High wind occurred across Natrona County ahead of an advancing Pacific trough. The highest wind gust reported was 84 mph along Wyoming Boulevard on the south side of Casper.
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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.
High wind occurred across Natrona County ahead of an advancing Pacific trough. The highest wind gust reported was 84 mph along Wyoming Boulevard on the south side of Casper. Other notable gusts included 68 mph at I-25 and Hat Six Road and 63 mph at the Casper-Natrona County International Airport.
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 Dec 7, 10:19 PM MST, 4 hours 41 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1019 PM MST Tue Dec 7 2021 .SHORT TERM...(This evening through Wednesday night) Issued at 330 PM MST Tue Dec 7 2021 Currently in northwest flow aloft which will keep mountain snow shower chances elevated through tonight. Winds have increased across central areas a bit more than expected and the Wind River Basin has mixed out, with temperatures peaking above earlier guidance. Flow turns more westerly tonight as a trough approaches. Wind will begin to increase Wednesday morning as the surface pressure gradient tightens. The strongest wind will as usual be across the Wind Corridor, where gusts to 50 mph look possible. There could be some stronger gusts but these should be brief as wind will likely peak by early afternoon. Based on the sub-par inversion performance today, have warmed Wednesday highs a bit in some parts of the central basins. A cold front will arrive Wednesday night, with snow increasing across the west and then southern areas through Thursday morning. .LONG TERM...(Thursday through Tuesday) Issued at 330 PM MST Tue Dec 7 2021 On Thursday, a strengthening jet streak aloft ahead of an incoming shortwave trough will provide favorable dynamic support for lift and snow across southern Wyoming. Light accumulating snow will begin in the morning, and will last through much of the day. Those along and south of the I-80 corridor will likely see tricky winter travel, with lowered visibility and patchy blowing snow. Higher amounts of moisture will remain over Utah, Colorado, and southeast Wyoming, where Winter Storm Watches have been issued. Winter weather highlights may be needed for Sweetwater through Natrona county eventually, especially if the system shifts further north. Snow ends for southwest and south central Wyoming during the overnight hours, but the Casper area could see continued accumulations through Friday AM, as the low center to the southeast continues to wrap moisture around the northern side of the circulation. This combined with the upslope nature of this wind direction could cause the southeast half of Natrona county to receive 4 to 6 inches of snow over the 24 hour period from noon Thursday through noon Friday. Snow ends for central Wyoming Friday afternoon, and skies will begin to clear around sunset. Efficient radiational cooling should allow single digit lows for most locations, making it feel quite wintry on Saturday morning. Southwest flow Saturday through early next week causes a warming temperature trend, but the tighter gradient will mean gusty winds for the wind corridor from Sweetwater to Natrona county. A large trough could bring additional winter weather during the middle of next week, but details are uncertain at this point. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1016 PM MST Tue Dec 7 2021 Most winds have decreased for the evening, with remaining sites expected to decrease in the next couple hours. Winds ramp up quickly tomorrow, with KCPR already gusting to 30kts by 15z. Cigs will remain VFR for most sites, with high cirrus moving in in the afternoon. KJAC will see lower clouds sooner Wednesday evening, with some snow developing closer to 06Z. && .FIRE WEATHER... Issued AT 330 PM MST Tue Dec 7 2021 Northwest flow continues, with light snow showers chances remaining across the western and northern mountains through Wednesday. A stronger system will approach the area Wednesday. Southwest winds will increase along the Wind Corridor ahead of this with gusts 40 to 50 mph expected. Smoke dispersal will improve on Wednesday with the stronger winds. Snow will increase across the west Wednesday night, spreading across south Wyoming Thursday morning. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...Myers LONG TERM...VandenBoogart AVIATION...Straub FIRE WEATHER...Myers
Hazardous Weather Outlook National Weather Service Riverton WY 253 AM MST Wed Dec 8 2021 WYZ001>020-022>030-091200- 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- 253 AM MST Wed Dec 8 2021 ...Winter Weather Advisories are in effect from Thursday through Friday morning for portions of southern and central Wyoming... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Strong winds in the lee of the Absaroka mountains, and from east of Rock Springs to Jeffrey City to Natrona County. Snow showers will become more numerous in the west toward sunset and through tonight. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Thursday through Friday morning...Snow likely in the central and southern Wyoming, with the greatest impacts south of a Rock Springs to Casper line. Please see Winter Weather Advisories for details. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to standard operating procedures.
Special Weather Statement National Weather Service Riverton WY 237 AM MST Wed Dec 8 2021 WYZ019-020-090000- Green Mountains and Rattlesnake Range- Natrona County Lower Elevations- Including the cities of Jeffrey City and Casper 237 AM MST Wed Dec 8 2021 ...Strong Winds today... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Southwest winds 25 to 35 mph with gusts to 50 to 55 mph. Locally higher gusts are likely in more wind prone areas, such as along Wyoming Boulevard south of Casper. * WHERE...Natrona County and the Green and Rattlesnake Range. * WHEN...Through this afternoon. * ADDITIONAL DETAILS...Mainly to transportation. Expect control issues with light and high profile vehicles, including campers and tractor trailers. WYZ002-003-090000- Absaroka Mountains-Cody Foothills- Including the cities of Clark, Cody, and Meeteetse 237 AM MST Wed Dec 8 2021 ...Strong Winds today... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...West winds 25 to 35 mph with gusts to around 50 mph. Locally higher gusts are possible in the vicinity of Clark and the Absarokas. * WHERE...Cody Foothills and the Absarokas. * WHEN...Through this afternoon. * ADDITIONAL DETAILS...Mainly to transportation. Expect control issues with light and high profile vehicles, including campers and tractor trailers. WYZ001-012-013-023-024-090000- Yellowstone National Park-Teton and Gros Ventre Mountains- Jackson Hole-Star Valley-Salt River and Wyoming Ranges- Including the cities of Lake, Mammoth, Old Faithful, Jackson, Afton, Alpine, Star Valley Ranch, and Thayne 237 AM MST Wed Dec 8 2021 ...Steadier snow returning late this afternoon and tonight... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Snow showers. An inch or two possible in the valleys; 3 to 5 inches in the mountains. * WHERE...Western mountains and valleys. * WHEN...Late this afternoon through tonight. * ADDITIONAL DETAILS...Expect the possibility of wintery driving conditions. Snow and blowing snow may reduce visibility and create slick roadways.
The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
Wind gusts of 60 to 70 mph were reported at multiple stations around Casper. A peak gust to 84 mph was registered near the intersection of Wyoming Boulevard and McKinley Street.
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, December 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: 995525.