Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 210601
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
201 AM EDT TUE APR 21 2015

.SYNOPSIS...
DRY HIGH PRESSURE BUILDS IN TODAY...THEN SLIDES EAST OF THE AREA
WEDNESDAY. ANOTHER COLD FRONT WILL PUSH IN FROM THE NORTHWEST ON
THURSDAY...POSSIBLY BRINGING SHOWERS BACK TO THE AREA. A STRONGER
STORM SYSTEM WILL MOVE IN FOR THE WEEKEND.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 145 AM...FCST ON TRACK. UPDATED WINDS AND SKY COVER FOR THE
06Z TAFS...BUT OTHERWISE NO CHANGES NEEDED.

AS OF 1050 PM...I WILL ISSUE A QUICK UPDATE TO REDUCE SKY COVER AND
POPS ACROSS THE CWA. TEMPS AND DWPTS HAVE BEEN ADJUSTED TO MATCH
OBSERVATIONS.

AS OF 930 PM...COMMUNICATION LINKS WERE RESTORED TO OUR OFFICE AND
RADAR AROUND 9 PM. AT THIS TIME...ONE SEVERE CLUSTER OF STORMS
EXISTED ACROSS SOUTHERN GREENWOOD COUNTY. THIS ACTIVITY WILL SLIDE
EAST OVER THE NEXT 45 MINS. OTHERWISE...THE PRIMARY FORECAST CONCERN
WILL BE THE TIMING AND PLACEMENT OF THE SFC COLD FRONT TONIGHT.
LATEST OBS AND RADAR DATA INDICATE THAT THE FRONT WAS LOCATED ACROSS
THE SOUTHERN APPALACHIANS. THE FRONT WILL SWEEP WEST THROUGH THE
OVERNIGHT HOURS...RESULTING IN VEERING FLOW AND GENERALLY THIN CLOUD
COVER.

PREVIOUS DISCUSSION...
SCATTERED SVR TSTMS WILL CONTINUE TO FORM WITHIN LLVL MOIST
CONVERGENCE AXIS IN THE IMMEDIATE LEE WITH A STEADY EXPANSION ALONG
AND EVENTUALLY SE OF I-85 DURING LATE AFTERNOON HOURS. OBSERVED/FCST
AREA SOUNDINGS DEPICT STEEP LAPSE RATES AND MODERATE AMOUNTS OF CAPE
WITHIN THE HAIL GROWTH REGION. VWP/S AND SOUNDINGS ALSO SHOWING
STRONG AND MOSTLY UNIDIRECTIONAL WIND SHEAR...BUT LOCALIZED BACKING
OF THE NEAR SFC FLOW COULD RESULT IN A SOME SPIN-UPS. THE CONSENSUS
AMONG THE CONVECTION ALLOWING MODELS IS FOR DISCRETE DEEP CONVECTION
TO DIMINISH 22Z TO 00Z...AND HAVE TEMPERED POPS DOWNWARD ACCORDINGLY
DURING THE PERIOD.

PROGRESSIVE POST FRONTAL DRYING IS STILL ON TAP FOR TONIGHT AND
NOTICEABLY COOLER AIR WILL BE SEEN OVERNIGHT...WITH TUESDAY MORNING
MINIMUM TEMPERATURES CLOSER TO THE MID APRIL CLIMO. CONTINENTAL
AIRMASS WILL LINGER ATOP THE SE CONUS UNDER THE LARGE BROAD VERY LOW
AMPLITUDE UPPER TROUGH. LOTS OF SUNSHINE WILL PUSH MAX TEMPERATURES
TO AROUND NORMAL.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 200 PM MONDAY...LARGE UPPER LOW NORTH OF THE GREAT LAKES WILL
CONTRIBUTE TO W-NW FLOW IN THE UPPER LEVELS ACROSS THE SE STATES.
DRY HIGH PRESSURE MOVING ACROSS THE DEEP SOUTH WILL DOMINATE THE
WEATHER IN THE WESTERN CAROLINAS AND NE GA TUE NIGHT INTO WEDNESDAY.
AS THE UPPER LOW MOVES SLOWLY SE AND A SHORT WAVE MOVES SE THROUGH
ITS BASE...A SFC COLD FRONT WILL PUSH SE ACROSS THE AREA WED NIGHT.
MOISTURE WILL BE LIMITED WITH THE FRONT DUE TO THE DEEP LAYER
WESTERN FLOW. HOWEVER...A FEW SHOWERS AND THUNDERSTORMS MAY REACH
THE NC MOUNTAINS BY LATE WED AFTERNOON...BUT WEAKEN AND/OR DISSIPATE
AS THEY MOVE EAST INTO THE PIEDMONT WED NIGHT. HIGH PRESSURE WILL
THEN BUILD SE INTO THE WESTERN CAROLIANS AND NE GA ON THU. MAX TEMPS
WILL BE NEAR CLIMO ON WED AND THEN COOL A LITTLE BELOW AVERAGE ON
THU.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
OF 200 PM MONDAY...HIGH PRESSURE WILL DOMINATE BRIEFLY THU NIGHT
AND FRI. AN UPPER LOW OVER THE DESERT SW IS FORECAST TO MOVE
EASTWARD AND WEAKEN INTO A SHORT WAVE OVER THE SOUTHERN PLAINS AND
THEN MINOR OUT ACROSS THE SE STATES LATE THIS WEEKEND AS A LARGE
UPPER LOW REMAINS OVER THE NE U.S. BOTH THE GFS AND ECM DEVELOP A
SFC LOW NEAR THE 4-CORNERS AND MOVE IT EASTWARD INTO THE SOUTHERN
PLAINS AND THEN WEAKEN IT AS IT MOVES INTO THE DEEP SOUTH BY EARLY
SUNDAY. THE MODELS DEVELOP PRECIP ACROSS THE AREA SAT AS ISENTROPIC
UPGLIDE DEVELOPS OVER AN IN SITU WEDGE. A BACKDOOR COLD FRONT THEN
IS FORECAST TO MOVE THROUGH THE AREA SAT NIGHT IN THE WAKE OF THE
LOW. DRY HIGH PRESSURE IS FORECAST TO BUILD SOUTH OVER THE REGION
DURING SUNDAY AND CONTINUE INTO MONDAY. ANOTHER SOUTHERN STREAM LOW
MAY BRING SHOWERS TO THE REGION AGAIN LATE MONDAY. TEMPS ARE
EXPECTED TO BE BELOW CLIMO THROUGH THE PERIOD.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AT KCLT AND ELSEWHERE...MUCH QUIETER WX FOR THE NEXT 24 HOURS...AS
DRY HIGH PRES BUILDS IN BEHIND A DEPARTING COLD FRONT. THE MAIN
CONCERN WILL BE WINDS...WITH GUIDANCE SHOWING LLVL FLOW OUT OF THE
WEST-NORTHWEST...WHILE A LEE TROF WILL SET UP AGAIN THIS
AFTN...BACKING WINDS TO SW. A FEW LOW-END GUSTS ARE EXPECTED
STARTING AROUND MIDDAY...THEN ENDING AROUND SUNSET. THERE MAY BE
ENUF MOISTURE AT TOP OF MIXED LAYER FOR FEW-SCT VFR LVL CUMULUS THIS
AFTN...ESP AT KCLT AND KHKY WITH BASES AROUND 5000 FT. DESPITE WET
SOILS FROM LAST FEW DAYS OF RAIN...EXPECT ENUF LINGERING WIND AND
DROPPING SFC DEWPTS TO LIMIT FOG POTENTIAL THIS MORNING.

OUTLOOK...A COLD FRONT WILL CROSS THE AREA ON WEDNESDAY...WITH A
LITTLE MOISTURE. NOT EXPECTING MUCH LOW CLOUDS OR PRECIP WITH THE
FROPA. THEN ANOTHER DRY HIGH PRES SYSTEM BUILDS IN THURSDAY THRU
FRIDAY...BEFORE ANOTHER WET STORM SYSTEM IS EXPECTED TO APPROACH THE
AREA FROM THE WEST ON SATURDAY.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     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 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/NED
SHORT TERM...LG
LONG TERM...LG
AVIATION...ARK



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