Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 132152
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
552 PM EDT SUN JUL 13 2014

.SYNOPSIS...
WEAK HIGH PRESSURE WILL LINGER OVER THE WESTERN CAROLINAS AND
NORTHEAST GEORGIA THROUGH MONDAY. AN UNSEASONABLY STRONG COLD FRONT
WILL THEN CROSS THE REGION...BRINGING ENHANCED CHANCES FOR SHOWERS
AND THUNDERSTORMS ON TUESDAY. AFTER THE FRONT PASSES...COOLER THAN
NORMAL TEMPERATURES WILL PREVAIL FOR THE SECOND HALF OF THE WEEK.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 545 PM...A CLUSTER OF WEAK SHOWERS WAS DRIFTING OVER THE LAKE
NORMAN AREA AND NORTH ACROSS DAVIE COUNTY. OTHERWISE...WIDELY
SCATTERED SHOWERS EXISTED ACROSS THE NC MTNS. I WILL UPDATE THE
FORECAST TO ADJUST POPS AND SKY. TEMPERATURES APPEARS IN GOOD
SHAPE...BUT I WILL ADJUST AREAS UNDER AND AROUND SHOWERS.

AS OF 230 PM EDT SUNDAY...RATHER NICE DAY ACROSS THE MAJORITY OF THE
FORECAST AREA AS MOSTLY SUNNY SKIES HAS ALLOWED TEMPERATURES TO SOAR
INTO THE UPPER 80S TO LOWER 90S FOR MOST AREAS.  AS A
CONSEQUENCE...STEEPENING LOW LEVEL LAPSE RATES HAVE YIELDED ABUNDANT
INSTABILITY ACROSS THE REGION AS LATEST SPC MESOANALYSIS INDICATES
UPWARDS OF 1500-2000J/KG SURFACE BASED CAPE AMONGST A WEAKLY CAPPED
ENVIRONMENT.  WEAK SOUTHERLY UPSLOPE FLOW HAS ALLOWED FOR INITIATION
OF CONVECTION ACROSS PORTIONS OF THE HIGH TERRAIN...EAST INTO THE
FOOTHILLS.  EXPECTING THIS ACTIVITY TO REMAIN ISOLATED/SCATTERED AT
BEST WITH A FEW CELLS PROPAGATING INTO THE LOWER TERRAIN OF THE NC
PIEDMONT AND WESTERN UPSTATE OF SC.  ANY STORMS THAT DO SPILL INTO
THE ABOVE MENTIONED AREAS WILL PRESENT A MINOR THREAT FOR DAMAGING
DOWNBURST WINDS DUE TO ENHANCED DCAPE ACROSS THESE AREAS.  FAVORED
LIKELY POPS ALONG PORTIONS OF THE NORTHERN/SMOKY MOUNTAINS TAPERING
DOWN TO SLIGHT CHANCE POPS FURTHER EAST ALONG THE I77/I85 CORRIDORS.

POPS WILL TAPER FURTHER INTO THE OVERNIGHT HOURS AS DIURNAL HEATING
IS LOST AND UPSLOPE FLOW BECOMES WEAKER.  MEANWHILE...POTENT UPPER
TROF AND FIRST OF TWO ASSOCIATED COLD FRONTS WILL APPROACH THE AREA
FROM THE WEST ON MONDAY.  THAT SAID...MONDAY WILL PRESENT THE
TYPICAL SUMMERTIME DIURNAL POP/TEMP TRENDS AS SOUTHERLY FLOW RAMPS
UP AHEAD OF THE APPROACHING SURFACE TROF.  GUIDANCE WARRANTED
SLIGHTLY HIGHER POPS ON MONDAY AS DEWPOINTS IMPROVE...AND UPPER
HEIGHTS BEGIN TO FALL.  THUS CARRIED LIKELY POPS ACROSS THE
MOUNTAINS AND CHANCE POPS ELSEWHERE.  CANNOT RULE OUT A FEW
STRONG/SEVERE THUNDERSTORMS ON MONDAY DUE TO THE ABOVE MENTIONED
FALLING H5 HEIGHTS AND ABUNDANT WARM SECTOR...NOT TO MENTION WEAK
LEE TROF JUST TO THE EAST THAT COULD PROVIDE A FOCUS FOR SURFACE
CONVERGENCE THEREFORE CONVECTION.  TEMPERATURES THROUGH THE PERIOD
WILL REMAIN AT OR JUST ABOVE NORMAL LEVELS.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 210 PM SUNDAY...ANOMALOUSLY STRONG HEIGHT FALLS WILL OVERTAKE
THE EASTERN CONUS DURING THE SHORT TERM...ALLOWING A RATHER
RESPECTABLE MID-SUMMER COLD FRONT TO PUSH INTO THE REGION BY EARLY
TUESDAY. AHEAD OF THE FRONT...LINGERING DIURNAL CONVECTION AND POPS
SHOULD DIMINISH SOMEWHAT MONDAY EVENING. HOWEVER...POPS BEGIN TO
RAMP UP TOWARD THE LIKELY RANGE ACROSS THE WESTERN NC MTNS BY THE
END OF THE PERIOD...OWING EITHER TO THE FRONT ITSELF...OR TO THE
POTENTIAL FOR ORGANIZED CONVECTION TO OUTRUN THE FRONT ACROSS THE
TENN VALLEY. AS ONE WOULD EXPECT WITH SUCH ANOMALOUSLY LOW MID/UPPER
HEIGHTS OVERSPREADING THE AREA...THE FLOW ALOFT IS INDEED STRONGER
THAN IS TYPICALLY SEEN THIS TIME OF YEAR. HOWEVER...PER FORECAST
SOUNDINGS...THE FLOW THROUGH THE DEPTH OF THE TROPOSPHERE IS ALSO
QUITE VEERED AND UNIDIRECTIONAL...AND THE RESULT IS MODEST BULK
SHEAR VALUES (MAYBE 25 KTS IN THE 0-6KM LAYER). CONSIDERING THE TIME
OF DAY/EXPECTED MODEST LEVELS OF BUOYANCY...THE POTENCY OF ANY
ORGANIZED CONVECTION PUSHING INTO THE SOUTHERN APPALACHIANS TUE
MORNING IS NOT CLEAR-CUT ATTM. SPC CURRENTLY HAS WESTERN AREAS
HIGHLIGHTED IN A LATE DAY 2 SLIGHT RISK/15 PERCENT ...AND I CAN/T
REALLY ARGUE WITH THIS...BUT IF ANYTHING THIS MAY BE OVERSTATING THE
SITUATION A BIT.

THE SEVERE WEATHER SITUATION MAY BECOME MORE INTERESTING LATER
TUESDAY...AS THE FRONT EMERGES EAST OF THE BLUE RIDGE DURING THE
AFTERNOON. WHILE SHEAR WILL REMAIN SOMEWHAT LIMITED...THE FRONT
SHOULD ENCOUNTER SOMEWHAT BETTER THERMO PROFILES IN THE PIEDMONT...
POSSIBLY REINVIGORATING ANY FRONTAL/PRE-FRONTAL CONVECTION MOVING
OUT OF THE MTNS DURING THIS TIME. EITHER WAY...LIKELY POPS ARE
WARRANTED IN ALL AREAS AT SOME POINT TUE.

CONVECTION/COLD FRONT IS EXPECTED TO SCOOT EAST OF THE AREA BY TUE
EVENING...USHERING IN A RARE PLEASANT/UNSEASONABLY DRY/COOL AIR MASS
INTO THE AREA FOR MID-WEEK. IN FACT...WED WILL PROBABLY FEEL MORE
LIKE MID-SEPTEMBER THAN MID-JULY.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 130 PM SUNDAY...REMNANT OF THE STRONG MIDWEEK COLD FRONT WILL
BE NEAR THE CAROLINA COAST AT 00Z THU...EXTENDING SWWD TO THE GULF
COASTAL PLAIN. COOL SFC HIGH PRESSURE WILL BUILD EWD IN ITS WAKE.
LEADING H5 SHORTWAVE EMBEDDED IN THE LONG TROUGH OVER THE ERN CONUS
LIFTS NEWD BY THU NIGHT...BUT A SECOND WAVE QUICKLY BEGINS TO SWING
THRU THE CENTRAL STATES THEREAFTER. THIS IS IMPORTANT FOR THE LOWER
MISS VLY AND AREAS EAST...AS IT EVENTUALLY PRODUCES A SFC WAVE AND
ABUNDANT PRECIP ALG/N OF THE REMNANT FRONT. THOUGH THE 12Z GFS AND
00Z EC EXHIBIT SOME DIFFERENCES IN THEIR DEPICTION/TIMING OF THE
UPPER WAVE...BY FRI AFTN THEY BASICALLY BOTH SUPPORT WARM FRONTAL QPF
OVER THE CWFA. HIGHEST POPS ARE IN FACT ON FRI WITH THIS FEATURE
OVERHEAD. THE CLOUDY/WET PATTERN CONTINUES THRU THE REMAINDER OF THE
PERIOD. GFS IS MORE PROGRESSIVE...TAKING THE FRONTAL WAVE EAST OF OUR
AREA BY SATURDAY...COMPARED WITH THE EC WHICH DEPICTS IT TAKING ABOUT
ANOTHER DAY TO PASS. NEVERTHELESS THE PATTERN WILL BE MORE SUMMERLIKE
ONCE THE WARM FRONT LIFTS NWD...WITH THE FA IN MOIST SOUTHERLY FLOW.
TEMPS BEGIN TO REBOUND OVER THE WEEKEND BUT MAXES WILL BE LIMITED BY
CLOUD COVER...REMAINING A FEW DEGREES BELOW NORMAL. MINS WILL BE NEAR
NORMAL.

&&

.AVIATION /22Z SUNDAY THROUGH FRIDAY/...
AT KCLT AND ELSEWHERE...VFR CONDITIONS WILL PREVAIL THROUGH THE
PERIOD AS DIURNAL CONVECTION WILL LIKELY STAY WEST OF ALL SITES WITH
THE POSSIBLE EXCEPTION OF KAVL AND KHKY WHERE VCTS WAS PREVAILED.
OTHERWISE...STEEPENING LOW LEVEL LAPSE RATES IN A MOIST BOUNDARY
LAYER WILL ALLOW FOR FURTHER CU DEVELOPMENT THIS AFTERNOON THEREFORE
FEATURED EITHER SCT/BKN LOW VFR DECK AT ALL SITES.
OVERNIGHT...GUIDANCE IS HINTING AT SURGING LOW LEVEL MOISTURE FROM
THE SOUTH THEREFORE KEPT MENTION OF LOW VFR CLOUDINESS AT ALL SITES
OUTSIDE OF KAVL WHERE MODELS INDICATE POTENTIAL FOR IFR/LIFR LEVEL
STRATUS IN AND AROUND THE MOUNTAINS VALLEYS.  DECIDED TO START THE
DOWNWARD TREND IN THE KAVL TAF...BUT WAS NOT CONFIDENT ENOUGH TO
INCLUDE A CIG AT THIS TIME HENCE THE SCT004 MENTION.  LOW CLOUDINESS
WILL SCT OUT BY...OR JUST AFTER DAYBREAK GIVING WAY TO A FEW
MID/HIGH CLOUDS.  WINDS THROUGH THE PERIOD WILL REMAIN SOUTH
SOUTHWESTERLY AND IN THE 5-8KTS RANGE BEFORE WEAKENING SOMEWHAT
OVERNIGHT.  LASTLY...SOUTHERLY WINDS WILL BEGIN TO RAMP UP AFTER
DAYBREAK FROM THE WEST AS THE PRESSURE GRADIENT TIGHTENS DUE TO THE
APPROACHING FRONTAL BOUNDARY.

OUTLOOK...RESTRICTIONS IN THUNDERSTORMS ARE POSSIBLE MONDAY AND
TUESDAY. VFR WILL RETURN ON WEDNESDAY BEHIND A COLD FRONT.

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%     HIGH  93%     MED   78%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH  97%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     HIGH  97%     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...CDG/NED
SHORT TERM...JDL
LONG TERM...JPT
AVIATION...CDG






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