A pair of thunderstorms moved across central Fremont County and produced hail in different locations. Off duty National Weather Service employees reported up to nickel size hail around Riverton.
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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 pair of thunderstorms moved across central Fremont County and produced hail in different locations. Off duty National Weather Service employees reported up to nickel size hail around Riverton.
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 Jul 25, 1:08 PM MST, 1 hour 20 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 208 PM MDT Wed Jul 25 2018 .SHORT TERM...This evening through Thursday Much cooler temperatures this afternoon, after last night cold front. Also, skies are a bit hazy as smoke from fires in N CA and S OR have infiltrated over the region as the upper level flow has become more E-W orientated. Thunderstorms could be strong to severe this afternoon and evening over Hot Springs, Washakie, Fremont and Natrona counties. Cape values of 1000 to 1500 J/kg, bulk shear 30 to 40kt, sfc dewpoints in the upper 40s to lower 50s and sfc winds from the northeast to east are in place this afternoon. Otherwise, the storm threat will subside by 06Z, with isolated showers trending northeast toward 12Z Thursday. Temperatures will remain cooler Thursday, with isolated to widely scattered thunderstorms remaining confined to areas east of the Divide. Some storms could be strong to severe again, as similar conditions will once again be in place. Areas west of the Divide will remain dry, while critical fire weather conditions could be in place across southern zones. RH values will drop to the middle teens, with wind gusts of 25 mph possible. A Red Flag Warning may be needed and will let the next shift have another look, before issuing any highlights. .LONG TERM...Thursday night through Wednesday Somewhat active weather looks to continue through the first period of the longer range, followed by a quieter period. Convection will be ongoing Thursday night, before becoming more isolated at night. Like previous days, the main concentration will be across northern and eastern portions of the county warning area with gradually tapering POPs further south and west. Friday is also looking rather active. The Storm Prediction Center has a slight risk not too far east of the area. We will also have some extra lift with a decent cold front that will be sliding across the area. The best forcing and moisture will likely remain over eastern Wyoming, but some could try to creep back westward, especially into Natrona and Johnson County. Definitely something to watch. There will be one more day of the thunderstorms for Saturday, with a shortwave sliding across the state. Again, the best chance will be in northern Wyoming to the north of the divide with gradually decreasing chances south and west. With less moisture over the area, we should see a decrease in coverage of thunderstorms for Sunday, especially if the GFS is right. For now, we kept some POPS over the mountains but most areas should be rain free. Monday through Wednesday at this point look seasonably warm to hot and mainly dry, with ridging building over the state. There is some QPF over the mountains, but this could be the models overdoing the orographic lift. The best chance of any precipitation in this period would likely be Tuesday as a weak shortwave could be moving through, but timing of these features in questionable at best this far out. && .AVIATION...For the 00Z TAFS through 00Z Friday Showers and thunderstorms will become isolated to widely scattered by this evening, with showers ending over KCPR by 07z. A few strong to severe storms (wind gusts over 40kts, hail, and brief heavy rain) possible along a vicinity KDUB- KRIW- KCPR line through 04z Thursday, with brief MVFR/IFR conditions possible. Isolated showers will remain possible over NE portions 07z - 14z. Isolated to widely scattered thunderstorms will remain east of the Divide Thursday afternoon. && .FIRE WEATHER... Temperatures tonight will mainly be slightly cooler. RH values will also generally be higher, except far western zones, which will be 5 to 15 percent lower. A few strong to severe thunderstorms will be possible through 04Z east of the Divide. Otherwise, showers and thunderstorms will end across the area by 07Z. Temperatures Thursday will once again be slightly cooler, with RH values approaching critical values across the southern zones. Thus, a Red Flag Warning may be needed for zones 277 and 279. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...LaVoie LONG TERM...Hattings AVIATION...LaVoie FIRE WEATHER...LaVoie
Hazardous Weather Outlook National Weather Service Riverton WY 200 AM MDT Wed Jul 25 2018 WYZ001>020-022>030-261100- 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- 200 AM MDT Wed Jul 25 2018 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight Isolated to locally scattered thunderstorms, especially along and east of the Continental Divide in East Central Wyoming. Some storms will likely contain small hail and wind gusts at and above 45 mph. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday Thursday afternoon through Saturday night...Scattered thunderstorms, especially along and east of the Continental Divide. Sunday...Isolated afternoon and evening thunderstorms along and east of the divide. .SPOTTER INFORMATION STATEMENT... Spotters urged to report wind gusts past 45 mph and hail size. Thank you. TEAM RIVERTON
Special Weather Statement National Weather Service Riverton WY 144 PM MDT WED JUL 25 2018 WYZ002-005-007-017-252015- Owl Creek and Bridger Mountains-Wind River Basin-Southwest Big Horn Basin-Absaroka Mountains- 144 PM MDT WED JUL 25 2018 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN HOT SPRINGS AND NORTH CENTRAL FREMONT COUNTIES UNTIL 215 PM MDT... At 143 PM MDT, Doppler radar was tracking a strong thunderstorm 8 miles northwest of Anchor Dam, or 31 miles south of Meeteetse, moving southeast at 30 mph. Half inch hail and winds in excess of 30 mph will be possible with this storm. This strong thunderstorm will be near... Anchor Dam around 200 PM MDT. PRECAUTIONARY/PREPAREDNESS ACTIONS... 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 4367 10928 4388 10911 4373 10848 4339 10867 TIME...MOT...LOC 1943Z 293DEG 30KT 4371 10898 Hattings
Special Weather Statement National Weather Service Riverton WY 211 PM MDT WED JUL 25 2018 WYZ002-007-016-017-252100- Owl Creek and Bridger Mountains-Wind River Basin-Upper Wind River Basin-Absaroka Mountains- 211 PM MDT WED JUL 25 2018 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN HOT SPRINGS AND CENTRAL FREMONT COUNTIES UNTIL 300 PM MDT... At 210 PM MDT, Doppler radar was tracking a strong thunderstorm near Anchor Dam, or 27 miles northwest of Pavillion, moving southeast 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 southwestern Hot Springs and central Fremont Counties. PRECAUTIONARY/PREPAREDNESS ACTIONS... 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. 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 4360 10921 4378 10892 4355 10847 4330 10887 TIME...MOT...LOC 2010Z 310DEG 17KT 4361 10891 Hattings
Special Weather Statement National Weather Service Riverton WY 248 PM MDT WED JUL 25 2018 WYZ007-017-252115- Owl Creek and Bridger Mountains-Wind River Basin- 248 PM MDT WED JUL 25 2018 ...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL HOT SPRINGS AND NORTHEASTERN FREMONT COUNTIES UNTIL 315 PM MDT... At 247 PM MDT, Doppler radar was tracking a strong thunderstorm 13 miles north of Pavillion, moving southeast at 25 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 south central Hot Springs and northeastern Fremont Counties, including the following locations... Midvale and Pavillion Natural Gas Processing Plant. LAT...LON 4340 10880 4359 10858 4337 10815 4312 10846 TIME...MOT...LOC 2047Z 306DEG 21KT 4343 10862 Hattings
Special Weather Statement National Weather Service Riverton WY 314 PM MDT WED JUL 25 2018 WYZ017-252200- Wind River Basin- 314 PM MDT WED JUL 25 2018 ...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL FREMONT COUNTY UNTIL 400 PM MDT... At 314 PM MDT, Doppler radar was tracking a strong thunderstorm 13 miles southwest of Boysen State Park Headquarters, or 15 miles east of Pavillion, moving southeast at 30 mph. Nickel size hail and winds in excess of 40 mph will be possible with this storm. This strong thunderstorm will be near... Shoshoni and Hidden Valley around 340 PM MDT. Other locations impacted by this storm include Midvale, Pavillion Natural Gas Processing Plant and Bonneville. PRECAUTIONARY/PREPAREDNESS ACTIONS... 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 4328 10862 4344 10844 4322 10797 4301 10819 TIME...MOT...LOC 2114Z 304DEG 28KT 4332 10840 Hattings
The Riverton/Lander radar (KRIW), 5 km away, was scanning. The volume nearest the first event began at 21:27 UTC.
2 hail. Local standard time, as filed.
A National Weather Service employee reported nickel size hail west of Riverton near the Riverton Country Club.
An off duty National Weather Service employee reported nickel size hail at the intersection of US 26 and Missouri Valley Road.
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, July 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: 765066, 765065.