Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 272102
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
502 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 500 PM...CONVECTION CONTINUES OVER THE MOUNTAINS AND UPPER
SAVANNAH VALLEY...BUT BUFR SOUNDINGS STILL INDICATING A BIT OF A CAP
OVER THE PIEDMONT...AND NEW HIRES REFLECTIVITY GUIDANCE IS
INDICATING LESS CONVECTION OVER THE PIEDMONT THROUGH THE EVENING.
HAVE REDUCED POPS ACCORDINGLY...RAMPING BACK UP DURING THE LATE
OVERNIGHT PERIOD.  OTHERWISE...ALTHOUGH BULK SHEAR VALUES ARE
WEAK...EFFECTIVE SHEAR VALUES WILL APPROACH MODERATE LEVELS ACROSS
THE NORTHERN TIER. CANNOT RULE OUT A STRONG OR EVEN SEVERE STORM
THERE...BUT CHANCE IS LOW.

ALTHOUGH COVERAGE WILL BE MAINLY DIURNAL...THERE IS A SHORT WAVE
THAT MOVES 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 /21Z WEDNESDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...HAVE REMOVED TEMPO SHRA AT KCLT FOR THE 21Z
AMD THIS EVENING WITH WEAK CAP IN PLACE AND NEW GUIDANCE NOT
INDICATING AS MUCH CONVECTION OVER THE PIEDMONT UNTIL THURSDAY
MORNING. OTHERWISE...ALL AIRPORTS WILL REMAIN IN THE WARM SECTOR
THROUGH THE PERIOD...SOUTH OF A STALLED FRONTAL ZONE OVER THE
VIRGINIAS AND A SLOWLY APPROACHING COLD FRONT FROM THE WEST.
CONVECTION SOUTH OF THE WARM FRONT WILL DEVELOP ACROSS THE NC
MOUNTAINS AND MOVE EAST ACROSS THE NORTHERN FOOTHILLS AND POSSIBLY
NORTHWEST PIEDMONT THIS AFTERNOON AND EARLY EVENING. THEREFORE...
HAVE GONE WITH VCTS FOR KAVL AND KHKY. CHANCE OF OTHER TAF SITES
SEEING ANY TSRA IS LOW.  TSRA CHANCE INCREASES THURSDAY AS THE FRONT
APPROACHES FROM THE WEST. HAVE A PROB30 FOR ALL AREAS AFTER 14Z.
CANNOT RULE OUT A BRIEF VSBY OR CIG RESTRICTION OVERNIGHT...BUT
CHANCE TOO LOW AND TIMING TOO UNSURE TO INCLUDE FOR NOW. GUSTY SW
WIND THIS AFTERNOON BECOMES LIGHTER SW THIS EVENING. SW WINDS PICK
BACK UP THURSDAY MORNING.

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...

            21-03Z        03-09Z        09-15Z        15-18Z
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  98%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  94%     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...RWH/TDP



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