Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 172359

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
759 PM EDT Mon Jul 17 2017

A weak frontal boundary across the area today will dissipate over
the next few days. A strong upper ridge will then gradually build
into the region during the mid-to-late week, bringing hot
temperatures and reducing the coverage of diurnal showers and


As of 745 pm...scattered slow moving thunderstorms continue to
migrate W/SW mainly across the NC foothills and Srn Piedmont/w side
of metro Charlotte. Precip chances will be amended to account for
the radar trend. Expect that some of this activity will continue
to redevelop over parts of Upstate SC where a supply of sbCAPE
in the 2000-2500 J/kg range remains. The dCAPE was greater than
800 J/kg across the same area, so I will not rule out a few more
severe storms this evening, particularly given the number of hail
reports already received.

Otherwise...a well agreed upon h5 s/w will cross the FA this
evening and will interact with elev instability keeping -shra/tstms
active through the overnight to some degree. Expect lingering
debris clouds and moisture leading to stcu development to persist
arnd daybreak. The best chance for denser fg development will be
across the mtn valleys....yet all areas could see patchy ground fg
lifting by 14z or so. Afternoon and evening convection will once
again be probable Tue as the upper trof continues to influence
the pattern. Mid-level LRs will be conducive for stg/svr storms
as LFCs are easily reached once again and sbCAPE reaches moderate
levels. Max and min temps thru the period will remain near normal


As of 200 PM EDT Monday:  The short term fcst period kicks off
on Tuesday evening as a weak upper trof/disturbance slides east
across the Carolinas, while high pressure dominates at the surface.
Meanwhile to the west, a large H5 anticyclone will build, before
sliding east through the entire period.  With that, heights will
gradually rise through Wednesday and into Thursday atop northeast GA
and the western Carolinas leading to warming temperatures through
the profile.  Said warming will work to gradually tamp down
convective chances on Wednesday, and even further on Thursday.
With below climo pops fcst given decreased chances for diurnal
convection, the primary headline for the short term will be the
building heat.  Temperatures will warm each day with mid 90s
prevailing by Thursday across the piedmont, while upper 80s are
expected in the mtn valleys.  As such, given dewpoints in the upper
60s to lower 70s, am expecting heat indices to approach/exceed
100 degrees by Thursday.


As of 240 PM EDT Monday: Mid level ridging will be in place across
the area for Friday through the weekend into Monday leading to the
hottest period of the summer so far. Expect highs climbing into the
middle to upper 90s outside the mountains each day. Afternoon heat
indices will reach 100-105 in the Piedmont so will have to consider
heat advisories. Overnight lows will be warm also with mid to upper
70s common across the lower terrain.

Due to mid level warming, afternoon and evening thunderstorm
activity will be limited to the more favorable areas. The exception
will be Monday as the ridge begins to break down.


At KCLT: A thunderstorm complex continues to slowly move away to
the west/southwest at issuance time. Will keep the -TSRA going for
the first half-hour and then transition back to VFR with extensive
convective debris cloudiness. Expect wind direction to be variable,
but will favor a light NW wind from outflows out the back end of
the activity to the west. Given the precip that fell across the
vicinity, suspect that will lead to MVFR/IFR conditions after
05Z once the boundary layer cools sufficiently. The guidance was
aggressive with developing IFR stratus in the pre-dawn hours and
this is a reasonable scenario. Will limit to MVFR for now because
of the ongoing issues, but will not rule out including a lower
restriction in a later amendment for the period around the start
of morning operations. Wind will eventually become light/variable
overnight. On Tuesday, after some morning low clouds burn off,
expect VFR conditions with a light SSE wind as high pressure to
the east has an influence. Showers and storms are expected to
remain closer to the mtns.

Elsewhere: leftover convective debris at KHKY at the start, with
vicinity thunderstorms around KAVL/KGSP/KGMU. This activity should
weaken and be done by 02Z or so. Thereafter, expect the typical
light/var wind with convective debris clouds. Expect further
restrictions in the early morning hours at KHKY, similar to
KCLT with all the rain, but a more difficult call concerning low
stratus/fog around daybreak at the other TAF sites. Some mention
of fog/low stratus was kept based on the guidance, but confidence
not as high unless precip falls later this evening. Otherwise,
mainly VFR for Tuesday. Most of the convection is expected to
occur over the higher terrain, so only KAVL and KHKY get a PROB30
for the afternoon hours.

Outlook: Scattered to afternoon and evening thunderstorms are
expected into Wednesday across the area, with better coverage
over the mountains. Morning fog development can be expected
in the mountain valleys and in areas that receive rainfall the
previous afternoon/evening. Drier air will likely limit convective
coverage for Thursday, with typical mid-summer conditions returning
by Friday.

Confidence Table...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       High 100%     High  81%     High  83%     High 100%
KGSP       High 100%     High  85%     High  85%     High 100%
KAVL       High  97%     High  97%     High  92%     High 100%
KHKY       High 100%     High  94%     High  96%     High 100%
KGMU       High 100%     High  83%     High  89%     High 100%
KAND       High 100%     High  83%     High  89%     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:




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