Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 030229
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1029 PM EDT TUE JUN 2 2015

.SYNOPSIS...
UPPER LEVEL LOW PRESSURE WILL GRADUALLY DRIFT ACROSS THE
SOUTHEASTERN STATES THROUGH THE REMAINDER OF THE WORK WEEK...WHILE
SURFACE HIGH PRESSURE WILL BUILD DOWN FROM THE NORTH ON WEDNESDAY.
THIS PATTERN WILL PRODUCE GREATER CHANCES FOR SHOWERS AND
THUNDERSTORMS...AND HELP KEEP TEMPERATURES A FEW DEGREES BELOW
NORMAL.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 1025 PM EDT TUESDAY...AS LEADING EDGE OF INTRUDING HIGH
PRESSURE WEDGE BOUNDARY SLIDES IN FROM THE NORTHWEST...SURFACE
OBSERVATIONS FEATURE BACKED NORTHERLY WINDS AND LOWERED DEWPOINTS.
THUS MOST RECENT SPC MESOANALYSIS INDICATES DECREASING SB
INSTABILITY ACROSS THE REGION...WITH ONLY LIMITED ELEVATED CAPE
AVAILABLE.  THEREFORE...EXPECTING COVERAGE TO REMAIN SPARSE ACROSS
WESTERN NC...IF AT ALL.  FURTHER SOUTH INTO THE UPSTATE AND
NORTHEAST GA...CONVECTION SHOULD CONTINUE TO WAIN FROM THE NORTH
WITH THE SOUTHERN TIER OF THE FCST AREA BEING THE MOST LIKELY
CONVECTIVE SUPPORT REGIONS.  THEREFORE POPS WE ADJUSTED TO REFLECT
THESE CHANGES WHICH FEATURE CHANCE POPS NORTH...AND LIKELY POPS
ALONG THE SOUTHERN TIER.  POPS THEN DECREASE FURTHER TO LOW END
CHANGE LEVELS BY MORNING AS RECENT GUIDANCE HAS TRENDED DRIER
THROUGH 12Z.  BEYOND THAT...THE FCST REMAINS UNCHANGED.
TEMPERATURES AND DEWPOINTS WERE ALSO TWEAKED TO REFLECT LATEST
OBSERVATIONS.

PREVIOUS DISCUSSION...

AS OF 150 PM...THE UPPER LOW SPINNING ACRS THE TN VALLEY AND
SOUTHERN APPALACHIANS IS ENHANCING CONVECTION ACRS THE CWFA...WHICH
IS NOW MODERATELY UNSTABLE. SO EXPECT LIKELY TO CATEGORICAL COVERAGE
OF CONVECTION THRU THE AFTN AND EARLY EVENING. THE LATEST CAMS SHOW
MARGINAL ORGANIZATION OF ACTIVITY AS IT PUSHES OFF THE BLUE RIDGE
AND ACRS THE PIEDMONT. SO A SMALL SEVERE WIND/HAIL THREAT WILL
CONTINUE. ALSO...SOME CELLS HAVE HAD A TENDENCY TO TRAIN...SO
LOCALLY HEAVY RAIN AND ISOLD FLOODING IS ALSO A THREAT. TEMPS ARE
CREEPING INTO THE LOWER 80S ACRS THE PIEDMONT AND MID TO UPR 70S IN
THE MTNS.

TONIGHT...THE UPPER LOW IS FCST TO STALL OVER THE SOUTHERN
APPALACHIANS...KEEPING OUR AREA UNDER WEAK BUT PERSISTENT Q-VECTOR
CONVERGENCE. MEANWHILE...A 1025 MB SFC HIGH WILL SETTLE ACRS NEW
ENGLAND...NOSING A WEDGE-LIKE ISOBAR CONFIGURATION BY DAYBREAK
WEDNESDAY. GUIDANCE ALSO SHOWS A WEAK WAVE DEVELOPING ALONG THE
WEDGE FRONT OVER THE CWFA...ENHANCING AN EASTERLY LLVL WIND ACRS THE
NC PIEDMONT. THESE FEATURES WILL LIKELY KEEP AT LEAST A CHC OF
LINGERING SHWRS OVERNIGHT...WITH AN ISOLD EMBEDDED TSTM OR TWO
POSSIBLE. THE OVERALL FORCING DOESN/T LOOK TOO THREATENING FOR HEAVY
RAIN...BUT AN ISOLD THREAT WILL LINGER OVERNIGHT. THERE WILL ALSO BE
SOME PATCHY FOG OUT THERE GIVEN THE WET GROUND. TEMPS WILL BE HELD A
COUPLE CATEGORIES ABOVE NORMAL UNDER THE CLOUD COVER AND MOIST AIR
MASS.

WEDNESDAY...GUIDANCE IN DECENT AGREEMENT THAT THE LOW WILL ONLY INCH
SLIGHTLY EAST THRU THE DAY...KEEPING OUR AREA UNDER THE PVA SIDE OF
THE SYSTEM. MEANWHILE...WIDESPREAD LOW STRATUS IS EXPECTED TO
DEVELOP ACRS MOST OF THE CWFA ATOP THE WEAK WEDGE. THIS CLOUD COVER
SHUD SCATTER OUT ACCORDING TO THE GUIDANCE...AS IT DOESN/T LOOK LIKE
TRUE COLD AIR DAMMING. HOWEVER WEAK EASTERLY UPSLOPE FLOW WILL
PERSIST LONGEST ACRS THE I-40 CORRIDOR...SO THEY MAY STAY CLOUDY AND
MORE STABLE. THE REST OF THE AREA IS PROGGED TO BECOME WEAK TO
MODERATELY UNSTABLE WITH ANOTHER ROUND OF SHOT-GUN CONVECTION. THERE
IS LESS SHEAR AND INSTBY IN THE FCST SOUNDINGS THAN TUESDAY/S...SO
EXPECT A SMALLER SEVERE THREAT. STORMS MAY BE
SLOW-MOVING...HOWEVER...SO A HEAVY RAIN AND ISOLD FLOODING THREAT
WILL CONTINUE. TEMPS WILL BE HELD BELOW NORMAL UNDER THE
CLOUDS...WITH ABOUT A 10 DEG GRADIENT FROM NORTH TO SOUTH.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 240 PM TUE...GUIDANCE NOW SHOWING THE CLOSED UPPER LOW ONLY
SLOWLY FILLING AS IT MOVES ACROSS THE AREA THU. AT THE SFC...HIGH
PRESSURE BUILDS IN FROM THE NORTH ON A CAD LIKE CONFIGURATION. EVEN
THO COOLER MID LEVEL TEMPS WILL BE MOVING ACROSS THE AREA WITH THE
UPPER LOW...INSTABILITY WILL BE WEAKER THAN THE PREVIOUS FEW DAYS AS
TEMPS AND DEW POINTS WILL BE LOWER. STILL...FORCING WILL BE ENOUGH
TO HELP CONVECTION DEVELOP AND INCREASE TO NUMEROUS COVERAGE. SHEAR
AND DCAPE WILL BE LOWER AS WELL...BUT PW VALUES WILL INCREASE.
THEREFORE...EXPECT SVR STORM CHC TO BE LOWER...BUT CHC OF HEAVY RAIN
WILL BE HIGHER. THE UPPER LOW MOVES EAST OF THE AREA FRI LEAVING A
WEAK NWLY FLOW IN PLACE. AT THE SFC...THE RIDGE OF HIGH PRESSURE
BEGINS TO WEAKEN BUT REMAINS IN PLACE. EXPECT A RETURN TO A MORE
NORMAL DIURNAL CONVECTIVE MODE WITH HIGHEST POP FAVORING THE MTNS.
INSTABILITY AND SHEAR WILL AGAIN BE RELATIVELY WEAK...BUT DCAPE
VALUES WILL BE HIGHER. SVR CHC AND HEAVY RAIN CHC WILL PROBABLY EVEN
OUT FOR THE AFTERNOON. A LITTLE BELOW NORMAL TEMPS THU WILL RISE TO
AROUND NORMAL FOR FRI.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 2 PM TUESDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
SATURDAY WITH THE REMNANTS OF THE LONG LIVED UPPER LOW FINALLY
OPENING BACK UP TO THE MEAN FLOW AS IT LIFTS OFF THE NC COAST. AT
THE SAME TIME...AN UPPER SHORTWAVE ROUNDS THE EASTERN PERIPHERY OF
THE UPPER RIDGE TO OUR WEST. AS WE MOVE INTO LATE SUN AND THEN
MON...THE LONG RANGE MODELS AMPLIFY THE NORTHERN STREAM AND DIG
ANOTHER UPPER TROF DOWN OVER THE GREAT LAKES. AS IS TYPICAL IN THE
WARM SEASON...THE TROF WONT MAKE IT FAR ENOUGH SOUTHWARD TO HAVE
MUCH DIRECT INFLUENCE ON OUR FCST AREA...BUT IT WILL HELP SUPPRESS
TEMPS THRU THE END OF THE MEDIUM RANGE.

AT THE SFC...A FAIRLY STRONG CANADIAN HIGH WILL BE SLIDING ACROSS
THE GREAT LAKES ON SAT AS DEEP LYR MOISTURE LINGERS OVER THE FCST
AREA. AS WE MOVE INTO SUN AND THE HIGH SLIDES FARTHER EAST...A BRIEF
WEDGE PATTERN TRIES TO DEVELOP OVER THE CAROLINAS. THE MODEL
GUIDANCE INDICATES THAT THIS WILL LIKELY BE SHORT LIVED AS THE HIGH
GETS PUSHED WELL OFFSHORE AND A LOW DEVELOPS NEAR THE GREAT LAKES BY
EARLY MON. THE COLD FRONT ASSOCIATED WITH THIS LOW IS PROJECTED TO
MOVE ACROSS THE CWFA BY LATE MON WITH SOME DEGREE OF DRYING AND
DOWNSLOPE FLOW IN ITS WAKE. AS FOR THE SENSIBLE FCST...I KEPT A
SOLID CHANCE FOR SHOWERS AND TS EACH DAY WITH TEMPS TRENDING BACK UP
ABOVE CLIMO ON DAYS 6 AND 7.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE EARLY
EVENING ASIDE FOR POSSIBLE SHRA/TSRA IN THE NEXT FEW HOURS.  THUS
KEPT PREVIOUS TEMPO TO ACCOUNT FOR SUCH...ALTHOUGH CONFIDENCE IS
WANING FAST.  OTHERWISE...HIGH LEVEL CLOUDS WILL DOMINATE THROUGH
MIDNIGHT BEFORE LOWER CIGS START TO WORK THEIR WAY IN FROM THE NE
ASSOCIATED WITH LOW LEVEL MOISTURE AHEAD OF SFC WEDGE INTRUSION.
THEREFORE TAF FEATURES IFR CIGS AROUND DAYBREAK WITH SLIGHT
IMPROVEMENT EXPECTED AROUND THE 14Z TIMEFRAME WHEN MIXING
COMMENCES...HOWEVER LCLS WILL REMAIN LOW THROUGH THE DAY THUS
CARRIED LOW VFR CU WITH MVFR MENTIONED IN PROB30 TO ACCOUNT FOR
AFTERNOON CONVECTION.  WINDS THROUGH THE PERIOD WILL REMAIN
NORTH/NORTHEAST AT AROUND 5-10KTS...EXCEPT ADJACENT TO ANY STRONG
CONVECTION WHERE WINDS WILL LIKELY BE VRB/GUSTY.

ELSEWHERE...SIMILAR TO THAT OF KCLT ABOVE WITH VCTS MENTIONED AT ALL
SITES THROUGH THE NEXT FEW HOURS TO ACCOUNT FOR CONTINUED CONVECTIVE
ACTIVITY.  HOWEVER EXPECTING SAID SHRA/TSRA TO DIMINISH FROM
WEST/EAST AFTER DARK LEADING TO NO WX IN THE TAF.  AS THE ABOVE
MENTIONED WEDGE BOUNDARY SLIDES SOUTH OVERNIGHT...CIGS WILL LOWER
ACROSS THE REGION WITH MVFR/IFR LEVELS FAVORED AT THE NC SITES...AND
MVFR AT THE SC SITES.  ALONG WITH THE CIGS...VISB RESTRICTIONS ARE
ALSO POSSIBLE DUE TO PATCHY FOG...HOWEVER DENSE FOG IS NOT EXPECTED
AT ANY SITE.  MUCH THE SAME ON WEDNESDAY AS TODAY WITH ALL TAFS
FEATURING SHRA/VCTS THROUGH THE PERIOD WITH CIGS RECOVERING TO LOW
VFR LEVELS.  WINDS WILL REMAIN NORTHERLY THROUGH MIDDAY TOMORROW
BEFORE GRADUALLY VEERING SOUTHEASTERLY AS THE WEDGE BOUNDARY
ATTEMPTS TO RETREAT TO THE NORTH.

OUTLOOK...A MID LEVEL LOW WILL LINGER OVER THE AREA THRU AT LEAST
THURSDAY...WITH DEEP MOISTURE. SO NUMEROUS SHOWERS AND THUNDERSTORMS
ARE EXPECTED EACH AFTERNOON AND EVENING. MORNING STRATUS AND FOG
WILL ALSO REMAIN A POSSIBILITY...ESPECIALLY OVER WET GROUND...THRU
AT LEAST FRIDAY.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       HIGH  97%     MED   66%     HIGH  91%     HIGH  95%
KGSP       HIGH  97%     MED   70%     HIGH  89%     HIGH  89%
KAVL       HIGH  91%     LOW   41%     HIGH  80%     HIGH  93%
KHKY       HIGH  80%     MED   68%     HIGH  87%     HIGH 100%
KGMU       HIGH 100%     MED   73%     HIGH  81%     HIGH  91%
KAND       HIGH 100%     MED   64%     HIGH  83%     HIGH 100%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

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

&&

$$
SYNOPSIS...JPT
NEAR TERM...ARK/CDG
SHORT TERM...RWH
LONG TERM...JPT
AVIATION...CDG


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