A shortwave moved through Wyoming, tightening the pressure gradient and bringing high winds to some areas. The strongest reported wind gust was 83 mph along Chief Joseph Highway in the Absaroka Range.
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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 shortwave moved through Wyoming, tightening the pressure gradient and bringing high winds to some areas. The strongest reported wind gust was 83 mph along Chief Joseph Highway in the Absaroka Range. High winds were also observed in Johnson and Fremont counties.
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 Nov 12, 9:34 PM MST, 3 hours 42 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 934 PM MST Fri Nov 12 2021 .SHORT TERM...This afternoon through Saturday night Issued at 206 PM MST Fri Nov 12 2021 Moist northwest mid- and upper-level flow continues over the forecast area today, bringing light snow with brief rain to parts of western WY. The higher elevations should see about an inch of accumulation by the end of the day. Low clouds with patchy fog remains settled in Star Valley and other surrounding areas while the showers move through. The surface pressure gradient also extends the windy conditions across southwest and southern WY with west to northwest wind around 15-20 mph gusting over 30 mph. Light showers will continue into the evening, primarily over the northwest mountains. The winds across southern WY will decrease somewhat overnight, but remain breezy with gusts around 25 mph through the night. A shortwave trough will move through Montana early Saturday, helping to focus precipitation from NW WY across northern WY around sunrise, with the wide band moving south during the morning. Some moderate precipitation rates will occur during this time frame as the mid-levels destabilize slightly. Of note however, is that max temps Saturday will occur earlier than normal across northern and central WY as a cool front pushes south during the afternoon. Winds increase again across southern and central WY, and gusty north wind with gusts of 20-25 mph will occur with the cool front as well in the Bighorn Basin and from northern Johnson County south into Natrona County. Lingering showers will continue during the afternoon and evening mainly over and around the mountains, with a slight chance around Buffalo too. The typical northwest flow then continues Saturday night into early Sunday as another weak shortwave trough rides the top of the ridge on Sunday. .LONG TERM...Sunday through Friday Issued at 206 PM MST Fri Nov 12 2021 Shortwave that sweeps through Saturday will be digging into the Midwest Sunday morning. A building ridge across the western US will leave northwest flow aloft across the forecast area. There will be enough lingering moisture to generate low precipitation chances across the northwest mountains Sunday. Daytime highs will be above normal as heights and 700 mb temperatures rise Sunday. The ridge sharpens Monday in response to a digging Pacific Northwest trough. 700 mb temperatures rise further with almost all locations climbing to daytime highs 10F to 20F above normal. Dry conditions prevail through Monday before the leading edge of moisture associated with the Pacific Northwest trough reaches the far west around sunrise Tuesday. Current track projections and jet stream orientation would favor precipitation west of the Divide first before spreadings across the north Tuesday into Tuesday evening. The trough swings a cold front across the state Tuesday, so high temperatures will likely occur during the morning and early afternoon. However, with a mild start to the day readings still max out above normal for many locations, especially east of the Continental Divide. Have increased west-northwest wind in favored areas of Johnson, Big Horn, and Fremont counties to account for the post-frontal wind Tuesday afternoon. Wednesday will be substantially cooler with highs only in the 30s. The forecast area looks dry Wednesday in this colder, drier post-frontal airmass. The upper flow backs from the northwest to the west Thursday with at least some moisture returning to the west. Temperatures moderate Thursday, a trend that continues into Friday within the zonal flow. && .AVIATION...(For the 06Z TAFS through 06Z Saturday night) Issued at 932 PM MST Fri Nov 12 2021 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals locally MVFR ceilings will persist periodically tonight, particularly at KJAC and KPNA ahead of another moisture surge into the west between 12Z- 15Z. KJAC to likely see periodic MVFR in light rain or snow Saturday morning with lowering cloud decks elsewhere. Tail end of a northern stream shortwave then tracks across the region around midday Saturday, with drier northwest flow to follow. Gusty west to northwest wind increases at KRKS, KBPI, and KPNA in the wake of this system. All terminals to return to VFR after 18Z. Mountain tops obscured throughout the forecast period. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals Terminals to be VFR through the forecast period. Approaching shortwave will aid gusty west-southwest surface wind increasing this evening at KCPR and KCOD. The tail end of this shortwave will sweep through the region around midday Saturday. Gusty west-northwest wind to increasing significantly in the wake of this shortwave, most especially at KRIW. The best chance for any brief showers would be at KCOD late in the period. Mountain tops in the Absaroka and Bighorn mountains and along the Continental Divide to be occasionally obscured after 12Z. 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 206 PM MST Fri Nov 12 2021 Moist northwest flow continues to bring clouds and light showers into western WY today, with windy conditions across southern and parts of central WY. Temperatures will remain near or above normal through Saturday, though a weak system will bring slightly increased showers from western to northern WY Saturday morning. Windy conditions will continue across southern and central WY Saturday as a cool front moves down east of the divide Saturday afternoon. Gusty north winds will push down into the Bighorn Basin and through Johnson County late Saturday afternoon. Light snow showers continue from Saturday night through Sunday night over NW WY. Warmer and drier as well as breezy to windy conditions will move in late Sunday into Monday with a storm expected to push through Tuesday into Wednesday. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...McDonald LONG TERM...CNJ AVIATION...Hensley FIRE WEATHER...McDonald
Hazardous Weather Outlook National Weather Service Riverton WY 241 PM MST Fri Nov 12 2021 WYZ001>020-022>030-131400- 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- 241 PM MST Fri Nov 12 2021 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Rest of Today and Tonight Light rain and snow showers continue over the northwest mountains and valleys tonight. The showers will become heavier just prior to sunrise Saturday with possible impacts to early morning commuters over the western mountain passes. .DAYS TWO THROUGH SEVEN...Saturday through Thursday Saturday...Light snow in the northwest and northern mountains will diminish in the afternoon and evening. Northwest wind gusting 40 to 50 mph will blow in northern sections of Big Horn and Johnson counties Saturday afternoon following passage of a cold front. Monday...Unseasonably warm with temperatures 15 to 20 degrees above normal for many areas. Tuesday...Light snow in the western mountains and valleys spreads east during the day with a possible mix of rain and snow Tuesday afternoon and evening. Gusty northwest wind in northern and central sections in the afternoon. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report snowfall amounts.
Special Weather Statement National Weather Service Riverton WY 929 PM MST Fri Nov 12 2021 WYZ010-131400- Northeast Johnson County- Including the city of Buffalo 929 PM MST Fri Nov 12 2021 ...Wind Gusts 40 to 50 mph Likely Saturday Afternoon... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Northwest wind 25 to 35 mph with gusts 40 to 50 mph. * WHERE...Northern Johnson County including Buffalo. * WHEN...Saturday Afternoon. * ADDITIONAL DETAILS...The passage of a cold front around midday will usher in very gusty northwest wind and colder temperatures for the afternoon. Localized wind gusts to 55 mph are possible along I-90 where sudden crosswinds could pose a hazard. WYZ004-131400- North Big Horn Basin- Including the cities of Basin, Greybull, Lovell, Powell, and Shell 929 PM MST Fri Nov 12 2021 ...Wind Gusts 35 to 45 mph Likely Saturday Afternoon... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Northwest wind 25 to 35 mph with gusts to 45 mph. * WHERE...Big Horn County, especially from Greybull north to the Montana line. * WHEN...Saturday Afternoon. * ADDITIONAL DETAILS...The passage of a cold front around midday will usher in gusty northwest wind for the afternoon along with falling temperatures. The strongest winds are likely to occur around Frannie, Cowley, and Greybull. WYZ023-131400- Star Valley- Including the cities of Afton, Alpine, Star Valley Ranch, and Thayne 929 PM MST Fri Nov 12 2021 ...Patchy Dense Fog Tonight... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Patchy dense fog. Visibilities of a quarter of a mile or less in the thickest patches. * WHERE...Star Valley. * WHEN...Until 7 AM Saturday. * ADDITIONAL DETAILS...Motorists should be prepared for rapidly changing visibility. When fog is encountered, turn on your headlights so others can see you, and slow down.
The national radar mosaic for the moment the first event began.
5 high wind. Local standard time, as filed.
A maximum wind gust of 83 mph was reported at the wind sensor along Chief Joseph Highway.
An anemometer on the west side of Cody recorded a maximum wind gust of 60 mph.
A peak wind gust of 61 mph was registered at Central Wyoming Regional Airport in Riverton.
An automated station in Crowheart recorded a 59 mph wind gust.
A 59 mph wind gust was reported at the Johnson County Airport on the north side of Buffalo. A wind sensor along Interstate 90 measured a peak wind gust of 60 mph.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2021Every state in 2021This day in weather historyWarnings in Wyoming, November 2021
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: 990887, 990888, 990891, 990890, 990889.