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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 201055
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
655 AM EDT Sat Jul 20 2019

.SYNOPSIS...
Ridge of high pressure will allow for hot and humid conditions to
persist through the weekend, with a cold front bringing relief from
the heat early next week. Showers and thunderstorms will be possible
each day.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
As of 632 AM Saturday...quiet across the region at daybreak. A
large area of low stratus was left behind across the Upstate and
northeast Georgia by overnight convection that moved westward from
metro CLT. The low clouds could delay heating in those locations,
and thus the development of new convection later today. Temps will
get a warm start once again.

An upper anticyclone and sfc high over the Ohio Valley region will
be the dominant factor across our region today and tonight. Mid
and upper forcing should be scant, but low level moisture remains
plentiful enough for the sfc-based instability to make up for
the lack of forcing. The convection-allowing models once again
develop only widely scattered storms, but we suspect it might be
underdone as was the case the past few days. Precip prob climbs up
into the chance range across the whole area, with some likely over
the higher terrain, based on recent performance and the depiction
on the synoptic scale guidance. In general, lapse rates remain
relatively poor, so severe storms will be isolated. The main
story for today will be the heat, with temps climbing into the
middle 90s over the Upstate and wrn Piedmont of NC, and dewpts
remaining in the lower 70s. The result is a heat index up around
105 mainly in the nw Piedmont and Charlotte metro area in the
mid/late afternoon, so the fcst continues to support the Heat
Advisory issued yesterday. Actually, the 105 plus area has expanded
westward a bit, so Lincoln and Catawba counties will be added as
well. Expect a diurnal wane to the thunderstorm activity by late
evening. Precip chances were retained along the TN border to guard
against convection coming down from the NW in the pre-dawn hours
on Sunday. Min temps will remain seasonally mild.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 300 AM Sat: Not much remarkable change in the pattern from
Saturday to Sunday. Strong, broad subtropical ridging will continue
across the Southern states, with a weakness in the form of an
inverted trough over the central Gulf region. This along with
moist southerly flow in place to our west may allow some precip
activity to continue and/or initiate around the start of the period
Sunday morning. Otherwise the day looks fairly typical for the
season, with 1500-2000 J/kg of SBCAPE developing by peak heating,
very little shear, but strong theta-e lapses and DCAPE, so we may
deal with a few severe pulse storms. Light southerly flow implies
initiation along or north of the Escarpment and PoPs reflect that.

Sunday night a well defined upper trough will dig into the
Mississippi Valley; with a weak axis of vorticity shown to approach
the southern Appalachians overnight, can`t rule out some nocturnal
convection impinging on our area from the west. Heights fall
gradually through Monday and into early Tuesday, but the arrival
of the cold front no longer looks likely prior to 12z Tuesday. The
falling heights suggest a bit better storm coverage on Monday, but
the thermodynamic environment is more or less the same as Sunday,
albeit with ever so slightly more shear. Pulse-mode convection
should continue to dominate. Elevated PoPs are warranted thru
Monday night as the front inches closer.

Thickness trends are virtually flat over the weekend, though
Sunday`s max temp guidance is not as hot as that for Saturday;
given that and dewpoints expected to mix out into the upper 60s in
many locations, heat indices currently look to remain below 105 and
out of Heat Advisory territory. This trend continues into Monday.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 330 AM Sat: No major shake-up in the medium range fcst. Cold
front will enter the area in earnest on Tuesday, which will bring us
our best widespread precip chance of the period, gradually working
its way southeast of the region through midweek. An amplified
upper pattern will develop for the second half of the week, with
a deep blocking anticyclone centered over the southern Rockies,
and a couple of troughs swinging thru the East. Some PoPs will
continue to be warranted mainly over the southern CWFA invof the
stalling front, but fcst chances are slightly lower this cycle, with
the front being shown more progressive. We will experience below-
normal max temps thru Thursday, rising back to about normal on
Friday.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
At KCLT and elsewhere: A persistence fcst for today, with model
guidance once again suggesting that convective storms will be
widely scattered at best, but in reality will probably be more
numerous. Will employ at PROB30 at all sites for part of the
afternoon and early evening, however, the timing was pushed back
at several sites...mainly the Upstate...because of extensive low
stratus left behind by overnight convection. A light easterly flow
has pushed this low convective debris west across the Upstate and
northeast Georgia, which means we will begin with an IFR ceiling
restriction at those TAF sites. Fortunately, the low clouds should
lift and scatter by mid-morning, then the deep convection will
get going. Later this evening, expect more of the same.

Outlook: Scattered diurnal convection is expected Sunday, especially
over the mountains. Patchy mountain valley fog and low cigs remain
possible during the overnight and early morning hours. A transition
to a more active pattern may occur beginning Monday.

Confidence Table...

            11-17Z        17-23Z        23-05Z        05-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       Med   60%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       Med   60%     High 100%     High 100%     High 100%
KAND       Med   70%     High  95%     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
-- End Changed Discussion --

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Heat Advisory from noon today to 8 PM EDT this evening for
     NCZ036-037-056-057-069>072-082.
SC...Heat Advisory from noon today to 8 PM EDT this evening for
     SCZ009-014.

&&

$$
SYNOPSIS...SGL
NEAR TERM...PM
SHORT TERM...Wimberley
LONG TERM...Wimberley
AVIATION...PM