Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 212203
AFDGSP

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

.SYNOPSIS...
A COLD FRONT WILL CROSS THE REGION FROM THE NORTHWEST TONIGHT
BRINGING COOLER AIR TO THE REGION FOR THE UPCOMING WEEK. COOL AND
DRY CONDITIONS ARE LIKELY TO PERSIST FOR THE REST OF THE WORK
WEEK...WITH RAIN CHANCES INCREASING OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 555 PM...PRE FRONTAL SHOWERS WERE REACHING THE WESTERN SLOPES
OF THE SOUTHERN APPALACHIANS. I WILL CONTINUE TO MENTION CHC
POPS...FOR BOTH SHOWERS AND THUNDERSTORMS. I WILL UPDATE TO ADJUST
SKY AND TEMPERATURE...BUT CHANGES WILL BE MINOR. OVERALL...THE
FORECAST IS ON TRACK.

AS OF 255 PM...AN UPPER TROUGH AMPLIFYING ACROSS THE ERN CONUS WILL
PUSH A COLD FRONT ACROSS THE AREA TONIGHT. CONVECTION IS CURRENTLY
ISOLATED AHEAD OF THE FRONT. HOWEVER...INSTABILITY IS INCREASING
WITH HEATING ACROSS THE WRN CWFA. GIVEN THE GOOD FORCING WITH THIS
SYSTEM AND THE DEVELOPING INSTABILITY...EXPECT SCT CONVECTION TO
DEVELOP OR MOVE INTO THE MTNS THIS AFTERNOON AND CONTINUE INTO THE
EVENING. CANNOT RULE OUT A FEW TS OR SHRA MOVING OUT ACROSS THE
PIEDMONT THIS EVENING. HOWEVER...INSTABILITY IS MUCH LESS THERE SOME
CAPPING SHOWN ON FCST SOUNDINGS. WITH THE MODERATE INSTABILITY...
INCREASING SHEAR AND MID LEVEL DRY AIR IN PLACE...A SEVERE DOWNBURST
OR TWO ARE POSSIBLE ACROSS THE MTNS IN THE STRONGEST STORMS. LOWS
WILL BE ABOVE NORMAL AS THE COOLER AIR BEHIND THE FRONT WILL BE
DELAYED.

DRY HIGH PRESSURE BUILDS IN BEHIND THE FRONT MON. HOWEVER...THE
FRONT WILL LIKELY SLOW AND STALL JUST SOUTH OF THE CWFA. THIS COULD
KEEP SOME LOW LEVEL MOISTURE LINGERING ACROSS THE SRN PORTIONS OF
THE CWFA DURING THE MORNING. SOME LINGERING LOW CLOUDS WILL ALSO
REMAIN ACROSS THE MTNS DURING THE MORNING IN THE WRAP AROUND
MOISTURE BEHIND THE FRONT. HOWEVER..THE FCST WILL REMAIN DRY. HIGHS
WILL BE BELOW NORMAL ACROSS THE MTNS AND NEAR NORMAL ELSEWHERE AS
THE COOLER AIR MASS FILTERS IN.

&&

.SHORT TERM /MONDAY NIGHT 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 CAD 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
MAJORITY OF 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.  ALTHOUGH WITH LOW CONFIDENCE...POPS
ARE SLOWLY REINTRODUCED WEDNESDAY AFTERNOON ALONG AND SOUTH OF THE
INTERSTATE 85 CORRIDOR AS WEAK UPGLIDE REGIME IS INDICATED BY
GUIDANCE.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 2 PM SUNDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON
THURSDAY WITH A VERY BROAD AND STEEP UPPER RIDGE SPREAD ACROSS MOST
OF THE CONUS. THE RIDGE IS EXPECTED TO REMAIN IN PLACE THRU
NEW DAY 7 OVER THE EASTERN HALF OF THE CONUS WHILE ANOTHER STEEP
UPPER TROF DIGS DOWN OVER THE ROCKIES BY THE END OF THE MEDIUM RANGE.

AT THE SFC...STRONG CANADIAN HIGH PRESSURE WILL BE CENTERED TO OUR
NORTHEAST AND OVER NEW ENGLAND WITH COOL AND DRY NELY LOW LVL FLOW
OVER THE FCST AREA. OVER THE NEXT FEW DAYS...THE LATEST LONG RANGE
GUIDANCE GRADUALLY MOVES THE HIGH A BIT WESTWARD BACK TOWARDS THE
GREAT LAKES. THIS DIFFERS FROM WHAT THE MODELS HAVE BEEN ADVERTISING
THE PAST COUPLE OF DAYS WITH THE HIGH DRIFTING SLOWLY EASTWARD OR
REMAINING NEARLY STATIONARY. THE ECMWF STILL REMAINS MORE BULLISH
WRT DEEPER LYR MOISTURE ENCROACHING UPON THE CWFA FROM THE SOUTH AND
EAST WHILE THE LATEST 12Z GFS KEEPS THE HIGHER RH VALUES JUST TO OUR
SOUTH THRU SAT. BY SUN...THE GFS DOES TRY TO SPIN UP SOME SORT OF
GULF OF MEX LOW WHICH SPREADS DEEPER MOISTURE OVER MOST OF THE CWFA
BY LATE SUN. THE ECMWF ALSO APPEARS TO SPIN UP SOMETHING IN THE
NORTHERN GOM BY THE END OF THE MEDIUM RANGE WITH DEEPER MOISTURE
SPREADING ACROSS THE SE REGION. WITH THAT SAID I BUMPED UP POPS JUST
A BIT ON THURS AND FRI...BUT KEPT MOST OF THE CWFA AT JUST SLIGHT
CHANCE OR BELOW. TEMPS WERE CHANGED VERY LITTLE WITH THE COOLEST
VALUES EXPECTED AT THE BEGINNING OF THE PERIOD ON THURS WITH SOME
MINOR WARMING GOING INTO THE WEEKEND...HOWEVER HIGHS SHOULD REMAIN
BELOW CLIMO THRU DAY 7.

&&

.AVIATION /22Z 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...

            22-04Z        04-10Z        10-16Z        16-22Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     MED   69%     MED   77%     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...NED/RWH
SHORT TERM...CDG
LONG TERM...JPT
AVIATION...RWH






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