Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 230803
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
403 AM EDT THU APR 23 2015

.SYNOPSIS...
COOL AND DRY HIGH PRESSURE BUILDS IN FROM THE NORTH TODAY THROUGH
FRIDAY.  A WARM FRONT BRINGS BETTER CHANCES FOR RAINFALL TO OUR
REGION OVER THE WEEKEND. DRY HIGH PRESSURE PREVAILS AT THE START OF
NEXT WEEK...THEN A LOW WILL MOVE ALONG THE GULF COAST MIDWEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 AM...THE UPPER LOW THAT HAS BEEN SPINNING OVER THE GREAT
LAKES THE LAST FEW DAYS WILL FINALLY START TO DRIFT EAST...WITH
RISING HEIGHTS AND SUBSIDENCE ATOP THE CWFA TODAY THRU TONIGHT. AT
THE SFC...DRY HIGH PRES NOSE SOUTH INTO THE AREA...WITH THE CENTER
OF THE HIGH SETTLING INTO THE OHIO VALLEY TONIGHT. IT WILL BE A NICE
DAY...WITH BREEZY CONDITIONS IN THE MTNS. HIGHS WILL BE IN THE 50S
TO LWR 60S IN THE MTNS AND UPR 60S IN THE NW NC PIEDMONT TO MID 70S
ACRS THE UPPER SAVANNAH VALLEY.

TONIGHT...THE NAM AND GFS AGREE ON ANOTHER SURGE OF 850 MB CAA
WITHIN NWLY FLOW OF 20 TO 35 KTS. THE MOS BLEND HAS LOWS DIPPING
INTO THE UPR 20S TO MID 30S IN THE MTNS...AND MID 30S TO LWR 40S
ACRS THE PIEDMONT. THIS SEEMS REASONABLE...SO WILL ISSUE A FREEZE
WARNING FOR THE NC MTNS. THE I-40 CORRIDOR OF THE NC FOOTHILLS AND
NW PIEDMONT HAVE SOME MID 30S...WHICH MAY RESULT IN PATCHY FROST.
HOWEVER...GIVEN THE LLVL CAA OVERNIGHT...EXPECT ENUF MIXING TO LIMIT
MORE WIDESPREAD FROST.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 230 AM THU...AS AN UPPER RIDGE BUILDS INTO THE AREA FRI AND
FRI NITE...SHORT WAVES UNDERCUT THE RIDGE AND MOVE ACROSS THE AREA.
A DAMPENING UPPER LOW KNOCKS DOWN THE RIDGE AND BRINGS A TROF ACROSS
THE AREA SAT AND SAT NITE. AT THE SFC...HIGH PRESSURE OVER THE AREA
SLIDES EAST FRI NITE AS A WARM FRONT APPROACHES FROM THE WEST. THE
WARM FRONT MOVES INTO THE AREA FRI NITE AND ACROSS THE AREA SAT. A
WAVE OF LOW PRESSURE FORMS ALONG THE FRONT NEAR THE COAST SAT NITE
AND MOVES EAST PULLING A BOUNDARY ACROSS THE AREA ALONG WITH ANOTHER
WAVE FORMING ALONG THE FRONT. DEEP MOISTURE AND ISENTROPIC LIFT
DEVELOP AS THE FRONT MOVES THRU LEADING TO CAT POP FOR SAT. THE LIFT
WEAKENS SAT NITE...BUT MOISTURE REMAINS HIGH. THIS WILL COMBINE WITH
THE FORCING TO KEEP LIKELY POP ACROSS THE AREA. ALTHOUGH WIDESPREAD
PRECIP IS EXPECTED...QPF AMOUNTS REMAIN IN QUESTION. PW VALUES WILL
BE QUITE HIGH AND A GOOD LOW LEVEL JET DEVELOPS. HOWEVER...THE GFS
CONTINUES TO HINT THAT CONVECTION COULD DEVELOP SOUTH OF THE AREA
LIMITING NORTHWARD MOISTURE FLUX...AND RESULTANT QPF. WILL HAVE TO
KEEP AN EYE ON THIS SYSTEM AS SOME HEAVY RAIN IS POSSIBLE BUT
UNCERTAIN. IN ADDITION...INSTABILITY DOES INCREASE OVER THE WRN
PORTIONS OF THE CWFA WHERE SOME HEATING CAN DEVELOP. WIND SHEAR WILL
INCREASE WITH THE INCREASING LOW LEVEL JET AS WELL. WITH THE
POTENTIAL FOR A BOUNDARY SETTING UP IN THAT AREA...WILL HAVE TO KEEP
AN EYE OUT FOR SVR STORM POTENTIAL AS WELL. BELOW NORMAL HIGHS FRI
COOL MOST AREAS SAT WITH PRECIP MOVING IN...BUT REMAIN NEARLY STEADY
ACROSS THE MTNS AND WRN UPSTATE/NE GA. ABOVE NORMAL LOWS FRI NITE
RISE SEVERAL DEGREES SAT NITE.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 400 AM THURSDAY...SCT SHRA WILL LINGER ACROSS THE AREA SUNDAY
AS THE BOUNDARY SLIDES ACROSS THE AREA AND A LOW PRESSURE WAVE MOVES
ALONG THE BOUNDARY. HIGHS WILL BE NEAR TO A LITTLE ABOVE NORMAL.

GUIDANCE IS NOW DRY FOR MONDAY AS WEAK SFC HIGH MOVES IN UNDER A
DEEP UPPER LOW SETTING UP OVER NEW ENGLAND. THE UPPER LOW WEAKENS
ALLOWING SYSTEMS TO THE WEST TO MOVE TOWARD THE AREA. THE ECMWF
RETAINS ITS FORECAST OF A SRN STREAM UPPER LOW MOVING TOWARD THE
AREA TUE AND ACROSS THE AREA WED. HOWEVER...IT NOW HAS ITS MILLER-A
LOW MUCH FARTHER SOUTH IN THE GULF KEEPING THE BULK OF THE
ASSOCIATED PRECIP SOUTH OF THE CWFA AS WELL. THE GFS STILL SHOWS
SEPARATE NRN AND SRN STREAM WAVES MOVING EAST AND MERGING OVER THE
MID MS VALLEY BEFORE MOVING INTO THE AREA LATE WED. THE SFC PATTERN
STARTS WITH WHAT LOOKS LIKE A MILLER-A THEN DEVELOPS INTO A HYBRID
MILLER-B WITH A LOW MOVING UP WEST OF THE APPALACHIANS AND ANOTHER
UP THE ATLANTIC COAST. THE GFS IS ALSO MUCH WETTER AND BRINGS THE
PRECIP IN SOONER. HAVE GONE WITH A MDL BLEND WHICH TONES DOWN THE
POP...KEEPING IT IN THE CHC RANGE...AND SLOWING THE ONSET. HIGHS
START OUT NEAR NORMAL MONDAY AND FALL AROUND 10 DEGREES BELOW NORMAL
BY WED. LOWS REMAIN NEARLY STEADY A LITTLE BELOW NORMAL. THE GFS
WOULD INDICATE THE POTENTIAL FOR HEAVY RAIN...BUT THIS IS HIGHLY
UNCERTAIN GIVEN THE GUIDANCE DIFFERENCES.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS EXPECTED THRU THE TAF 06Z
TAF PERIOD. A BATCH OF MID LVL CLOUDS WILL EXIT TO THE EAST DURING
THE OVERNIGHT HOURS...WITH JUST FEW-SCT CIRRUS EXPECTED FROM THEN
ON. WINDS WILL SHIFT FROM WEST-SOUTHWEST TO NORTHWEST OUTSIDE THE
MTNS...WHILE THE NW WIND WILL CONTINUE AT KAVL THRU THIS MORNING. A
LEE TROF WILL SET UP THIS AFTN...SHIFTING WINDS BACK TO SW ACRS THE
PIEDMONT SITES. MAY SEE OCCASIONAL LOW-END GUSTS IN THE 15-19 KT
RANGE. AT KAVL...THE NW WIND WILL PICK UP AND SHUD SEE LOW-END
GUSTS. WINDS WILL SUBSIDE THIS EVENING.

OUTLOOK...DRY HIGH PRESSURE WILL BUILD IN ACRS THE REGION THROUGH
FRIDAY...BEFORE ANOTHER WET STORM SYSTEM APPROACHES THE AREA FROM
THE WEST OVER THE WEEKEND ALONG WITH RESTRICTIONS.

CONFIDENCE TABLE...

            08-14Z        14-20Z        20-02Z        02-06Z
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...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT FRIDAY FOR
     NCZ033-048>053-058-059-062>065-501-503-505.
SC...NONE.

&&

$$
SYNOPSIS...ARK
NEAR TERM...ARK
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...ARK



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