A cold front swept across Wyoming on the afternoon and evening of June 5th. With some additional upper level support from a vorticity maximum, thunderstorms developed across central Wyoming.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS RIW wrote it up.
A cold front swept across Wyoming on the afternoon and evening of June 5th. With some additional upper level support from a vorticity maximum, thunderstorms developed across central Wyoming. A couple of these storms become severe. Quarter size hail was reported near Evansville. In addition, very heavy rain fell with some of these storms and caused localized flash flooding along Webb Creek Road when Webb Creek overflowed it's banks.
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 5, 1:11 PM MST, 5 hours 9 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 211 PM MDT Mon Jun 5 2017 .SHORT TERM...(This evening through Thursday) Issued at 211 PM MDT Mon Jun 5 2017 Cold front pushing south through our central zones attm and this may set the stage for some strong evening thunderstorms over sern Fremont over into swrn Natrona. Sw winds ahead of the front to the south converge with the n winds in the Wind River Basin and e-ne winds moving swwd into swrn Natrona county leading to strong convergence where they meet over sern Fremont County this evening. Thunderstorms may also form and move off the south end of the Winds and meet up with these storm before they start moving off to the ne through Natrona County. We could get some late evening right entrance region jet support to keep these going as they move ne overnight. Other storms will be around central wyo but most will need upper support or orographic/convergence near the mtns to break the cap behind the front. On Tuesday, the front is stalled out near the swrn corner of Wyoming with some building cape over swrn Wyoming. We could also get some evening support from an approaching disturbance in the sw flow. A few stronger storms are possible in the sw late Tue/Tue evening. Several ripples in the flow including our Tuesday night one may keep some nocturnal showers going overnight Tuesday night into Wednesday morning before convection builds again Wednesday over the mountains with a few storms making it to the lower elevations. On Thursday, the ridge builds overhead with warming mid level temps and little or now convection. Maybe a few over the higher mountains, mainly north but the main focus will be very warm to hot again and breezy from the central zones westward. H7 temps could soar near or above 15C around the central basins late Thursday. 15C equates to around 90 at 5K feet. Combine that with some breezy afternoon winds and snowmelt will be rapid. This will continue into the medium-range period .LONG TERM...(Thursday night through Monday) Issued at 211 PM MDT Mon Jun 5 2017 Large scale upper-level low will approach the Pacific Northwest Coast Thursday night and Friday. Medium-range models in good agreement with the timing and location of this upper-low as we head through the weekend. Ahead of this feature, warm, windy pre-frontal southwest flow will be in place. 700mb temperatures will approach +16C, so basin temperatures in the 90s and mountain temperatures 65-75F are a good bet. The wind will work to boost highs a degree or two, so have increased Friday maximums. Have also adjusted winds upward several mph from model blended guidance, and it still may be windier than what is currently forecast. Combination of warm, windy conditions will provide another day for efficient snowmelt between 9K-10K feet. This will be the final push of water for now, as a cold front will track east across the forecast area Friday night. 700mb temperatures fall several degrees Saturday, especially across western Wyoming. Best chance for precipitation Friday night and Saturday will be across northwest Wyoming as the upper low moves into southern Alberta and impulses rotate northeast into Wyoming. Precipitation looks to be more widespread, particularly across the northwest and north, Sunday and Monday. ECMWF forecast for both Saturday and Sunday is more aggressive in bringing even cooler air across the forecast area. Regardless, there will be a 20-25 degree cool-down between Friday and Sunday. In fact, it will be cool enough late Saturday night and Sunday night for light snow to fall on the higher mountain peaks. Looks like the trough axis will shift east of our area for Monday with cooler northwest flow to prevail through Monday. This will favor the best chance of precipitation to remain across the northern-third of the state. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday) Issued at 211 PM MDT Mon Jun 5 2017 West of the Continental Divide...KBPI/KJAC/KPNA/KRKS Terminals VFR conditions are anticipated through 00Z/Wed. Ongoing convection will provide the best chance for thunder at KBPI and KPNA through 00Z-01Z/Tue. Could be some brief MVFR with localized convection along with occasional mountain top obscurations, mainly over the Wind River Range. Some showers will move off the Uinta Mountains and into Sweetwater County during the same time. KJAC will remain dry. A cold front east of the Continental Divide will backdoor into KRKS around 04Z/Tue providing a gusty east-northeast wind of 15-20kts. Diurnally and orographically driven convection possible over the western mountains Tuesday after 20Z. Main hazard would be gusty outflow wind to 35kts. East of the Continental Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals Conditions through the forecast period will remain VFR. Scattered showers and thunderstorms this afternoon and evening could produce small hail and gusty outflow wind to 40kts. Best chance will come around KCOD this afternoon and around KCPR late this afternoon and evening. Cold front pushing south through all terminals by 00Z/Tue will focus and enhance convection. Gusty north wind of 10-20kts will follow frontal passage. Some localized MVFR conditions possible during the 21Z/Mon to 03Z/Tue time frame in association with the strongest convection, particularly around KCPR. Mid-level cloud cover will linger overnight with showers persisting until around 12Z/Tue in the east. Convection late Tuesday will generally be tied to the terrain with little impact to the terminals. KCOD and KCPR would be the most likely candidates for isolated showers given their proximity to the higher terrain. && .FIRE WEATHER... Issued AT 211 PM MDT Mon Jun 5 2017 A cold front pushing south across the area will aid in some stronger evening thunderstorms for parts of central wyoming, mainly in eastern 283, 289 and southern 280. A chance of showers/storms will cover much of Central Wyoming into at least this evening. On Tuesday, scattered showers and thunderstorms will develop in the mountains with more isolated coverage across the lower elevations and mainly near and west of the divide. Mixing heights will only be fair to good east of the divide but generally very good west of the divide. On Wednesday, more scattered showers/thunderstorms will fire over the high country with a few more making it across the lower elevations with gusty wind. Thursday and Friday will see rapidly warming temperatures, increasing wind and lowering min rh's. Fire danger will increase significantly for the lower elevations of the central and southern district. && .RIW WATCHES/WARNINGS/ADVISORIES... Flood Watch through late Tuesday night for WYZ002-013-025-026. && SHORT TERM...Skrbac LONG TERM...Jones AVIATION...Jones FIRE WEATHER...Skrbac
Hazardous Weather Outlook National Weather Service Riverton WY 240 AM MDT Mon Jun 5 2017 WYZ001>020-022>030-061100- 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- 240 AM MDT Mon Jun 5 2017 ...Flood Watches and Warnings Covers Parts of Central and Western Wyoming... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight A few stronger thunderstorms are possible over central Wyoming this afternoon and evening, especially around Eastern Fremont, Johnson, and Natrona Counties. Area streams and rivers will remain high with flooding concerns continuing for some areas. .DAYS TWO THROUGH SEVEN...Tuesday through Saturday Tuesday...Isolated afternoon and evening thunderstorms. Wednesday and Thursday...Isolated afternoon and evening showers and thunderstorms. Thursday and Friday will see very warm temperatures again. This will increase snow melt in the higher mountain elevations and the likelihood of some flooding will exist once again. Saturday...A slight chance of afternoon thunderstorms in the west. A chance of snow above 9000 feet in Northwest Wyoming. Much cooler temperatures expected Saturday. .SPOTTER INFORMATION STATEMENT... Please report any flooding, or thunderstorm wind gusts over 50 mph, or hail.
Special Weather Statement National Weather Service Riverton WY 557 PM MDT MON JUN 5 2017 WYZ009-011-060045- Southeast Johnson County-Bighorn Mountains Southeast- 557 PM MDT MON JUN 5 2017 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN JOHNSON COUNTY UNTIL 645 PM MDT... At 554 PM MDT, Doppler radar was tracking a strong thunderstorm near Barnum, which is 13 miles west of Kaycee, moving east at 10 mph. Half inch hail, torrential rainfall in a short amount of time, and frequent lightning will occur with this storm. This strong thunderstorm will be near Kaycee around 645 PM MDT if it holds together. 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. 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 4349 10661 4349 10711 4377 10710 4382 10659 TIME...MOT...LOC 2357Z 268DEG 11KT 4368 10691 21
Special Weather Statement National Weather Service Riverton WY 601 PM MDT MON JUN 5 2017 WYZ007-009-020-060045- Owl Creek and Bridger Mountains-Bighorn Mountains Southeast-Natrona County Lower Elevations- 601 PM MDT MON JUN 5 2017 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN NATRONA COUNTY UNTIL 645 PM MDT... At 601 PM MDT, Doppler radar was tracking a strong thunderstorm 11 miles east of Lost Cabin Gas Plant, which is 36 miles east of Shoshoni, moving east at 10 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 northwestern Natrona County, including the following locations: Arminto. 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 4322 10751 4339 10743 4333 10704 4308 10716 TIME...MOT...LOC 0001Z 290DEG 9KT 4329 10738 21
Special Weather Statement National Weather Service Riverton WY 615 PM MDT MON JUN 5 2017 WYZ028-029-060100- Flaming Gorge-Rock Springs and Green River- 615 PM MDT MON JUN 5 2017 ...SIGNIFICANT WEATHER ADVISORY FOR WESTERN SWEETWATER COUNTY UNTIL 700 PM MDT... At 614 PM MDT, Doppler radar was tracking a thunderstorm near Little America, which is 7 miles southeast of Granger, moving east at 10 mph. Half inch hail and winds in excess of 40 mph will be possible with this storm. This strong thunderstorm will be near... Little America around 630 PM MDT. This includes Interstate 80 between mile markers 58 and 78. 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 4136 11004 4159 11005 4164 10968 4137 10965 TIME...MOT...LOC 0014Z 265DEG 9KT 4149 10990 21
Special Weather Statement National Weather Service Riverton WY 626 PM MDT MON JUN 5 2017 WYZ030-060115- East Sweetwater County- 626 PM MDT MON JUN 5 2017 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL SWEETWATER COUNTY UNTIL 715 PM MDT... At 623 PM MDT, Doppler radar was tracking a strong thunderstorm over Adobe Town Rim, which is 37 miles southwest of Wamsutter, moving east at 15 mph. This storm will remain mover rural south-central and southeast Sweetwater County. The main hazard from this storm will be torrential rainfall that could cause sudden rises of small streams and creeks including Alkali and Kinney Creeks. Also small hail, gusty winds to 45 mph, and frequent lightning will occur with this storm. 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. 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 4108 10870 4135 10872 4140 10812 4110 10812 TIME...MOT...LOC 0023Z 256DEG 11KT 4123 10842 21
Special Weather Statement
National Weather Service Riverton WY
644 PM MDT MON JUN 5 2017
WYZ011-060130-
Southeast Johnson County-
644 PM MDT MON JUN 5 2017
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN JOHNSON COUNTY UNTIL
730 PM MDT...
At 643 PM MDT, Doppler radar was tracking thunderstorms along a line
extending from 15 miles northeast of Mayoworth to 6 miles southwest
of Kaycee. Movement was east at 10 mph.
Winds in excess of 40 mph will be possible with these storms, along
with torrential rainfall.
This includes the city of Kaycee and Interstate 25 between mile
markers 243 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.
&&
LAT...LON 4411 10616 4379 10620 4357 10654 4360 10691
4377 10664 4405 10662
TIME...MOT...LOC 0043Z 266DEG 9KT 4396 10653 4378 10655 4366 10674
21Special Weather Statement National Weather Service Riverton WY 658 PM MDT MON JUN 5 2017 WYZ019-020-022-060230- Green Mountains and Rattlesnake Range-Casper Mountain-Natrona County Lower Elevations- 658 PM MDT MON JUN 5 2017 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN NATRONA COUNTY UNTIL 830 PM MDT... At 653 PM MDT, Doppler radar was showing developing showers and a few thunderstorms across the southeastern half of Natrona County including Casper and Casper Mountain. These showers and thunderstorms were moving very slowly, and have the potential to produce torrential rainfall in a short amount of time. This could cause sharp rises on small creeks, and could cause some flooding along small creeks, and in urban areas depending how long the rain lasts. PRECAUTIONARY/PREPAREDNESS ACTIONS... Torrential rainfall is also occurring, and may lead to localized flooding. Do not drive your vehicle through flooded roadways. && LAT...LON 4244 10742 4324 10608 4243 10608 TIME...MOT...LOC 0053Z 266DEG 9KT 4284 10644 21
The Riverton/Lander radar (KRIW), 184 km away, was scanning. The volume nearest the first event began at 01:22 UTC.
1 hail, 1 flash flood. Local standard time, as filed.
A trained spotter reported nickel to quarter size hail, two miles east-southeast of Evansville.
The Natrona County emergency manager reported heavy thunderstorm rain, causing Webb Creek to overflow on Webb Creek Road on the evening of June 5th.
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: 697583, 697584.