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Area Forecast Discussion

467
FXUS62 KGSP 040535
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
135 AM EDT WED MAY 4 2016

.SYNOPSIS...
A COLD FRONT WILL MOVE SLOWLY EAST OF THE AREA THROUGH TONIGHT. A
COOLER AND DRIER AIR MASS WILL MOVE IN BEHIND THE FRONT ON
WEDNESDAY. ANOTHER COLD FRONT WILL CROSS THE REGION WEDNESDAY NIGHT
AND USHER IN A MUCH COOLER AIR MASS FROM CANADA FOR THE END OF THE
WORK WEEK. HIGH PRESSURE SHOULD RETURN WITH A WARMING TREND FOR THE
BALANCE OF THE WEEKEND...WITH A FRONT SLOWLY APPROACHING FROM THE
NORTH.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 135 AM...A COLD FRONT WILL SWEEP EAST OF THE CWA DURING THE
PRE DAWN HOURS. NW WINDS SHOULD DEVELOP IN THE WAKE OF THE
FRONT...INCREASING TO AROUND 10KTS DURING THE HEAT OF THE AFTERNOON.
IT IS POSSIBLE THE KAND WILL DEVELOP MARGINAL WIND GUSTS DURING THE
HEAT OF THE AFTERNOON. A SECONDARY COLD FRONT WILL APPROACH THE
FOOTHILLS AND PIEDMONT DURING THE EVENING HOURS...RESULTING IN WINDS
TO BACK FROM THE SW.

AS OF 1020 PM...CONVECTION ALONG THE ROWAN/CABARRUS BORDER SHOULD
MOVE EAST OF THE AREA BY MIDNIGHT. RADAR DOES NOT SHOW ANY SHOWERS
OVER OR IMMEDIATELY UPSTREAM OF THE NC MOUNTAINS. HAVE UPDATED POP
TRENDS TO SHOW THESE FEATURES. STILL EXPECT SOME ISOLATED SHOWERS TO
DEVELOP IN THE MOUNTAINS ALONG THE TN BORDER. THIS IS DUE TO A
POTENT SHORTWAVE TROF APPROACHING FROM THE WEST AS IT ROUNDS THE
BASE OF THE LONG WAVE TROF OVER THE OH/TN VALLEYS. ALTHOUGH DRIER
AIR IS MOVING IN BEHIND THE COLD FRONT CROSSING THE AREA...NW FLOW
AND LINGERING MOISTURE ALONG THE BORDER SHOULD COMBINE WITH THE WAVE
TO CREATE THE SHOWERS. GUIDANCE SHOWS SOME LINGERING MID LEVEL
MOISTURE ACROSS THE AREA...SO I EXPECT THIS WAVE WILL AT LEAST FORCE
A FAIR AMOUNT OF MID LEVEL CLOUDINESS OVERNIGHT. TEMPS WILL RUN A
CATEGORY OR TWO ABOVE NORMAL.

WEDNESDAY...ANOTHER POTENT SHORTWAVE WILL DIVE THRU THE LONGWAVE
TROF AXIS...SHARPENING THE TROF AND CLOSING OFF AN UPPER LOW BY END
OF THE DAY OVER THE OHIO VALLEY. A SECONDARY COLD FRONT ASSOCIATED
WITH THIS ENERGY WILL BE KNOCKING ON THE DOOR OF THE NC MTNS BY 00Z
THU. THE FRONT WILL HAVE SOME MOISTURE WITH IT...AND POPS WILL START
TO RAMP UP ALONG THE TN/NC BORDER DURING THE DAY. EAST OF THE
MTNS...MID CLOUDS ARE EXPECTED TO THIN OUT RESULTING IN A PARTLY TO
MOSTLY SUNNY DAY. HOWEVER...THICKNESSES FALL SHARPLY FROM PREVIOUS
DAY...SO TEMPS WILL BE NOTICEABLY COOLER WITH LESS HUMIDITY. HIGHS
WILL BE AT OR SLIGHTLY BELOW NORMAL.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...
AS OF 230 PM EDT TUESDAY...A 500 MB LOW CENTER WILL MOVE SOUTHEAST
OVER THE SOUTHERN APPALACHIANS WED NIGHT THROUGH THU. H5 TEMPS WILL
DIP TO MINUS 25 DEG C OR COLDER UNDER THE LOW CENTER...WITH STEEP
MID LEVEL LAPSE RATES RESULTING THROUGH THE SHORT RANGE PERIOD. MOST
OF THE MOISTURE ASSOCIATED WITH THE UPPER LOW AND REINFORCING
SURFACE COLD FRONT SHOULD BE AT LOW LEVELS...WITH NW UPSLOPE
MOISTURE BEING THE MAIN DRIVER FOR WESTERN MOUNTAIN PRECIPITATION
EARLY THU THROUGH FRI. ALTHOUGH PROFILES GET MARGINALLY COLD ENOUGH
FOR SNOW OR GRAUPEL ALONG THE HIGHEST RIDGES...ESPECIALLY THU
MORNING...A SURFACE BASED WARM LAYER SHOULD KEEP ANY ACCUMULATIONS
AT BAY. WILL ALSO PERMIT LOWER CHANCE PROBABILITIES FOR SHOWERS TO
SPREAD EAST ALONG MAINLY THE INTERSTATE 40 CORRIDOR THROUGH THU
AFTN. THE 500 MB LOW CENTER WILL THEN MEANDER AND VERY SLOWLY FILL
ALONG THE EASTERN SEABOARD THU NIGHT THROUGH FRI...WITH WESTERN
CAROLINA PRECIPITATION CHANCES SLOWLY DIMINISHING.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 240 PM EDT TUESDAY...500 MB HEIGHTS WILL RISE FROM THE WEST ON
SATURDAY AS THE CLOSED UPPER LOW DEPARTS TO THE EAST. DRIER SURFACE
HIGH PRESSURE MOVE INTO PLACE...BUT WITH A SLOWLY APPROACHING BACK
DOOR COLD FRONT OVER THE WEEKEND. BETTER MOISTURE POOLING ALONG THE
COLD FRONT COULD FLIRT WITH THE NORTHERN TIER LATE IN THE
WEEKEND...BUT WITH FAIRLY LOW PRECIPITATION CHANCES. THE BOUNDARY
SHOULD STALL SOMEWHERE IN THE REGION SUNDAY INTO MONDAY...BEFORE
RETURNING NORTH AS A WARM FRONT EARLY NEXT WEEK. DIURNAL ISOLATED TO
SCATTERED MOUNTAIN SHOWERS WILL RETURN AND INCREASE INTO
TUESDAY...ALONG WITH RISING TEMPERATURES.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT AND ELSEWHERE EAST OF THE MTNS...VFR THROUGH THE PERIOD. A
COLD FRONT WILL SWEEP EAST OF THE CWA DURING THE PRE DAWN HOURS. NW
WINDS SHOULD DEVELOP IN THE WAKE OF THE FRONT...INCREASING TO AROUND
10KTS DURING THE HEAT OF THE AFTERNOON. IT IS POSSIBLE THE KAND WILL
DEVELOP MARGINAL WIND GUSTS DURING THE HEAT OF THE AFTERNOON. A
SECONDARY COLD FRONT WILL APPROACH THE FOOTHILLS AND PIEDMONT DURING
THE EVENING HOURS...RESULTING IN WINDS TO BACK FROM THE SW.

AT KAVL...WINDS CHANNELED WITHIN THE FRENCH BROAD VALLEY SHOULD
YIELD WINDS FROM THE 350 DEGREES THROUGH MOST OF THE TAF PERIOD.
WINDS ARE FORECAST TO FREQUENTLY GUST INTO THE MID 20S DURING THE
AFTERNOON. WEAK INSTABILITY...FALLING MID LEVEL HEIGHTS...AND THE
APPROACH OF A SECONDARY COLD FRONT WILL SUPPORT SCT SHRAS/TSRAS
DURING THE 23Z TO 5Z PERIOD...I WILL HIGHLIGHT WITH A PROB30. THE
ARRIVAL OF LLVL MOISTURE ON THE WEST SIDE OF THE MTNS SHOULD YIELD
PERIODS OF MVFR UPSLOPE CEILINGS BY 5Z.

OUTLOOK...A STRONG UPPER LOW WILL SWING THRU THE AREA THRU
FRIDAY...AND WILL BRING SHRA AND TSRA MAINLY ACROSS THE NC SITES
BOTH THU AND FRI AFTN.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       LOW   57%     MED   66%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     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...HG
NEAR TERM...NED/RWH
SHORT TERM...HG
LONG TERM...HG
AVIATION...NED



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