The combination of a couple of fronts moving across the region, a strong jet over Wyoming and strong boundary layer winds mixing to the surface brought a period of high winds to portions of central Wyoming. The highest winds were in and in the lee of the Absarokas.
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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.
The combination of a couple of fronts moving across the region, a strong jet over Wyoming and strong boundary layer winds mixing to the surface brought a period of high winds to portions of central Wyoming. The highest winds were in and in the lee of the Absarokas. Winds along with Chief Joseph Highway gusted as high as 88 mph. In the Cody Foothills, Clark, Wyoming had winds gusts as high as 87 mph with 61 mph gusts at the Cody, Wyoming Airport. Wind gusted as high as 72 mph south of Casper, Wyoming. In Riverton, Wyoming, strong winds tore the roof off an auto repair shop. Wind gusts over 60 mph were also reported in Johnson and Sweetwater Counties in central and southwest Wyoming.
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 Feb 21, 2:44 AM MST, 5 hours 50 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 244 AM MST Sun Feb 21 2021 .SHORT TERM...Today through Monday Northwest flow will set up over the Cowboy State today, as a ridge over the EPAC folds over and a very strong (150+kt) jet moves onshore over central British Columbia. This pattern will be in place for the next few days, as a storm system upstream over the Gulf of Alaska makes its way to the region by Tuesday. The focus will shift to wind under this pattern. Strong to high winds will continue through Monday morning for the Absaroka Mountains and Cody Foothills, as 700mb winds continue to increase over these areas. In addition, the temperature gradient at 700mb will tighten along the east slopes of the Absarokas. This will lead to strong gap flow to occur near Clark, with gusty winds also occurring near the Buffalo Bill Reservoir. The pressure gradient across the state will be somewhat tight as well, leading to very windy conditions across the south this afternoon. Gusty winds will also occur over portions of the Wind River Basin this afternoon, with favorable northwest flow. These conditions will remain in place Monday, with 700mb winds increasing. The gradient across the Cowboy State will tighten, as the aforementioned jet sags southward. 700mb winds also increase, with 40-50kt occurring across much of the area east of the Divide. The current High Wind Warnings will likely have to be extended through Monday night, as a result. There are also signs of a downsloping signature developing along the southern end of the Absarokas into the Wind River Basin. This could lead to high winds mixing to the surface in the basin. Confidence is still a bit low to issue a High Wind Watch for the Wind River Basin, but will not be surprised if guidance starts leaning in this direction. The windy conditions across the south will return Monday and expand into Natrona County. Light snow showers will remain possible over the far west today and Monday. Accumulations will remain minor, with a couple of inches expected over the higher peaks today and Monday. The arctic airmass that has plagued the forecast area for the last couple of weeks will finally get mixed out by Monday, with temperatures reaching the 40s east of the Divide. .LONG TERM...Monday night through Saturday Moving into the period starting Monday night, winds still look to be a big story across the entire state through the day Tuesday. Snow looks to be confined to the usually favored western areas through the first part of Tuesday. Models then show the moisture moving southward with a front dropping across the state. Ahead of this front, temperatures look to be in the 30s and 40s for much of the state, with 20s over the mountains. It is possible that precipitation could be in the form of rain, or a mixture in the warmer spots, until the colder air takes over. For Wednesday, expect temperatures to be several degrees colder with highs remaining below freezing. The upper level trough supporting the cold front finally moves through the area Wednesday, strengthening as it digs southward over CO. Expect spotty activity across the west and north, in the wake of this system. A transitory ridge will quickly build over the region on Thursday, ahead of a quickly approaching trough. Snow could develop over northwest portions late Thursday afternoon ahead of the trough. The trough will continue its fast pace and clear the Cowboy State by 12Z Friday. Snow looks likely for the far west through the day Friday into Saturday, as a second system dives southward over the Great Basin. Snow will become possible across the south, as the northern edge of the downstream jet nudges northward over southern WY. There is a possibility a surface low could develop along Friday's cold front in this area. && .AVIATION...For the 12Z TAFS through 12Z Monday East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals VFR conditions will prevail at the terminal sites today and tonight. Patchy fog is possible at all sites, except KCOD until 15Z with local IFR conditions. A gusty wind will occur at KCOD and KCPR today through tonight. Gusty winds could also develop at KRIW this afternoon. West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals VFR conditions will occur at the terminal sites today and tonight. KJAC airport may see off and on flurries today, with a more general light snow developing after 03Z. MVFR conditions are expected by 04Z at KJAC. Some light snow will occur over the western mountains today and tonight, with partial mountain obscuration. Windy at KRKS today and tonight. Around 18Z, a gusty wind will occur at KBPI and KPNA, decreasing around 02Z. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .FIRE WEATHER... Strong to high winds will occur over zones 276/286 today through Monday morning. Strong winds will also occur across zone 279. Gusty winds will develop this afternoon across zones 277, 278, 280 and 283. Light snow showers will remain possible across the western zones. Expect these conditions to return for Monday. && .RIW WATCHES/WARNINGS/ADVISORIES... High Wind Warning until noon MST Monday for WYZ002-003. High Wind Watch from noon MST today through Monday afternoon for WYZ016. && SHORT TERM...LaVoie LONG TERM...Clayton AVIATION...Ross FIRE WEATHER...LaVoie
Hazardous Weather Outlook National Weather Service Riverton WY 612 AM MST Sun Feb 21 2021 WYZ001>020-022>030-221315- 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- 612 AM MST Sun Feb 21 2021 ...High Wind Warnings for the Cody Foothills and Absaroka Mountains today through Monday morning... ...High Wind Warning for the Upper Wind River Basin this afternoon through Monday... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Strong to high wind across the Cody Foothills, Absaroka Mountains, Upper Wind River Basin, and Sweetwater County. Please see the high wind statements for further details. Gusty winds also possible across the Wind River Basin. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Monday...Strong to high wind across the Cody Foothills, Absaroka Mountains and the Upper Wind River Basin. Very windy conditions across the Wind River Basin, Sweetwater County and Natrona County. Tuesday...Snow across the west and north. High winds possible across the Wind Corridor, as a strong cold front quickly moves through the area. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant winter weather conditions, according to standard operating procedures. Team Riverton
Special Weather Statement National Weather Service Riverton WY 258 AM MST Sun Feb 21 2021 WYZ028>030-220100- Rock Springs and Green River-Flaming Gorge-East Sweetwater County- Including the cities of Rock Springs, Green River, and Wamsutter 258 AM MST Sun Feb 21 2021 This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...West winds 25 to 35 with gusts 45 to 55 mph. * WHERE...Sweetwater County. * WHEN...Today through 7 pm. * IMPACTS...Mainly to transportation. There could be control issues especially for light and high profile vehicles, including campers and tractor trailers. * ADDITIONAL DETAILS...Please keep two hands on your steering wheel in case of a sudden, strong wind gust. WYZ017-220100- Wind River Basin- Including the cities of Riverton and Shoshoni 258 AM MST Sun Feb 21 2021 This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...West-northwest winds 20 to 30 with gusts up to 40 mph. * WHERE...The Wind River Basin. * WHEN...12 pm through 7 pm. * IMPACTS...Mainly to transportation. There could be control issues especially for light and high profile vehicles, including campers and tractor trailers. * ADDITIONAL DETAILS...Please keep two hands on your steering wheel in case of a sudden, strong wind gust.
The national radar mosaic for the moment the first event began.
8 high wind. Local standard time, as filed.
The wind sensor along the Chief Joseph Highway had a prolonged period of high wind. The maximum wind gust reported was 88 mph.
High winds occurred in the Cody Foothills. The strongest winds were around Clark, Wyoming, where a maximum wind gust of 87 mph was reported. A wind gust of 61 mph was reported at the Cody, Wyoming airport.
The periods of high wind occurred in eastern Sweetwater County, Wyoming, the first on the 21st and the second of the 23rd. The maximum wind gust reported was 61 mph at the Sweetwater County, Wyoming airport.
High winds were reported around the Wind River Basin, including a maximum gust of 66 mph at the Riverton, Wyoming airport. In Riverton, Wyoming, a sheet metal roof was peeled off of an auto repair shop.
A maximum wind gust of 60 mph was reported at Crowheart, Wyoming.
High winds occurred in the wind prone areas to the south and east of Casper, Wyoming. The maximum wind gusts reported was 72 mph along Wyoming Boulevard to the south of Casper, Wyoming.
High winds occurred in northern Johnson County, Wyoming. The strongest wind gusts reported was 64 mph at the Johnson County Airport near Buffalo, Wyoming.
A 75 mph wind gust was recorded at the Camp Creek RAWS site.
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, February 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: 940626, 940627, 940633, 940630, 940628, 940631, 940632, 940629.