Severe Thunderstorm Warning 110, NWS Riverton, WY

Area Forecast Discussion
National Weather Service Riverton WY
129 PM MDT Sat Aug 18 2018

.SHORT TERM...This evening through Tuesday

This mornings cold front and the associated band of showers,
continues its exit over Johnson and Natrona counties. Although skies
had quickly cleared behind these showers, clouds (and additional
showers) have already begun to develop over the Absarokas and Wind
River Mountains. Unfortunately, smoke has also already begun to
filter back in from the west.

Showers and storms will continue to develop over the western
mountains this afternoon. Most of this convection will be along and
north of the Divide, including Yellowstone National Park. These
storms will move from northwest to southeast over these portions
east of the Divide. With the clearing conditions, cooler
temperatures aloft and residual low level moisture, there will be
enough instability for strong storms in these areas this afternoon.
Hail and strong gusty winds will be the main threats with these
storms. Elsewhere, isolated thunderstorms will be possible.

Despite the high (middle to upper 40s/low 50s) dewpoints across
southern and southwestern portions this morning, have opted to issue
a Red Flag Warning across southern portions of the forecast area.
Guidance continues to keep RH at critical values, so coupled with
the expected gusty west-northwest winds this afternoon and isolated
thunderstorms, felt better to issue a warning.

As storms weaken this evening, showers will be confined east of a
Cody-to-Casper line due to wrap around moisture from the upper low.
Gusty northerly winds will aid in advecting drier air over northern
and eastern portions. At the same time, the overnight showers will
begin to end from north to south. Additional showers and possibly
thunderstorms will redevelop over the northern and central
mountains Sunday afternoon.

Models continue to resolve a shortwave moving over western portions
Monday afternoon, bringing the next round of showers and
thunderstorms to the area. Some of this activity could linger
overnight Monday night.

.LONG TERM...Tuesday night through Saturday

Next shortwave to our west will be weakening and shearing apart with
minimal energy remaining over our area to start the period. Cold
front pushing south Tuesday may keep a focus of some storms in
mainly our south half into Tuesday evening. The parent trough will
likely be pushed back towards us from the west late in the day
Wednesday into Wednesday night with an increasing threat of showers
and thunderstorms spreading into the west by Wednesday night. As
this shortwave weakens and moves across us Thursday, there will
be some marginal instability east of the Divide, especially ern
third for some thunderstorms. Another weak wave may skim the area
Friday, but with limited moisture/forcing. A few storms could
fire off the Uintas and hit srn Sweetwater County. A stronger
system is expected to move into the Pacific Northwest Saturday
with an increasing sw flow over our area ahead of the associated
cold front. Some limited moisture will be drawn nwd into the swrn
zones with a little better chance of some storms forming over the
nrn UT mtns and moving into our swrn zones. It will be warm to
quite warm through the period with mostly 80s east of the Divide
Wed and Fri with a few more 90s possible Thursday and especially
Saturday with the increasing sw flow.

&&

.AVIATION...For the 00Z TAFS through 00Z Monday

A strong weather system will bring areas of gusty to strong west
through north wind and areas of showers and thunderstorms into
Sunday morning. The best chance for thunderstorms will be across the
northwest and along and east of the divide including KCOD, KWRL,
KLND, KRIW and KCPR. Showers and strong north wind will continue
overnight around Johnson County including KBYG down to around KCPR.
MVFR conds due to low cigs are expected between 08z and 14z from
KBYG to KCPR. On Sunday, a few morning showers will occur between
KBYG and KCPR. Otherwise, expect only isolated afternoon showers in
and near the mountains Sunday with VFR conds after the morning low
clouds lift

&&

.FIRE WEATHER...

...RED FLAG WARNING IN EFFECT FOR SOUTHWESTERN WYOMING THIS
AFTERNOON...

Showers with isolated embedded thunderstorms will be confined east
of the Divide, with the best chances over the Bighorns, Johnson
and Natrona counties. Winds will quickly weaken by sunset and
begin to turn more northerly. With this turn, winds will remain
gusty tonight across Johnson County and eastern portions of the
Bighorn Basin. Temperatures will be 5 to 10 degrees cooler across
the area tonight. RH values will be 20 to 30 percent higher from
281 to northeast portions of 279, and 20 to 40 percent lower over
414, 277, 278 and western portions of 279.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for WYZ277>279.

&&

SHORT TERM...LaVoie
LONG TERM...Skrbac
AVIATION...Skrbac
FIRE WEATHER...LaVoie

Hazardous Weather Outlook
National Weather Service Riverton WY
1048 AM MDT Sat Aug 18 2018

WYZ001>020-022>030-191700-
Yellowstone National Park-Absaroka Mountains-Cody Foothills-
North Big Horn Basin-Southwest Big Horn Basin-
Southeast Big Horn Basin-Owl Creek and Bridger Mountains-
Bighorn Mountains West-Bighorn Mountains Southeast-
Northeast Johnson County-Southeast Johnson County-
Teton and Gros Ventre Mountains-Jackson Hole-
Wind River Mountains West-Wind River Mountains East-
Upper Wind River Basin-Wind River Basin-Lander Foothills-
Green Mountains and Rattlesnake Range-
Natrona County Lower Elevations-Casper Mountain-Star Valley-
Salt River and Wyoming Ranges-Upper Green River Basin Foothills-
Upper Green River Basin-South Lincoln County-
Rock Springs and Green River-Flaming Gorge-East Sweetwater County-
1048 AM MDT Sat Aug 18 2018

...RED FLAG WARNING FOR SOUTHERN AND SOUTHWESTERN WYOMING THIS
AFTERNOON AND EVENING...

This Hazardous Weather Outlook is for Western and Central Wyoming.

.DAY ONE...Today and Tonight.

Isolated to widely scattered thunderstorms, mainly in the
afternoon and evening. Increasing west to northwest winds will
quickly drop relative humidity values to critical values over
portions of southern Lincoln, southern Sublette and Sweetwater
counties this afternoon. Please see Red Flag Warning for details.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Sunday...Isolated afternoon thunderstorms East of the Divide,
especially in northern Wyoming.

Monday through Wednesday...Isolated to locally scattered
thunderstorms.

.SPOTTER INFORMATION STATEMENT...

Spotters are urged to report winds past 45 mph and hail. Thank you.

Special Weather Statement
National Weather Service Riverton WY
236 PM MDT SAT AUG 18 2018

WYZ019-026-028-182100-
Upper Green River Basin-Green Mountains and Rattlesnake Range-Rock
Springs and Green River-
236 PM MDT SAT AUG 18 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL SWEETWATER COUNTY
UNTIL 300 PM MDT...

At 236 PM MDT, Doppler radar was tracking a strong thunderstorm 7
miles east of Farson, moving east at 25 mph.

Dime size hail and wind gusts up to 50 mph will be possible with this
storm.

This strong thunderstorm will be near...
  Killpecker Dune Field around 250 PM MDT.
  Boars Tusk around 255 PM MDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 4204 10942 4221 10934 4214 10889 4189 10901
TIME...MOT...LOC 2036Z 289DEG 21KT 4211 10929

TL

<!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>