Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 221831
AFDGSP

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

.SYNOPSIS...
COOL AND DRY HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH MID
WEEK. MOISTURE AND RAIN CHANCES INCREASE AS WE GO INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 230 PM EDT MON...THIS AFTERNOON AND EVENING...AREAS OF SHOWERS
AND THUNDERSTORMS WERE DEVELOPING ALONG AND IN THE VICINITY OF
THE SURFACE BOUNDARY TO OUR SOUTH THIS AFTERNOON. A DEEP MOISTURE
AXIS JUST TO OUR SOUTH WILL CONTINUE TO BRING CONSIDERABLE LOW-MID
LEVEL CLOUDINESS TO THE SOUTHERN HALF OF THE CWA THROUGH THIS
EVENING. CONDITIONS SHOULD REMAIN MOSTLY DRY FOR MOST LOCATIONS AS
A CANADIAN HIGH PRESSURE CONTINUES TO BUILD IN FROM THE N/NE. THE
EXCEPTION WILL BE OVER THE EXTREME SOUTHERN ZONES OF THE FORECAST
AREA WHERE SLIGHT TO LOW END CHANCES FOR SHOWERS WERE WARRANTED AT
LEAST THRU LATE THIS AFTERNOON.

TONIGHT AND TOMORROW...LATEST NEAR TERM MODELS CONTINUE TO INDICATE
THAT A POTENT UPPER SHORTWAVE ENERGY WILL ROUND THE BASE OF THE
EASTERN CONUS TROUGH...CLOSING OFF AS AN UPPER LOW AS IT MOVES
ACROSS THE REGION TONIGHT. THIS UPPER FEATURE IS EXPECTED TO SLOWLY
PULL NE AWAY FROM THE REGION TOMORROW. DESPITE THIS UPPER
FEATURE...CONDITIONS SHOULD REMAIN DRY AS A COOL CANADIAN HIGH
PRESSURE BUILDS IN FROM THE NE AND THE BEST UPPER FORCING REMAINS
SOUTH AND EAST OF THE CWA. WITH STRONG CAA IN N/NE FLOW (H85 TEMPS
OF 10C-12C WILL PUSH SOUTH INTO THE UPSTATE SC) TEMPS...OVERNIGHT
LOWS WILL PLUNGE TO THE UPPER 30S/LOW 40S OVER THE HIGHER TERRAIN
AND 50S OVER THE PIEDMONT. AFTERNOON HIGHS FOR TOMORROW WILL REMAIN
5-10 DEGREES BELOW NORMAL GIVEN PERSISTENT COOL NE WINDS.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
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 NIGHT THROUGH MONDAY/...
AS OF 2 PM MONDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON FRIDAY
WITH BROAD AND STEEP UPPER RIDGING PERSISTING ACROSS MOST OF THE
CONUS. THE RIDGE IS EXPECTED TO BEGIN BREAKING DOWN OVER THE WEEKEND
AS SOME SORT OF COMPLEX...SPLIT UPPER FLOW PATTERN DEVELOPS OVER THE
CENTRAL CONUS. BECAUSE THE POLAR JET WILL LIKELY REMAIN WELL TO THE
NORTH...THE UPPER FLOW WILL REMAIN WEAK OVER MUCH OF THE CENTRAL AND
EASTERN CONUS. THIS MAKES IT DIFFICULT TO PREDICT EXACTLY HOW THE
UPPER PATTERN WILL EVOLVE AS THE RIDGE BREAKS DOWN ON DAYS 6 AND 7.
THE OLDER 00Z RUN OF THE ECMWF CLOSES OFF AN H5 LOW OVER ARKANSAS BY
EARLY MON AND MOVES THAT LOW TO OUR DOORSTEP BY EARLY TUES. THE
NEWER 12Z GFS JUST MAINTAINS SOME DEGREE OF UPPER SWV ENERGY OVER
THE SAME REGION AND DOES NOT FORM A CLOSED LOW.

AT THE SFC...HIGH PRESSURE WILL BE CENTERED TO OUR NORTH WITH COOL
NELY LOW LVL FLOW OVER THE FCST AREA. OVER THE NEXT FEW DAYS THE
LATEST GUIDANCE KEEPS THE HIGH NEARLY STATIONARY...EXCEPT FOR THE
ECMWF...WHICH MOVES IT SLIGHTLY WESTWARD. THE ECMWF STILL REMAINS MORE
BULLISH WRT DEEPER LYR MOISTURE PERSISTING OVER THE CWFA FROM THE
SOUTH AND EAST ON FRI AND SAT WHILE THE LATEST 12Z GFS...AND
CMC...CONTINUE TO KEEP THE HIGHER RH VALUES JUST TO OUR SOUTH THRU
AT LEAST SAT. BY SUN...THE MODELS TRY TO SPIN UP SOME SORT OF GULF
OF MEXICO LOW WHICH SPREADS DEEPER MOISTURE OVER MOST OF THE CWFA BY
LATE SUN. MON APPEARS TO HAVE THE BEST CHANCE FOR ANY WIDESPREAD
PRECIP WITH DEEPER MOISTURE OVER MOST OF THE REGION AND SOME DEGREE
OF UPPER LVL SUPPORT JUST TO OUR WEST. AS FOR THE SENSIBLE FCST...I
KEPT POPS AT JUST A SLIGHT CHANCE OR BELOW ON FRI AND SAT WITH
VALUES INCREASING TO SOLID CHANCE OVER THE MOST OF THE CWFA BY LATE
SUN AND HIGHER END SOLID CHANCE BY MON AFTERNOON. TEMPS WERE LARGELY
UNCHANGED FROM THE PREVIOUS FCST WITH THE COOLEST VALUES EXPECTED AT
THE BEGINNING OF THE PERIOD ON FRI WITH SOME MINOR WARMING GOING
INTO THE WEEKEND.

&&

.AVIATION /19Z 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...JPT
NEAR TERM...JOH
SHORT TERM...LG
LONG TERM...JPT
AVIATION...JOH





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