RESTRICTIONS ARE
EXPECTED TO CONTINUE THROUGH ABOUT TUESDAY. DRYING IS EXPECTED BY
WEDNESDAY...AND THE DRY WEATHER SHOULD PERSIST THROUGH THE END OF
THE WEEK.

CONFIDENCE TABLE...

            23-05Z        05-11Z        11-17Z        17-18Z
KCLT       HIGH 100%     HIGH  94%     MED   72%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     LOW   55%     HIGH 100%
KAVL       HIGH 100%     LOW   55%     HIGH  83%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     LOW   55%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     LOW   55%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULE TAF ISSUANCE FLIGHT RULE CATEGORY.  COMPLET HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK:

WWW.WEATHER.GOV/GSP/AVIATION

&&

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

&&

SYNOPSIS...SBK
NEAR TERM...JAT/JDL
SHORT TERM...CSH
LONG TERM...SBK
AVIATION...JAT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
429 AM EDT SUN MAY 1 2016

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-020830-
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-
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-CHESTER-GREENWOOD-
429 AM EDT SUN MAY 1 2016

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

.DAY ONE...TODAY AND TONIGHT.

THUNDERSTORMS WILL CONTINUE TO DEVELOP ACROSS THE REGION ON SUNDAY.
A FEW STRONG THUNDERSTORMS WILL BE POSSIBLE...PRODUCING SMALL HAIL
AND/OR GUSTY WIND...BUT THE BIGGEST THREAT WILL COME FROM
LOCALIZED VERY HEAVY RAINFALL.

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

..MONDAY...THUNDERSTORMS ARE EXPECTED...SOME MAY BE ON THE STRONG
SIDE WITH AN ADDITIONAL RISK FROM LOCALIZED HEAVY RAINFALL.
..TUESDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..WEDNESDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..THURSDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..FRIDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.
..SATURDAY...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

NONE.

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