Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
227 PM EDT Tue Aug 7 2018

.SYNOPSIS...
Weak high pressure will persist over the area into Wednesday. Then
a cold front will approach from the northwest and settle just
southeast of the area by Thursday. Seasonally warm temperatures and
scattered to numerous afternoon and evening showers and
thunderstorms will continue through the end of the week. The front
will persist in the vicinity through the weekend, with deeper
moisture returning from the south.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 220 PM: A seasonably weak pressure field exists over the
Southeast, with a lobe of the Bermuda High extending onshore, while
a trough extends down the northern half of the Eastern Seaboard. A
corresponding low-amplitude upper ridge is present overhead, with
light southwesterly winds. Dewpoints remain exceptionally high at
many obs sites, in the lower to mid 70s, but may mix out a bit in
the next couple of hours. As has occurred the past couple of days,
SBCAPE values have shot up past 2500 J/kg, and storms fired over
the mountain ridges around noon. The CAMs depict scattered coverage
propagating slowly east into the Piedmont thru the afternoon,
but weak shear and steering flow should limit how much so. DCAPE
values are marginally high where coverage will be the greatest,
and a couple severe storms could occur, mainly producing damaging
microbursts if so.

Flat upper ridging will prevail over the region tonight into
Wednesday. As the upper trough advects east the flow becomes more
zonal, but heights do not fall appreciably across the Carolinas
or north Georgia. Low-level flow thus responds little and remains
west-southwesterly. In advance of the cold front moving thru the
Ohio/Tenn valleys, the trough east of the mountains does become a
bit better defined during the day Wed. Lapse rates manage to improve
a wee bit, and under slightly warmer sfc conditions, SBCAPE values
are progged to be a little higher at peak heating Wed. Given the
trough and better instability, we will advertise likely PoPs over
the mountains and chance values in the Piedmont. Height contours do
become a little better packed aloft tomorrow, and accordingly 0-6km
and 0-3km shear are slightly better. However, those are not strong
enough to suggest a significant enhancement to severe threat beyond
that posed by the large SBCAPE and marginally strong sfc-midlevel
delta-theta-E. Max temps will be normal across most of the area,
but perhaps a category above in the lower Piedmont zones.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 210 pm Tuesday: Broad upper trough will remain in place across
much of the East through the period, with attendant weak frontal
zone and associated deep moisture plume expected to ooze into the
forecast area through the end of the week. As such, very typical
mid-summer weather is expected to end the week, with much of the
area expected to see near-normal temps and near-climo pops for
primarily diurnal convection through the period. A possible
exception to this trend will be the NC mtns, particularly closer to
the TN border, where pops are advertised in the 50-60% range Thu and
Fri afternoon/evening to account for potential impacts from
convection developing along the frontal zone across the TN Valley
and wandering into the southern Appalachians by the end of the day.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 145 PM EDT Tuesday: An upper trough will close off into a low
over the Great Lakes over the weekend. The models are in decent
agreement on the depth and position of the low, but the GFS is just
a little SW of the ECMWF and more elongated N-S. Overall, the
differences do not have much impact on our sensible weather
forecast. A frontal boundary will remain draped across the
Southeast, from the Arklatex region thru the I-85 corridor of the
Carolinas. This should be a focus for enhanced convective coverage
thru the weekend, still mostly diurnally driven. The upper low will
quickly pivot NE and allow another front to drop in from the NW.
This front should push thru by Tuesday and bring some drier air into
the CWFA. The highest PoPs look to be Sunday and Monday, with
possibly a dry day on Tuesday. Temps will be near to slightly below
normal for afternoon highs, but still above normal for overnight
lows due to the expected enhanced moisture across the area. The 12z
Guidance doesn't seem to be hinting at much of a widespread heavy
rain threat. Although, isolated excessive rainfall/flooding will be
possible thanks to our we antecedent conditions.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Isolated to scattered TSRA across the region
this aftn into early evening in a typical mid-summer regime. The
chance is small enough to mention as VCSH/VCTS today, except at
KAVL due to its proximity to the rugged terrain. Light SW winds are
mainly expected except at KAVL where they will tend to be a bit more
NW. Any storm will be capable of gusty outflows and brief WSHFTs,
though the risk of strong to severe wind is small. Following the
dissolution of diurnal convection, the main concerns tonight will
be IFR mountain valley fog and patchy MVFR fog in the Piedmont,
though impacts are expected to be relatively brief and close
to daybreak. TSRA chances are a bit better at all sites on Wed,
after noon.

Outlook: Typical mid-summer conditions are fcst the next several
days. Diurnal, scattered thunderstorms will continue mainly
in the afternoons, with coverage tending to increase toward the
weekend. Associated morning restrictions will be possible each day,
especially in mountain valleys.

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  97%     High 100%
KAVL       High 100%     High 100%     High  94%     High  94%
KHKY       High 100%     High 100%     High  97%     High 100%
KGMU       High 100%     High 100%     High  88%     High 100%
KAND       High 100%     High 100%     High  94%     High  94%

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...ARK
NEAR TERM...Wimberley
SHORT TERM...JDL
LONG TERM...ARK
AVIATION...Wimberley

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
502 AM EDT Tue Aug 7 2018

NCZ033-048>053-058-059-062>065-501-503-505-507-509-080915-
Avery-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Graham-
Northern Jackson-Macon-Southern Jackson-Transylvania-Henderson-
Caldwell Mountains-Burke Mountains-McDowell Mountains-
Rutherford Mountains-Polk Mountains-
502 AM EDT Tue Aug 7 2018

This Hazardous Weather Outlook is for the mountains of western North
Carolina.

.DAY ONE...Today and tonight.

Scattered thunderstorms will develop this afternoon and evening. Any
of these thunderstorms may produce cloud-to-ground lightning, locally
heavy rainfall, and briefly gusty winds.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Thunderstorm coverage will increase from Wednesday onward, especially
during the afternoon and evening periods. Primary impacts will
include cloud-to-ground lightning, heavy rainfall, and gusty winds.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ010-017-018-026-028-029-NCZ035>037-056-057-068>072-082-502-504-
506-508-510-SCZ001>014-019-080915-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Alexander-Iredell-
Davie-Catawba-Rowan-Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-
Union-Greater Caldwell-Greater Burke-Eastern McDowell-
Greater Rutherford-Eastern Polk-Oconee Mountains-Pickens Mountains-
Greenville Mountains-Greater Oconee-Greater Pickens-
Greater Greenville-Spartanburg-Cherokee-York-Anderson-Abbeville-
Laurens-Chester-Greenwood-
502 AM EDT Tue Aug 7 2018

This Hazardous Weather Outlook is for northeast Georgia, Upstate
South Carolina, and the foothills and piedmont of western North
Carolina.

.DAY ONE...Today and tonight.

Isolated to scattered thunderstorms will develop this afternoon and
evening. Any of these thunderstorms may produce cloud-to-ground
lightning, locally heavy rainfall, and briefly gusty winds.

In addition, Heat Index values will rise to between 95 and 100
degrees for much of the area this afternoon. |

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Thunderstorm coverage will increase from Wednesday onward, especially
during the afternoon and evening periods. The main impacts will
include cloud-to-ground lightning, heavy rainfall, and gusty
winds.

Heat Index values of 95 to 100 will be likely once again on Wednesday
and Thursday. A few lower piedmont locations may see values as high
as 102 on Wednesday afternoon.

.SPOTTER INFORMATION STATEMENT...

None.

HG

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>