Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1054 AM EDT Fri Aug 13 2021

.SYNOPSIS...
A stormy pattern will persist over the area into this weekend, with
scattered if not numerous showers and thunderstorms developing each
afternoon. Temperatures will remain above normal through Saturday.
Cooler but still rainier weather will arrive Sunday with a stalling
cold front and possibly the remnants of Tropical Storm Fred Monday
night into Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1035 AM:  Per the latest SPC mesoanalysis, the atmosphere has
already become moderately unstable late this morning...and sbCAPE is
likely well on its way to exceeding 3000 J/kg in most areas by the
time of peak afternoon heating. Congestus...and even a shower or two
has already been observed along the higher ridges of northeast GA
and southwest NC, and expect scattered deep convective coverage in
these areas by early afternoon. Meanwhile, signals are mixed
regarding coverage of showers and storms across the lower
elevations, with guidance from the latest GFS exhibiting forecast
soundings that are not especially hospitable to deep convection
(high LFCs and a decent amount of CIN), while NAM soundings are
considerably more favorable. The incoming 12Z convection-allowing
models continue to be none-too-excited about development southeast
of the Blue Ridge. All things considered, the inherited PoP forecast
of 40-60% across the mountains, 30% across the foothills, and slight
chance across the Piedmont appears to be in pretty good shape.

The biggest threat with deeper updrafts will be a few strong/
possibly severe microbursts as the sub-cloud layer remains quite dry
and llvl lapse rates steepen. Winds will remain aligned sw/ly with
low end gusts possible occasionally. Very good insol will be had and
along with llvl WAA, max temps will be able to reach a cat or so abv
normal. Thus, muggy conds will continue as sfc td/s are maintained
in the u60s to arnd 70 F. Mins tonight will also remain a few
degrees abv normal.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 303 AM EDT Friday: The weekend looks like a transition
into a more wet period as a sfc boundary drifts southward
and stalls under a confluent nearly-zonal flow aloft by late
Saturday or early Sunday. We will initially lack much in the
way of mid/upper forcing on Saturday, but the approach of the
sfc boundary from the north will help to trigger/focus deep
convection in the afternoon. Expect a gradient in precip prob
between a categorical over the higher terrain and a chance over
the southeastern fringe. Saturday might be the last day of the
period when the threat for severe storms outranks the threat for
heavy rain because we should still have some residual mid-level dry
air and dCAPE in the boundary layer in the afternoon. High temps
should top out on the warm side of normal. This will change as the
boundary stalls Saturday night. Convective precip production may
continue well into the overnight hours and moisture will begin
to pool across the region. The combination of low level focus,
deep moisture, and the injection of some vorticity moving up
from the south should allow for widespread showers and storms
in the afternoon. Precipitable water will rise to 2 inches or
slightly higher on Sunday afternoon/night. A deep warm cloud
layer and slow storm motion seen on NAM fcst soundings suggest
an increasing heavy rain/flash flooding threat. At this point,
it is too early to entertain any watches, however. High temps
should be below normal on Sunday because of the extensive cloud
cover. Precip chances should continue through Sunday night as the
sfc boundary effectively slides to the south of the fcst area. An
upper ridge amplifying over the Northeast will temporarily hold
a sfc high over New England, allowing the sfc ridge to poke down
east of the mtns overnight. Although the sfc high should be weak,
guidance shows a nascent cold air damming wedge setting up over
the fcst area by daybreak on Monday, supported by low level warm
advection/isentropic upglide over the shallow cool air mass.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 330 AM EDT Friday: By sunrise Monday, model guidance suggests
that a summertime cold air damming wedge will be established across
the region, with temps remaining in the 70s during the day. Deep
tropical moisture is poised to run up from the south ahead of
the circulation associated with Fred. Pattern recognition points
toward a favorable setup for heavy rain during the first half of the
week. What remains to be seen is exactly how what remains of Fred
will interact with the old frontal boundary. Some of the latest
guidance shows Fred weakening inland long before it would make it
this far north, but at that point it might be academic. Even if
the circulation of Fred was washed out, we would still probably
have all the ingredients we need for heavy rain, including very
high PW, deep warm cloud, and a persistent low level southeast
upslope flow from Monday into Wednesday. The GFS solution seems
anemic compared to the more robust ECMWF, which would support a
QPF more toward the high side of the range of solutions. All that
being said, we still have several model cycles to consider before
we need to put anything in motion. Eventually, by late in the week,
we should transition back to a more diurnal summer pattern.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: High pressure has allowed sfc winds to become
calm most locales this morning and will anticipate lowering CIGs and
VSBY into MVFR/IFR, mainly across KAVL and KHKY before daybreak. With
the recent rainfall, have TEMPO LIFR/VLIFR conds as well for the
same sites. Expect another convec afternoon, however, the latest
hires models indicate less coverage likely than the past few days.
Existing and/or newly formed outflow bndrys will provide focusing
zones near or at all terminals, so will maintain PROB30 -TSRA thru
the afternoon period. With a llvl lee trof developing, winds will
remain aligned sw/ly to w/ly with occasional low-end gusts
possible.

Outlook: Diurnal convection remains in the fcst for the rest of
the week and into the weekend. Fog and low stratus will be possible
each morning, especially over mountain valleys and areas primed by
rainfall from the previous evening.

Confidence Table...

            15-21Z        21-03Z        03-09Z        09-12Z
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%     Med   67%
KHKY       High 100%     High 100%     High 100%     High  83%
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 are available at
the following link:

www.weather.gov/gsp/aviation

&&

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

&&

SYNOPSIS...MPR
NEAR TERM...JDL/SBK
SHORT TERM...PM
LONG TERM...PM
AVIATION...SBK

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
618 AM EDT Fri Aug 13 2021

NCZ033-048>053-058-059-062>065-501>510-141030-
Avery-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Graham-
Northern Jackson-Macon-Southern Jackson-Transylvania-Henderson-
Caldwell Mountains-Greater Caldwell-Burke Mountains-Greater Burke-
McDowell Mountains-Eastern McDowell-Rutherford Mountains-
Greater Rutherford-Polk Mountains-Eastern Polk-
618 AM EDT Fri Aug 13 2021

This Hazardous Weather Outlook is for western North Carolina.

.DAY ONE...Today and tonight.

Scattered thunderstorms will develop across the North Carolina
mountains and foothills this afternoon. Along with cloud to ground
lightning, a couple of these storms could become quite strong and
produce large hail and damaging outflow winds.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

The remnants of tropical cyclone Fred may interact with an old
frontal boundary to produce heavy rainfall early next week.
Altogether, an increasing threat of localized flash flooding is
expected over the coming days, especially in areas that receive
multiple rounds of heavy rainfall.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ010-017-018-026-028-029-NCZ035>037-056-057-068>072-082-SCZ001>014-
019-141030-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Alexander-Iredell-
Davie-Catawba-Rowan-Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-
Union NC-Oconee Mountains-Pickens Mountains-Greenville Mountains-
Greater Oconee-Greater Pickens-Greater Greenville-Spartanburg-
Cherokee-York-Anderson-Abbeville-Laurens-Union SC-Chester-Greenwood-
618 AM EDT Fri Aug 13 2021

This Hazardous Weather Outlook is for northeast Georgia, piedmont
North Carolina and upstate South Carolina.

.DAY ONE...Today and tonight.

Isolated thunderstorms will develop across the Piedmont of the
Carolinas and northeast Georgia this afternoon. The main threat will
be cloud to ground lightning.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

The remnants of tropical cyclone Fred may interact with an old
frontal boundary to produce heavy rainfall early next week.
Altogether, an increasing threat of localized flash flooding is
expected over the coming days, especially in areas that receive
multiple rounds of heavy rainfall.

.SPOTTER INFORMATION STATEMENT...

None.

Krentz

<!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>