Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 211746
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
146 PM EDT SUN SEP 21 2014

.SYNOPSIS...
A COLD FRONT WILL CROSS THE REGION FROM THE NORTHWEST TONIGHT
BRINGING COOLER AIR TO THE AREA FOR THE UPCOMING WEEK. EXPECT DRY
WEATHER FOR THE WHOLE WEEK...THEN NEXT WEEKEND COULD HAVE SOME RAIN
FOR PART OF THE REGION.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 145 PM...PRECIP REMAINS LIMITED AND WELL WEST NEAR THE FRONT.
HAVE SLOWED PRECIP ONSET SLIGHTLY IN RESPONSE AND HAVE CLEANED UP
SKY CONDITION BASED ON SAT PIX. OTHERWISE...GOING FCST ON TRACK WITH
LITTLE CHANGE NEEDED OTHER THAN CURRENT CONDITIONS.

AS OF 1035 AM...MOSTLY CLEAR SKIES OUTSIDE OF THE MTNS WILL ALLOW
QUITE A BIT OF SUNSHINE AND HEATING TODAY BEFORE CLOUDS INCREASE
LATER THIS AFTERNOON. MTN VALLEY FOG IS DISSIPATING WITH WLY UPSLOPE
CLOUDS DEVELOPING. THE MTN CLOUDS WILL BRIEFLY DISSIPATE BEFORE
CONVECTIVE CU QUICKLY DEVELOPS. MCS ALONG COLD FRONT TO OUR WEST IS
DISSIPATING WITH LITTLE ADDITIONAL ACTIVITY ALONG THE FRONT.
GUIDANCE STILL SUGGESTS BEST PRECIP CHC ACROSS THE MTNS WHERE
MOISTURE...FORCING AND INSTABILITY WILL BE BEST. CONVECTIVE CHC
OUTSIDE OF THE MTNS IS MUCH LESS GIVEN THE RELATIVE LACK OF
MOISTURE...WLY FLOW AND LOWER INSTABILITY. CANNOT RULE OUT A SEVERE
WIND GUST FROM STORMS OVER THE MTNS GIVEN THE INCREASING SHEAR AND
DRY MID LEVELS. FCST ALREADY HAS THIS COVERED...SO ONLY MINOR
CHANGES NEEDED...MAINLY FOR CURRENT CONDITIONS.

1030 UTC UPDATE...SKY COVER HAS BEEN UPDATED PER SATELLITE IMAGERY
AND OBSERVATIONS. AREAS OF FOG HAVE BEEN ADJUSTED PER OBSERVATIONS.
WINDS WERE UPDATED TO INCORPORATE THE 06Z NAM.

AT 245 AM EDT SUNDAY...AN UPPER TROUGH WILL AMPLIFY OVER THE GREAT
LAKES TODAY...WHILE AN UPPER LOW WEAKENS AS IT MOVES UP THE CAROLINA
COAST. THE UPPER TROUGH AXIS REACHES THE EAST COAST TONIGHT...WHILE
A STRONG SHORTWAVE MOVING INTO ITS BASE APPROACHED THE SOUTHERN
APPALACHIANS.

DRY HIGH PRESSURE BETWEEN A LOW OFF THE CAROLINAS COAST AND AN
APPROACHING COLD FRONT NOW IN THE OH RIVER VALLEY WILL BREAK DOWN
THIS MORNING. THE COLD FRONT WILL REACH THE SOUTHERN APPALACHIANS BY
THIS EVENING...PRECEDED BY CONVECTION. CAPE APPEARS TO BE LIMITED TO
UNDER 1000 J/KG...ESPECIALLY EAST OF THE MOUNTAINS...BUT WIND SHEAR
AND DRY AIR ALOFT WILL BE PRESENT. GUSTY WINDS AND HAIL CANNOT BE
RULED OUT. THE FRONT CROSSES THE FOOTHILLS AND PIEDMONT THIS
EVENING. THE MODELS DIFFER SLIGHTLY ON THE TIMING OF THE
BOUNDARY...BUT BY DAYBREAK MONDAY IT APPEARS TO BE JUST ABOUT OUT OF
OUR AREA.

HIGH TEMPERATURES TODAY WILL RUN SEVERAL CATEGORIES ABOVE NORMAL IN
WARM ADVECTION AHEAD OF THE FRONT. MINIMUM TEMPERATURES WILL RUN A
BIT ABOVE NORMAL AS POST FRONTAL WINDS REMAIN UP AND SOME CLOUD
COVER LINGERS.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 130 PM EDT SUNDAY...THE SHORT TERM FORECAST PERIOD INITIALIZES
MONDAY EVENING WITH A SURFACE COLD FRONT TO THE SOUTH ACROSS THE LOW
COUNTRY WHILE A SHARP UPPER TROF AXIS SLIDES THOUGH THE SOUTHEAST
AND MID ATLANTIC.  HIGH PRESSURE WILL SPILL INTO NORTHEAST GA AND
THE WESTERN CAROLINAS THROUGH MONDAY NIGHT INTO TUESDAY LEADING TO A
DRY/COOL FORECAST.  ON TUESDAY...THE UPPER PATTERN FEATURES RISING
HEIGHTS WITH ABOVE MENTIONED CANADIAN SURFACE HIGH SLIDING THROUGH
THE OHIO VALLEY WITH COOLER NORTHERLY FLOW PREVAILING ACROSS THE
SOUTHERN/CENTRAL APPS.  AS THE SURFACE RIDGE SLIDES EAST ON
WEDNESDAY IT WILL EXTEND SOUTHWARD IN AN EARLY FALL WEDGE
CONFIGURATION FURTHER REINFORCING THE COOLER/DRIER AIRMASS.
THUS...AS ENHANCED DEEP LAYER MOISTURE REMAINS TO THE SOUTH TIED TO
OLD FRONTAL BOUNDARY...SKIES SHOULD REMAIN MOSTLY SUNNY ON TUESDAY
AND WEDNESDAY.  THEREFORE THE FORECAST WILL REMAIN DRY THROUGH THE
PERIOD WITH THE HIGHLIGHTS BEING COOLER MORE FALL LIKE TEMPERATURES
ON TUESDAY...AND ESPECIALLY ON WEDNESDAY WHEN DAYTIME HIGHS STRUGGLE
TO REACH INTO THE MID 70S AND OVERNIGHT LOWS DIP INTO THE 50S ACROSS
NORTHEAST GA AND THE NC/SC PIEDMONT REGION.  AS FOR THE
MOUNTAINS...MID TO UPPER 60S ARE FEATURED EACH AFTERNOON WITH
OVERNIGHT LOWS IN THE 40S.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
AS OF 145 AM SUNDAY...THE MEDIUM RANGE FCST PICKS UP AT 12Z ON
WEDNESDAY UNDER AN UPPER RIDGE WITH SURFACE HIGH PRESSURE OVER NEW
ENGLAND AND A COOL NE FLOW INTO OUR REGION. ALTHOUGH BOTH THE GFS
AND ECMWF ARE VERY SIMILAR WITH A BROAD UPPER RIDGE FROM THE ROCKIES
TO THE EAST...THERE ARE MORE DIFFERENCES BY DAY 7. THE RIDGE WILL
HOLD OVER THE EAST WHILE A TROUGH DIGS ACROSS THE WESTERN STATES
DAYS 6 AND 7.

AT THE SURFACE...STRONG CANADIAN HIGH PRESSURE WILL BE CENTERED TO
OUR NORTH WITH COOL AND DRY AIR OVER THE FCST AREA. FOR THURSDAY AND
FRIDAY THE CENTER OF THE HIGH SHIFTS A BIT EAST WITH THE WIND GOING
FROM NE TO FROM A MORE EASTERLY DIRECTION WITH A MOIST FETCH OFF THE
ATLANTIC. THIS FLOW WILL CREATE AN INCREASE IN CLOUDS AND BRING
SLIGHT POPS TO THE EASTERN AND SOUTHERN FORECAST ZONES. THUS...THE
SLIGHT CHANCE POPS WILL INITIALLY BE OVER THE PIEDMONT...THEN OVER
THE WEEKEND THE FLUX OF MOISTURE SHOULD AFFECT NE GA AND THE UPSTATE
MORE THAN THE NC PIEDMONT. THE GFS HAS A PLUME OF MOISTURE ROTATING
NORTH FROM THE EASTERN GULF OVER THE WEEKEND MOVING ACROSS AL AND GA
THEN INTO TN BY SATURDAY NIGHT. THE EC ON THE OTHER HAND IS DRIER
FOR OUR REGION OVER THE WEEKEND...BUT CERTAINLY SHOWS A LARGE PLUME
OF MOISTURE MOVING NORTH FROM THE GULF SATURDAY NIGHT...BUT FARTHER
WEST THAN THE GFS MOISTURE PLUME.

ALTHOUGH WE WILL BE UNDER AN UPPER RIDGE THROUGH THIS PERIOD...THE
COOL SURFACE HIGH TO OUR NORTH WILL KEEP TEMPS A FEW DEGREES BELOW
NORMAL FROM DAY 4 THROUGH DAY 7.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
AT KCLT...CONVECTIVE CU DEVELOPING AHEAD OF THE FRONT AND MOVING
TOWARD THE AIRFIELD. THESE WILL CONTINUE TO BUILD AND BECOME BKN
THIS EVENING. EXPECT THE LOWER VFR CIGS TO CONTINUE OVERNIGHT AS
THE FRONT MOVES THRU...THEN SCATTER OUT BEFORE DAYBREAK. CHC OF
CONVECTION IS LOW GIVEN THE LIMITED INSTABILITY AND LOW LEVEL
MOISTURE. THEREFORE...NO TAF MENTION ATTM. SCT LOW VFR CONTINUES
THRU THE MORNING MON. WSW WIND WITH LOW END GUSTS TURN SWLY THIS
EVENING...THEN NW AND N OVERNIGHT AS THE FRONT MOVES THRU. NELY WIND
WITH LOW END GUSTS EXPECTED MON MORN AS HIGH PRESSURE BUILDS IN.

ELSEWHERE...SIMILAR CONDITIONS TO KCLT. KAVL THE EXCEPTION WHERE
CONVECTIVE CHC HIGH ENUF TO INCLUDE A VCTS FOR THIS EVENING. ALSO...
WINDS WILL REMAIN NLY AND GUSTY AT TIMES THRU THE PERIOD. ALSO...
MOS BASED GUIDANCE CONTINUES TO HIT MORNING FOG CHC QUITE HARD.
HOWEVER...MDLS AND FCST SOUNDINGS SHOW ONLY A LOW CHC. THEREFORE...
HAVE LIMITED RESTRICTIONS TO MVFR AS MVFR CIGS LIKELY IN THE WRAP
AROUND MOISTURE AND NLY FLOW BEHIND THE FRONT.

OUTLOOK...HIGH PRESSURE BUILDS BACK IN EARLY NEXT WEEK WITH VFR
CONDITIONS. MOISTURE MAY RETURN FROM THE COAST BY LATE IN THE WEEK.

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%     LOW   52%     LOW   50%
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...DEO
NEAR TERM...JAT/RWH
SHORT TERM...CDG
LONG TERM...DEO
AVIATION...RWH






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