A combination of heavy rain, snow melt and a clogged culvert resulted in flooding near the Highway 16 bridge along Ten Sleep Creek. Several campgrounds were flooded.
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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 combination of heavy rain, snow melt and a clogged culvert resulted in flooding near the Highway 16 bridge along Ten Sleep Creek. Several campgrounds were flooded. The water got close the top of the bridge but never topped it.
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 May 23, 9:46 PM MST, 3 hours 14 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1046 PM MDT Wed May 23 2018 .SHORT TERM...(This evening through Saturday) Issued at 123 PM MDT Wed May 23 2018 Main circulation center is finally lifting nwd into srn MT with significant wraparound rain/snow continuing in the northwest. Snow level was as low as 7500 feet in YNP with Lake Yellowstone snowing all morning long. Pcpn amounts from this system were substantial in the north half with 1 to 2 inches in the nrn Bighorns (2.99 at Rock Creek) with two-thirds to around an inch in the srn Bighorns. The Cody Foothills received widespread 1"+ amounts with local 1.50". The Dubois to Crowheart area received .60 to .70. Anderson Ridge on the west side of South Pass received almost 2 inches. Rain and some higher elevation snow will continue in the northwest into this evening before gradually decreasing. There will be a few tstms out and about into early this evening, especially in the sern zones where an area of 500+ 100mb ML CAPE is brewing along with storms already. Even the far north has some building CAPE so we're not quite done yet. The far nrn part of Johnson County has some potential for a few stronger storms with convergence around nearby sfc low. Slight risk covers the a tiny part of nern Johnson. On Thursday, we start to see shortwave ridging but low level moisture and daytime heating will start to fire storms over the mountains. A weak disturbance may get the far west going by late morning (possibly). More substantial ridging moves in Friday for continued warming and dry for all but a few mountain locations. On Saturday, the future Memorial Day storm begins to dig into NV. It is currently out near 36N/135W. In the short term period, the main effect from this system (besides the pre-storm warmup) will be the threat of thunderstorms in the west Saturday. We see the cyclonic nose of the jet moving nwd into swrn WY Saturday along with the first shortwave lifting nwd across wrn WY. A few of these storms could be quite strong. One other area could be nrn Johnson if the frontal boundary hangs in across the area. This is showing up more on the NAM than the GFS. The weather just deteriorates after this period the remainder of the Memorial Day weekend but more on that below. .LONG TERM...(Saturday night through Wednesday) Issued at 123 PM MDT Wed May 23 2018 Saturday night into Sunday morning a Pacific Low will move across Northern Nevada/Utah headed towards Southern Wyoming. Widespread shower and thunderstorm activity should be expected through Sunday and into Monday. Temperatures will cool slightly with the increased cloud cover. GFS indicates the highest rain amounts could be in Southern Big Horn Basin where a significant amount of rain has already fallen and flooding issues are already a concern. As the low progresses over Wyoming Monday expect more showers and thunderstorms through the day, but coverage should be more isolated. The low will be to the east by Tuesday but showers and afternoon thunderstorms will linger in and around the mountainous areas. Wednesday will see weak ridging and dryer weather. && .AVIATION...(For the 06Z TAFS through 06Z Friday) Issued at 1040 PM MDT Wed May 23 2018 West of the Continental Divide...KJAC/KBPI/KPNA/KRKS Isolated showers will occur overnight. Patchy fog will be possible in the valleys with IFR conditions until 15Z. Isolated showers and storms will form after 18Z and continue through 03Z Fri. Local MVFR conditions will occur with thunderstorms along with wind gusts up to 30 knots. Mountains will be obscured at times. East of the Continental Divide...KCPR/KCOD/KRIW/KLND/KWRL Isolated showers will occur overnight. Patchy fog is possible in the basins until 15Z with IFR conditions. Isolated shower or storms will occur over the north after 19Z and continue through 03Z Fri. Local MVFR conditions will occur with thunderstorms along with wind gusts up to 30 knots. Mountains will be obscured at times. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .FIRE WEATHER... Issued AT 123 PM MDT Wed May 23 2018 After the showers gradually wind down in the northwest, the overall Thursday into Friday will show a considerable drying and warming trend. There will still be a good chance of showers and thunderstorms Thursday in the northwest though but otherwise, most areas will be dry Thursday through Friday. Temperatures will become quite warm with 60s and 70s across the lower elevations Thursday and 70s to 80s Friday. Min rh's will dry out by Friday but most areas will still be in the 20 to 30 percent range except for 279 where min rh's could drop to around 15 percent or less Friday afternoon. There will be some breezy areas Thursday from Rock Springs to Casper and in the lee of the mountain ranges. Less wind is expected Friday. Mixing and smoke dispersal will range from very good to excellent on Thursday and generally good to very good Friday except excellent in the southeast part of the district. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && SHORT TERM...Skrbac LONG TERM...Hulme AVIATION...AR FIRE WEATHER...Skrbac
Hazardous Weather Outlook National Weather Service Riverton WY 229 AM MDT Wed May 23 2018 WYZ001>020-022>030-241100- 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- 229 AM MDT Wed May 23 2018 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Isolated afternoon and evening thunderstorms; most numerous in northern and western Wyoming. Localized flooding possible. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Thursday...A chance of afternoon and evening thunderstorms over and near the mountains. Saturday...Isolated afternoon and evening thunderstorms in the west. Sunday and Memorial Day...Scattered mainly afternoon and evening thunderstorms most areas. Isolated strong to severe thunderstorms possible on Sunday across central Wyoming. .SPOTTER INFORMATION STATEMENT... Spotters are urged to report hail, wind gusts past 45 mph and any flooding. Thank you.
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
Washakie County sheriff deputies reported flooding around the Ten Sleep Creek bridge along Highway 16. The water flooded several campsites. The water also got close to surface of the bridge but never topped it.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2018Every state in 2018This day in weather historyWarnings in Wyoming, May 2018
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: 749610.