Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 280249
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1049 PM EDT WED APR 27 2016

.SYNOPSIS...
A NEARLY STATIONARY FRONT WILL LINGER OVER KENTUCKY AND VIRGINIA
THROUGH THURSDAY. A COLD FRONT CROSSES THURSDAY EVENING WITH HIGH
PRESSURE BRIEFLY IN CONTROL FOR FRIDAY INTO SATURDAY. EXPECT LOW
PRESSURE TO MOVE IN FROM THE WEST OVER THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
AS OF 1030 PM...STILL SEEING CONVECTION ACROSS THE NORTHERN TIER OF
THE FORECAST AREA...WITH A LINE OF MORE SOLID CONVECTION TO THE WEST
STRETCHING NORTH-SOUTH FROM THE OHIO VALLEY TOWARD THE GULF COAST
ASSOCIATED WITH A PREFRONTAL TROUGH. MOST RECENT RUNS OF THE HRRR
ALL SEEM TO INDICATE THAT THIS CONVECTION WILL BREAK UP OVER THE
MOUNTAINS AND PERHAPS RE-FORM OVER THE FOOTHILLS AND NORTHERN
PIEDMONT. WRF MEMBERS STILL WANT TO HOLD ONTO A MASS OF
THUNDERSTORMS ABLE TO CROSS THE MOUNTAINS. CONFIDENCE IS PRETTY LOW
AND HAVE TRIED TO UPDATE POPS AND OTHER RELATED GRIDS BASED ON
TRENDS AS MUCH AS POSSIBLE...BUT EARLY OVERNIGHT POPS COULD VERY
WELL BE TOO HIGH.

OTHERWISE...A SHORT WAVE WILL MOVE INTO THE AREA LATE TONIGHT. THIS
MAY PROVIDE ENOUGH FORCING FOR NUMEROUS COVERAGE TO RETURN TO THE
MOUNTAINS AFTER MIDNIGHT. CONVECTION MAY LINGER OTHER LOCATIONS AS
WELL...WITH THE LOWEST CHANCE OVER MOST OF THE NC PIEDMONT AND
EASTERN UPSTATE. LOWS WILL BE 10 TO 15 DEGREES ABOVE NORMAL.

THE SHORT WAVE FROM LATE TONIGHT CROSSES THE AREA THURSDAY. UPPER
DIVERGENCE INCREASES OVER THE AREA AS A JET MAX MOVES OVER THE AREA.
THIS COMBINED WITH A COLD FRONT MOVING IN FROM THE WEST WILL PROVIDE
ENOUGH FORCING FOR LIKELY POP TO SPREAD ACROSS THE CWFA THROUGH THE
DAY. GUIDANCE SHOWS MODERATE SHEAR WILL DEVELOP ACROSS THE AREA AS
WIND SPEEDS INCREASE WITH THE SYSTEMS MOVING INTO THE AREA. GUIDANCE
SHOWS MODERATE INSTABILITY DEVELOPING MOST LOCATIONS AS WELL. THE
COMBINATION WILL PROVIDE DECENT CHANCES OF STRONG TO SEVERE STORMS
FOR THE CWFA. THE LIMITING FACTOR WILL BE CLOUD COVER AND ONGOING
CONVECTION POSSIBLY LIMITING HEATING AND THE RESULTING INSTABILITY.
WILL HAVE TO KEEP AN EYE ON THIS AS IT DEVELOPS. HIGHS LOOK TO BE A
COUPLE OF DEGREES COLDER THAN THE PREVIOUS COUPLE OF DAYS.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
AS OF 145 PM WED...SFC FRONT SHOULD PUSH THRU THE AREA THU NIGHT
USHERING IN NWLY WINDS AND CLEARING SKIES. COLD ADVECTION IS
WEAK...BUT MAY PROVIDE SLIGHT LOW LEVEL LIFT ALLOWING LINGERING
ELEVATED INSTABILITY TO BE REALIZED. POPS DIMINISH GRADUALLY...WITH
A CHANCE LINGERING THRU EARLY FRI MRNG OVER THE I-77 CORRIDOR
AND VICINITY. A VERY SHALLOW MOIST LAYER WILL PERSIST IN THE
UPSLOPE AREAS ALONG THE TENN BORDER BUT MODEL QPF IS ESSENTIALLY
NIL THERE...SO NO TRAILING NW FLOW PRECIP IS REFLECTED IN
THE FCST. MIN TEMPS WILL REMAIN 7-10 DEGREES ABOVE NORMAL. THE
DOWNSLOPE FLOW WILL CONTINUE ACRS THE PIEDMONT THRU FRIDAY...AND
HEIGHTS RISE ALOFT. DEEP MIXING APPEARS LIKELY TO PERMIT A CU
FIELD TO DEVELOP...BUT LAPSE RATES ALOFT ARE NOT SUPPORTIVE OF
DEEP CONVECTION. NO PCPN CHANCES WILL BE ADVERTISED. MAX TEMPS
FRI AFTN WILL BE ABOUT 10 DEGREES ABOVE NORMAL.

LATE FRI INTO FRI NIGHT HIGH PRESSURE WILL BEGIN TO RIDGE DOWN
THE EAST COAST. SFC FLOW WILL VEER TO NORTHERLY OVERNIGHT...AND
NE BY SAT MRNG. CONCURRENTLY THE WARM FRONT ASSOCIATED WITH THE
NEXT PLAINS LOW WILL LIFT NWD ACRS THE LOWER OHIO VALLEY AND THE
SRN APPALACHIANS. IN COMBINATION THEY WILL ALLOW MOIST UPGLIDE TO
SET UP OVER THE CWFA...AND SET THE STAGE FOR A WEDGE EVENT. PRECIP
CHANCES WILL RAMP UP FROM WEST TO EAST ON SATURDAY. SOME CONVECTION
AGAIN WILL BE POSSIBLE NEAR THE WEDGE BOUNDARY SAT AFTN. I HAVE
INCLUDED A SCHC TO CHC RANGE THUNDER MENTION OVER MOST OF THE
MTNS...UPSTATE...AND NE GA. WHILE THE COLUMN WILL BE PRETTY
MOIST...RELATIVELY HIGH CLOUD BASES COULD PERMIT A FEW TSTMS TO
GENERATE STRONG DOWNBURSTS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AT 230 PM WEDNESDAY, ON SATURDAY EVENING AN UPPER TROUGH WILL
DEAMPLIFY OVER THE SOUTHEAST, WITH ZONAL FLOW RESULTING. LOW
AMPLITUDE UPPER TROUGHING WILL SET UP OVER THE EAST BY MONDAY
EVENING, BUT WILL PROGRESS OFFSHORE ON TUESDAY, WITH ZONAL FLOW
RETURNING. BY WEDNESDAY A HIGHER AMPLITUDE UPPER TROUGH WILL SET UP
OVER THE EASTERN USA.

AT THE SURFACE, ON SUNDAY HIGH PRESSURE WILL BE BANKED UP AGAINST
THE EASTERN SLOPES OF THE APPALACHIANS, WHILE LOW LEVEL MOISTURE
STREAMS NORTH FROM THE GULF OF MEXICO OVER A WARM FRONT OVER THE
GULF STATES. THE WARM FRONT LIFTS NORTH OF OUR AREA ON SUNDAY NIGHT,
WHILE A COLD FRONT APPROACHES FROM THE WEST. THE COLD FRONT CROSSES
OUR AREA ON MONDAY NIGHT, STALLING JUST TO OUR SOUTH BY DAWN ON
TUESDAY. A SURFACE WAVE MOVING ALONG THE FRONT WILL MOVE ACROSS OUR
AREA ON TUESDAY, REACHING THE NC COAST BY WEDNESDAY MORNING.

PRECIPITATION ASSOCIATED WITH THE FRONTS WILL PERSIST AT LEAST UNTIL
THE SECOND FRONT MOVES OFFSHORE EARLY WEDNESDAY, AND POSSIBLY
THROUGH THE DAY ON WEDNESDAY IF MOISTURE SPREADS INLAND NORTH OF THE
COASTAL SURFACE WAVE. THE BEST CHANCE OF CONVECTION WILL BE ON
SUNDAY AS THE WARM FRONT MOVES NORTH AND THE COLD FRONT APPROACHES
FROM THE WEST. LOW TEMPERATURES WILL RUN ABOVE NORMAL, AND HIGH
TEMPERATURES NEAR NORMAL.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...CONVECTION HAS MOVED TO THE NORTH OF MOST OF
THE TAF SITES THIS EVENING...BUT SOME CONVECTION IN THE SW NC
MOUNTAINS MAY STILL MAKE IT TO KAVL SO WILL MONITOR OVER THE NEXT
FEW HOURS. COLD FRONT APPROACHES FROM THE WEST OVERNIGHT...WITH SHRA
AND TSRA CHANCES INCREASING THROUGH THE MORNING. BEST CHANCES WILL
BE AT KAVL AND SPREAD EAST THROUGH MIDDAY. HAVE INTRODUCED VCTS AT
KAVL AND KHKY BUT KEPT PROB30 AT OTHER SITES GIVEN LACK OF
CONFIDENCE IN TIMING. HAVE INTRODUCED MVFR CIGS FOR KAND IN THE
MORNING AS LOW-LEVEL MOISTURE INCREASES...BUT FOR NOW NO
RESTRICTIONS AT OTHER SITES. EXCEPT FOR KAVL...WINDS GENERALLY SW
THROUGH THE PERIOD PICKING UP THURSDAY AFTERNOON WITH LOW-END GUSTS.
KAVL WILL SEE WINDS FLIP FROM UP-VALLEY TO DOWN-VALLEY OVERNIGHT.

OUTLOOK...SOME DRYING IS EXPECTED ON FRIDAY...WITH BRIEF VFR
CONDITIONS...BEFORE UNSETTLED WEATHER AND POSSIBLE RESTRICTIONS
RETURN FROM THE WEST OVER THE WEEKEND.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       HIGH 100%     HIGH 100%     HIGH  96%     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  98%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     MED   64%     HIGH  86%     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...DEO/TDP
NEAR TERM...RWH
SHORT TERM...WIMBERLEY
LONG TERM...JAT
AVIATION...TDP



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