Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 282334
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
734 PM EDT MON JUL 28 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 TUESDAY/...
730 PM EDT UPDATE...COMP RADAR SHOWING VERY WEAK AND SHORT LIVED
-SHRA MOVING ACROSS ERN TN AND REACHING THE WRN NC MTNS. THUS...ISOL
POP COVERAGE IS WORKING OUT VERY WELL THERE. EXPECT THIS ACTIVITY TO
CONTINUE THROUGH THE NEXT UPDATE...POSSIBLY TIL 06Z BASED ON
UPSTREAM MOISTURE AND THE STRONG UPSLOPE FLOW. TD/S CONTINUE TO DROP
THE MOST ACROSS THE SRN ZONES WHERE 3-4 F DROP OFFS OCCURRED IN THE
PAST 3 HRS. THUS...THE TD GRIDS WILL BE TWEAKED THE MOST ALONG WITH
MINOR ADJS TO SKY AND HR/LY TEMPS.

430 PM EDT UPDATE...VERY NICE DRY AIRMASS CONTINUES WORKING IN FROM
THE NORTH WITH FAIRLY DEEP VERTICAL MIXING PRODUCING MODERATE GUSTS
MTNS AND LOW END GUSTS NON/MTNS. NO SIGFNT CHANGE NEEDED TO THE FCST
WITH ONLY MINOR TWEAKS MADE TO THE T/TD GRIDS.

AS OF 2 PM MONDAY...AN ANOMOLOUSLY 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 /TUESDAY NIGHT 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 /00Z TUESDAY THROUGH SATURDAY/...
AT KCLT AND ELSEWHERE...VFR CONDS THROUGHOUT THE TAF PERIOD AT ALL
SITES. THERE IS NOT ENUF LLVL MOISTURE AND BL WINDS WILL BE JUST
HIGH ENUF TO OFFSET AN EARLY MORNING BR/FG THREAT...THE EXCEPTION
MAYBE BEING KAVL WHERE MFVR VSBY IS POSSBILE AROUND DAYBREAK. NOT
ENUF CONFIDENCE TO INCLUDE IN TAF ATTM. FAIRLY WEAK N/LY TO NNW/LY
WINDS TUE AFTERNOON...WITH KAVL MAINTAINED UP VALLEY.

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...

            23-05Z        05-11Z        11-17Z        17-23Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  99%     HIGH  94%     HIGH  85%     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...LGL/SBK
SHORT TERM...PM
LONG TERM...PM
AVIATION...SBK





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