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000
FXUS62 KGSP 242030
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
430 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/...
415 PM UPDATE...NO CHANGES TO FCST OTHER THAN TO TOUCH UP TEMP/DEWPT
TRENDS PER OBS. WITH WINDS RELAXING A TAD OVER THE NEXT HOUR IN
DIMINISHING PRESSURE GRADIENT...THERE MAY BE TIME FOR SUNSHINE TO
WARM TEMPS ANOTHER DEGREE OR SO.

THIS AFTERNOON...GUSTY NW WINDS WILL CONTINUE THROUGH SUNSET WITH A
FEW CLOUDS...OTHERWISE COOL AND DRY LIKE LATE APRIL.

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.

&&

.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 /21Z FRIDAY THROUGH WEDNESDAY/...
21Z KCLT UPDATE...FCST ON TRACK THOUGH WINDS HAVE COME AROUND TO THE
NORTH A BIT FASTER THAN ANTICIPATED...SO WILL VEER WINDS SLIGHTLY IN
TAF. PRESSURE GRADIENT WILL CONTINUE TO WEAKEN WITH THE STRONGEST
GUSTS LIKELY BEHIND US ALREADY...BUT WILL KEEP GUST MENTION THRU
SUNSET AS IN PREV PACKAGE.

AT KCLT AND ELSEWHERE...VFR THROUGH THE PERIOD. A FEW STRATOCU WITH
BASES AT 050 TO 060 THROUGH SUNSET...THEN CLEAR AFTER 01Z. WIND WILL
REMAIN GUSTY FROM THE NW THROUGH SUNSET BUT WILL QUICKLY DIMINISH
AFTER THAT AS THE CENTER OF THE HIGH BUILDS IN. MOST PLACES WILL GO
LIGHT AND VARIABLE EARLY SATURDAY MORNING AND STAY THAT WAY THROUGH
THE REST OF THE TAF PERIOD...THE EXCEPTION BEING KAVL WHERE A NW
UPVALLEY WIND WILL BE MAINTAINED. COULD BE SOME FOG OR FROST IN THE
LITTLE TN RIVER VALLEY AROUND DAYBREAK SATURDAY...BUT NOT AROUND
KAVL.

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...

            20-02Z        02-08Z        08-14Z        14-20Z
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

&&

.FIRE WEATHER...
IT WILL BE WINDY OVER THE MOUNTAINS AND BREEZY OVER MUCH OF THE REST
OF THE FORECAST AREA THIS AFTERNOON. AFTERNOON MINIMUM RELATIVE
HUMIDITY VALUES WILL FALL TO BETWEEN 25 AND 30 PERCENT. WITH RECENT
WIDESPREAD RAINFALL...FUEL MOISTURE VALUES ARE GENERALLY STILL
HIGH...AND WE DO NOT ANTICIPATE NEEDING ANY FIRE DANGER PRODUCTS.

&&

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

&&

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