Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 290515
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
115 AM EDT TUE JUL 29 2014

.SYNOPSIS...
CANADIAN HIGH PRESSURE WILL MOVE IN BEHIND A COLD FRONT TONIGHT AND
WILL DOMINATE THE SURFACE PATTERN THROUGH MIDWEEK...LEADING TO WELL
BELOW NORMAL TEMPERATURES MORE TYPICAL OF LATE SUMMER OR EARLY
AUTUMN. THE SURFACE HIGH WILL WEAKEN AND MOISTURE WILL RETURN FOR
THE WEEKEND...BUT TEMPERATURES WILL REMAIN BELOW NORMAL.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 100 AM EDT TUESDAY...ISOLATED UPSLOPE INDUCED SHOWERS ARE
POSSIBLE OVER THE NEXT FEW ALONG THE TN BORDER...BUT SHOULD SUBSIDE
BY MID MORNING AT THE LATEST.  SCATTERED MID LEVEL CLOUDS ACROSS THE
PIEDMONT REGIONS HAVE DISSIPATED WITH SOME LINGERING LOW CLOUDS
ALONG PORTIONS OF THE HIGH TERRAIN DUE TO ABOVE MENTIONED UPSLOPE
EFFECTS.  LATEST GUIDANCE INDICATES MINOR POTENTIAL FOR MOUNTAIN
VALLEY FOG IN THE FRENCH BROAD RIVER VALLEY...AND TO A GREATER
EXTENT IN THE LITTLE TN RIVER VALLEY.  THUS...TWEAKED VSBY GRIDS TO
ACCOUNT FOR PATCHY FOG DESPITE LOW CONFIDENCE.  ALSO ADJUSTED
TEMPERATURES AND DEWPOINTS IN THE EXTREME NEAR TERM AND LEFT THE
REMAINDER OF THE FORECAST AS IT WAS.

PREVIOUS DISCUSSION...

EVENING UPDATE...UPSTREAM MOISTURE IS BEGINNING TO WANE AND A LITTLE
LESS -SHRA COVERAGE IS NOTED ACROSS THE WRN NC MTNS. EXPECT THIS
DOWNWARD TREND TO CONTINUE OVER THE NEXT FEW HRS AND POPS WILL BE
NIL AFT 06Z. AN AREA OF LEE WAVE CLOUDINESS IS PERSISTING ACROSS THE
ERN UPSTATE AND LOWER NC PIEDMONT WHICH WILL SLOWLY DISSIPATE WITHIN
THE NEXT SEVERAL HRS. THIS ISN/T MAKING MUCH OF AN IMPACT ON CURRENT
HR/LY TEMPS AS MIXING WAS ACCOUNTED FOR...BUT MIN TEMPS COULD BE
AFFECTED A BIT AND THIS WAS ADJ IN THE GRIDS. OTHER THAN THAT...HIGH
TDD/S AND SOME MIXING WILL LIMIT ANY SIGFNT BR/FG THREAT. SHELTERED
MTN VALLEYS COULD SEE SOME FG BEFORE DAYBREAK...HOWEVER KAVL AND THE
FRENCH BROAD VALLEY MAY REMAIN TOO DRY AND MIXED OVERNIGHT.

AS OF 2 PM MONDAY...AN ANOMALOUSLY STRONG UPPER TROUGH WILL CONTINUE
TO ESTABLISH ITSELF OVER THE EASTERN U.S. THROUGH TUE AN UPPER LOW
SPINS OVER THE NORTHERN GREAT LAKES. THE SURFACE COLD FRONT HAS
CLEARED THE AREA EARLY THIS AFTERNOON AND WILL REACH THE COAST BY
EVENING. BEHIND THE FRONT...GUSTY NW WINDS ARE BRINGING MUCH DRYER
AND COOLER AIR INTO THE REGION. THE AIRMASS THAT IS OVERSPREADING
THE REGION IS SIMILAR TO WHAT YOU WOULD EXPECT IN MID TO LATE
SEPTEMBER. OUTSIDE OF THE MOUNTAINS...SKY CONDITIONS WILL BE MOSTLY
CLEAR THROUGH TUE WITH WINDS DIMINISHING EARLY TONIGHT. IN THE
MOUNTAINS...A FEW NW FLOW SHOWERS ARE EXPECTED AS DEEPER MOISTURE
NOTED IN SATELLITE PICS OVER THE OHIO VALLEY PIVOTS SE AND REACHES
THE NC BORDER COUNTIES TONIGHT. WILL CARRY LOW END POPS IN THE NC
BORDER COUNTIES TO ACCOUNT FOR THAT. THE NW FLOW SHOWERS SHOULD END
EARLY TUE AS DRYER AIR ARRIVES. MINIMUM TEMPERATURES TONIGHT ARE
FORECAST TO BE IN THE LOW TO MID 50S OVER THE MOUNTAINS WITH EVEN
SOME 40S POSSIBLE AT ELEVATIONS ABOVE 5000 FT. OUTSIDE THE
MOUNTAINS...LOW TO MID 60S ARE EXPECTED. ON TUESDAY...MAX TEMPS WILL
BE 8-10 DEGREES BELOW CLIMO.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
AS OF 145 PM...THE MAIN STORY FOR MID-TO-LATE WEEK WILL BE THE
ABNORMALLY DEEP UPPER TROF OVER THE EAST. THE UPPER TROF BOTTOMS OUT
WITH 500 MB HEIGHT VALUES MORE THAN 3 STANDARD DEVIATIONS BELOW
NORMAL ON WEDNESDAY MORNING CENTERED OVER NC. THE CONTINENTAL
SURFACE HIGH MOVING IN BEHIND THE TROF IS NOT ESPECIALLY STRONG...
BUT THICKNESS VALUES WILL BE SUCH THAT TEMPS WILL BE ON THE ORDER OF
TEN DEGREES BELOW NORMAL. THE TEMPS ARE EXPECTED TO BE SIMILAR TO
WHAT IS NORMAL FOR THE LAST DAY OF SUMMER...AND WITH THE DRYNESS OF
THE AIR MASS...IT WILL FEEL MORE LIKE EARLY AUTUMN BOTH WEDNESDAY
AND THURSDAY. THERE SHOULD BE SOME RETURN OF MOISTURE AT LOW LEVELS
WITH A LIGHT SE OR E FLOW...SO ISOLATED SHOWERS WERE INCLUDED MAINLY
OVER THE BALSAMS ON WEDNESDAY AFTERNOON...AND THEN ACROSS MOST OF
THE MTNS ON THURSDAY AFTERNOON. FCST SOUNDINGS SHOW WARMER AIR AT
MID LEVELS WHICH WILL CUT DOWN ON BUOYANCY TO A GREAT DEGREE...SO
THUNDERSTORMS ARE NOT LIKELY.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 230 PM MONDAY...THE LATEST GUIDANCE SHOWS AN UPPER TROF
REMAINING OVER EASTERN NORTH AMERICA THROUGH THE WEEKEND...ALTHOUGH
THE AXIS OF THE TROF MIGRATES TO THE WEST ON FRIDAY. THIS SHOULD
ALLOW FOR CONTINUED WEAK MOISTURE RETURN AT LOW LEVELS THROUGH THE
PERIOD...MAKING THE ATMOSPHERE A BIT LESS INHOSPITABLE TO DEEP
CONVECTION. THAT SHOULD PERMIT THE DEVELOPMENT OF MAINLY DIURNAL
SHOWERS AND THUNDERSTORMS EACH DAY...WITH THE BETTER CHANCES OVER
THE MTNS AS IS TYPICAL. THE UPPER TROF WILL PULL OUT A BIT ON
MONDAY AS AN ATLANTIC SUBTROPICAL RIDGE STRENGTHENS AND CONSOLIDATES
OVER BERMUDA. THAT SHOULD ALLOW FOR AN EVEN BETTER CHANCE FOR
SHOWERS AND STORMS ON MONDAY AFTERNOON. TEMPS WILL START TO SLOWLY
WARM FOR MONDAY ONWARD.

&&

.AVIATION /05Z TUESDAY THROUGH SATURDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS WILL PREVAIL THROUGH THE TAF
CYCLE WITH THE POSSIBLE EXCEPTION OF LIGHT PATCHY FOG AT KAVL.  HIGH
PRESSURE AND DOWNSLOPING FLOW WILL DOMINATE THROUGH THE PERIOD
LEADING TO WX FREE CONDITIONS.  HIGHLIGHTED ABOVE MENTIONED PATCHY
MVFR FOG AT KAVL BY WAY OF A 2HR TEMPO AROUND DAYBREAK.  MOISTURE
TRAPPED BENEATH LOW/MID LEVEL INVERSION WILL LIKELY CONDENSE BY LATE
MORNING INTO THE AFTERNOON HOURS ACROSS THE REGION LEADING TO
FEW/SCT LOW VFR FAIR WX CU.  WINDS WILL REMAIN IN THE 5-8KTS RANGE
AND NORTHERLY THROUGH THE PERIOD.

OUTLOOK...DRY HIGH PRESSURE WILL PREVAIL THROUGH MIDWEEK. THE ONLY
POSSIBLE RESTRICTIONS WILL BE EARLY MORNING FOG IN THE MOUNTAIN
VALLEYS. MOISTURE WILL INCREASE BY LATE WEEK AS EASTERLY FLOW
RETURNS LEADING TO INCREASING PRECIPITATION/FOG/STRATUS CHANCES.

CONFIDENCE TABLE...

            05-11Z        11-17Z        17-23Z        23-05Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  86%     HIGH  91%     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...NONE.
SC...NONE.

&&

$$
SYNOPSIS...PM
NEAR TERM...CDG/LGL/SBK
SHORT TERM...PM
LONG TERM...PM
AVIATION...CDG





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