A thunderstorm developed east of the Absarokas and became severe as it moved into the Wind River Basin. The storm dropped up to quarter size hail in and around Ethete.
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The episode as NWS RIW wrote it up.
A thunderstorm developed east of the Absarokas and became severe as it moved into the Wind River Basin. The storm dropped up to quarter size hail in and around Ethete.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Riverton, WY wrote its last area forecast discussion before the first event at Jun 29, 11:59 AM MST, 46 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1259 PM MDT Thu Jun 29 2017 .SHORT TERM...(This evening through Sunday) Issued at 100 PM MDT Thu Jun 29 2017 Most of the southwest will remain dry and windy tonight with colder temperatures moving in as a cold front moves through. To the north over and near the mountains, as a rather strong and cold upper level low pressure trough moves across the area through this evening, thunderstorms with hail, heavy rain and strong wind gusts will move through the area. Mostly showers with some snow down to 7500 feet is expected after midnight through early morning with colder air. Friday will be colder with some showers and isolated thunderstorms lingering over the area. Drying and warming will occur through the weekend with high pressure building over the area. .LONG TERM...(Sunday night through Thursday) Issued at 100 PM MDT Thu Jun 29 2017 Big picture shows our mean summer sern U.S. ridge building and expanding northwest towards the middle of next week. Threat of some very warm to hot weather will be in the forecast with this pattern. The only thing that could temper it somewhat is the potential for the ring of fire to get started by Tuesday (GFS) or Wednesday (Euro) to get some clouds and mainly late day showers/tstms going. Rather significant differences on where our high will set up between the GFS and ECMWF. ECMWF is further east fitting the GFS 5-wave pattern while the GFS builds the high nwd all the way into srn Wyoming Wednesday and Thursday. Leaning more towards a Euro type solution which fits the bigger picture longwave pattern. At the beginning of this period, a ewd moving shortwave is moving east across the area with some gusty showers and thunderstorms into Sunday night. GFS is much slower with this system lingering the trough into Monday. After that all the guidance generally agrees that the ridge will build nwd into our area Tuesday with considerable warming with h7 temps warming in the GFS and ECMWF into the 15 to 19C range across much of the area. That would push temps into the 90s east of the divide (upper 90s in the Bighorn Basin) and mainly 80s west of the divide with 60s and 70s in the mountains and little chances of pcpn. On Wednesday, we expect the upper ridge to start moving/developing ewd with a hot, sw flow over our area. Models showing just minimal mid level moisture moving n around the upper high leading in a few high based late day thunderstorms, mainly over and near the mountains Wednesday and Thursday. However, the GFS keeps the high centered over and just south of us (so does the GEM) while the Euro is much further east. As of now, the end result still looks hot with minimal thunderstorm chances. At least 90s east of the divide (maybe some 100+ in the Bighorn Basin) with 80s west of the divide. It is July in a couple days! && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 100 PM MDT Thu Jun 29 2017 Scattered to numerous showers and thunderstorms will impact the northern and central sections through this evening before tapering off and ending late. It will be quite windy as a cold front moves south across the area enhanced by the convection. There could also be brief periods of MVFR/IFR conditions in any convection. The convection is expected to end from northwest to southeast in the evening with possibly some lingering activity across Johnson/Natrona Counties after 06Z. Winds are expected to decrease, and become variable in most areas east of the Divide between 02Z and 06Z. Also low freezing levels could be an issue with icing for aviation going over the mountains. Friday will be dry with vfr conds. Across southwest Wyoming, a drier airmass will be present with little or no convection expected along and southwest of KBPI-40NE RKS. However breezy westerly winds will be observed. A cold front is expected to slide southwest/west across Sweetwater County during the evening shifting winds to northeast/east, but remaining dry. Friday will be dry with vfr conds and less wind. && .FIRE WEATHER... Issued AT 100 PM MDT Thu Jun 29 2017 Most of the southwest will remain dry and windy tonight with colder temperatures moving in as a cold front moves through. To the north over and near the mountains, as a rather strong and cold upper level low pressure trough moves across the area through this evening, thunderstorms with hail, heavy rain and strong wind gusts will move through the area. Mostly showers with some snow down to 7500 feet is expected after midnight through early morning with colder air. Friday will be colder with some showers and isolated thunderstorms lingering over the area. Drying and warming will occur through the weekend with high pressure building over the area. Mixing heights and transport winds will be favorable for very good to excellent smoke dispersal in the afternoons and evening through the weekend. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...Baker LONG TERM...Skrbac AVIATION...Skrbac FIRE WEATHER...Baker
Hazardous Weather Outlook National Weather Service Riverton WY 245 AM MDT Thu Jun 29 2017 WYZ001>020-022>030-301100- 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- 245 AM MDT Thu Jun 29 2017 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Today...Isolated to widely scattered thunderstorms across northern and central Wyoming. Some storms may be strong across portions of central Wyoming, producing wind gusts in excess of 40 mph and small hail in the afternoon and evening. .DAYS TWO THROUGH SEVEN...Friday through Wednesday Friday and Saturday...Isolated thunderstorms across extreme northwest. Sunday and Sunday night...A slight chance of thunderstorms over the region. Monday through Wednesday...Isolated afternoon and evening thunderstorms mainly over and near the mountains. .SPOTTER INFORMATION STATEMENT...Please report wind damage or gusts in excess of 50 mph and hail of penny size or larger.
Special Weather Statement
National Weather Service Riverton WY
1248 PM MDT THU JUN 29 2017
WYZ017-018-291915-
Wind River Basin-Lander Foothills-
1248 PM MDT THU JUN 29 2017
...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL FREMONT COUNTY UNTIL 115
PM MDT...
At 1247 PM MDT, Doppler radar was tracking a strong thunderstorm near
Winkleman Dome, which is 8 miles north of Fort Washakie, moving east
at 20 mph.
Half inch hail and winds in excess of 40 mph will be possible with
this storm along with very heavy rain.
This strong thunderstorm will be near...
Winkleman Dome around 1255 PM MDT.
Fort Washakie around 105 PM MDT.
Ethete around 115 PM 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.
If on or near area lakes and streams, get out of the water and move
indoors or inside a vehicle. Remember, lightning can strike out to
10 miles from the parent thunderstorm. If you can hear thunder, you
are close enough to be struck by lightning. Move to safe shelter
now! Do not be caught on the water in a thunderstorm.
Persons in campgrounds should consider seeking sturdy shelter until
this storm passes.
&&
LAT...LON 4323 10903 4322 10863 4289 10878 4301 10903
4302 10902 4302 10905 4303 10907 4304 10905
4305 10905 4304 10909 4307 10912
TIME...MOT...LOC 1847Z 289DEG 16KT 4312 10899
13Special Weather Statement National Weather Service Riverton WY 102 PM MDT THU JUN 29 2017 WYZ011-291930- Southeast Johnson County- 102 PM MDT THU JUN 29 2017 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN JOHNSON COUNTY UNTIL 130 PM MDT... At 102 PM MDT, Doppler radar was tracking a strong thunderstorm over Kaycee, moving east at 15 mph. Half inch hail and winds in excess of 40 mph will be possible with this storm. This includes Interstate 25 between mile markers 241 and 259. 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 4362 10670 4379 10666 4379 10627 4352 10634 TIME...MOT...LOC 1902Z 279DEG 13KT 4370 10659 13
Special Weather Statement National Weather Service Riverton WY 104 PM MDT THU JUN 29 2017 WYZ012-014>016-291930- Wind River Mountains West-Upper Wind River Basin-Wind River Mountains East-Teton and Gros Ventre Mountains- 104 PM MDT THU JUN 29 2017 ...SPECIAL WEATHER STATEMENT... At 104 PM MDT, Doppler radar was tracking a strong thunderstorm 7 miles west of Union Pass, which is 19 miles west of Dubois, moving east at 15 mph. Half inch hail and winds in excess of 30 mph will be possible with this storm. This strong thunderstorm will be near... Union Pass around 130 PM MDT. Other locations impacted by this storm include Crooked Creek Guest Ranch. LAT...LON 4340 11011 4358 11012 4364 10974 4337 10973 TIME...MOT...LOC 1904Z 267DEG 13KT 4350 11002 13
Special Weather Statement National Weather Service Riverton WY 120 PM MDT THU JUN 29 2017 WYZ007-017-291945- Owl Creek and Bridger Mountains-Wind River Basin- 120 PM MDT THU JUN 29 2017 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL HOT SPRINGS AND EAST CENTRAL FREMONT COUNTIES UNTIL 145 PM MDT... At 119 PM MDT, Doppler radar was tracking a strong thunderstorm 14 miles west of Boysen State Park Headquarters, which is 15 miles northeast of Pavillion, moving southeast at 20 mph. Very strong outflow winds over 50 mph are also expected ahead of the actual thunderstorm. Half inch hail and wind gusts up to 50 mph will be possible with this storm. This storm will remain over mainly rural areas of south central Hot Springs and east central Fremont Counties, including the following locations: Midvale, Owl Creek Kampgrounds, Boysen U S Bureau Of Reclamation Power Plant, Boysen State Park and Pavillion Natural Gas Processing Plant. 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. To report severe weather, contact your nearest law enforcement agency. They will relay your report to the National Weather Service office in Riverton. && LAT...LON 4326 10868 4359 10842 4343 10806 4310 10829 TIME...MOT...LOC 1919Z 299DEG 16KT 4340 10845 13
Special Weather Statement
National Weather Service Riverton WY
135 PM MDT THU JUN 29 2017
WYZ011-292000-
Southeast Johnson County-
135 PM MDT THU JUN 29 2017
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN JOHNSON COUNTY UNTIL
200 PM MDT...
At 135 PM MDT, Doppler radar was tracking a strong thunderstorm near
Linch, which is 16 miles east of Kaycee, moving southeast at 30 mph.
Half inch hail and winds in excess of 40 mph will be possible with
this storm.
This strong thunderstorm will be near...
Linch around 145 PM MDT.
Other locations impacted by this storm include Sussex.
LAT...LON 4349 10606 4349 10627 4357 10646 4373 10636
4366 10602 4350 10602
TIME...MOT...LOC 1935Z 292DEG 26KT 4363 10632
13Special Weather Statement
National Weather Service Riverton WY
143 PM MDT THU JUN 29 2017
WYZ007-017-292015-
Owl Creek and Bridger Mountains-Wind River Basin-
143 PM MDT THU JUN 29 2017
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN HOT SPRINGS AND EAST
CENTRAL FREMONT COUNTIES UNTIL 215 PM MDT...
At 143 PM MDT, Doppler radar was tracking a strong thunderstorm 12
miles west of Cottonwood Pass, which is 21 miles northeast of
Shoshoni, moving east at 10 mph.
Half inch 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 east central Fremont Counties.
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 4335 10757 4337 10791 4355 10793 4356 10786
4355 10786 4357 10784 4355 10783 4357 10782
4360 10766 4358 10764 4359 10761 4348 10760
4348 10759
TIME...MOT...LOC 1943Z 264DEG 8KT 4347 10782
13The Riverton/Lander radar (KRIW), 24 km away, was scanning. The volume nearest the first event began at 19:43 UTC.
1 hail. Local standard time, as filed.
There were numerous reports of hail across the Wind River Reservation from Ethete to near around Fort Washakie. The largest report was southeast of Arapahoe where hail of quarter size was reported.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2017Every state in 2017This day in weather historyWarnings in Wyoming, June 2017
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 699178.