Severe Thunderstorm Warning 45, NWS Riverton, WY

Area Forecast Discussion
National Weather Service Riverton WY
148 PM MDT Thu Jul 4 2019

.SHORT TERM...This afternoon through Friday
Issued at 1051 AM MDT Thu Jul 4 2019

Atmosphere starting to percolate this afternoon, as local
temperatures begin to reach the convective temperature. Good shear
and CAPE values around 1500 bring a threat for strong to severe
thunderstorms through midevening. Main threat is large hail, but
isolated tornadoes are also a threat early this evening.

Axis of the H5 trough sweeps toward Wyoming overnight, adding a
final surge of midlevel lift to the region. Showers and a few
thunderstorms are expected to redevelop and spread northeastward
overnight, mainly for west Wyoming. As the vort rotates through
to the northeast Friday morning, and few lingering showers and
thunderstorms could be continuing across the far northern zones
into the early afternoon. Activity should be ending south to north
through the day.

.LONG TERM...Friday night through Wednesday
Issued at 1051 AM MDT Thu Jul 4 2019

Showers and thunderstorms will linger in the north and east Friday
night as a shortwave moves out of the area. This activity should
will dissipate quickly after midnight. With continued southwesterly
flow, areas of south and southwest Wyoming will stay in a drier
airmass on Saturday, with relative humidities dropping into the
teens. By Sunday the low humidities will spread throughout southern
and central Wyoming. Gusty winds will help to elevate fire weather
conditions at times through the weekend, especially on Sunday
afternoon when winds will increase in response to a tightening
pressure gradient. Additionally, temperatures will warm Saturday
onward as stronger southwest flow advects a warmer airmass into the
area. There still looks to be enough forcing and moisture for
continued rain chances during the weekend but most areas should
remain dry. Warmer temperatures will continue into next week, with
continued afternoon rain chances mainly across the north as weak
shortwave move through Montana.

&&

.AVIATION...For the 18Z TAFS through 18Z Friday afternoon
Issued at 1051 AM MDT Thu Jul 4 2019

Thunderstorm activity will be on the increase this afternoon for
all TAF sites, except maybe RKS. First wave of thunderstorms still
looking to happen between now and 01z. A another shortwave sweeps
toward Wyoming this evening, another round of showers and
isolated thunderstorms is expected to develop roughly around
midnight, impacting all locations. This wave will sweep to the
northeast on Friday, leaving most areas mostly clear. A few
lingering thunderstorms may develop on the higher elevations of
the Big Horn and Absaroka ranges, possibly drifting toward
COD/WRL/BYG during the afternoon.

&&

.FIRE WEATHER...
Issued AT 1051 AM MDT Thu Jul 4 2019

Isolated to scattered thunderstorms will occur over much of the area
this afternoon and evening. Some thunderstorms could be severe with
large hail, high winds, along with torrential rainfall with the
greatest risk across the southern Bighorn Basin, Fremont, Natrona,
and S. Johnson counties. The highest fire weather conditions this
afternoon will be in southeast Sweetwater County with RHs in the mid
to upper teens and southwesterly winds about 20 mph gusting to
around 30 mph. On Friday, drier conditions are expected over the far
west and southwest. Winds will be gusty but not over the critical
threshold. Thunderstorms are expected again over the rest of the
area.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SHORT TERM...Straub
LONG TERM...Hulme
AVIATION...Straub
FIRE WEATHER...Hulme

Hazardous Weather Outlook
National Weather Service Riverton WY
448 AM MDT Thu Jul 4 2019

WYZ001>020-022>030-051200-
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-
448 AM MDT Thu Jul 4 2019

This Hazardous Weather Outlook is for Western and Central Wyoming.

.DAY ONE...Today and Tonight.

Isolated to scattered thunderstorms. Some storms could be severe
especially across the southern Bighorn Basin, Fremont County,
Natrona County, southern Johnson County and surrounding mountains.
Large hail will be the primary hazard, but damaging winds and an
isolated tornado could occur.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Friday...Isolated to scattered thunderstorms over the north and
east.

Saturday...Strong thunderstorms are possible over the north and
east.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

TEAM RIVERTON

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Special Weather Statement
National Weather Service Riverton WY
424 PM MDT Thu Jul 4 2019

WYZ005>007-042300-
Owl Creek and Bridger Mountains-Southeast Big Horn Basin-Southwest
Big Horn Basin-
424 PM MDT Thu Jul 4 2019

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN HOT SPRINGS AND
CENTRAL WASHAKIE COUNTIES UNTIL 500 PM MDT...

At 424 PM MDT, Doppler radar was tracking a strong thunderstorm near
Lucerne, which is 10 miles northeast of Thermopolis, moving northeast
at 20 mph.

Nickel size hail and winds in excess of 40 mph will be possible with
this storm.

This storm will remain over mainly rural areas of southeastern Hot
Springs and central Washakie Counties.

A Severe Thunderstorm Watch remains in effect until 1000 PM MDT for
central Wyoming.

LAT...LON 4358 10818 4388 10824 4391 10773 4365 10757
TIME...MOT...LOC 2224Z 245DEG 18KT 4372 10803

Hulme

Special Weather Statement
National Weather Service Riverton WY
431 PM MDT Thu Jul 4 2019

WYZ005-007-042315-
Owl Creek and Bridger Mountains-Southwest Big Horn Basin-
431 PM MDT Thu Jul 4 2019

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN HOT SPRINGS COUNTY
UNTIL 515 PM MDT...

At 431 PM MDT, Doppler radar was tracking a strong thunderstorm near
Hot Springs State Park, which is near Thermopolis, moving east at 20
mph.

Half inch hail and winds in excess of 30 mph will be possible with
this storm.

This storm will remain over mainly rural areas of southeastern Hot
Springs County.

A Severe Thunderstorm Watch remains in effect until 1000 PM MDT for
central Wyoming.

LAT...LON 4346 10831 4358 10834 4364 10819 4359 10817
      4362 10783 4346 10781
TIME...MOT...LOC 2231Z 261DEG 19KT 4356 10818

Hulme

Special Weather Statement
National Weather Service Riverton WY
445 PM MDT Thu Jul 4 2019

WYZ020-042315-
Natrona County Lower Elevations-
445 PM MDT Thu Jul 4 2019

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL NATRONA COUNTY UNTIL 515
PM MDT...

At 444 PM MDT, Doppler radar was tracking a strong thunderstorm over
Powder River, which is 35 miles west of Casper, moving east at 25
mph.

Half inch hail and winds in excess of 30 mph will be possible with
this storm.

This strong thunderstorm will be near...
  Goldeneye Reservoir around 515 PM MDT.

Other locations impacted by this storm include Natrona.

A Severe Thunderstorm Watch remains in effect until 1000 PM MDT for
central Wyoming.

LAT...LON 4291 10708 4309 10710 4315 10664 4288 10663
TIME...MOT...LOC 2244Z 267DEG 20KT 4301 10699

Straub

Special Weather Statement
National Weather Service Riverton WY
446 PM MDT Thu Jul 4 2019

WYZ007-017-042315-
Owl Creek and Bridger Mountains-Wind River Basin-
446 PM MDT Thu Jul 4 2019

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN FREMONT COUNTY UNTIL
515 PM MDT...

At 446 PM MDT, Doppler radar was tracking a strong thunderstorm 9
miles northeast of Pavillion, moving east at 25 mph.

Nickel size hail and winds in excess of 30 mph will be possible with
this storm.

This storm will remain over mainly rural areas of northeastern
Fremont County.

A Severe Thunderstorm Watch remains in effect until 1000 PM MDT for
central Wyoming.

LAT...LON 4319 10878 4330 10880 4350 10831 4347 10830
      4346 10819 4328 10811
TIME...MOT...LOC 2246Z 251DEG 22KT 4333 10854

Hulme