Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 151444
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1044 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 1045 AM EDT MONDAY...LITTLE CHANGE FROM THE PREVIOUS UPDATE.
THE SFC COLD FRONT IS SHOWING UP AS A RADAR FINE LINE...AND HAS NOW
MOVED INTO THE WRN UPSTATE...AND ABOUT HALF WAY ACROSS THE NC MTNS.

AS OF 905 AM EDT MONDAY...LOWERED POPS AND CUT BACK THUNDER CHANCES
OVER THE REGION FOR THE NEXT COUPLE HOURS. SPC HAS CUT THE SLIGHT
RISK AREA FROM OUR EASTERN ZONES AND THE LOW OVERCAST THAT IS NOW
DEVELOPING AHEAD OF THE COLD FRONT SHOULD INHIBIT WHAT WAS ALREADY
EXPECTED TO BE LIMITED HEATING. AS THE FRONT MOVES ACROSS THE
FORECAST AREA...I STILL THINK WE WILL SEE AN INCREASE IN SHOWERS AND
FEW TSTMS. THE HRRR AND OUR LOCAL WRF-ARW INDICATE THIS. SO I DID
KEEP HIGHER POPS OVER THE EASTERN ZONES A LITTLE LATER IN THE DAY.
I/M GOING TO START THE WIND ADVISORY OVER THE MOUNTAINS EFFECTIVE
IMMEDIATELY. THE NAM AVL BUFKIT SOUNDING SHOWS A NEARLY 10 DEG C
TEMP DROP FROM 14 TO 15 UTC. THAT KIND OF COLD ADVECTION SHOULD
BRING SOME GOOD GUSTS TO THE MTNS.

AS OF 7 AM...SHRA WILL REMAIN ACROSS THE AREA AS THE COLD FRONT
APPROACHES THIS MORNING. EXPECT PRECIP TO TAPER OFF FROM SW TO NE
THRU THE DAY. SYNOPTIC AND MESOSCALE GUIDANCE SUGGEST A WAVE
DEVELOPING ALONG THE FRONT AND MOVING ACROSS THE CLT AREA AROUND 18Z
WITH FROPA. HAVE KEPT POP HIGH ACROSS THIS AREA THE LONGEST TO COVER
THIS SCENARIO. IF THIS WAVE DOES DEVELOP...SVR STORM CHC WILL
DEVELOP AS THE SHEAR AND HELICITY INCREASE SIGNIFICANTLY. THERE WILL
BE LITTLE IN THE WAY OF INSTABILITY...BUT WHAT THERE IS WILL BE OVER
THAT AREA. UPDATED TO COVER THESE CONCERNS AND CURRENT CONDITIONS.

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 /15Z TUESDAY THROUGH SATURDAY/...
AT KCLT...LOW CLOUDS HAVE DISSIPATED AS HEAVY RAIN HAS MOVED EAST OF
THE AREA. EXPECT A RETURN TO MVFR LATER THIS MORNING AHEAD OF A COLD
FRONT MOVING INTO THE AREA...ALONG WITH CONTINUED SHRA. THERE IS A
CHANCE THAT IFR CIGS WILL DEVELOP OVER THE NEXT COUPLE
HOURS...THOUGH CONFIDENCE ISN/T HIGH ENOUGH TO INCLUDE THAT AT THIS
TIME. THE CHC FOR TSRA LOOKS TO BE AROUND 18Z NEAR THE TIME OF
FROPA. HAVE MADE THE WIND SHIFT TO NW AT THAT TIME AS WELL. GUSTY NW
WINDS WITH CLEARING SKIES THRU THE AFTERNOON. GUSTS CONTINUE INTO
THRU MUCH OF THE NITE WITH WINDS TURNING NLY AND GUSTS DIMINISHING
TOWARD DAYBREAK.

ELSEWHERE...SIMILAR CONDITIONS TO KCLT...EXCEPT EARLIER
ONSET...FROPA AND IMPROVEMENT. TSRA CHC MUCH LESS AT THESE
LOCATIONS...SO HAVE LEFT OUT FOR NOW. VERY GUSTY WINDS EXPECTED ALL
LOCATIONS AS WELL. KAND WILL SEE MORE WLY WIND THAN NW. KAVL MAY SEE
SOME LINGERING LOW VFR CLOUDS DURING THE AFTERNOON AND 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...

            14-20Z        20-02Z        02-08Z        08-14Z
KCLT       HIGH  93%     HIGH  94%     HIGH 100%     HIGH 100%
KGSP       HIGH  90%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  84%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH  88%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH  89%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH  92%     HIGH 100%     HIGH 100%     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 WARNING FROM 11 PM THIS EVENING TO 10 AM EDT WEDNESDAY
     FOR GAZ010-017-018-026-028-029.
     WIND ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR GAZ010-017.
NC...FREEZE WARNING FROM 11 PM THIS EVENING TO 10 AM EDT WEDNESDAY
     FOR NCZ035>037-048-051>053-056>059-062>065-068>072-082-
     501>510.
     WIND ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR NCZ033-048>053-
     058-059-062>065-501-503-505-507-509.
SC...FREEZE WARNING FROM 11 PM THIS EVENING TO 10 AM EDT WEDNESDAY
     FOR SCZ001>014-019.
     WIND ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR SCZ001>003.

&&

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






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