Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 270714
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
314 AM EDT WED APR 27 2016

.SYNOPSIS...
WARM ATLANTIC HIGH PRESSURE WILL PERSIST OVER THE SOUTHEAST THROUGH
MIDWEEK. AFTER A WEAK COLD FRONT MOVES IN FROM THE WEST THURSDAY
NIGHT...WEAK HIGH PRESSURE WILL RETURN BRIEFLY ON FRIDAY. A LOW
PRESSURE SYSTEM WILL MOVE IN FROM THE WEST OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 245 AM EDT...THE LATEST SURFACE ANALYSIS DEPICTS A WEST TO
EAST ORIENTED FRONT DRAPED ACROSS THE MID ATLANTIC REGION EARLY THIS
MORNING. OUTFLOWS FROM EARLIER CONVECTION ALONG THIS BOUNDARY ARE
GENERATING NOCTURNAL CONVECTION FARTHER SOUTH FROM EASTERN KY TO
SOUTHERN VA...BUT THE BOUNDARY IS EXPECTED TO REMAIN NORTH OF OUR
FORECAST AREA THROUGH THE NEAR TERM PERIOD. MEANWHILE...
SOUTHWESTERLY FLOW AT LOW LEVELS WILL PERMIT MOISTURE TO GRADUALLY
RETURN TO THE REGION TODAY ALONG WITH WARMER TEMPERATURES. THIS WILL
RESULT IN SLIGHTLY BETTER INSTABILITY IN VERTICAL PROFILES THAN WERE
OBSERVED ON TUESDAY...WITH MLCAPE VALUES LIKELY PEAKING AT 1500 TO
2000 J/KG LATE DAY. LOW LEVEL WIND CONVERGENCE WILL BE GREATEST OVER
THE MOUNTAINS THIS AFTERNOON...BUT WITH ADDITIONAL WEAK FORCING OVER
THE NORTHERN FOOTHILLS/PIEDMONT. WILL FEATURE SOLID CHANCES FOR TSRA
IN NORTHERN AND WESTERN SECTIONS LATE IN THE DAY AND TAPER DOWN TO
SLIGHT CHANCES SOUTHEAST. MAXES SHOULD REACH THE MID 80S OUTSIDE OF
THE MOUNTAINS AND EVEN AROUND 80 IN LOWER MOUNTAIN VALLEYS DESPITE
SOME HIGH CLOUDS.

CONVECTIVE OUTFLOWS WILL GET A BIT CLOSER FOR TONIGHT...BUT WITH
DIURNAL ACTIVITY TO THE NORTH AND WEST LIKELY DIMINISHING BEFORE
REACHING THE SOUTHERN APPALACHIANS. EXPECT A MILD NIGHT WITH MINS
GREATER THAN 10 DEGREES ABOVE CLIMO AND CONTINUED NOCTURNAL
CONVECTIVE CHANCES...HIGHEST IN NW SECTIONS AND LOWEST SE.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 245 AM WEDNESDAY...THURSDAY STILL LOOKS LIKE THE DAY WITH
HIGHEST CONVECTIVE COVERAGE WITH A MARGINAL SEVERE TSTM THREAT. A
POTENT VORT MAX WILL EJECT OUT OF THE WESTERN CONUS TROUGH AND
RIPPLE AROUND THE NORTHERN PERIPHERY OF THE SOUTHEAST FLAT RIDGE.
THIS WILL INCREASE THE MID AND UPPER FLOW ENOUGH TO PRODUCE 0-6 KM
BULK SHEAR OF 30-40 KTS...HIGHEST IN THE NORTHERN TIER. INSTBY
SHOULD MANAGE TO TOP OUT WITH SBCAPE OF 1000-1500 J/KG BY PEAK
HEATING. A COLD FRONT WILL BE APPROACHING FROM THE WEST...BUT MODELS
HAVE TRENDED SLOWER WITH ITS ARRIVAL...STILL SHOWING IT OVER THE
CUMBERLAND PLATEAU THRU 00Z FRIDAY. SO POPS JUST MAY BE OVERDONE ON
THURSDAY...ESP EAST OF THE MTNS. WHATEVER CONVECTION DOES FIRE MAY
NOT PUSH INTO THE PIEDMONT UNTIL THURSDAY EVENING.  WILL CONTINUE TO
FORECAST SOLID CHC TO LOW-END LIKELY POPS THU-THU NIGHT. TEMPS WILL
BE ABOVE NORMAL.

FRIDAY...ALL THE MODELS EXCEPT FOR THE NAM PUSH THE FRONT THRU THE
AREA...AND BRING SOME DRY AIR AND LLVL CAA THRU THE DAY. I WILL
THROW OUT THE NAM WITH THIS FCST AND CONTINUE THE DRY FCST. ASSUMING
WE HAVE THE 20 KTS OR SO OF NWLY DOWNSLOPE FLOW...TEMPS WILL BE IN
THE MID TO UPR 80S EAST OF THE MTNS. OVERNIGHT SHOULD BE DRY WITH
LOWS STILL ABOUT 10 DEG ABOVE NORMAL.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 300 AM WEDNESDAY...THE MEDIUM RANGE GUIDANCE SHOWS A RATHER
COMPLEX UPPER LEVEL FLOW ACRS THE CONUS WITH DISAGREEMENTS ON THE
DETAILS. THIS MAKES FOR A BELOW AVERAGE CONFIDENCE FORECAST THRU THE
EXTENDED. ON SATURDAY...A LARGE AREA OF HIGH PRES WILL BUILD IN
ACROSS THE GREAT LAKES...WITH DRY ONSET CAD EXPECTED TO DEVELOP ATOP
THE CWFA. AS DEEP-LAYER SWLY FLOW DEVELOPS ATOP THE WEDGE...EXPECT
INCREASING CLOUDS AND POPS FROM SATURDAY AFTN THRU SUNDAY NIGHT.
WITH THAT SAID...MODELS ARE IN DISAGREEMENT ON HOW FAST WE MOISTEN
UP AND HOW MUCH QPF CAN BE EXPECTED. AT SOME POINT...A LOW PRESSURE
SYSTEM IS EXPECTED TO ORGANIZE OVER THE SOUTHERN PLAINS...THEN LIFT
NE INTO THE OH VALLEY. THIS SHOULD BRING A WARM CONVEYOR BELT OF
CLOUDS AND PRECIP ACRS THE AREA EITHER SUNDAY OR SUNDAY NIGHT. SO I
STILL THINK THE LIKELY POPS LOOK GOOD.

FOR MONDAY AND TUESDAY...THE CENTER OF THE LOW SHOULD BE INVOF THE
MID ATLANTIC OR NORTHEAST BY MONDAY AFTN...PLACING THE CWFA ON THE
NW FLOW/DRYING SIDE OF THE SYSTEM. THE GFS SLOWS THE LOW DOWN AND
MANAGES TO KEEP ENUF MOISTURE AROUND FOR BETTER INSTBY AND SOME
CONVECTION MONDAY. THE ECMWF IS FASTER AT PUSHING THE LOW OFF THE
EAST COAST...BUT SHOWS A STRONGER REINFORCING COLD FRONT APPROACHING
FROM THE NW. SO WILL FCST A SHOTGUN CHC POP FOR MONDAY...TAPERING
OFF TO MAINLY SLGT CHC TO LOW-END CHC FOR TUESDAY. TEMPS WILL
SLIGHTLY COOLER MONDAY...AND CLOSE TO NORMAL TUESDAY.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT AND ELSEWHERE...ALL TERMINAL LOCATIONS TODAY WILL REMAIN IN
THE WARM SECTOR SOUTH OF A STALLED FRONTAL ZONE OVER THE VIRGINIAS
AND A SLOWLY APPROACHING COLD FRONT FROM THE WEST NEAR THE MS RIVER
VALLEY. FEW TO SCATTERED CUMULUS WILL DEVELOP WITH HEATING AND
CIRRUS BLOWOFF FROM UPSTREAM DECAYING CONVECTION MAY PROVIDE SOME
CEILINGS AT TIMES. THE BEST CHANCES OF SCATTERED THUNDERSTORMS
AFFECTING THE NC TERMINALS WILL OCCUR LATE DAY THROUGH EARLY
EVENING...WHILE CHANCES LOOK EVEN LESS AT THE SC TERMINALS. EXPECT
MAINLY SW WINDS...WITH LOW END GUSTS AT TIMES...EXCEPT LIGHTER AND
MORE VARIABLE WINDS AT KAVL THROUGH THE PERIOD.

OUTLOOK...PRECIPITATION CHANCES AND ASSOCIATED RESTRICTIONS SHOULD
INCREASE ON THURSDAY AHEAD OF A COLD FRONT APPROACHING FROM THE
NORTHWEST. SOME DRYING IS EXPECTED ON FRIDAY...WITH VFR
CONDITIONS...BEFORE UNSETTLED WEATHER POSSIBLE RESTRICTIONS RETURN
FROM THE WEST OVER THE WEEKEND.

CONFIDENCE TABLE...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       HIGH  98%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     MED   75%
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...ARK/WIMBERLEY
NEAR TERM...HG
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...HG


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