Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 022356
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
756 PM EDT TUE SEP 2 2014

.SYNOPSIS...
A WEAK COLD FRONT WILL PUSH THROUGH THE REGION TONIGHT FOLLOWED BY
BERMUDA HIGH PRESSURE WEDNESDAY INTO FRIDAY. ANOTHER COLD FRONT WILL
SWEEP THROUGH THE REGION OVER THE WEEKEND PROVIDING AN ADDITIONAL
FOCUS FOR THUNDERSTORMS ON SATURDAY AND SUNDAY. BUILDING HIGH
PRESSURE WILL HIGHLIGHT THE WEATHER PATTERN FOR THE START OF THE
NEXT WORK WEEK LEADING TO COOLER TEMPERATURES AND MORE STABLE
WEATHER.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 730 PM EDT...ISOLD TSTMS PERSIST IN THE EXTREME EASTERN
SECTIONS OF OUR PIEDMONT THIS EVENING AS OUTFLOWS CONTINUE TO
INTERACT WITH UNTAPPED HIGHER SBCAPE REGIONS. THE PIEDMONT
CONVECTION SHOULD STEADILY SLIP EAST AND THEN ATTENTION WILL TURN TO
THE LINE OF THUNDERSTORMS STRETCHING FROM BLUEFIELD WV TO NEAR
KNOXVILLE TN AHEAD OF AN UPPER SHORTWAVE AND WEAK SFC FRONT. THIS
LINE WILL MAKE A RUN INTO THE NC MOUNTAINS THROUGH THE LATE EVENING
HOURS...BUT MESOSCALE MODELS SHOW A SLIGHT WEAKENING TREND AS IT
REACHES THE HIGHER TERRAIN. WILL STILL NEED TO ACCOUNT FOR HIGHER
POPS ALONG THE SPINE OF THE MTNS THROUGH LATE EVENING AND THEN
DIMINISHING CHC TO SCHC POPS INTO THE ADJACENT FOOTHILL AND POSSIBLY
THE PIEDMONT INTO THE EARLY MORNING HOURS. MIN TEMPS HAVE BEEN
RAISED SLIGHTLY SINCE PLENTY OF DEBRIS CLOUDS ARE EXPECTED OVERNIGHT.

ON WEDNESDAY...THE MODELS AGREE WITH STALLING THE REMNANTS OF THE
UPPER WAVE OVER THE PIEDMONT TO OUR SOUTH AND EAST...YET STILL
DEVELOP CONVECTION IN THE AFTERNOON BECAUSE OF AMPLE MOISTURE AT LOW
LEVELS. THIS SEEMS LIKE A DECENT BET OVER THE MTNS AND ALONG THE
EASTERN BORDER CLOSE TO THE WAVE REMNANTS...BUT THERE IS UNCERTAINTY
IN BETWEEN THESE TWO AREAS. THE GUIDANCE PAINTS A SLIGHT CHANCE POP
ACROSS THE ENTIRE AREA WHILE THE ONGOING FCST HAS A CHANCE. WILL
KEEP THE CHANCE EVERYWHERE BASED ON THE LATEST SREF FOR THE TIME
BEING. TEMPS SHOULD BE A FEW DEGREES COOLER BASED ON INCREASED CLOUD
COVER.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 230 PM TUESDAY...ON THURSDAY...MID LEVEL RIDGE WILL REMAIN
CENTERED ACROSS THE CAROLINAS AND WESTERN ATLANTIC. SHORT RANGE
MODELS INDICATE THAT MOISTURE WILL LIFT NORTH ACROSS THE REGION
DURING THE DAYLIGHT HOURS ON THURSDAY. MOISTURE IS LIKELY INCREASING
SOUTH OF WEAK WARM FRONT LIFTING NORTH ACROSS THE CAROLINAS.
FORECAST SOUNDINGS INDICATE THAT PW WILL INCREASE TO 1.75
INCHES...WITH CAPES AROUND 1500-2000 J/KG. THIS ENVIRONMENT SHOULD
PRIMARILY SUPPORT AIR MASS TSRA...FORMING OVER THE MTNS DURING THE
EARLY AFTERNOON...EXPANDING EAST THROUGH THE REMAINDER OF THE
AFTERNOON. PULSE SVR TSRA APPEAR POSSIBLE ACROSS THE CWA. ON
FRIDAY...CONDITIONS WILL CHANGE LITTLE FROM THURSDAY. FORECAST
SOUNDINGS INDICATE THE PW WILL INCREASE TO 1.8 INCHES WITH BROAD
LLVL SE FLOW. WEAK UPSLOPE FLOW WILL FAVOR THE HIGHER ELEVATIONS FOR
TSRA. BOTH DAYS...I WILL FORECAST 30 POPS ACROSS THE PIEDMONT TO
40-50 ACROSS THE MTNS. THURSDAY AND FRIDAY...HIGH TEMPERATURES ARE
FORECAST TO RANGE NEAR NORMAL.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 200 PM EDT TUESDAY...LATEST GLOBAL MODELS CONTINUE TO AGREE
THAT AN UPPER TROUGH WILL PROGRESS EASTWARD ACROSS THE GREAT LAKES
REGION SAT AND INTO THE EASTERN SEABOARD BY SUN. THIS WILL PUSH A
TRAILING COLD FRONT INTO THE SOUTHERN APPALACHIANS BY LATE SAT.
WITH INCREASING ATLANTIC MOISTURE ADVECTION IN SELY FLOW ALONG WITH
DIURNAL BUOYANCY...POPS RAMP UP INTO THE SOLID CHANCE RANGE OVER THE
PIEDMONT AND INTO THE LIKELY RANGE OVER THE NC MTNS SAT AFTERNOON.
THE FRONT WILL THEN CONSIDERABLY SLOWS DOWN ITS SEWARD PROGRESSION
AS IT REACHES THE TN/NC BORDER LINE. BOTH THE GFS AND THE ECMWF
INDICATE THAT THE FRONTAL BOUNDARY WILL BECOME STATIONARY OVER THE
PIEDMONT BY EARLY SUN BEFORE IT EVENTUALLY PUSHES SOUTH OF THE AREA
BY MON. THIS WILL YIELD WIDESPREAD CONVECTION ONGOING SUNDAY INTO
EARLY MON AND THUS HAVE MENTIONED SOLID TO LIKELY POPS ACROSS MUCH
OF THE REGION DURING THIS PERIOD. GIVEN THE MOIST PROFILE (PW VALUES
NEAR 2")...GOOD LLVL CONVERGENCE AND MODERATE INSTABILITY...HEAVY
RAINFALL LOOKS TO BE THE MAIN CONCERN ATT. MON AND TUE...POPS RAMP
DOWN AS THE FRONT REMAINS SOUTH OF THE AREA AND A WEDGE OF SURFACE
HIGH BUILDS IN FROM THE NE. TEMPERATURES WILL STAY NEAR NORMAL
FRI/SAT BEFORE COOLING DOWN CONSIDERABLY BY MON.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...STRONG TO SEVERE CONVECTION DEVELOPING ALONG EARLIER
OUTFLOWS REMAINS WELL EAST OF THE AIRFIELD THIS EVENING AND SHOULD
POSE NO IMMEDIATE THREAT GIVEN THE WESTERLY STEERING FLOW. THE NEXT
CONCERN WILL BE THE LINE OF THUNDERSTORMS EXPECTED TO MOVE INTO THE
NC MTNS FROM THE WEST LATE THIS EVENING. ALTHOUGH THE TSTMS SHOULD
WEAKEN OVER THE HIGHER TERRAIN...THERE IS A SMALL CHANCE THAT SOME
TSRA ALONG THE LINE COULD SURVIVE INTO THE FOOTHILLS AND POSSIBLY
THE PIEDMONT INTO THE EARLY MORNING HOURS. CONFIDENCE IS TOO LOW TO
INCLUDE THIS IN THE TAF SO WILL FEATURE JUST DEBRIS CIGS OVERNIGHT
WITH NO RESTRICTIONS. WINDS MAY TOGGLE BRIEFLY NW ON ANY
OUTFLOWS...BUT EXPECT MAINLY WSW TO SSW SFC WINDS WITH MIXING ON
WED...BUILDING CUMULUS...CONTINUED HIGH LEVEL CIGS...AND THEN
SCATTERED LATE DAY TSTM COVERAGE ONCE AGAIN.

ELSEWHERE...A CONVECTIVE LULL IS EXPECTED AT THE FOOTHILL TAF SITES
THIS EVENING AS A SOLID LINE OF THUNDERSTORMS MOVES SE FROM KY/WV/TN
TOWARD THE NC MOUNTAINS. THE LINE IS EXPECTED TO WEAKEN OVER THE
HIGHER TERRAIN...BUT CONFIDENCE IS HIGH ENOUGH TO WARRANT A TEMPO
FOR TSRA AT KAVL. WILL MENTION NOTHING MORE THAN VCSH AT KHKY FOR
NOW...BUT SCT TSTMS MAY SURVIVE THE TRIP TO THREATEN THE FOOTHILL
SITES INTO THE EARLY MORNING HOURS. OTHERWISE...DEBRIS CLOUDS SHOULD
INHIBIT LOW CLOUDS AND FOG AT MOST LOCATIONS...BUT BRIEF
RESTRICTIONS WILL BE POSSIBLE ANYWHERE RAIN FALLS TONIGHT. KAVL
REMAINS HARD TO PIN DOWN...BUT SOUNDINGS AND MOS HAVE GOOD CONSENSUS
ON IFR CIGS AND VSBY TOWARD DAYBREAK...SO WILL GO AHEAD AND INCLUDE
THAT DESPITE INCONSISTENT PERFORMANCE THE PAST FEW MORNINGS. WINDS
MAY GO NW THROUGHOUT AS ANY BOUNDARIES SLIP THROUGH...BUT PREVAILING
SW WINDS ARE EXPECTED AT THE FOOTHILL SITES ON WED. WILL FEATURE
PROB30 THROUGHOUT FOR AFTN/EVENING TSTMS TRIGGERING IN THE UNSTABLE
AIRMASS AGAIN ON WED.

OUTLOOK...GENERALLY VFR CONDITIONS ARE EXPECTED THROUGH THE REST OF
THE WEEK...BUT LOW CLOUD AND FOG RESTRICTIONS ARE LIKELY EARLY EACH
MORNING IN THE MOUNTAIN VALLEYS. DIURNALLY DRIVEN TSRA ARE EXPECTED
EACH AFTERNOON AND EARLY EVENING...WITH THE MOST COVERAGE OVER THE
MOUNTAINS. THUNDERSTORM COVERAGE MAY INCREASE THIS WEEKEND AS A COLD
FRONT ARRIVES.

CONFIDENCE TABLE...

            00-06Z        06-12Z        12-18Z        18-24Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH  95%     HIGH 100%     HIGH 100%
KAVL       HIGH  95%     MED   60%     MED   70%     HIGH 100%
KHKY       HIGH 100%     HIGH  87%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH  95%     HIGH  95%     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...JOH
NEAR TERM...HG/PM
SHORT TERM...NED
LONG TERM...JOH
AVIATION...HG





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