Area Forecast Discussion
Issued by NWS Greer, SC

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723
FXUS62 KGSP 180239
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1039 PM EDT Mon Jul 17 2017

.SYNOPSIS...
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
thunderstorms.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 1015 pm...still a few showers eating up what is left of the
instability over the nrn Upstate and upper French Broad Valley,
but for the most part it looks like the convection has calmed down
for the evening. The mesoscale models show very little response
for the rest of the night, but it is not out of the question that
a few more showers or storms could form over northeast GA or the
western Upstate where the most remaining sbCAPE...upwards of 2000
J/kg...resides. Precip chances will be scaled back to account for
the radar trend and model guidance.

Otherwise...a weak short wave will cross the region overnight.
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 levels.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
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.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
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.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
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...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       High 100%     Med   69%     High 100%     High 100%
KGSP       High 100%     High  83%     High  97%     High 100%
KAVL       High  95%     High  95%     High  95%     High 100%
KHKY       High 100%     High  95%     High 100%     High 100%
KGMU       High 100%     Med   71%     High 100%     High 100%
KAND       High 100%     High  87%     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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$
SYNOPSIS...SW
NEAR TERM...PM/SBK
SHORT TERM...CDG
LONG TERM...SW
AVIATION...PM



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