Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 041443
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1043 AM EDT FRI SEP 4 2015

.SYNOPSIS...
A COLD FRONT IS EXPECTED TO PUSH SOUTH ACROSS THE REGION TODAY.
THIS WILL BE FOLLOWED COOL AND MOIST HIGH PRESSURE WHICH WILL
PERSIST THROUGH THROUGH THE HOLIDAY WEEKEND. A GRADUAL WARMING TREND
WILL FOLLOW TOWARD THE MIDDLE OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1030 AM...ALMOST ENTIRELY CLEAR ACROSS THE WESTERN CAROLINAS
AND NE GEORGIA...SAVE FOR TWO SMALL PATCHES OF STRATOCU AND SOME FOG
LIFTING TO STRATUS IN THE LITTLE TN VALLEY. THAT SHOULD ALLOW FOR A
STEADY WARM-UP THROUGH MIDDAY...WHICH SHOULD THEN ALLOW FOR STEADY
DESTABILIZATION. THE LATEST MODEL GUIDANCE SUGGESTS THAT IT WILL
TAKE SOME TIME FOR CONVECTIVE INITIATION...PERHAPS NOT UNTIL
EARLY/MID AFTERNOON. WILL BACK UP PRECIP ONSET. FCST SOUNDINGS
SUGGEST SUFFICIENT CAPE FOR THUNDERSTORM DEVELOPMENT THIS AFTERNOON.
SEVERITY POTENTIAL LOOKS LIKE A MIXED BAG. ON THE ONE HAND...WE LACK
MID LEVEL DRY AIR...BUT ON THE OTHER HAND THE CLOUD BASE WILL BE SO
HIGH THAT WE SHOULD HAVE AT LEAST 1000 J/KG OF DCAPE. CANNOT RULE
OUT SOME DAMAGING WIND GUSTS IN ONE OR TWO OF THE STRONGER/TALLER
STORMS. HAVE RAISED MAX TEMP A DEG OR TWO IN SOME SPOTS.

PREVIOUS DISCUSSION...

AS OF 650 AM...ONLY PATCHY LIGHT FOG BEING REPORTED OUTSIDE OF THE
MTNS WITH PATCHY DENSE FOG IN THE VALLEYS...MAINLY IN THE SWRN MTNS.
THIS FOG SHUD BURN OFF QUICKLY THIS MORNING...LEAVING SUNNY SKIES
UNTIL VFR CU DEVELOPS WITH HEATING. FCST HAS THIS IN PLACE...SO
UPDATES MAINLY FOR CURRENT CONDITIONS.

AS OF 255 AM...A WEAK SHORT WAVE AND AREA OF UPPER DIVERGENCE DROP
INTO THE AREA THRU THE PERIOD. AT THE SFC...A WEAK BOUNDARY MOVES
ACROSS THE AREA TODAY. HIGH PRESSURE BUILDS IN FROM THE NE
REINFORCING THE NELY FLOW ACROSS THE AREA. COPIOUS LOW LEVEL
MOISTURE REMAINS OVER THE AREA. THIS COMBINED WITH THE EXPECTED
HEATING WILL LEAD TO MODERATE INSTABILITY. EXPECT CONVECTION WILL
DEVELOP AGAIN TODAY...BUT WILL HAVE A LITTLE LATER START TIME.
CONVECTION BEGINS NEAR THE BLUE RIDGE AND SPREADS EAST AND SOUTH
THRU THE DAY AND INTO THE EARLY EVENING. BEST COVERAGE WILL BE
ACROSS NC WITH LIKELY POP FOR THE I-40 CORRIDOR. THERE WILL BE
MINIMAL SHEAR...BUT ISOLATED SVR STORMS ARE POSSIBLE GIVEN THE
INSTABILITY AND DCAPE APPROACHING 1000 J/KG. CONVECTION DIMINISHES
THRU LATE EVENING...BUT RETURNS OVERNIGHT AS THE E TO NE FLOW
STRENGTHENS. HIGHS TODAY WILL AGAIN RISE INTO THE 90S OUTSIDE OF THE
MTNS AND MID 80S FOR THE VALLEYS. LOWS WILL BE ABOVE NORMAL.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AT 230 AM EDT FRIDAY...ON SATURDAY MORNING A POSITIVELY TILTED
UPPER RIDGE WILL EXTEND FROM TX TO NEW ENGLAND...WHILE A AN UPPER
TROUGH EXTENDS FROM THE WESTERN ATLANTIC TO THE CAROLINAS AND GA. BY
SUNDAY AN UPPER LOW CLOSES OF NEAR THE SC COAST...SOUTH OF THE
PERSISTENT UPPER RIDGE. WEAK MID LEVEL ENERGY ROUNDING THE UPPER
LOW WILL MOVE INLAND FROM THE COAST TO THE SOUTHERN APPALACHIANS.

AT THE SURFACE...ON SATURDAY A RIDGE OF HIGH PRESSURE WILL BE IN
PLACE ALONG THE EASTERN SEABOARD. MODEL DATA SHOWS A LACK OF
ISENTROPIC UPGLIDE OVER THE RIDGE...AND EVEN LOW LEVEL FLOW LACKS AN
ORTHOGONAL COMPONENT INTO THE BLUE RIDGE. ELEVATED INSTABILITY WILL
BE PRESENT HOWEVER...SUPPORTING CONVECTION THAT WILL BE MAXIMIZED
DURING DAYTIME HEATING. TEMPERATURES WILL EXHIBIT A REDUCED DIURNAL
RANGE...WITH MAXIMUMS BELOW NORMAL...AND MINIMUMS NEAR NORMAL.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AT 230 AM EDT FRIDAY...ON MONDAY MORNING AN UPPER RIDGE WILL EXTEND
FROM NORTHERN MEXICO TO THE NORTHEAST USA. THE MODELS DISAGREE ON
THE POSITION OF AN UPPER LOW SOMEWHERE NEAR THE CAROLINAS AND GA.
THIS DISAGREEMENT BECOMES MORE PRONOUNCED BY TUESDAY...WHEN THE GFS
HAS A TROUGH FROM THE GULF TO NC WITH THE UPPER RIDGE SETTLING SOUTH
OF THE OH RIVER VALLEY...WHILE THE ECMWF HAS A TROUGH FROM THE OH
VALLEY TO THE GULF. BY WEDNESDAY THE TWO MODELS START TO AGREE ON
THE ALIGNMENT OF THE TROUGH OVER THE GULF STATES...WHILE LOW
AMPLITUDE UPPER TROUGHING PROGRESSES TO THE NORTHERN PLAINS. ON
THURSDAY THE NORTHERN STREAM TROUGH MOVES OVER THE GREAT
LAKES...COMING INTO PHASE WITH THE GULF TROUGH.

AT THE SURFACE...ON MONDAY A SURFACE RIDGE WILL EXTEND ALONG THE
EASTERN SEABOARD...WITH WEAK TROUGHING OFF THE COAST. THIS PATTERN
PERSISTS INTO TUESDAY. THE RIDGE WEAKENS ON WEDNESDAY...WHILE A COLD
FRONT MOVED INTO THE OH RIVER VALLEY. THIS FRONT MOVES SOUTH INTO
THE CAROLINAS ON THURSDAY.

MODEST INSTABILITY WILL SUPPORT A SMALL CHANCE OF DIURNALLY
MODULATED CONVECTION THROUGH MUCH OF THE EXTENDED FORECAST...WITH
THE BOUNDARY ARRIVING THURSDAY PROVIDING A FOCUSING MECHANISM FOR
CONVECTION...A AND PERHAPS MORE SUPPORT FOR OVERNIGHT CONVECTION.
STEERING FLOW REMAINS PRESENT FOR MOST OF THE PERIOD...WHICH SHOULD
KEEP CELLS MOVING. PERIOD OF LIGHT UPSLOPE FLOW COULD ENHANCE
CONVECTION ALONG THE BLUR RIDGE AT TIMES...BUT AT THIS POINT NO
PROLONGED BOUTS OF HEAVY RAINFALL ARE ANTICIPATED. TEMPERATURES WILL
TREND UPWARD...FROM SLIGHTLY BELOW NORMAL..TO SLIGHTLY ABOVE NORMAL.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
AT KCLT AND ELSEWHERE...GENERALLY VFR THROUGH THE PERIOD. MAINLY
JUST SOME HIGH CLOUDS EARLY THIS MORNING. ANY FOG WILL BURN OFF
QUICKLY AFTER DAYBREAK. SHUD BE ANOTHER ROUND OF 5-8KFT CU
DEVELOPING NEAR NOON AND CONTINUING THRU THE AFTERNOON. CONTINUED
PROB30 TSRA FOR THE AFTERNOON AS SCT CONVECTION EXPECTED AGAIN.
ADDED PROB30 FOR THE EVENING AS CONVECTION SHUD LINGER. WINDS WILL
REMAIN N TO NE AND LIGHT THRU THE EVENING. HOWEVER...WINDS WILL
LIKELY PICK UP SOME SPEED OVERNIGHT AS HIGH PRESSURE BUILDS IN FROM
THE NORTH. GUIDANCE KEEPING ANY NON-MOUNTAIN LOW CLOUDS OUT OF THE
AREA UNTIL AFTER THIS FORECAST PERIOD.

OUTLOOK...OVER THE WEEKEND...A MOIST EASTERLY FLOW SHOULD DEVELOP...
BRINGING BETTER CHANCES FOR SHOWERS AND RESTRICTIONS...IN PARTICULAR
ON SATURDAY. LOW CLOUDS AND FOG WILL BE POSSIBLE EACH NIGHT IN THE
MOUNTAIN VALLEYS.

CONFIDENCE TABLE...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     MED   70%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  87%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  95%

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

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JAT
NEAR TERM...PM/RWH
SHORT TERM...JAT
LONG TERM...JAT
AVIATION...RWH



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