Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 171842
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
242 PM EDT Wed Jul 17 2019

.SYNOPSIS...
Summertime heat and humidity will continue through the upcoming
weekend. Good chance for afternoon and evening showers and
thunderstorms through the period as well. A cold front will provide
relief from the heat and humidity early next week. However, chances
for showers and storms continue.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 2:15pm EDT Wednesday: Areas of showers and thunderstorms this
afternoon will have somewhat greater coverage due to influence of a
weakening upper trough crossing over the region.  850mb flow with
this system is also elevated, giving some wind gusts this afternoon
to 20kts.  Combination of deep-layer shear and instability are still
marginal for any severe weather, but some risk of isolated strong to
severe outflow will continue until things quiet-down diurnally this
evening.  Storms will be most numerous today over the mountains
which lie just east of the upper disturbance, but models indicate
some development into piedmont areas with areas of cumulus now seen
on satellite developing into convective showers over the next few
hours.

Upper system is east of the region by Thursday afternoon, and, while
thunderstorms are still anticipated Thursday afternoon, the coverage
will be reduced from what is being seen today due to reduced
dynamical forcing. On the other hand, CAPE is about the same, and
high-res models have slightly stronger updrafts in the storms that
do form.  Passage of upper system will leave area in a very low-
amplitude, tropical environment, with hot and somewhat humid
conditions for Thursday and beyond.  Temperatures will continue to
run 5 or so degrees above normal.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 220 PM Wednesday: An expansive mid-level ridge will build
across much of the eastern CONUS in the wake of Barry`s remnants,
resulting in temps back into the mid 90s along with sticky
dewpoints. Despite the building ridge, scattered diurnal convection,
favoring the mountains, is expected to develop thanks to strong
insolation and those sticky dewpoints. PoPs mainly in the chc range
except for likely across the mountains Saturday. Heat index values
will climb into the 100-105 range across the entire piedmont and
even much of the foothills. Values rise well into the 90s in many
mountain valleys.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
As of 235 PM Wednesday: A weakness in the broad mid-level ridge
develops on Sunday as a trough begins to dig into the upper Midwest.
The ridge continues to break down as the trough becomes entrenched
over the eastern CONUS by Wednesday. A series of waves move through
the trough and push a cold front into the area. This will bring an
increasing chance of afternoon and evening convection as the forcing
increases. Deeper moisture moves in with this system as well
creating the potential for excessive rainfall. The good news will be
the developing cooling trend. Sunday will only be slightly cooler
and less oppressive than Saturday. Monday will be even cooler but
still above normal with heat index values near 100 across much of
the Piedmont. Better relief on Tuesday with highs falling just below
normal with well below normal temps potentially developing
Wednesday.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
At KCLT and elsewhere: Latest round of afternoon thunderstorms
underway with most activity confined to the foothills and mountains,
though some high-res models have some isolated showers at any other
location.  Upper wave responsible for some enhancement of showers
today moves northeast past the area tonight, but enough moisture
remains to give some chance for thunderstorms Thursday afternoon.

As upper synoptic system passes, surface trough moves east and winds
over the mountains veer to more northwesterly. 850mb winds have
increased to 20-25kts, and are resulting in gusts to 20kts most
places this afternoon with decent mixing.  Gusts will decline after
sunset and 850mb flow weakens quite a bit on Thursday as synoptic
system moves out, so gusts are less likely Thursday afternoon.

Fairly shallow near-saturation layer in overnight BUFKIT soundings
suggests somewhat limited chances for morning fog most locations,
with some mention of fog restricted to the KAVL TAF site where some
fog and low CIGs will be possible in the morning.

Outlook: Typical scattered diurnal convection is expected into the
weekend, especially over the mountains. Patchy mountain valley fog
and low cigs remain possible during the overnight and early morning
hours.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High  92%     Low   54%     High  94%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     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:

www.weather.gov/gsp/aviation

&&

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

&&

$$
SYNOPSIS...RWH
NEAR TERM...WJM
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...WJM



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