Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 302025
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
425 PM EDT SUN AUG 30 2015

.SYNOPSIS...
WEAK SURFACE HIGH PRESSURE WILL LINGER OVER THE REGION FOR THE NEXT
SEVERAL DAYS. MOISTURE OF VARYING DEGREES FROM THE REMNANTS OF
TROPICAL CYCLONE ERIKA WILL CONTINUE TO SPREAD NORTH ACROSS THE
SOUTHEAST THROUGH THE END OF THE WORK WEEK...WITH INCREASING CHANCES
FOR AFTERNOON SHOWERS AND THUNDERSTORMS.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 425 PM...UPDATED POP TO ACCOUNT FOR THE INCREASING COVERAGE
ACROSS THE WRN CWFA AND BRIEF LULL OVER THE ERN AREAS. LITTLE
INSTABILITY SEEN ACROSS THE AREA...BUT THERE IS SOME THUNDER ALONG
THE CENTRAL SAVANNAH RIVER VALLEY. THEREFORE...HAVE LIMITED THUNDER
TO ISOLATED FOR THE REST OF THE AFTERNOON INTO THE EVENING. TEMPS
ARE RUNNING SIGNIFICANTLY COOLER ACROSS THE WRN PORTIONS DUE TO
CLOUDS AND PRECIP...AND SLIGHTLY COOLER ACROSS THE EAST. HAVE
UPDATED TEMP TRENDS TO ACCOUNT FOR THIS AS WELL.

AS OF 240 PM EDT SUNDAY...CLOSED UPPER LOW CONTINUES TO SLIDE
NORTHEAST ACROSS THE DEEP SOUTH THIS AFTERNOON YIELDING A BROAD
REGION OF GULF/ATLANTIC MOISTURE ADVECTION OVER NORTHEAST GA AND
THE CAROLINAS.  MID ATLANTIC HIGH PRESSURE THAT HAS BEEN SO DOMINATE
THE LAST FEW DAYS WILL STRUGGLE TO SURVIVE...HOWEVER ACCORDING TO
GUIDANCE...SHOULD DO JUST THAT.  MOIST UPGLIDE ATOP SAID SURFACE
RIDGE WILL CONTINUE THROUGH THE AFTERNOON/EVENING WITH DEEP LAYER
SYNOPTIC SCALE Q VECTOR CONVERGENCE SPREADING OVERHEAD.  THUS...THE
FCST FEATURES CLOUDY SKIES WITH CATEGORICAL POPS SOUTH...TAPERING
TO CHANCE POPS FURTHEST NORTH THIS AFTERNOON.  POPS WILL GRADUALLY
ROTATE AS SAID SYNOPTIC SCALE LIFT TIED TO THE UPPER VORTEX SLIDES
THROUGH THE NC PIEDMONT REGION TONIGHT THEREFORE LIKELY POPS ARE
FAVORED OVER BOTH THE NC/SC PIEDMONTS THIS EVENING BEFORE LOWERING
OVERNIGHT.  PATCHY FOG AND LOW STRATUS WILL PREVAIL OVERNIGHT BEFORE
BURNING OFF AFTER DAYBREAK ON MONDAY.  THE REMNANTS OF TROPICAL
CYCLONE ERIKA WILL PROVIDE SOME INFLUENCE ON THE WEATHER CLOSER TO
HOME ON MONDAY...BUT MAINLY IN THE FORM OF SOME MID/HIGH CLOUDINESS.
NEVERTHELESS...MODELS DO FAVOR ENOUGH INSTABILITY ON MONDAY TO
WARRANT AT LEAST CHANCE POPS ACROSS THE ENTIRE REGION...WITH THE
MTNS BEING THE MOST LIKELY PLACE FOR CONVECTION.  THAT SAID...POOR
LAPSE RATES ALOFT WILL LIMIT THE DEPTH OF SAID CONVECTION THEREFORE
NOT EXPECTING ANYTHING MORE THAN A FEW RUMBLES OF THUNDER AT BEST.
TEMPERATURES ON MONDAY WILL BE NEAR CLIMO LEVELS.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 230 PM EDT SUNDAY...UPPER WEAKNESS OVER THE SOUTHERN PLAINS
WILL CONTINUE TO WEAKEN AS RIDGING CONTINUES TO BUILD OVER MOST OF
THE COUNTRY. A WEAKNESS WILL CROSS THE OHIO VALLEY THROUGH THE SHORT
TERM BUT ANY INFLUENCE FROM IT SHOULD STAY JUST TO OUR NORTH UNTIL
THE END OF THE PERIOD WHEN THE ASSOCIATED FORT MAX DIVES SOUTH
TOWARD THE CAROLINAS...ROTATING AROUND THE UPPER RIDGE. MEANWHILE
THE REMNANTS OF ERIKA ARE NOW PROGGED TO STAY TO OUR SOUTH AND
GRADUALLY DISSIPATE. SHOULD SEE A GRADUAL INCREASE IN PW VALUES BUT
REMAINING BELOW 2 INCHES...AND FOR THE MOST PART BELOW 1.75 INCHES.
HAVE CONTINUED TREND OF MAINLY DIURNAL POPS THROUGH THE SHORT TERM
AND SHOWING A SLIGHT WARMING TREND AS WELL...CLOSER TO SEASONAL
HIGHS...TO ACCOUNT FOR LESS AVAILABLE MOISTURE IN THIS FORECAST
CYCLE THAN PREVIOUSLY SHOWN. BETTER CHANCE FOR CONVECTION WEDNESDAY
AFTERNOON THAN TUESDAY JUST DUE TO THE APPROACHING UPPER VORT
MAX...BUT STILL ONLY CHANCES AT BEST /AND BEST CHANCES LIMITED TO
THE MOUNTAINS/.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 245 PM EDT SUNDAY...UPPER RIDGING WILL BEGIN TO WEAKEN INTO
THE EXTENDED AS A SHORTWAVE ALOFT DIVES DOWN THE NORTHWEST FLOW ON
THE EASTERN EDGE OF THE UPPER RIDGE...BRINGING A SLIGHT INCREASE IN
DIURNAL CONVECTION CHANCES AS WE MOVE INTO THE EXTENDED. STILL SOME
UNCERTAINTY AS TO WHAT THE REMNANTS OF ERIKA WILL DO BUT BOTH THE
GFS AND ECMWF HAVE THE MOISTURE SPREADING ACROSS THE DEEP SOUTH
TOWARD THE END OF THE WEEK...WITH INCREASING PW VALUES INTO THE
WEEKEND /HOVERING JUST UNDER 2 INCHES AT LEAST ON THE GFS/. 12Z
ECMWF IS MORE ROBUST WITH THE MOISTURE THAN THE GFS BUT BOTH BRING
DECENT QPF VALUES...ESPECIALLY ON SATURDAY AS THE WAVETRAIN SLIDES
EAST AND VERY VERY WEAK SOUTHWEST FLOW DEVELOPS AS THE RIDGE AXIS IS
MORE OVER THE WESTERN ATLANTIC THAN THE APPALACHIAN SPINE.
HOWEVER...CONTINUED TO KEEP POPS AT CHANCE AT BEST FOR NOW JUST
BECAUSE WE ARE LOOKING SEVERAL DAYS OUT AND QUITE A BIT COULD STILL
CHANGE BETWEEN NOW AND THEN. TEMPERATURES FAIRLY CLOSE TO SEASONAL
NORMALS.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
AT KCLT...A MIXTURE OF VFR/MVFR AND POSSIBLY IFR THROUGH THIS TAF
CYCLE AS GULF/ATLANTIC MOISTURE CONTINUES TO BE ADVECTED NORTHWARD
BY WAY OF NORTHWARD MIGRATING MID/UPPER LOW.  INITIALIZED TAF VFR
WITH VCSH MENTION AS LIGHT RETURNS CONTINUE TO SPREAD NORTHWARD
ON RADAR WITH A 4HR TEMPO STARTING AT 20Z FOR LIGHT SHRA.
SHRA WILL PREVAIL FROM 00Z-03Z WHEN NAM/HRRR AGREE ON TIMING OF
PRECIPITATION OVER THE NC PIEDMONT WITH MODERATE SHOWERS POSSIBLY
YIELDING MVFR VISB.  CIGS THROUGH THIS ENTIRE PERIOD WILL START
OUT AT MID LEVELS...GRADUALLY LOWERING LOW VFR BY AROUND MIDNIGHT.
FROM THAT POINT GUIDANCE FAVORS DETERIORATING CONDITIONS AMONGST
THE MOIST PBL WITH MVFR CIGS FAVORED BY 03Z WITH POSSIBLE IFR
AROUND/AFTER MIDNIGHT.  GUIDANCE TRENDS HAVE BEEN AWAY FROM
IFR...HOWEVER NOT CONFIDENT ENOUGH TO COMPLETELY REMOVE ANY
MENTION THUS KEPT SCT008 IN TAF.  OTHERWISE...CONDITIONS WILL
IMPROVE TO LOW VFR AFTER DAYBREAK.  WINDS THROUGH THE TAF CYCLE
WILL INITIALIZE SOMEWHAT VARIABLE...ALTHOUGH TAF FEATURES SE WINDS.
THESE LIGHT SE WINDS WILL PREVAIL SHORTLY AFTER ISSUANCE...LASTING
THROUGH THE PERIOD PERHAPS CALMING OVERNIGHT.

ELSEWHERE...SIMILAR TO THAT OF KCLT ABOVE WITH SITES OUTSIDE OF
THE MTNS EXPERIENCING THE GREATEST CHANCES FOR PRECIPITATION THIS
AFTERNOON EVENING DUE TO THE TRACK OF THE MIGRATING MID/UPPER
LOW AND ANY SYNOPTIC SCALE FORCING TIED TO IT.  THUS...ALL SC
SITES FEATURE PREVAILING SHRA THIS AFTERNOON WITH KHKY HAVING A
TEMPO INCLUDED FOR SUCH.  TAF REMAINS DRY REGARDING ANY PREVAILING
PRECIP AT KAVL THEREFORE OPTED FOR VCSH ONLY THROUGH LATE EVENING.
OTHERWISE...EXPECTING SIGNIFICANT RESTRICTIONS IN THE MTNS THIS
EVENING AS THE PBL CONTINUES TO MOISTEN AND WINDS CALM.  THUS KAVL
TAF FEATURES MVFR/IFR CIGS WITH EVEN AN LIFR VISB AROUND DAYBREAK.
GUIDANCE ALSO FAVORED IFR/LIFR AT THE SC SITES...MAINLY IN THE
FORM OF CIGS THEREFORE THOSE WERE ALSO INCLUDED.  LOOKS AS IF KHKY
WILL SEE THE LEAST IMPACT OVERNIGHT HOWEVER STILL COULD EXPERIENCE
MVFR CIGS/VISB BY MORNING.  OTHERWISE...ALL TAFS ARE DRY BY MID
EARLY/MORNING WITH ALL CONDITIONS IMPROVING SLOWLY AFTER DAYBREAK
ON MONDAY.  WINDS WILL REMAIN LIGHT AND SOMEWHAT VARIABLE THIS
AFTERNOON...CALM OVERNIGHT...AND INCREASING OUT OF THE SOUTHEAST
BY LATE MORNING MONDAY.

OUTLOOK...THE SOUTHEAST REGION IS FORECAST TO REMAIN UNDER A PLUME
OF GULF AND ATLANTIC MOISTURE THROUGH THE MIDDLE OF NEXT WEEK. IN
ADDITION...MOISTURE ASSOCIATED WITH THE REMNANTS OF ERIKA COULD
REACH THE SOUTHERN APPALACHIANS DURING THE MID WEEK. RESTRICTIONS
ARE POSSIBLE DURING PERIODS OF RAIN AND WITH THE MTN VALLEY FOG
AROUND DAWN.

CONFIDENCE TABLE...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       HIGH 100%     HIGH  90%     HIGH  84%     HIGH  85%
KGSP       HIGH 100%     HIGH  87%     LOW   56%     HIGH  85%
KAVL       HIGH 100%     HIGH  85%     MED   69%     HIGH  93%
KHKY       HIGH 100%     HIGH  91%     MED   79%     HIGH  81%
KGMU       HIGH 100%     HIGH  84%     MED   66%     HIGH  83%
KAND       HIGH  97%     HIGH  83%     LOW   58%     HIGH  85%

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...TDP
NEAR TERM...CDG/RWH
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...CDG


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