Flash Flood Warning 23, NWS Morristown, TN

Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
704 AM EDT Thu Jul 20 2023

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 336 AM EDT Thu Jul 20 2023

Key Messages:

1. Thunderstorms with locally heavy rainfall will impact central
and southern portions of the area this morning. A Flood Watch will
be issued.

2. Another round of showers and thunderstorms is expected late
tonight, but confidence is low.

Discussion:

A shortwave trough and jet streak over IL/IN will be dropping
southward into KY in the next few hours, with the LLJ strengthening
in response. Convection is expected to blossom around 09-12Z across
northern Middle TN and the Cumberland Plateau along a NW-SE axis,
extending into the central TN Valley. The main concern with these
storms will be heavy rainfall and flooding, due to the expected NW-
SE orientation of the convection and storm motion being about the
same direction. High PW and tall/skinny CAPE profiles in forecast
soundings point to efficient warm cloud processes and heavy
rainfall, but just a low-end threat of some strong downburst wind
gusts. FFG values for 1 hour are between 1.75-2 inches, and this
amount could be exceeded in an hour from training cells.
Therefore, a Flood Watch will be issued for parts of the Plateau
and central/southern TN Valley until 17Z.

Storms are expected to be tapering off in the early to mid
afternoon, but there is poor agreement among the CAMS on this, with
the HRRR alone in bringing a second MCS through the area late in the
afternoon. Most other models have storms moving south of the area
after the initial round, and the forecast will follow that trend,
with PoPs dropping off in the afternoon from north to south.
Similar to yesterday, the rain-cooled air mass and lingering
cloud cover will hold temperatures down below NBM guidance. Some
late day partial clearing is possible, but how much is uncertain.
Probably not enough to warm temps up to NBM numbers, so the
forecast will have highs mainly in the lower 80s in most spots.

Tonight, a cold front will be located along the OH Valley region,
pushing southward into KY. Convection along this front may start to
move into northern portions of the area late tonight, but with poor
model agreement, confidence is low. Will have a trend of PoPs rising
to the chance range between 06Z-12Z.

&&

.LONG TERM...
(Friday through Wednesday)
Issued at 336 AM EDT Thu Jul 20 2023

Key Messages:

1. Best chances for another round of heavy storms Friday afternoon
in the southern valley.

2. Frontal passage on Saturday brings drier air and a break from
widespread rainfall. Isolated chances for a shower or thunderstorm
next week primarily in high terrain.

Discussion:

Shortwave impulse moving in the flow will provide sufficient lift
for another round of showers and thunderstorms on Friday. Best
chances seem to be primarily south of Interstate 40, GFS and some of
the CAM guidance depicts a small MCS moving through southern
Tennessee from west to east Friday afternoon. Alternatively, the
Euro and NBM keep the storms south of Tennessee. Increased PoPs to
reflect the GFS/HRRR but low confidence in the outcome. Rain related
impacts will be dependent on how much rain has been received up
until then. QPF wise, a half inch is possible, greater amounts in
thunderstorms. Should the thunderstorm complex progress through
southern Tennessee, strong gusty winds would be possible given 1500
J of MLCAPE and marginally favorable lapse rates and DCAPE in the
GFS/HRRR depictions.

Heading into Saturday, the trough over the Great Lakes deepens, and
pushes a frontal boundary south through Tennessee. The front will
scour out the rich low level moisture, and effectively bring an end
to the daily monotonous risk of heavy storms. Early next week the
trough briefly stalls over us before the strong southwestern ridge
nudges eastward again and the trough lifts out. Best chances for
rain next week will be in the afternoon over high terrain. Low level
moisture will gradually increase but is forecast to remain in normal
summertime levels.

&&

.AVIATION...
(12Z TAFS)
Issued at 701 AM EDT Thu Jul 20 2023

Thunderstorms with heavy rain will affect TYS this morning. MVFR
conditions will be common, with IFR at times with heavier rain
showers. CHA has a chance of TSRA in the early afternoon, with
isolated to scattered coverage expected around TRI. VFR conditions
return to all sites in the late afternoon, followed by a
potential for low clouds to form overnight at TRI.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             86  72  90  69 /  50  30  60  40
Knoxville McGhee Tyson Airport, TN  82  71  87  68 /  80  40  40  30
Oak Ridge, TN                       83  70  87  65 /  80  40  40  30
Tri Cities Airport, TN              80  68  84  64 /  40  50  30  20

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Flood Watch until 1 PM EDT /noon CDT/ this afternoon for
     Anderson-Bledsoe-Blount Smoky Mountains-Campbell-Knox-
     Loudon-McMinn-Meigs-Morgan-Northwest Blount-Northwest
     Monroe-Rhea-Roane-Scott TN-Southeast Monroe.

VA...NONE.
&&

Hazardous Weather Outlook
National Weather Service Morristown TN
401 AM EDT Thu Jul 20 2023

NCZ060-061-TNZ012>018-035>047-067>074-081>087-098>102-VAZ001-002-
005-006-008-210815-
Cherokee-Clay-Scott TN-Campbell-Claiborne-Hancock-Hawkins-
Sullivan-Johnson-Morgan-Anderson-Union-Grainger-Hamblen-
Northwest Cocke-Cocke Smoky Mountains-Northwest Greene-
Southeast Greene-Washington TN-Unicoi-Northwest Carter-
Southeast Carter-Roane-Loudon-Knox-Jefferson-Northwest Blount-
Blount Smoky Mountains-North Sevier-Sevier Smoky Mountains-
Sequatchie-Bledsoe-Rhea-Meigs-McMinn-Northwest Monroe-
Southeast Monroe-Marion-Hamilton-Bradley-West Polk-East Polk-Lee-
Wise-Scott VA-Russell-Washington VA-
401 AM EDT Thu Jul 20 2023 /301 AM CDT Thu Jul 20 2023/

This Hazardous Weather Outlook is for portions of southwest North
Carolina...east Tennessee and southwest Virginia.

.DAY ONE...Today and Tonight

Showers and thunderstorms are expected to develop and move into
the Cumberland Plateau and central Tennessee Valley this morning.
These storms will be capable of producing heavy rainfall, which
may lead to flash flooding. Strong wind gusts may also be possible
with a few storms.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Showers and thunderstorms are expected primarily for the southern
Tennessee valley Friday afternoon. These storms will be capable
of heavy rainfall, which may lead to isolated flooding.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed today and Friday.

<!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>

<!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>