Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 161747

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
147 PM EDT Sat Jun 16 2018

Hotter high pressure will gradually build atop the region through
the middle of next week. Mainly scattered afternoon and evening
thunderstorms are expected each day, mainly over the mountains. A
cold front may arrive from the north toward the end of next week.


As of 1025 AM...Skies are mostly clear with some sct cirrus high
above the area. All of the fog/low stratus has dissipated over the
mtn valleys over the past few hours. Interestingly, a deck of low
stratus has persisted over Rowan, Cabarrus, and Union Counties since
early this morning and is just now starting to dissipate. It has
remained just east of CLT and is not expected to directly impact the
city. Otherwise, an upper trough will shift east off the East Coast
today, as a large ridge builds in across the region. At the sfc and
in the low-levels, an axis of high pressure will also shift east,
allowing a light southeasterly flow to set up atop the CWA. This
will bring a return of a little more moisture, and guidance is in
good agreement that most of the forecast area will be more unstable
this aftn than yesterday. So PoPs increase into the high-end CHC to
even some likelies in the mountains, favoring the southern and
eastern escarpment (where convergence will be maximized). The
Upstate and NE GA will also see better coverage today. The NC
Piedmont will closest to the sfc high and will see just isolated to
widely scattered convection. Severe storms will be possible, in the
usual summertime pulse mode. Locally damaging winds and hail up to
quarter-sized looks possible. Temps will be similar to yesterday`s
readings, one to two categories above normal, along with slightly
more humidity.

Tonight, convection should wane during the late evening hours, with
clearing skies and patchy fog developing in the mountain valleys and
areas that received rain. Min temps will be about a 5-8 degrees
above normal.


As of 320 am Saturday: An upper ridge will become increasingly
dominant over the Southeast during the short term, meaning that heat
will become the main weather story during at least the first half of
the new week. Max temps in the lower to mid 90s and mins in the
lower to mid 70s appear likely across the Piedmont and much of the
foothills through the period. In terms of the Heat Advisory
potential, forecast soundings generally appear well-mixed, while
forecast mean boundary layer dewpoints (typically a good indicator
of the surface dewpoint mixing potential) are in the mid/upper 60s
both afternoons. As such, we should fall well short of any advisory
concerns on Sunday, while even Monday`s forecast is only offering a
smattering of ~100 maximum Heat Indices. The heat may become more of
a concern during the medium range.

In terms of the convective potential, despite the overall
unfavorable synoptic setup, forecast soundings are quite unstable
and generally uncapped both afternoons. Thus, the thermodynamic
situation will be conducive to initiation of convection due due to
differential heating/ridge top convergence, and 40-50 pops are
carried across the mountains both days. Steering flow will be
extremely weak, generally 5 kts or less, thus little movement of
convection into the foothills can be expected, although small pops
are carried both afternoons to account for cells firing on outflow
boundaries. A handful of severe downbursts from pulse storms, and
locally heavy/perhaps excessive rainfall owing to very slow cell
movement are possible each day.


As of 335 am Saturday: At least the first half of the medium range
will offer little more than a continuation of the short term, only a
little hotter (widespread high temps in the mid 90s through Wed,
with some upper 90s likely across portions of the Piedmont) with
perhaps more in the way of Heat Advisory concerns. While the highest
diurnal convective chances will remain over the high terrain,
increasing prominence of a lee/thermal trough should result in
slightly improved chances across the foothills and Piedmont Tue and
Wed. The global models continue to struggle to reach a consensus
regarding the evolution of the synoptic pattern across the East
during the latter half of the week, as the GFS drops a frontal zone
into the area by Thursday, while the ECMWF maintains the boundary
well to our north. Nevertheless, all guidance sources suggest
improving chances for diurnal convection during the latter half of
the week (albeit for varying reasons), so pops will be advertised at
levels slightly higher than climo Thu through Fri.


At KCLT and elsewhere: Expect predominately VFR conditions thru
the 18z TAF period. The only restrictions I have included are a
few hours of MVFR visby at KAVL tomorrow morning. Some convective
cells have begun to develop SW of KAVL over the past hour or so,
therefore I included a TEMPO for TSRA and reduced visby from 19
to 22z for KAVL. Overall convective coverage is expected to be
greater than yesterday, but still mostly confined to the mountains
and portions of the SC Upstate. Convection should wane this evening
as winds become light and mainly out of the south. Winds are expected
to remain SLY to SWLY tomorrow as well with convective potential
similar to today, if not a bit more widespread.

Outlook: Typical summertime potential for diurnally-driven showers
and thunderstorms will persist into early next week. Some morning fog
will also be possible in the mountain valleys and over lakes each day.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     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       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:




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