Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 221652
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1252 PM EDT MON SEP 22 2014

.SYNOPSIS...
COOL AND DRY HIGH PRESSURE WILL BUILD OVER THE AREA THROUGH MID
WEEK. MOISTURE AND RAIN CHANCES INCREASE TOWARD THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1230 PM EDT...HAVE MADE MINOR ADJUSTMENTS TO THE TEMPS...SKY
COVER AND POPS OVER THE SOUTHERN ZONES OF THE FORECAST AREA TO
ACCOUNT FOR THE LATEST OBS/RADAR TRENDS. OTHERWISE...QUIET AND
COOLER CONDITIONS WILL CONTINUE THROUGH TONIGHT.

AS OF 930 AM EDT...HAVE UPDATED POPS TO INCREASE TO SLIGHT CHANCE TO
LOW END CHANCE RANGE MAINLY OVER THE SOUTHERN ZONES INCLUDING
GREENWOOD...ABBEVILLE AND ELBERT COUNTIES PER LATEST RADAR TRENDS.
OTHERWISE...THE CURRENT FORECAST IS ON TRACK.

AS OF 700 AM EDT...THE LATEST SFC ANALYSIS SHOWS THE DEPARTING COLD
FRONT DRAPED ALONG THE EXTREME SRN PERIPHERY OF THE FORECAST AREA.
ANY LINGERING ISOLD PRE/FRONTAL SHOWERS SHOULD ONLY IMPACT LOCATIONS
S OF AN ELBERTON TO GREENWOOD LINE...WITH POPS THEN DWINDLING
SHORTLY AFTER DAYBREAK.

ALTHOUGH DEEP LAYER DRYING IS EXPECTED BEHIND THE FRONT TODAY...A
POTENT H5 SHORTWAVE CURRENTLY DROPPING THROUGH WRN KY AND TN IS
EXPECTED TO ROUND THE ERN TROUGH AND CROSS THE FORECAST AREA THIS
AFTERNOON. IT WILL SHARPEN UP AS IT MOVES TOWARD THE BASE OF THE SRN
APPALACHIANS...GENERATING STRONG 850 TO 500 DPVA ALONG WITH LAPSE
RATES BETTER THAN 6.5 DEG C/KM ACROSS THE SRN TIER THIS AFTERNOON.
DRYING IS EXPECTED TO GENERALLY WIN OUT ACROSS OUR FORECAST
AREA...BUT ISOLD SHRA POPS WILL BE FEATURED ACROSS THE EXTREME SRN
PIEDMONT MID TO LATE AFTN. OTHERWISE...COOLING AND DRYING N TO NE
FLOW COULD PRODUCE SOME LOW END GUSTS AT TIMES THROUGH THE
DAY...WITH TEMPS SLIGHTLY BELOW CLIMO.

MOST NUMERICAL MODELS SHOW THE UPPER SHORTWAVE SLOWING DOWN AND
CLOSING OFF OVER THE LOWER PIEDMONT OR SC MIDLANDS TONIGHT. ANY
RESIDUAL MOISTURE IS EXPECTED TO BE EAST OF THE FORECAST AREA AND NO
FURTHER POPS WILL BE MENTIONED AS SPRAWLING 1024 MB HIGH PRESSURE
BUILDS FROM THE MIDWEST TO THE ERN SEABOARD OVERNIGHT. JUST ENOUGH
OF A PRES GRADIENT S OF THE SFC HIGH WILL LINGER THROUGH THE EARLY
MORNING HOURS TO PREVENT IDEAL RADIATING CONDITIONS. STILL...EXPECT
THE FIRST MORNING OF AUTUMN TO FEATURE MIN TEMPS IN THE UPPER 30S IN
SOME MOUNTAIN LOCATIONS.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AT 230 AM EDT MONDAY...ON TUESDAY MORNING AND UPPER TROUGH WILL
EXTEND FROM EASTERN CANADA TO THE CAROLINAS AND GA...WITH WELL
DEFINED CLOSED UPPER LOW OVER SC. THE UPPER TROUGH PROGRESSES TO THE
CANADIAN EAST COAST BY WEDNESDAY...WHILE THE SOUTHEASTERN LOW DRIFTS
SLOWLY NORTH AND STARTS TO FILL. THE GFS AND NAM DIVERGE IN THEIR
MOVEMENT OF THE UPPER LOW LATE WEDNESDAY...WITH THE NAM MOVING IT TO
GA...AND THE GFS TO WESTERN MD.

AT THE SURFACE...HIGH PRESSURE WILL BE CENTERED OVER THE OH RIVER
VALLEY EARLY TUESDAY...WITH A STALLED FRONT OVER THE GULF STREAM.
BOTH THE GFS AND NAM SHOW A TONGUE OF MOISTURE EXTENDING INLAND OVER
THE EASTERN CAROLINAS...DUE TO EASTERLY FLOW ASSOCIATED WITH THE
UPPER LOW TO THE WEST. BY EARLY WEDNESDAY THE SURFACE HIGH REACHES
NEW ENGLAND...WHILE THE STATIONARY FRONT REMAINS OVER THE GULF
STREAM...AND ASSOCIATED MOISTURE REMAINS CONFINED TO THE COAST.
COASTAL MOISTURE MAKES A RUN INLAND LATE WEDNESDAY...AS THE UPPER
LOW MOVES FARTHER INLAND. ALTHOUGH MOISTURE INCREASES OVER THE
INTERSTATE 77 CORRIDOR...SURFACE FLOW APPEARS TO HAVE A NORTHERLY
DOWNSLOPE COMPONENT THAT MAY LIMIT RAIN CHANCES. TEMPERATURES WILL
RUN BELOW NORMAL...WITH A DECREASING DIURNAL TREND AS CLOUD COVER
INCREASES.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AT 230 AM EDT MONDAY...ON THURSDAY MORNING THE ECMWF AND GFS AGREE
ON ZONAL FLOW ACROSS EASTERN CANADA...AND A UPPER LOW OFF THE WEST
COAST OF CANADA. BOTH AGREE ON AN UPPER RIDGE OVER THE ROCKIES. BUT
CONSIDERABLE DISAGREEMENT EXISTS WITH THE POSITION OF UPPER LOWS AND
UPPER RIDGING OVER THE EASTERN HALF OF THE USA. THE MODELS COME MORE
INTO ALIGNMENT BY FRIDAY AS THE UPPER RIDGE MOVES TO THE NORTHERN
PLAINS...ANOTHER SETTLES OVER THE OH RIVER VALLEY...AND YET ANOTHER
RDIGE REMAINS BETWEEN BERMUDA AND THE BAHAMAS. MEANWHILE...LOW
PRESSURE ALOFT WILL EXIST OVER THE CENTRAL PLAINS AND THE SOUTHERN
APPALACHIANS. BY SATURDAY THE UPPER HIGH MOVES OVER THE GREAT
LAKES....WHILE ANOTHER REMAINS NORTHEAST OF THE BAHAMAS. ON SUNDAY
THE GFS BRIDGES ITS GREAT LAKES RIDGE WITH THE BAHAMAS RIDGE...
WHILE THE ECMWF LEAVES A WEAK TROUGH OVER THE SOUTHEAST.

THURSDAY WILL FEATURE HIGH PRESSURE EXTENDING FROM NEW ENGLAND TO
THE GREAT LAKES AND GULF STATES...WHILE A STATIONARY FRONT RESIDES
OVER FL AND THE NORTHERN GULF OF MEXICO. ON FRIDAY THE UPPER RIDGE
RETROGRADES TO THE WEST...WHILE THE SURFACE FRONT MOVES NORTH OVER
THE GULF STREAM TOWARD THE CAROLINA AND GA COASTS. BY SATURDAY THE
UPPER RIDGE REACHES MI...WHILE THE COASTAL FRONT REMAINS STALLED
NEAR THE GULF STREAM. ON SUNDAY THE SURFACE HIGHS PROGRESSES TO THE
WEST...REACHING THE NORTHEAST USA...WHILE MAINTENANCE ITS PRESENCE
OVER THE SOUTHERN APPALACHIANS.

EASTERLY FLOW OFF THE ATLANTIC WILL RUN UPSLOPE INTO THE MOUNTAINS
FROM THURSDAY THROUGH SUNDAY...FAVORING PRECIPITATION. TEMPERATURES
WILL RUN BELOW NORMAL...BUT WITH A REDUCED DIURNAL RANGE DUE TO
CLOUDS AND PRECIPITATION.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
AT KCLT...THE SFC COLD FRONT HAS MOVED WELL S OF THE AIRFIELD THIS
MORNING AND WILL CONTINUE TO PULL AWAY TO THE S. BRIEF NRLY GUSTS
WILL BE POSSIBLE TODAY. MIXING DOES NOT APPEAR ESPECIALLY DEEP TO
SUPPORT FREQUENT GUSTS...SO A TEMPO STARTING MID MORNING SHOULD
SUFFICE. OTHERWISE...STEADY NE FLOW AT 10 KT OR LESS IS EXPECTED.
EXPECT JUST FEW TO SCT VFR STRATOCUMULUS EARLY...TRANSITIONING TO
MAINLY HIGH CLOUDS LATE DAY AHEAD OF THE UPPER SHORTWAVE CLOSING OFF
THROUGH THE EVENING HOURS. PROFILES STILL LOOK TOO DRY TO SUPPORT
ANY SHOWERS WITH THE STRONG SHORTWAVE THIS AFTN/EVENING.

ELSEWHERE...DRY CONDITIONS WILL CONTINUE WITH THE FRONTAL BOUNDARY
SETTLING S OF THE TERMINALS THIS MORNING. ANY LINGERING FEW TO SCT
VFR STRATOCUMULUS THIS MORNING WILL GIVE WAY TO MAINLY HIGHER CLOUDS
THIS AFTN/EVENING AHEAD OF THE NEXT APPROACHING SHORTWAVE. BRIEF
NRLY FLOW GUSTS CANNOT BE RULED OUT AT THE FOOTHILL SITES AS THE
COOLER AND DRIER AIR SPILLS IN TODAY...HOWEVER...MIXING LOOKS FAIRLY
SHALLOW...SO GUSTS WILL ONLY BE MENTIONED IN THE HIGHER TERRAIN AT
KAVL. ANY INTERACTION OF LINGERING BOUNDARY LAYER MOISTURE AND UPPER
SUPPORT WITH THE SHORTWAVE THIS AFTN/EVENING SHOULD AFFECT MAINLY
THE EXTREME SRN PIEDMONT...BUT WITH ANY ISOLD SHRA POTENTIAL S OF
KAND. EXPECT STEADY N TO NE FLOW AT 10 KT OR LESS...EXCEPT NW WINDS
WITH LOW END GUSTS AT KAVL. THE MAV/MET MOS ARE INDICATED LOW
RESTRICTIONS FOR KAVL LATE TONIGHT...BUT WILL ONLY FEATURE BRIEF
MVFR AT THIS POINT GIVEN THE DRY AIR.

OUTLOOK...DRY HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH THE
WEEK...WITH EASTERLY FLOW MOISTURE POSSIBLY RETURNING FROM THE COAST
THIS WEEKEND.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-17Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  91%     HIGH  88%
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...JAT
NEAR TERM...HG/JOH
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...HG






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