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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 250226
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1026 PM EDT FRI MAY 24 2013

.SYNOPSIS...
AN UPPER LEVEL TROUGH WILL MOVE OFF THE ATLANTIC COAST TONIGHT AND
SATURDAY WHILE SURFACE HIGH PRESSURE CONTINUES THE COOLER THAN
NORMAL TEMPERATURES THIS WEEKEND. EXPECT AFTERNOON SHOWERS AND
THUNDERSTORMS NEXT WEEK...MAINLY OVER THE MOUNTAINS. A RATHER STRONG
UPPER RIDGE WILL BRING VERY WARM TEMPERATURES FOR THE SECOND HALF
OF THE WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
-- Changed Discussion --
1000 PM UPDATE...NO SIGNIFICANT CHANGES OTHER THAN TO UPDATE EVENING
TEMP/DEWPT TRENDS. 00Z NAM DID TREND WARMER...AS DID 18Z GUIDANCE
WRT 12Z. STILL FAVORING THE TEMPS FCST EARLIER WHICH WERE WEIGHTED
MUCH MORE TOWARD MOS...GIVEN LIGHT FLOW AND CLOUDLESS SKIES. WILL
MAINTAIN CURRENT LOWS AND MTN FOG/FROST WORDING.

715 PM UPDATE...18Z GUIDANCE TRENDING A LITTLE WARMER FOR LOWS
THOUGH ALSO SUGGESTS LIGHTER WINDS. MTN MESONET SITES VARY ON
DEWPOINTS...WITH VALUES FROM AROUND FREEZING INTO THE UPPER 30S.
THINK SITES WILL BE ABLE TO COOL EASILY TO THEM GIVEN THE CALM
CONDITIONS. LOWERED OVERNIGHT LOWS JUST A TAD. PROG SOUNDINGS ARE
UNFAVORABLE FOR FOG AND NEWEST LAMP GUIDANCE SIGNIFICANTLY INCREASED
ITS VSBYS IN THE LITTLE TENN VALLEY. IN LIGHT OF THE COOLING
POTENTIAL AS WELL AS THESE LATTER POINTS...INCREASED EXTENTS OF
PATCHY FROST A BIT IN THE SW MTNS BUT BACKED OFF FOG FCST
SIGNIFICANTLY. STILL LOOKING LIKE A VERY NICE DAY TOMORROW WITH
LIGHT WINDS AND MAINLY CLEAR SKIES. A FEW CIRRUS MOVE IN BY
AFTERNOON AS DEBRIS FROM UPSTREAM CONVECTION PRESENTLY OVER THE
MIDWEST FILTER DOWN THE UPPER RIDGE...BUT THIS SHOULD NOT IMPACT
HIGHS.

PREV DISCUSSION...FOR TONIGHT...AN UPPER TROF AXIS WILL SWING OFF
THE EAST COAST LEAVING BEHIND A DEEP NW FLOW THAT WILL BRING DOWN
HIGH PRESSURE AND COOL TEMPS...MORE THAN TEN DEGREES BELOW NORMAL.
THE WIND SHOULD DIMINISH SIGNIFICANTLY BY EARLY SATURDAY MORNING.
THIS COULD BE ENOUGH TO ALLOW FOR PATCHY FROST TO DEVELOP IN SOME OF
THE SHELTERED MOUNTAIN VALLEYS...PARTICULARLY THE LITTLE TN RIVER
VALLEY. THE AREA IMPACTED DOES NOT LOOK LARGE ENOUGH FOR A FROST
ADVISORY SO THE MENTION WILL REMAIN RELEGATED TO THE HWO.

SATURDAY IS SHAPING UP TO BE A BRIGHT...SUNNY...COOL...AND DRY DAY
WITH A LIGHT BREEZE...COURTESY OF SURFACE HIGH PRESSURE RIDGING DOWN
FROM THE GREAT LAKES. CHAMBER OF COMMERCE WEATHER FOR THE FIRST PART
OF MEMORIAL DAY WEEKEND. OPEN UP THE WINDOWS AND ENJOY IT NOW
BECAUSE IT WILL NOT LAST. TEMPS WERE KEPT CLOSE TO A GUIDANCE
BLEND...WHICH IS A COMFORTABLE FIVE DEGREES OR SO BELOW NORMAL.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM FRIDAY...NW FLOW ALOFT WILL CONTINUE THROUGH SUNDAY AS
AN INTENSE UPPER LOW MOVES THROUGH NEW ENGLAND. THE FLOW WILL
DE-AMPLIFY ON MONDAY WITH BUILDING HEIGHTS AS THE LOW MOVES OUT THE
PICTURE. AT THE SURFACE...HIGH PRESSURE WILL RIDGE SOUTH FROM THE
SOUTHERN GREAT LAKES WITH A WEAK BACKDOOR FRONT MOVING THROUGH THE
AREA ON SUNDAY. THIS FRONT WILL MOVE NORTH AS A WARM FRONT ON
MONDAY. A MORE DOMINATE HIGH IS FORECAST TO DEVELOP OFF THE SE COAST
ON MONDAY.

A SERIES OF IMPULSES EMBEDDED IN THE NW FLOW ARE FORECAST TO MOVE
ACROSS THE AREA SUNDAY AND MONDAY. THE AIRMASS OVER THE REGION WILL
BE QUITE DRY IN THE LOWER LEVELS INITIALLY WITH DEWPOINTS IN THE 30S
AND 40S ON SUNDAY. HENCE...THE LACK OF SIGNIFICANT QPF RESPONSE IN
THE MODEL FORECASTS FOR SUN/SUN NIGHT IS NOT SURPRISING. WOULD EXPECT
THAT ANY PRECIP THAT FALLS SUNDAY AND SUNDAY NIGHT WILL BE MAINLY
VIRGA OR PERHAPS SOME SPRINKLES IN THE MOUNTAINS. MONDAY IS A
SLIGHTLY DIFFERENT STORY AS LOW LEVEL MOISTURE IMPROVES WITH
DEWPOINTS RISING INTO THE 50S AS THE WARM FRONT LIFTS NE.
THEREFORE...WOULD EXPECT SOME SCATTERED SHOWERS DEVELOPING IN THE
MOUNTAINS IN THE MORNING...WITH SCATTERED SHOWERS AND PERHAPS EVEN
SOME THUNDERSTORMS IN THE AFTERNOON....MAINLY OVER THE MOUNTAINS AND
THE NC FOOTHILLS/PIEDMONT.

TEMPERATURES WILL BE BELOW AVERAGE SAT NIGHT AND SUNDAY...WITH
MODERATING TEMPS ON MONDAY APPROACHING SEASONAL LEVELS.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 150 PM FRIDAY...STARTING AT 00Z TUESDAY ALL MODELS SHOW SOME
MID LEVEL MOISTURE BETWEEN THE DEPARTING UPPER TROUGH WITH AXIS JUST
OFF THE NEW ENGLAND COAST AND THE EXPANDING UPPER RIDGE WITH AXIS
OVER EAST TEXAS. THIS LINEAR AREA OF MOISTURE EXTENDS FROM KY TO NC
MONDAY NIGHT THEN SHIFTS EAST AS RIDGE BUILDS FROM SW. SOUTHWESTERLY
LOW LEVEL FLOW WILL BRING WARMER AIR INTO THE REGION AS TEMPERATURES
WILL BE A LITTLE ABOVE NORMAL TUESDAY AND WEDNESDAY AND THEN TWO
CATEGORIES ABOVE NORMAL FOR HIGHS THURSDAY AND FRIDAY. INSTABILITY
WILL SUPPORT PM SHOWERS AND STORMS BUT FAVORING DIFFERENTIAL HEATING
OF THE MOUNTAINS. CAPE VALUES ARE MOST UNSTABLE ON ECMWF WITH 1000
TO 2000 VALUES EACH AFTERNOON. GFS IS MORE REASONABLE WITH 800 TO
1200 TUES...DROPPING TO LESS THAN 1000 FOR THE REST OF THE WEEK WITH
HIGHEST VALUES NORTH OF CLT TOWARD VA. MODELS HAVE CENTER OF 500MB
RIDGE OVER WESTERN NC THURSDAY. SEEMS MORE STABLE ON THURSDAY AND
EVEN MORE STABLE FRIDAY WITH DRIER LOW TO MID LEVEL. UPPER RIDGE
BEGINS TO MOVE OFF THE EAST COAST GOING INTO NEXT WEEKEND.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
AT KCLT AND ELSEWHERE...VFR AS DRY AND QUIET HIGH PRESSURE BUILDS
INTO THE REGION FROM THE GREAT LAKES. WINDS WILL REMAIN NORTHERLY
OVERNIGHT BECOMING LIGHT AND SOMEWHAT VARIABLE. NO FOG CONCERNS AT
TAF SITES DESPITE THE CALM CONDITIONS...THOUGH A FEW PATCHES OF MVFR
FOG COULD BE SEEN IN THE VALLEYS OF THE SW NC MTNS. HOWEVER MOST
PESSIMISTIC GUIDANCE /LAMP/ IS TRENDING TOWARD HIGHER VSBYS THERE.
WEAKER WIND PROFILES WILL PRECLUDE GUSTS ON SAT...WITH WINDS
POSSIBLY REFLECTING LEE TROUGHING BY AFTERNOON AND FLIPPING TO
SOUTHWEST. THIS IS MOST LIKELY AT KCLT/KGSP/KGMU.

OUTLOOK...WITH DRY HIGH PRES DOMINATING THE WEATHER ACRS THE REGION
THRU THE WEEKEND...NO SIGNIFICANT AVIATION CONCERNS ARE EXPECTED. A
RETURN TO DIURNAL THUNDERSTORMS IS EXPECTED FOR MONDAY THROUGH
WEDNESDAY WITH ASSOCIATED RESTRICTIONS IN THE VICINITY OF STORMS.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-02Z
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
-- End Changed Discussion --

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...DEO
NEAR TERM...PM/WIMBERLEY
SHORT TERM...LG
LONG TERM...DEO
AVIATION...WIMBERLEY