Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 150744
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
344 AM EDT TUE APR 15 2014

.SYNOPSIS...
A COLD FRONT WILL CROSS THE THE PIEDMONT AROUND MID DAY.
UNSEASONABLY COLD HIGH PRESSURE WILL BE IN CONTROL OF OUR WEATHER
FROM TONIGHT INTO FRIDAY. A DEEP UPPER TROUGH ARRIVES FROM THE WEST
TO START THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 320 AM...WIDESPREAD SHRA CURRENTLY ACROSS THE AREA WITH SCT
TSRA ACROSS THE I-77 CORRIDOR. WIDESPREAD SHRA SHOULD CONTINUE
ACROSS THE AREA THRU MID MORNING AHEAD OF AN APPROACHING COLD FRONT.
THE FIRST WAVE OF TSRA WILL MOVE EAST OF THE AREA BY DAYBREAK. THE
BIG QUESTION IS HOW MUCH...IF ANY...ADDITIONAL TSRA DEVELOP AS THE
FRONT MOVES THRU. FCST SOUNDINGS SHOW LITTLE TO NO INSTABILITY AFTER
DAYBREAK. HOWEVER...THERE WILL BE STRONG FORCING AND UPPER
DIVERGENCE ASSOCIATED WITH THE FRONT. ALSO...GUIDANCE SHOWS A WAVE
FORMING ALONG THE FRONT AND MOVING ACROSS THE SAME LOCATION WHERE
TSRA ARE CURRENTLY. ALTHOUGH NO LIGHTNING IS CURRENTLY ASSOCIATED
WITH THIS FEATURE...A SWIRL IS SEEN MOVING THIS WAY...AND WOULD
REACH THE I-77 CORRIDOR BY OR SHORTLY AFTER DAYBREAK. THEREFORE...
WILL KEEP CAT POPS ACROSS THE AREA THRU 12Z...THEN TAPER OFF POP
FROM SW TO NE THRU THE MORNING...WITH LINGERING CAT POP OVER THE
I-77 CORRIDOR THRU 18Z. WILL KEEP ISOLATED TO SCT TSRA ACROSS THE
ARE WITH BEST CHC ALONG AND SOUTH OF THE I-85 CORRIDOR AND ALONG AND
EAST OF THE I-77 CORRIDOR. WITH THE HIGH SHEAR AND LOW CAPE
ENVIRONMENT REMAINING IN PLACE...WILL HAVE TO WATCH ANY LINEAR STORM
FEATURES THAT DEVELOP FOR THE POSSIBILITY OF DAMAGING WIND GUSTS.
THAT SAID...BEST CHC OF ANY SEVERE STORMS WILL BE EAST AND SOUTH OF
OUR CWFA. THERE WILL BE QUITE A BIT OF ADDITIONAL RAINFALL ACROSS
THE AREA THIS MORNING...SO WILL HAVE TO KEEP AN EYE ON STREAM LEVELS.
ISOLATED FLOODING IS POSSIBLE...AND COULD BE LIMITED TO MAINLY MORE
URBANIZED LOCATIONS. WINDS WILL INCREASE AND BECOME QUITE GUSTY
BEHIND THE COLD FRONT THIS AFTERNOON. WIND GUSTS SHUD REACH ADVISORY
CRITERION ACROSS THE MTNS OF THE CAROLINAS AND NE GA. WILL ISSUE A
WIND ADVISORY FOR THESE LOCATIONS FROM 2 PM THRU MIDNIGHT.

PRECIP TAPERS OFF QUICKLY THIS EVENING...BUT LINGERING MOISTURE IN
THE NW FLOW AND CAA COULD LEAD TO RAIN SHOWERS CHANGING TO SNOW
SHOWERS BEFORE ENDING BY MIDNIGHT. ANY SNOW WOULD BE LIGHT WITH NO
ACCUMS. ELSEHWERE...DIMINISHING WINDS AND CLEARING SKIES EXPECTED.
WITH THE VERY COLD AIR MASS MOVING IN...AN ADVECTIVE FREEZE IS
EXPECTED ACROSS MOST OF THE CWFA. WILL UPGRADE THE WATCH TO A
WARNING FOR ALL BUT THE NRN MTNS WHICH HAVE NOT REACHED THE
CLIMATOLOGICAL GROWING SEASON YET. LOWS WILL BE 15 TO NEARLY 20
DEGREES BELOW NORMAL...AND WILL THREATEN RECORDS AT AVL AND CLT. THE
RECORD AT GSP IS QUITE COLD AND SHOULD BE SAFE.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 310 AM TUESDAY...ON WEDNESDAY...THE CENTER OF SFC HIGH
PRESSURE IS EXPECTED TO BE CENTERED OVER THE MID APPALACHIANS AROUND
SUNRISE. THE HIGH CENTER WILL REACH NEW ENGLAND BY 0Z THURSDAY...BUT
WILL CONTINUE TO RIDGE ACROSS THE SOUTHEAST. STRONG INSOLATION
SHOULD RESULT IN GRADUAL WARMING...BUT LLVL THICKNESSES AND
TEMPERATURES WILL REMAIN UNSEASONABLE COOL. A BLEND OF PREFERRED MOS
SUPPORTS HIGH TEMPERATURES RANGING FROM THE MID 50S ACROSS THE MTN
VALLEYS TO NEAR 60 ACROSS THE UPPER SAVANNAH RIVER VALLEY. FORECAST
SOUNDINGS INDICATE THAT AFTERNOON MIXING MAY REACH AROUND 3
KFT...WITH PW VALUES AROUND 0.20 INCHES. AFTERNOON DEWPOINTS MAY MIX
TO THE TEENS...RESULTING IN RH VALUES AROUND 20 PERCENT.

WEDNESDAY NIGHT...A DRY AND COOL AIR MASS WILL REMAIN RIDGED ACROSS
THE CWFA. LIGHT NE WINDS AND CLEAR SKY CONDITIONS SHOULD RESULT IN
FAVORABLE RADIATIONAL COOLING CONDITIONS. LOW TEMPERATURES ARE
EXPECTED TO RANGE FROM U20S TO NEAR 30 ACROSS THE NC
MTNS...FOOTHILLS...AND PIEDMONT. LOW TEMPERATURES ACROSS THE UPSTATE
AND NE GA MAY RANGE IN THE LOW TO MID 30S. ON THURSDAY...SHORT RANGE
MODELS INDICATE THAT H85 TEMPERATURES WILL WARM 2-4 DEGREES FROM
WED. HIGH TEMPERATURES ON THURSDAY SHOULD WARM AROUND 3 DEGREES
WARMER THAN VALUES OBSERVED ON WED.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 340 AM TUESDAY...MEDIUM RANGE GUIDANCE INDICATES THAT A H5
TROF AXIS WILL SLOWLY RIPPLE ACROSS THE SOUTHEAST LATE THIS WEEK.
THE PASSAGE OF THE TROUGH MAY RESULT IN A PERIOD OF UNSETTLED
WEATHER FOR FRIDAY AND SATURDAY. HOWEVER...BOTH THE GFS AND ECMWF
INDICATE THAT A LOW MAY DEVELOP OFF THE SOUTHEAST COAST LATE FRIDAY
AND SATURDAY...WITH A SECOND AREA OF LOW PRESSURE ACROSS THE UPPER
OHIO RIVER VALLEY. COVERAGE OF QPF ACROSS THE CWFA REMAINS VERY
LIMITED BETWEEN THE TWO SYSTEMS. I WILL MAINTAIN SCHC TO CHC POPS
FOR SHRA BETWEEN FRI TO SAT. SUN...MID LEVEL SHALLOW RIDGING WILL
BUILD ACROSS THE REGION...WITH WEAK WAA. TEMPERATURES ARE FORECAST
TO RETURN TO AROUND NORMAL VALUES. ON MON...A SOUTHERN STREAM LOW
MAY DEVELOP AHEAD OF MID LEVEL SHORTWAVE ACROSS THE DEEP SOUTH.
MOISTURE AND LIFT ASSOCIATED WITH THE LOW MAY SUPPORT A FEW SHRA MON
AFTERNOON.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
AT KCLT...MVFR CONDITIONS WILL BECOME IFR AS SHRA MOVE IN OVERNIGHT.
IFR CONTINUES THRU THE MORNING AS SHRA CONTINUE. MVFR EXPECTED THRU
MUCH OF THE AFTERNOON AS SHRA CONTINUE AND TSRA BECOME POSSIBLE. SLY
WINDS BECOME SWLY AROUND NOON THEN NWLY AND GUSTY BY MID AFTERNOON
AS A COLD FRONT MOVES THRU. GUSTY NW WIND AND CLEARING SKIES
EXPECTED THIS EVENING.

ELSEWHERE...IFR ALREADY IN PLACE OVER THE NON-MTN TAFS. EXPECT THE
IFR TO CONTINUE THRU THE MORNING...OR DEVELOP AT KAVL BY DAYBREAK.
CONDITIONS IMPROVE TO MVFR BY EARLY AFTERNOON THEN VFR BY MID
AFTERNOON AS DRIER AIR MOVES IN BEHIND THE COLD FRONT AND SHRA END.
DID NOT MENTION ANY TSRA AS CHC IS QUITE LOW. THAT SAID...A BRIEF
RUMBLE OF THUNDER CANNOT BE RULED OUT. S TO SW WIND CONTINUES THRU
THE MORNING...BECOMING W NEAR NOON THEN NW AND VERY GUSTY FOR THE
AFTERNOON. GUSTY N TO NW WIND AND CLEARING SKIES EXPECTED THIS
EVENING.

OUTLOOK...HIGH PRESSURE WILL PRODUCE VFR WEATHER WEDNESDAY AND
THURSDAY. CEILING AND VISIBILITY RESTRICTIONS WILL RETURN FRIDAY AND
SATURDAY AS A COLD FRONT APPROACHES FROM THE WEST AND A LOW PRESSURE
SYSTEM DEVELOPS ALONG THE COAST.

CONFIDENCE TABLE...

            07-13Z        13-19Z        19-01Z        01-07Z
KCLT       HIGH  88%     HIGH  86%     MED   70%     HIGH 100%
KGSP       MED   75%     LOW   54%     HIGH  92%     HIGH 100%
KAVL       HIGH  96%     MED   79%     HIGH  94%     HIGH 100%
KHKY       HIGH  92%     LOW   58%     HIGH  86%     HIGH 100%
KGMU       MED   69%     MED   66%     HIGH  94%     HIGH 100%
KAND       HIGH  89%     MED   78%     HIGH  92%     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

&&

.CLIMATE...
RECORD LOWS FOR WEDNESDAY APRIL 16...

AVL...26 IN 1943
CLT...29 IN 2008
GSP...24 IN 1907

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...FREEZE WATCH FROM THIS EVENING THROUGH WEDNESDAY MORNING FOR
     GAZ010-017-018-026-028-029.
NC...FREEZE WATCH FROM THIS EVENING THROUGH WEDNESDAY MORNING FOR
     NCZ035>037-048-051>053-056>059-062>065-068>072-082-
     501>510.
SC...FREEZE WATCH FROM THIS EVENING THROUGH WEDNESDAY MORNING FOR
     SCZ001>014-019.

&&

$$
SYNOPSIS...NED
NEAR TERM...RWH
SHORT TERM...NED
LONG TERM...NED
AVIATION...RWH
CLIMATE...






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