Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 171450
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1050 AM EDT FRI APR 17 2015

.SYNOPSIS...
A COOL AND DAMP WEDGE OF HIGH PRESSURE WILL GIVE WAY TO PROGRESSIVELY
WARMER AND DRIER AIR TODAY THROUGH SATURDAY. A WARM FRONT WILL LIFT
NORTHEAST ACROSS THE REGION SATURDAY NIGHT INTO SUNDAY...ACCOMPANIED
BY ABUNDANT MOISTURE AND MORE RAINFALL. A COLD FRONT WILL CROSS THE
AREA ON MONDAY...USHERING IN SEASONABLE TEMPERATURES AND DRY
CONDITIONS.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1045 AM EDT FRIDAY...WEAK ISENTROPIC LIFT CONTINUES TO YIELD
LIGHT PRECIP ACROSS PORTIONS OF NORTHEAST GA AND THE WESTERN
UPSTATE.  LATEST CAMS FAVOR INCREASED COVERAGE OVER THE UPPER
SAVANNAH RIVER VALLEY THROUGH LATE MORNING.  MODELS ALSO CONTINUE TO
FAVOR CAD EROSION THIS AFTERNOON AHEAD OF APPROACHING WEAK UPPER
IMPULSE.  POPS WERE LOWERED ACROSS THE NC/SC PIEDMONT THROUGH THE
REMAINDER OF THE MORNING ALL THE WHILE INCREASING POPS ACROSS THE
WESTERN TIER OF THE FCST AREA TO ACCOUNT FOR ABOVE MENTIONED INBOUND
PRECIP.  BEYOND THAT...KEPT POPS ELEVATED THROUGH THE AFTERNOON AS
COVERAGE OF SHOWERS INCREASES FROM THE SOUTHWEST.
OTHERWISE...TWEAKED SKY/TEMPS/DEWS TO REFLECT LATEST SAT/OBS
TRENDS.

PREVIOUS DISCUSSION...

AS OF 645 AM...STILL A LITTLE BIT OF RAIN AND DRIZZLE OUT THERE BUT
LESS FOG THAN EXPECTED OVERALL. SHOULD SEE IMPROVING CONDITIONS THRU
THE MORNING AS ISENTROPIC LIFT COMES TO AN END...WITH SCT SHOWERS
AND POSSIBLY TSRA FOR THE AFTERNOON. GOING FCST STILL LOOKS ON TRACK
WITH ONLY CHANGES FOR CURRENT CONDITIONS.

AS OF 320 AM...LOW CLOUDS...SPOTTY RAIN AND AREAS OF DRIZZLE AND FOG
WILL CONTINUE THRU THE MORNING AS COPIOUS LOW LEVEL MOISTURE AND
ISENTROPIC LIFT REMAIN ACROSS THE AREA. THE RAIN AND DRIZZLE WILL
TAPER OFF BY LATE MORNING AS THE LOW LEVEL FLOW TURNS MORE W TO SW
ENDING THE ISENTROPIC LIFT. WEAK SHORT WAVE ENERGY MOVES IN FROM THE
WEST FOR THE AFTERNOON TO PROVIDE SOME SYNOPTIC SCALE FORCING. WEAK
INSTABILITY DEVELOPS AS WELL AS THE WEAK CAD ERODES. WITH THE
COPIOUS LOW LEVEL MOISTURE IN PLACE...SCT SHRA AND TSRA SHUD DEVELOP
FOR THE AFTERNOON ACROSS THE WRN CWFA AND ISOLATED CONVECTION ACROSS
THE EAST. HIGHS SHUD BE QUITE A BIT WARMER AS WELL...WITH VALUES
NEAR TO SLIGHTLY ABOVE NORMAL.

TONIGHT...CONVECTION SHUD TAPER OFF WITH A DIURNAL TREND AS THE
SHORT WAVE ENERGY MOVES EAST OF THE AREA AND INSTABILITY WANES. WEAK
HIGH PRESSURE MOVES IN OVERNIGHT BRINGING CLEARING SKIES AND LIGHT
WINDS. A LOW LEVEL INVERSION DEVELOPS AS WELL. ALL THIS COMBINED
WITH THE VERY MOIST SURFACE...SHOULD CREATE A GOOD ENVIRONMENT FOR
FOG DEVELOPMENT. A LITTLE TOO EARLY TO KNOW IF THE FOG WILL BE DENSE
AND WIDESPREAD...BUT THE POTENTIAL IS CERTAINLY THERE. WILL GO AHEAD
AND ADD AREAS OF FOG TO THE FCST TO SHOW THE TREND IN THAT
DIRECTION. LOWS WILL BE AROUND 10 DEGREES ABOVE NORMAL.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 300 AM FRIDAY...AN UPPER RIDGE AXIS WILL CROSS THE AREA ON
SATURDAY...AS THE DEEP CUTOFF LOW FINALLY STARTS OPENING UP AND
BECOMING ABSORBED INTO THE NORTHERN STREAM FLOW INVOF THE FRONT
RANGE OF THE CENTRAL ROCKIES. WHILE THERE WILL BE SOME SBCAPE THANKS
TO A WARM AND MOIST BL...THERE WON/T BE MUCH OF A TRIGGER FOR
CONVECTION ON SATURDAY. THE LATEST HI-RES WINDOW NMM/ARW AGREE WITH
THE 00Z NAM ON JUST A FEW SHWRS AND PERHAPS A COUPLE OF TSTMS
SATURDAY AFTN...MAINLY ACRS THE MTNS. HIGHS WILL BE ABOUT 8-10 DEG
ABOVE NORMAL.

SATURDAY NIGHT THRU SUNDAY NIGHT...THE MAIN CONCERN WILL BE HEAVY
RAIN...AS A WARM FRONT WILL LIFT NE THRU THE AREA...WHICH WILL BE
MODERATELY TO STRONGLY FORCED. PWATS WILL BE AROUND 1.5-1.7" ON
SUNDAY PER THE NAM AND GFS...WITH A 35-50 KT SELY 850 MB JET ALONG
THE BLUE RIDGE. POPS WILL RAMP UP TO CATEGORICAL BY MIDDAY
SUNDAY...THEN START TO TAPER OFF IN THE WEST SUNDAY NIGHT...AS THE
AXIS OF DEEP MOISTURE AND FORCING SHIFT EAST. I BLENDED THE MODEL
CONSENSUS AND WPC QPF GUIDANCE...WHICH RESULTS IN 1.5" TO A LITTLE
OVER 2.0" FROM SATURDAY NIGHT THRU SUNDAY NIGHT. THE HIGHEST AMOUNTS
ARE EXPECTED TO BE NEAR THE BLUE RIDGE ESCARPMENT WHERE 2-3" OF RAIN
CAN BE EXPECTED. THESE VALUES ARE STILL WELL UNDER THE 12 TO 24 HOUR
FFG...DESPITE THE RAIN WE RECEIVED THE OTHER DAY. BUT STILL...THERE
MAY BE LOCALLY SOME EXCESSIVE RAINFALL...WHILE WIDESPREAD FLOODING
IS UNLIKELY. SO WILL CONTINUE TO MENTION HEAVY RAIN IN THE HWO.
TEMPS WILL BE COOLER ON SUNDAY...DUE TO THE EXPECTED PRECIP AND IN
SITU WEDGE. MIN TEMPS BOTH NIGHTS WILL BE WELL ABOVE NORMAL (50S TO
LWR 60S).

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 315 AM FRIDAY...MODELS COMING INTO BETTER AGREEMENT ON A COLD
FRONT CROSSING THE AREA ON MONDAY. THERE WILL BE A SUBSTANTIAL DRY
SLOT PUNCHING INTO THE AREA BY MIDDAY...WHICH SEEMS TO LIMIT QPF
RESPONSE IN THE GUIDANCE. THERE SHUD BE DECENT INSTBY AHEAD OF THE
FRONT...WITH THE GFS ADVERTISING 1000-1500 J/KG OF CAPE WITH
MARGINAL BULK SHEAR OF 30-35 KTS. IF THE TIMING OF THE FRONT AND
UPPER SHORTWAVE LINE UP WITH PEAK HEATING...THERE MAY BE A FEW
STRONG TO SEVERE STORMS. GOING WITH HIGH-END CHC TO LIKELY POPS WITH
HIGHS REBOUNDING ABOVE NORMAL IN THE 70S.

BEHIND THE FRONT...CONDITIONS SHUD BE GENERALLY DRY...AS A CONFLUENT
WEST-NORTHWESTERLY FLOW WILL PERSIST ACRS THE EASTERN STATES
ALOFT...AND SFC HIGH PRES SETTLES IN ACRS THE SOUTHEAST STATES.
TEMPS WILL BE NEAR NORMAL TUESDAY THRU THURSDAY.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
AT KCLT...LIFR CIGS AND TEMPO IFR VSBY IN DRIZZLE WILL CONTINUE
EARLY THIS MORNING. CONDITIONS SHUD IMPROVE THRU THE AFTERNOON AS
LOW LEVEL FLOW BECOMES MORE WLY AND ISENTROPIC LIFT ENDS. COULD BE
SOME SHRA OR EVEN TSRA DURING THE AFTERNOON. HOWEVER...CHC TOO LOW
TO INCLUDE ATTM. LOW VFR EXPECTED THRU THE EVENING. CONDITIONS
LOOKING FAVORABLE FOR FOG TONIGHT. HAVE GONE WITH MVFR VSBY FOR NOW
AS IT IS TOO EARLY TO TELL IF DENSE FOG DEVELOPS. HOWEVER...THE
POTENTIAL IS THERE FOR IFR OR EVEN LIFR VSBY BEFORE DAYBREAK. NLY
WIND BECOMES CALM NEAR NOON...THEN S TO SW FOR THE AFTERNOON. NEAR
CALM WINDS EXPECTED TONIGHT.

ELSEWHERE...SIMILAR CONDITIONS TO KCLT...EXCEPT LOWER CHC FOR VSBY
RESTRICTIONS THIS MORNING. HAVE INCLUDED VCSH FOR THE WRN SITES
WHERE PREICP CHC IS HIGHER.

OUTLOOK...ANY FOG SHUD DISSIPATE BY MID MORNING SAT. OTHERWISE...
DRIER WEATHER IS FAVORED SATURDAY AFTERNOON. DEEPER MOISTURE WILL
RETURN ALONG A WARM FRONT SAT NIGHT THROUGH SUNDAY...WITH HEAVY
RAINFALL AND WIDESPREAD RESTRICTIONS LIKELY ONCE AGAIN.
THUNDERSTORMS WILL THEN BE POSSIBLE THROUGH MONDAY AS A COLD FRONT
REACHES THE AREA FROM THE WEST.

CONFIDENCE TABLE...

            15-21Z        21-03Z        03-09Z        09-12Z
KCLT       HIGH  81%     HIGH  96%     HIGH  91%     HIGH  94%
KGSP       HIGH  87%     MED   68%     HIGH  87%     HIGH  89%
KAVL       MED   64%     HIGH  87%     MED   73%     LOW   59%
KHKY       MED   75%     HIGH 100%     HIGH 100%     HIGH  86%
KGMU       MED   79%     MED   76%     HIGH  87%     HIGH  92%
KAND       HIGH  85%     MED   74%     MED   64%     MED   79%

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...ARK
NEAR TERM...CDG/RWH
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...RWH


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