Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 022013
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
413 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 400 PM EDT TUESDAY...SCATTERED CONVECTION CONTINUES TO
HEADLINE THE WEATHER THIS AFTERNOON.  LATEST SPC MESOANALYSIS
INDICATE A BROAD REGION OF SBCAPE IN EXCESS OF 1500J/KG...AMONGST
25-30KTS EFF SHEAR.  THUS...EXPECTING CURRENT ACTIVITY TO SUSTAIN
AND PERHAPS SPREAD ACROSS THE REGION AS VARIOUS OUTFLOW BOUNDARIES
TRIGGER NEW CONVECTION.  THEREFORE TWEAKED POPS TO ACCOUNT FOR MOST
RECENT RADAR COVERAGE WHICH FEATURED THE ABOVE MENTIONED SUBSEVERE
THUNDERSTORMS.  MOST REPORTS AROUND THE REGION ASSOCIATED WITH SAID
CONVECTION HAVE FEATURED PEA SIZED HAIL AND WIND GUSTS IN THE
30-40MPH RANGE.  WITH THAT SAID...NO CHANGES WERE MADE TO THE HWO AS
CONDITIONS REMAIN SUPPORTIVE OF POSSIBLE SEVERE CONVECTION THROUGH
EARLY EVENING.  ALSO TWEAKED TEMPERATURES/DEWPOINTS IN THE EXTREME
NEAR TERM AND LEFT THE REMAINDER OF THE FCST UNCHANGED.

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 /20Z TUESDAY THROUGH SUNDAY/...
AT KCLT...CONVECTION IS DEVELOPING ACROSS THE AREA THANKS TO
MODERATE INSTBY AND AN UPPER LOW PROVIDING LIFT. COVERAGE SHUD
CONTINUE TO EXPAND TO NUMEROUS TO WIDESPREAD BY EARLY EVENING...THEN
START TO WANE. A CLUSTER OF TSTMS ARE SLOWLY DRIFTING NW TOWARD
KCLT. HAVE GONE WITH A TEMPO FOR THE FIRST FOUR HOURS OF THE 18Z
TAF. FROM THERE...EXPECT CONVECTION OFF THE BLUE RIDGE TO HOLD
TOGETHER AS IT CROSSES THE PIEDMONT THIS EVENING...SO WILL GO WITH
PREVAILING TSRA. OVERNIGHT...THERE WILL BE PLENTY OF MID AND HIGH
CLOUDS LEFT OVER FROM THE CONVECTION. THEN HIGH PRES WILL BUILD
SOUTHWARD INTO THE NC PIEDMONT BEFORE DAYBREAK...RESULTING IN LIGHT
EASTERLY FLOW AND STRATUS DEVELOPMENT. CIGS WILL LIKELY BE IFR...BUT
SOME GUIDANCE HAS IT AT MVFR. THE CLOUDS WILL BEGIN TO LIFT...BUT
SLOWLY...LATE WEDNESDAY MORNING. WINDS WILL FAVOR A SOUTH DIRECTION
THIS AFTN/EVE...THEN SHIFT OUT OF THE NE OVERNIGHT...AND INCREASE TO
5-8 KTS.

ELSEWHERE...AS WITH KCLT ABOVE...THE MAIN CHALLENGE IS HOW TO HANDLE
INCREASING CONVECTION ACROSS THE AREA. KAVL WILL LIKELY BE DIRECTLY
IMPACTED BY TSRA AT START OF TAF. THE OTHER SITES WILL ALSO AT SOME
POINT BETWEEN ABOUT 18-22Z. FROM THERE...GUIDANCE HAS CONVECTION
SLIDE EAST ACRS THE PIEDMONT...RESULTING IN A PERIOD OF PREVAILING
TSRA. CONVECTION SHUD DIMINISH LATE EVENING THRU THE OVERNIGHT. SOME
LINGERING SHRA AND ISOLD TSRA CANNOT BE RULED OUT OVERNIGHT...BUT
CONFIDENCE IS TOO LOW TO KEEP A MENTION. BEFORE DAYBREAK...GUIDANCE
SHOWS STRATUS DEVELOPING...ESP ACRS NC...AS HIGH PRES SURGES FROM
THE NORTH...SWITCHING THE LOW LVL FLOW OUT OF THE EAST. IFR TO MVFR
CIGS ARE EXPECTED...WITH HIGHEST CONFIDENCE AT KHKY AND KAVL. THE
STRATUS WILL BEGIN TO SCATTER AND LIFT TOWARD END OF 18Z TAF PERIOD.

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...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       HIGH 100%     HIGH  89%     MED   72%     HIGH  89%
KGSP       HIGH  90%     HIGH  91%     HIGH  81%     HIGH  91%
KAVL       MED   69%     HIGH  95%     MED   73%     HIGH  85%
KHKY       HIGH  87%     HIGH  82%     MED   64%     HIGH  87%
KGMU       HIGH  90%     HIGH  91%     HIGH  90%     HIGH  91%
KAND       HIGH 100%     HIGH  87%     MED   77%     HIGH  87%

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...ARK


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