Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 191449

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1049 AM EDT FRI AUG 19 2016

Warm and humid conditions will continue into this weekend within
lingering subtropical high pressure. A cold front will push in from
the northwest late Sunday bringing cooler and drier air to the
region for the first half of next week.


As of 1045 AM EDT...isolated showers will continue this morning with
deeper convection holding off until this afternoon. In fact, the
latest mesoscale guidance is in agreement on a later initiation than
previous days. Still expect decent forcing today as a short wave,
that is producing convection over Middle TN, moves into the area
this afternoon. This will be in addition to some upper divergence.
Forecast soundings show around 2 inches of PW over the area with
little mid level drying. Guidance and soundings show moderate
instability expected, although delayed due to the convective debris
retarding heating this morning. DCAPE will also be lower than the
past few days, but not non-existent. Therefore, expect the overall
severe threat should be low today, but cannot rule out isolated
damaging downbursts. Locally heavy rainfall will probably be the
greater threat, but storms should generally move enough to prevent
more than isolated flash flooding. Despite the slow start, highs
will be about 2-4 degrees above normal, with low 90s across most of
the Piedmont.

Tonight...Convection should gradually wane late this evening, but at
isolated showers could continue. Will be another muggy night under
plenty of mid and high cloudiness and some patchy fog, especially in
the mountain valleys. Lows will continue to be a few degrees above


As of 3:15 AM EDT Friday: The short term part of the forecast on
Saturday features a rather zonal looking H5 flow during the day,
with both the GFS and NAM showing ripples of energy riding along
this H5 wave train. Meanwhile the surface pattern has some flavor of
an old front or boundary in the area which will also help focus
thunderstorms. PW`s by both the NAM and GFS rise to near or over 2.0
inches. As a result we would expect another round or two of storms,
with likely POPS in the mountains and solid chances elsewhere.

The H5 trough digging into the middle part of the country Saturday
night will begin to back the mean flow. Isentropic upglide on
Saturday night, combined with deep moisture, will signal
precipitation hanging on a bit longer than the usual diurnal cycle.

As the deep upper trough swings through the Ohio/Tennessee Valleys
and the Great Lakes, a fairly decent cold front will sweep across
our forecast area Sunday and Sunday evening. We would expect more
thunderstorms, perhaps somewhat organized, considering a slight
uptick in shear, and instability still in place. We will have to
keep an eye out during this time particularly.

Perhaps less of a diurnal temperature cycle as well during this
period with high temperatures tempered by clouds and precipitation
both during the day and at night.


As of 3:15 AM Friday: It appears high pressure, both at the surface
and aloft, will settle across the southeast early in the work week.
Longer range models, at least at the onset, suggest cooler
temperatures and dry conditions.

Later in the week, high pressure slipping off the eastern seaboard,
may tend to drive some moisture into the Upper Savannah Valley, and
parts of the western Carolinas - from the Atlantic and eastern Gulf
of Mexico.

We start to notice POPS edging back toward climatology, as a result
we will run some lower POPS probably on Thursday in parts of our
western forecast area.

Meanwhile, we are in the ballpark with current guide temperatures,
which seem to be clustered around each other.


At higher level clouds move out, some lower CU beginning
to develop. Do not expect a cig, but MVFR bases could develop before
lifting to VFR into the afternoon. Later today, another round of
scattered SHRA and TSRA is expected to develop across the area. The
latest high-res models are in decent agreement on convection
starting in the mountains around midday, then tracking east into the
Piedmont late afternoon and early evening. So have timed a TEMPO for
TSRA from 21-24z. Winds and favor a SW direction, increasing
slightly during the afternoon.

Elsewhere: Similar conditions to KCLT, but with more of a chance of
cigs this morning or early afternoon. As with KCLT above, the main
concern will be another round of scattered SHRA and TSRA across the
area. All sites have VCTS and/or PROB30 this afternoon/early
evening. High-res models agree that most of the activity will start
midday in the mountains, and then shift east across the Piedmont
late afternoon into early evening. Tonight looks similar to last
night with patchy fog and stratus around under debris cloudiness and
light winds.

Outlook: Scattered to numerous showers and thunderstorms are
expected across the region again on Saturday. A cold front will push
in from the northwest on Sunday, enhancing the chance for
convection. Much drier air will filter in behind the front Monday,
resulting in fair weather through midweek.

Confidence Table...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       Med   77%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High  88%     High 100%     Low   52%
KHKY       Med   77%     High 100%     High 100%     High  91%
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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