Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 262009
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
409 PM EDT SUN JUL 26 2015

.SYNOPSIS...
WEAK BERMUDA HIGH PRESSURE WILL REMAIN OVER THE AREA WITH TYPICAL
SUMMERTIME CONDITIONS INTO MONDAY. THE CENTER OF A STRONG MID LEVEL
RIDGE WILL SLIDE WEST THROUGH THE WORK WEEK. A WEAK COLD FRONT WILL
THEN APPROACH THE REGION BY THE END OF THE WEEK...WITH INCREASING
CHANCES FOR AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS EACH DAY.

&&

.NEAR TERM /THROUGH MONDAY/...
2010 UTC UPDATE...POPS AND QPF HAVE BEEN UPDATED PER THE LATEST
RADAR TRENDS. SKY COVER HAS BEEN UPDATED PER VISIBLE SATELLITE
IMAGERY.

AS OF 230 PM...UPPER PATTERN CONTINUES TO FEATURE A BROAD UPPER RIDGE
CENTERED OVER THE SRN PLAINS AND A TROUGH OVER THE EAST COAST. THIS
PATTERN WILL REMAIN STAGNANT OVER THE NEXT 24 HRS. PER LATEST GOES
IMAGERY...CURRENTLY SEEING THE BEST CUMULUS OVER THE MTN RIDGELINES.
RADAR IS PICKING UP A COUPLE OF SHOWERS ALONG THE SAME RIDGES AS
WELL. OVERALL THE MESO MODELS ARE NOT ESPECIALLY RESPONSIVE THIS
AFTERNOON...ON ACCOUNT OF POOR LAPSE RATES ASSOCIATED WITH OUR
POSITION DOWNSTREAM OF THE RIDGE. THE MODELS KEEP THE CELLS THEY DO
DEVELOP OVER THE HIGH TERRAIN...NOT JUST BECAUSE OF POORER LAPSE
RATES AS ONE HEADS EAST...BUT ALSO GIVEN WEAK STEERING FLOW. PWAT
VALUES ARE SOMEWHAT LIMITED ON ACCOUNT OF DRY PROFILES...SO HEAVY
RAIN IS NOT OF GREAT CONCERN DESPITE THE EXPECTATION OF SLOW MOVING
CELLS.

A SHORTWAVE ROUNDING THE CENTRAL CONUS RIDGE WILL HELP AMPLIFY THE
TROUGH DURING THE DAY MONDAY. IT APPEARS MOST IF NOT ALL OF THE
DYNAMIC FORCING ASSOCIATED WITH THIS WAVE WILL PASS BY TO OUR NORTH
AND EAST. HOWEVER THE LOWER HEIGHTS/COOLER TEMPS ALOFT WILL IMPROVE
LAPSE RATES AND ONCE AGAIN MAKE DEEP CONVECTION FEASIBLE ACROSS THE
CWFA. EVEN THEN...INSTABILITY IS EXPECTED TO REMAIN BELOW
CLIMATOLOGICAL VALUES. THE FCST WILL REFLECT MAINLY SHOWERS...WITH
ANY TSTMS LIKELY TO REMAIN WEAK...PARTICULARLY IN LIGHT OF PROFILES
BEING FAIRLY MOIST.

MINS TONIGHT WILL BE A TAD ABOVE CLIMO...WITH HIGHS TOMORROW 3-5
DEGREES ABOVE...SIMILAR TO THOSE SUNDAY.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 230 PM EDT SUNDAY...THE SHORT TERM FCST PERIOD INITIALIZES
MONDAY EVENING WITH A BROAD H5 ANTICYCLONE CENTERED OVER THE
SOUTHERN PLAINS WHILE A TROF AXIS SLIDES OUT TO SEA OFF THE EAST
COAST.  AT THE SURFACE...A WEAK COLD FRONT WILL BE ADVECTING SOUTH
FROM THE GREAT LAKES INTO THE OHIO VALLEY REGION.  CLOSER TO
HOME...MODELS FAVOR CONTINUED SOUTHERLY FLOW OVER THE SOUTHEAST
THANKS TO SYNOPTIC INFLUENCES FROM BERMUDA HIGH.  PREVIOUS GUIDANCE
TRENDED TOWARD POSSIBLE TROPICAL DEVELOPMENT FROM A REGION OF LOW
PRESSURE THAT IS CURRENTLY ROTATING OVER CENTRAL FL...HOWEVER LATEST
RUNS FAVOR LESS ORGANIZATION AND THUS ONLY INDICATE EJECTION OF SAID
SFC DISTURBANCE OUT TO SEA.  EXPECTING ONGOING MTN CONVECTION AT
FCST INITIALIZATION WHERE GUIDANCE FAVORS THE MOST UNSTABLE AIRMASS
WILL RESIDE.  LACK OF SUBSTANTIAL DRY AIR IN THE PROFILES EAST OF
THE MTNS WILL WORK TO LIMIT LAPSE RATES THUS ANY CONVECTION SHOULD
BE LESS DENSE/ROBUST THAN OVER THE MTNS.

PROFILES ON TUESDAY DRY OUT SOMEWHAT AS THE ABOVE MENTIONED COLD
FRONT LINGERS TO THE NORTH THUS ALLOWING FOR SUBSTANTIALLY MORE CAPE
AS LOW/MID LEVEL LAPSE RATES STEEPEN.  CIN WILL LIKELY KEEP SAID
CONVECTION AT BAY THROUGH MORNING BEFORE ANY CAPPING IS ERODED OVER
THE MTNS ALLOWING FOR INITIATION AROUND MIDDAY.  MODELS FAVOR
EAST/SOUTHEAST STORM MOTIONS ON TUESDAY THUS EXPECTING ANY WESTERN
NC CONVECTION TO PROPAGATE INTO NORTHEAST GA AND THE NC/SC FOOTHILLS
AND PIEDMONT WHERE ADDITIONAL DEVELOPMENT COULD ALSO BE ONGOING.
NAM SOUNDINGS DUE EXHIBIT UPWARDS OF 2.5-3.0K J/KG SBCAPE ALONG WITH
FREEZING LEVELS AROUND 14.5KFT WHICH WOULD SUPPORT DEEP CONVECTION
CAPABLE OF LARGE HAIL AND DAMAGING WINDS ALONG WITH HEAVY RAINFALL
AS PWATS REMAIN AROUND THE 2IN MARK.  THAT SAID...THE USUALLY MORE
TAME GFS IS SOMEWHAT RESERVED WITH CAPES GENERALLY 800-1000J/KG
LESS.  THINK THE NAM DEWPOINTS ARE A TAD OVERDONE THEREFORE LEANING
MORE SO TOWARDS THE GFS WHICH WOULD STILL YIELD SCATTERED TO
WIDESPREAD CONVECTION...HOWEVER AT GENERAL THUNDER LEVELS WITH
PERHAPS A FEW STRONGER CELLS.  THE OVERALL PATTERN REALLY DOESNT
CHANGE ALL THAT MUCH ON WEDNESDAY...HOWEVER THE NAM DOES INDICATE A
FAIRLY SUBSTANTIAL NEGATIVE DEWPOINT FLUX LEADING TO MUCH MORE
STABLE PROFILES RELATIVE TO TUESDAY.  THIS INCONSISTENCY WAS ALSO
ANOTHER REASON THE FCST LEANED ON THE GFS/ECMWF WHICH WAS NEARLY A
CARBON COPY BOTH DAYS.  TEMPERATURES THROUGH THE SHORT TERM WILL
REMAIN AT OR JUST ABOVE NORMAL AS THE UPPER RIDGE CONTINUES TO
DOMINATE.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 2 PM SUNDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
THURSDAY WITH STEEP UPPER RIDGING CENTERED OVER NEW ENGLAND AND A
NORTHERN STREAM UPPER TROF MOVING ACROSS THE NORTHERN GREAT LAKES.
ON THURS...THE UPPER TROF WILL OPEN UP AS IT MOVES EASTWARD AND
BECOMES MORE NEGATIVELY TILTED. THIS WILL SUPRESS THE UPPER RIDGE
OVER OUR REGION AND HEIGHTS WILL FALL A FAIR AMOUNT. BROAD UPPER
TROFFING IS EXPECTED TO REMAIN IN PLACE OVER THE NE CONUS FOR THE
REMAINDER OF THE PERIOD WITH UPPER RIDGING RESTRENGHTENING OVER THE
WESTERN CONUS AND PERSISTING BEYOND DAY 7. AT THE SFC...A WEAK COLD
FRONT ASSOCIATED WITH THE UPPER TROF WILL MOVE OVER THE FCST ON
THURS. THE LATEST MODEL GUIDANCE SHOWS A LESS DEFINED FRONT OVERALL
WITH LESS DEEP LYR MOISTURE ASSOCIATED WITH THE FROPA. AS THE FRONT
DISSIPATES TO OUR SE...SFC RIDGING WILL SPREAD BACK OVER THE CWFA
FROM THE NW ON FRI AND LINGER INTO THE WEEKEND. AT PRESENT...THE
MODELS APPEAR TO BE LESS BULLISH WRT THE DEVEOPMENT OF A SFC LOW TO
OUR SOUTH. BOTH THE GFS AND ECMWF TRY TO DEVELOP SOME SORT OF
LOW...HOWEVER IT REMAINS DIFFUSE AND POORLY ORGANIZED THRU THE
WEEKEND. THEY DO KEEP A HEALTHY AMOUNT OF DEEP LYR MOISTURE OVER THE
EXTREME SE...ESPECIALLY ALONG THE COAST THRU THE WEEKEND...HOWEVER
OUR NW ZONES ARE LOOKING DRIER. AS FOR THE SENSIBLE FCST...WE CAN
EXPECT DIURNAL CHANCES FOR SCT TO WIDESPREAD CONVECTION EACH
DAY/EVENING WITH INCREASING CHANCES FOR WIDESPREAD CONVECTION ON FRI
AND SAT AS THE POTENTIAL FOR A LOW TO DEVELOP TO OUR SOUTH REMAINS
DECENT. TEMPS WILL START OUT JUST ABOVE NORMAL AND ARE EXPECTED TO
DROP BELOW NORMAL OVER THE WEEKEND.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
AT KCLT...VFR. FEW-SCT CU WILL BE SEEN THIS AFTN WITH SPOTTY
MIDLEVEL CLOUDS TONIGHT. LIGHT...MAINLY SE WINDS WILL CONTINUE INTO
THIS EVENING...LIKELY GOING CALM FOR PERIODS OVERNIGHT. UPPER TROUGH
AMPLIFIES OVER THE EAST COAST BEGINNING EARLY MON AS A SHORTWAVE
DIGS INTO IT. THE PASSAGE OF THE WAVE SHOULD VEER WINDS TO SW BY
MIDDAY.

ELSEWHERE...ISOLD TO WIDELY SCT SHRA MAY ROLL OFF THE RIDGETOPS THIS
AFTN...BUT CHC OF ONE HITTING EVEN KAVL APPEARS LOW...SO NO MENTION
MADE IN TAFS. CONDITIONS LOOK TO REMAIN VFR OVERNIGHT...WITH JUST
MIDLEVEL CLOUDS PASSING THRU...EXCEPT WHERE FOG FORMS IN VALLEYS.
UNDER SIMILAR CONDITIONS TO THE PAST COUPLE OF DAYS...KAVL SHOULD GO
IFR AGAIN. PATCHY MVFR EXPECTED ALONG THE CATAWBA...INCLUDING KHKY.
LIGHT SOUTHERLY WINDS WILL VEER SLIGHTLY MONDAY.

.OUTLOOK...MON AFTN ISOLD TO SCT SHRA/TSRA ARE EXPECTED ACRS THE
AREA BUT WITH THE BEST CHANCE OVER THE MTNS. EARLY MORNING
FOG/STRATUS WILL ALSO BE POSSIBLE EACH DAY MAINLY IN THE MTN
VALLEYS. PRECIPITATION CHANCES GRADUALLY INCREASE THROUGH THE WORK
WEEK.

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     MED   67%     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...JPT
NEAR TERM...JAT/WIMBERLEY
SHORT TERM...CDG
LONG TERM...JPT
AVIATION...WIMBERLEY



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