Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 221754
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
154 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/...
A CLOSED UPPER LOW OVER THE SE U.S. WILL GRADUALLY FILL THROUGH THE
SHORT TERM LEAVING A WEAK UPPER TROUGH OVER THE AREA BY THU. AT
THE SURFACE...HIGH PRESSURE INTIALLY OVER NEW ENGLAND WILL BE
DISPLACED INITIALLY TO THE EAST BY A WEAK LOW MOVING NORTHWARD FROM
OFF THE CAROLINA COAST. BY THU...THE HIGH IS FORECAST TO RE-DEVELOP
TO THE WEST OVER THE EASTERN GREAT LAKES AND RIDGE SOUTHWARD AGAIN
ALONG THE EAST SLOPES OF THE APPALACHIANS.

THE NET RESULT INITIALLY WILL BE AN INCREASE IN DEEP LAYER MOISTURE
ACROSS THE THE WESTERN CAROLINAS AND NE GA ON WED INTO WED NIGHT
THANKS TO SOME ISENTROPIC UPGLIDE AS THE COASTAL LOW DEVELOPS TO THE
EAST. HENCE...CLOUD COVER WILL INCREASE DURING WED. AS WE GET INTO
WED NIGHT...THE MODELS SHOW SOME LIGHT QPF RESPONSE MAINLY EAST OF
I-26. HENCE..WILL BUMP POPS UPWARD INTO THE CHANCE CATEGORY
ANTICIPATING SOME PATCHY LIGHT SHOWERS. THE SHOWERS SHOULD TEND TO
WANE ON THU AS THE COASTAL LOW MOVES NE. HOWEVER...MODEL
TIME-HEIGHTS INDICATE THAT CLOUD COVER WILL BE SLOW TO DISSIPATE.
TEMPS WILL REMAIN BELOW CLIMO THROUGH THE PERIOD.

&&

.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...VFR CONDITIONS WILL PERSIST THROUGH THE TAF PERIOD AS A
CANADIAN HIGH PRESSURE CONTINUES TO BUILD IN FROM THE N/NE. NE WINDS
WILL CONTINUE TONIGHT AND INTO TOMORROW WITH SOME GUSTS TO AROUND
15KT POSSIBLE AFTER SUNRISE ON TUE DUE TO TIGHTER SURFACE PRESSURE
GRADIENT. A LINE OF CONVECTION TO OUR SOUTH WILL SPREAD CONSIDERABLE
MID/HIGH CLOUDS TO THE TERMINAL THIS AFTERNOON INTO TONIGHT.

ELSEWHERE...DRY CONDITIONS WILL CONTINUE OVER MUCH OF THE REGION
THROUGH THE TAF PERIOD AS A CANADIAN HIGH PRESSURE CONTINUES TO
BUILD IN FROM THE N/NE. A LINE OF CONVECTION TO OUR SOUTH WILL BRING
CONSIDERABLE MID/HIGH CLOUDINESS TO THE REGION THROUGH THIS EVENING.
LATEST GUIDANCE SUGGESTS VFR CONDITIONS MAINLY EAST OF THE MTNS WITH
IFR TO MVFR VISBY/CIG STETTING UP OVER THE MTNS/VALLEYS TOWARD
DAYBREAK ON TUE. HENCE...HAVE MENTIONED TEMPO FOR IFR/CIGS AT KAVL
BETWEEN 9Z AND 12Z TUE. OTHERWISE...EXPECT NE WINDS TO CONTINUE WITH
OCCASIONAL WIND GUSTS TO AROUND 10-15KT POSSIBLE ACROSS THE REGION
AFTER SUNRISE TUE AS A TIGHT SURFACE PRESSURE GRADIENT SETS UP.

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...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH  83%     HIGH  91%
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...JOH






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