Severe Thunderstorm Warning 36, NWS Riverton, WY

Area Forecast Discussion
National Weather Service Riverton WY
439 AM MDT Thu Jul 4 2019

.SHORT TERM...(Today and tonight)
Issued at 427 AM MDT Thu Jul 4 2019

An mid-upper level shortwave trough over the Pacific Northwest/N.
Great Basin will gradually push east into the Intermountain West
today, before gradually lifting northeast across Wyoming tonight
into Friday morning. The synoptic lift associated with this
shortwave trough overspreading an unstable atmosphere will result
in scattered thunderstorms. Strong to severe thunderstorms are
possible over much of the area this afternoon and evening, with
the best chance for severe thunderstorms across the Wind River
Basin, Natrona, S. Bighorn Basin, S. Johnson County and
surrounding mountains. In this area CAPE is projected to be 1000
to 2000 j/kg with decent amount of shear. Large hail will be the
main hazard with damaging winds and an isolated tornado possible.
The strongest activity is expect to push out by around 9 PM, but
some convection will likely linger through the overnight hours and
could cause issues with firework shows tonight.

.LONG TERM...(Friday through Wednesday)
Issued at 427 AM MDT Thu Jul 4 2019

Showers and thunderstorms will continue on Friday, mainly across the
northern half of Wyoming, as a shortwave moves out of the area. With
continued southwesterly flow, areas of south and southwest Wyoming
will stay in a drier airmass through the period, with relative
humidities dropping into the teens and 20s. Gusty winds will add 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 after Friday 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 north.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 427 AM MDT Thu Jul 4 2019

Showers and isolated thunderstorms will occur through 14Z. Areas of
low clouds producing MVFR to IFR ceilings will occur east of the
continental divide through 18Z. Scattered showers and thunderstorms
will develop over the region between 19Z and 21Z. This activity will
continue through 03Z Friday with lingering showers east of the
continental divide through 06Z Fri. Local MVFR conditions will occur
with the stronger storms this afternoon and evening.

&&

.FIRE WEATHER...
Issued AT 427 AM MDT Thu Jul 4 2019

Some showers and even isolated thunderstorm over the north and
eastern zones will exit or dissipate by mid-morning. 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. On Friday, drier conditions are expected
over the far west and southwest, but thunderstorms are expected
again over the rest of the area.

&&

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

&&

SHORT TERM...Murrell
LONG TERM...Myers
AVIATION...Ross
FIRE WEATHER...Murrell

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

Special Weather Statement
National Weather Service Riverton WY
1237 AM MDT Thu Jul 4 2019

WYZ011-020-040715-
Southeast Johnson County-Natrona County Lower Elevations-
1237 AM MDT Thu Jul 4 2019

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN JOHNSON AND
NORTHEASTERN NATRONA COUNTIES UNTIL 115 AM MDT...

At 1237 AM MDT, Doppler radar was tracking a strong thunderstorm near
Midwest, which is 23 miles southeast of Kaycee, moving northeast at
35 mph.

Penny size hail will be possible with this storm.

This strong thunderstorm will be near...
  Linch around 1255 AM MDT.

This includes Interstate 25 between mile markers 230 and 233.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4349 10604 4349 10608 4347 10608 4336 10627
      4349 10644 4383 10601 4373 10602 4351 10602
TIME...MOT...LOC 0637Z 226DEG 30KT 4348 10629

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Special Weather Statement
National Weather Service Riverton WY
246 AM MDT Thu Jul 4 2019

WYZ017-040915-
Wind River Basin-
246 AM MDT Thu Jul 4 2019

...SPECIAL WEATHER STATEMENT...

At 243 AM MDT, Doppler radar was tracking a thunderstorm pushing
across Riverton, moving northeast at 40 mph.

The main hazard will be torrential rainfall. A quarter to half an
inch of rainfall could occur in less than 30 minutes. This will
cause ponding on area roads, and possibly minor flooding in low-
lying or poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4295 10829 4306 10849 4320 10830 4311 10807
TIME...MOT...LOC 0846Z 218DEG 49KT 4307 10833

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Special Weather Statement
National Weather Service Riverton WY
259 AM MDT Thu Jul 4 2019

WYZ017-040930-
Wind River Basin-
259 AM MDT Thu Jul 4 2019

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL FREMONT COUNTY UNTIL
330 AM MDT...

At 258 AM MDT, Doppler radar was tracking a strong thunderstorm 13
miles north of Sand Draw, which is 14 miles southeast of Riverton,
moving northeast at 35 mph.

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

This strong thunderstorm will be near...
  Moneta around 330 AM MDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4283 10811 4296 10828 4314 10819 4329 10789
      4315 10766
TIME...MOT...LOC 0858Z 226DEG 31KT 4295 10812

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Special Weather Statement
National Weather Service Riverton WY
454 AM MDT Thu Jul 4 2019

WYZ009-011-020-041200-
Southeast Johnson County-Bighorn Mountains Southeast-Natrona County
Lower Elevations-
454 AM MDT Thu Jul 4 2019

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN JOHNSON AND NORTH
CENTRAL NATRONA COUNTIES UNTIL 600 AM MDT...

At 453 AM MDT, Doppler radar was tracking thunderstorms along a line
extending from near Mayoworth to 7 miles west of Red Wall.
Movement was east at 20 to 30 mph.

Pea size hail and winds in excess of 40 mph will be possible with
these storms.

Strong thunderstorms will be near...
  Mayoworth around 500 AM MDT.
  Red Wall around 515 AM MDT.
  Kaycee around 525 AM MDT.
  Fort Reno Historical Site around 600 AM MDT.

Other locations impacted by these storms include Barnum.

This includes Interstate 25 between mile markers 232 and 266.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

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

&&

LAT...LON 4391 10617 4331 10647 4331 10717 4387 10689
TIME...MOT...LOC 1053Z 272DEG 18KT 4380 10684 4338 10705

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