Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 111802
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
202 PM EDT FRI JUL 11 2014

.SYNOPSIS...
A FRONTAL BOUNDARY WILL BE SOUTH OF OUR AREA TODAY AND GRADUALLY
WEAKEN AND DISSIPATE TONIGHT. WEAK HIGH PRESSURE WILL RETURN THROUGH
THE WEEKEND. A STRONG COLD FRONT IS EXPECTED TO REACH THE AREA ON
TUESDAY WITH THE POSSIBILITY OF STRONG STORMS.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 150 PM EDT FRIDAY...ISOLATED CONVECTION HAS INITIATED ALONG
PORTIONS OF THE BLUE RIDGE ESCARPMENT AS PREVIOUSLY FORECAST.
DECIDED TO GO AHEAD AND LOWER POPS ACROSS THE NC/SC PIEDMONTS AS
CAPPING IS EXPECTED TO INHIBIT CONVECTION.  OTHERWISE...FORECAST
REMAINS UNCHANGED FOR THE AFTERNOON AND FULL DISCUSSION REGARDING
THE OVERNIGHT AND SATURDAY WILL BE POSTED WITHIN THE HOUR.

PREVIOUS DISCUSSION...

AT 230 AM EDT FRIDAY...AN UPPER TROUGH EXTENDED FROM NORTHERN QUEBEC
TO FL..WITH A SHORTWAVE MOVING THROUGH ITS BASE OVER THE SOUTHERN
APPALACHIANS. A QUASI-STATIONARY FRONT WAS LOCATED OVER THE SOUTHERN
APPALACHIANS. MOST CONVECTIVE ACTIVITY HAS DIMINISHED OVER OUR
AREA... WITH THE BULK OF ACTIVITY LOCATED CLOSER TO THE COAST IN
MORE UNSTABLE AIR.

OBSERVATIONS SHOW LOW CLOUDS AND FOG FORMING IN PORTIONS OF THE
PIEDMONT AND IN MOUNTAIN VALLEYS...AND THIS TREND IS EXPECTED TO
CONTINUE THROUGH DAWN...ESPECIALLY IN RAIN SOAKED AREAS.

THE SLOW MOVING SHORTWAVE IS EXPECTED TO CROSS OUR AREA TODAY...AND
MOVE TO THE COAST TONIGHT...AS IS THE ASSOCIATED FRONT. MODEL TIME
HEIGHTS SHOW LOW LEVEL FLOW VEERING FORM NE TO E TODAY...AND THEN SE
THIS EVENING. THIS WILL RESULT IN A MOIST UPSLOPE FLOW INTO THE BLUE
RIDGE. THE LIMITING FACTOR FOR CLOUD COVER AND CONVECTIVE COVERAGE
WILL BE THE SHALLOW DEPTH OF THE MOIST LAYER BEHIND THE FRONT. THE
BEST CONVECTIVE COVERAGE IS EXPECTED TO BE OVER THE MOUNTAINS...
WHERE OROGRAPHIC EFFECTS ENHANCE LIFT. MAXIMUM TEMPERATURES WILL BE
SLIGHTLY BELOW NORMAL.

DESPITE PERSISTENT SHALLOW MOIST UPSLOPE FLOW...CONVECTION IS
EXPECTED TO WAN EARLY IN THE EVENING AS HEATING ABATES...AND A WARM
NOSE STRENGTHENS AT 650 MB. MINIMUM TEMPERATURES ARE EXPECTED TO RUN
SLIGHTLY BELOW NORMAL.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 145 PM FRI...LATEST GUIDANCE STILL SUGGESTS THAT THE SHORT
TERM WILL FEATURE RATHER TYPICAL JULY WEATHER FOR THE WESTERN
CAROLINAS AND NE GA. HIGH PRESSURE WILL REMAIN RIDGED OVER THE AREA
SATURDAY THROUGH SUNDAY AS A WESTWARD EXTENSION OF THE BERMUDA HIGH.
THE HIGH WILL BEGIN TO BREAK DOWN OVER THE AREA ON MONDAY AS HEIGHTS
BEGIN TO FALL ACROSS THE EASTERN U.S. IN RESPONSE TO A STRONG UPPER
LOW DROPPING SOUTHEAST OUT OF CANADA TOWARD THE GREAET LAKES.
HENCE...A MORE PROMINENT LEE TROUGH IS SHOWING UP IN THE MODEL
GUIDANCE FOR MONDAY...WHICH SHOULD SERVE AS A TRIGGER FOR MORE
CONVECTION OVER THE PIEDMONT THAN ON PREVIOUS DAYS. TO
SUMMARIZE...ON SUNDAY AFTERNOON CONVECTION SHOULD BE MOSTLY CONFINED
TO THE UPSLOPE AREAS IN THE MOUNTAINS...WHILE ON MONDAY ALL AREAS
SHOULD SEE SCATTERED CONVECTION DURING THE AFTERNOON. MAX TEMPS
SUNDAY AND MONDAY WILL BE AT OR A DEGREE OR TWO ABOVE CLIMO NORMALS.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 200 PM FRI...ONE THING THAT THAT THE MEDIUM RANGE GUIDANCE
CONTINUES TO AGREE UPON IS THE DISTINCT UPPER LEVEL PATTERN CHANGE
THAT IS FORECAST TO OCCUR IN THE EARLY TO MID WEEK PERIOD ACROSS THE
EASTERN PART OF THE NATION. A DEEP UPPER LOW IS STILL FORECAST TO
SWING SOUTH OUT OF NORTHERN CANADA AND ESTABLISH AN ANOMALOUS
UPPER TROUGH OVER THE EAST BY MIDWEEK. HOWEVER...THE DETAILS ARE
BECOMING A LITTLE MORE MURKY IN OUR REGION AS THE 12Z GFS HAS GONE
OUT ON ITS OWN IN REGARD TO FRONTAL TIMING, POSITION AND FRONTAL
WAVE DEVELOPMENT. THE 12Z GFS IS FASTER THAN ITS PREVIOUS RUNS AND
WITH THE CMC/ECF IN MOVING THE UPPER LOW INTO THE GREAT LAKES...AND
IT DOES NOT MOVE THE LOW AS FAR SOUTH. IN FACT...IT KEEPS THE UPPER
LOW CENTER ACROSS THE NORTHERN LAKES. THIS OF COURSE ULTIMATELY
AFFECTS HOW FAR SOUTH THE SURFACE COLD FRONT CAN BE DRIVEN. THE 12Z
GFS MOVES THE COLD FRONT INTO THE NC MOUNTAINS MONDAY NIGHT...THEN
STALLS THE BOUNDARY SOMEWHERE ACROSS THE PIEDMONT ON TUE. THEN IT
DEVELOPS A SERIES OF FRONTAL WAVES TUE-THU WITH WIDESPREAD PRECIP
EACH DAY. WPC ON THE OTHER HAND HAS GONE WITH A MORE EC/CMC
SOLUTION WHICH BRINGS THE FRONT INTO THE AREA ON TUE AND MOVES THE
FRONT FAR ENOUGH SOUTH OF THE AREA TO ALLOW DRIER AIR TO WORK INTO
THE REGION WED INTO THU. ALTHOUGH THE 00Z GFS ENSEMBLE IS ALSO
FARTHER NORTH WITH THE FRONTAL BOUNDARY...IT IS NOT AS FAR NORTH AS
THE 12Z OPERATIONAL POSTIION. AT THIS JUNCTURE...WE PREFER TO TREND
TOWARD THE WPC SOLUTION WHICH IS MORE CONSISTENT WITH PREVIOUS
FORECASTS. WE WILL LINGER SOME POPS OVER MOST OF THE AREA ON WED DUE
TO THE UNCERTAINTY INVOLVED...BUT WILL ALLOW FOR A DRY DAY ON THU.
WILL PROBALBY FEATURE CLIMO POPS ON FRI AS THE FRONT MAY BEGIN TO
RETURN NORTHWARD.

IN REGARD TO IMPACTS...THE FRONT WILL BE WELL FORCED FOR JULY AND
CAPES COULD POOL AHEAD OF THE FRONT TO PERHAPS 1500-2000J/KG
DEPENDING ON TIMING...SO THERE IS A POSSIBILITY FOR AN ORGANIZED
SEVERE STORM EVENT WITH THE FRONTAL PASSAGE. WIND SHEAR WILL BE
RATHER GOOD FOR JULY WITH FORECAST SOUNDINGS FEATURING UP TO 30-40KT
OF 0-6KM BULK SHEAR. ALSO..TEMPS ARE STILL EXPECTED TO BE AT LEAST 2
STANDARD DEVIATIONS BELOW AVERAGE WED AND THU. FOR INSTANCE...THE
12Z CONSRAW GUIDANCE FOR WED HAS MAX TEMPS CLOSE TO 10 DEGREES BELOW
CLIMO.

TO SUMMARIZE...A STRONG COLD FRONT IS FORECAST TO ARRIVE ON TUESDAY
BRINGING THE POTENTIAL FOR SEVERE THUNDERSTORMS. MUCH COOLER WEATHER
IS EXPECTED WED AND THU WITH A LINGERING CHANCE FOR SHOWERS ON WED.
THU MAY BE A DRY DAY...THEN A CHANCE FOR SHOWERS/STORMS WILL RETURN
FOR FRIDAY.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL THROUGH THE MAJORITY OF THE
FORECAST CYCLE AS UPPER HEIGHTS RISE LEADING TO BUILDING
SUBSIDENCE.  THUS...NO WX IS FORECAST THROUGH THE PERIOD.  BKN LOW
LEVEL CU WILL PERSIST THROUGH THE AFTERNOON BEFORE SCT OUT AFTER
COOLING SUBSIDES.  GUIDANCE HINTS AT LOW STRATUS AND FOG DEVELOPMENT
OVER THE NC PIEDMONT BY MID MORNING AS THE MOIST BOUNDARY LAYER
DECOUPLES. THEREFORE INCLUDED FM GROUP FOR MVFR LEVEL FOG AND AN
MVFR LEVEL SCT CLOUD DECK.  BY MID/LATE MORNING RESTRICITIONS WILL
LIFT AND CONDITIONS WILL IMPROVE BACK TO VFR LEVELS THROUGH THE
PERIOD.  WINDS WILL REMAIN A LITTLE TRICKY IN THE NEAR TERM HOWEVER
SHOULD BE PREDOMINATELY NE BEFORE QUICKLY VEERING SOUTHERLY THROUGH
THE TAF CYCLE.

ELSEWHERE...MUCH THE SAME AS KCLT ABOVE AS VFR CONDITIONS PREVAIL
OUTSIDE OF MVFR/IFR/LIFR FOG RESTRICITONS ON SATURDAY MORNING AT ALL
SITES...AND POTENTIAL RESTRICTIONS TO DUE CONVECTION AT KAVL THIS
AFTERNOON.  PREVAILED ALL SITES WITH NO WX THIS AFTERNOON ASIDE FOR
VCTS MENTION AT KAVL DUE TO MOUNTAIN UPSLOPE INDUCED CONVECTION.
ADDED MVFR/IFR LEVEL VSBY RESTRICITONS DUE TO FOG AT ALL SC
SITES...ALONG WITH IFR/LIFR CONDITIONS AT KHKY AND KAVL BY EARLY/MID
MORNING.  OTHERWISE...WINDS WILL VEER FROM THE NE TO MORE OF A
SOUTHERLY COMPONENT THROUGH THE PERIOD.

OUTLOOK...HIGH PRESSURE WILL SLOWLY SETTLE OVER THE AREA THIS
WEEKEND. ANY RESTRICTIONS SHOULD MAINLY BE CONFINED TO DIURNAL TSTMS
AND MORNING VALLEY FOG EACH DAY.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH 100%     LOW   54%     MED   75%
KGSP       HIGH 100%     HIGH 100%     MED   64%     MED   72%
KAVL       HIGH 100%     HIGH  92%     MED   66%     MED   79%
KHKY       HIGH 100%     HIGH  97%     MED   74%     HIGH  84%
KGMU       HIGH 100%     HIGH 100%     MED   64%     HIGH  80%
KAND       HIGH 100%     HIGH 100%     MED   63%     HIGH  80%

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...CDG/JAT
SHORT TERM...DEO
LONG TERM...DEO
AVIATION...CDG





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