A strong trough moved across Wyoming. At the same time, strong mid level winds and favorable jet dynamics brought high winds to many parts of western and central Wyoming.
Every event with a place to put it; 14 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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 strong trough moved across Wyoming. At the same time, strong mid level winds and favorable jet dynamics brought high winds to many parts of western and central Wyoming. The highest wind gust reported was 101 mph at the weather sensor at Red Canyon along Highway 28 in the Wind River Mountains. In the lower elevations, some of the more notable gusts included 70 mph at Buffalo, Wyoming, 68 mph at Riverton, Wyoming and 68 mph near Casper, Wyoming. The strong winds caused the closure of many roads to high profile vehicles during the height of the winds.
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 Jan 12, 10:09 PM MST, 7 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1009 PM MST Tue Jan 12 2021 .SHORT TERM...(This evening through Wednesday night) Issued at 150 PM MST Tue Jan 12 2021 Very active weather pattern will bring snow and wind to the forecast area over the next two days. A decent surface pressure gradient has set up over the area from the Great Basin to the northern Plains, resulting in breezy to windy conditions in the typical areas (south-central WY into Natrona County and along the lee sides of the Wind River and Absaroka mountains). Some locations are seeing mild conditions battle with cold stable inversion, resulting in rapid changes in temperatures and wind. Mid and high level clouds are already moving over the area in the strong westerly flow and will continue for the next couple of days. Areas east of the divide are likely to see more clearing at times as the flow increases and create downslope conditions. As the trough along the west coast moves eastward, increasing moisture will increase clouds across western WY this evening, with snow hitting the higher elevations by 9pm. Models are all showing the moisture increasing through the night into Wednesday morning, steadily increasing the snow through Wednesday afternoon. The caveat with this system is the temperatures though - with 700mb temps of -2 to -3C over western WY Wednesday morning, the lower elevations are likely to see a rain snow mix. This warm southwest flow will continue through the day until late Wednesday afternoon when colder air with the trough axis pushes into the state. As the axis moves through Wednesday evening, the flow will turn northwesterly and become less moist for lingering snow showers through midnight. Expecting 5 to 10 inches of snow in the mountains with some locally higher amounts, and anywhere from 1 to 3 inches in Star Valley and Jackson Hole, again with locally higher amounts depending on where snow actually manages to accumulate (rather than melt). Snow showers should also push into southern Lincoln County and the Dubois area, and possibly into the upper Green River Basin. The surface pressure gradient actually increases overnight as the surface low over northern Montana deepens. Thus, breezy to windy conditions are expected to continue overnight. The strong westerly flow with 700mb winds around 50kts will help develop good downslope conditions along the lee of the Absarokas and Wind Rivers, with the Meeteetse to Clark area looking the most favorable. Have continued the previously issued watch and now included the Absarokas and Cody Foothills starting at 12Z/Wed. The flow pattern is now as favorable for high wind along the Wind Rivers, but wind gusts 40-50+ kts are possible. As the trough axis moves overhead from Wednesday afternoon to Wednesday evening, models are showing the shift in direction to the NW and 700mb flow of 50-60 kts widespread. This flow pattern is favorable for wind gusts 50-60+ kts in many locations. A secondary area of strong wind is expected to move ESE across Montana during the day, and push southward along the Bighorns late Wednesday afternoon and overnight. MOS guidance is showing sustained northwest wind of 40-45 kts at Buffalo, which would easily bring wind gusts over 55-60 kts to northern Johnson County from Wednesday evening through Thursday morning. Snow showers with the unstable boundary will create hazardous travel conditions from Johnson into Natrona County at times. The post-trough environment early Thursday morning will result in cold breezy to windy northwest flow as high surface pressure builds over western Wyoming. Some areas may see record high temperatures Wednesday afternoon before the cold air moves in. .LONG TERM...(Thursday through Tuesday) Issued at 115 PM MST Tue Jan 12 2021 Thursday looks to continue to be quite windy over the state with about 540 decameters over the northeast corner at 500mb and about 570 decameters in the southwest corner. Models show some snow clipping the Bighorns and northeastern sections of the CWA with the strong northwesterly flow. The tight gradient is due a strong area of wrapped low pressure forecasted to be centered over the Upper Mississippi Valley and the ridge centered from the Central coast of California into eastern Washington. The first part of Friday seems pretty similar, but expect winds to diminish throughout the day as the deep trough and low move eastward. Some snowfall is again possible by late Friday and Friday night across the the far northwestern corner of the state and over the Bighorns. A bit of snowfall is possible on Saturday as the activity from the northwest dives down through the area. Models want to further develop this into a shortwave trough. Overall, precipitation again looks to be confined to the far western mountains and the Bighorns. Areas to the south of the state look to have a better opportunity for precipitation. Winds look to be on the increase again Saturday night into Sunday with snow again possible over the west and Bighorns. Models are not in good agreement heading into Monday and Tuesday of next week. They indicate unsettled weather, but vary on coverage. The EC/GFS and Canadian all show a good NNW flow with a longwave trough extending from somewhere in the Upper Great Lakes stretching back into the southwest. The Canadian hints at developing a cutoff low by 12z Tuesday near the Four Corners. && .AVIATION...(For the 06Z TAFS through 06Z Thursday) Issued at 945 PM MST Tue Jan 12 2021 East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals VFR conditions will prevail through the period at most terminal sites. Very windy conditions will occur at KCPR and KCOD through 00Z, then less windy through 06Z. KRIW will see windy conditions after 21Z and then a period of very windy conditions after 00Z through 06Z with the cold front passage. Scattered snow showers will be possible after 00Z with the best coverage from KBYG to KCPR from 01Z until 06Z. Local MVFR conditions will occur. West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals Snow will occur through 03Z Thursday in the western mountains and parts of the far west valleys. KJAC will see snow with MVFR to IFR conditions through 03Z, then improving conditions by 06Z. KPNA and KBPI may see snow showers at times after 18Z through 03Z with MVFR to IFR conditions at times. A gusty wind will be common at the terminals Wednesday into Wed night. KRKS will stay VFR through the period and windy. 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 200 PM MST Tue Jan 12 2021 Active weather pattern is expected across western and central Wyoming the next couple of days. Breezy to windy conditions are creating above normal temperatures in some areas, while inversions in other areas are keeping temps below normal. Winds will increase Wednesday, with high winds of 60+ mph gusts possible in many locations. The wind will shift to the northwest as the storm system moves through Wednesday afternoon. Snow will start again in the western mountains this evening, with a rain/snow mix in the western valleys through Wednesday mid-day. About 5 to 10 inches is expected in the mountains with 1-3 in the valleys. Other areas will just see snow showers with little accumulation through Thursday. Thursday into Friday will be colder and breezy with clearing skies. && .RIW WATCHES/WARNINGS/ADVISORIES... High Wind Watch from late tonight through Wednesday evening for WYZ002-003-019-020. High Wind Watch from Wednesday morning through Wednesday evening for WYZ016-017. High Wind Watch from Wednesday afternoon through Thursday morning for WYZ010-011. High Wind Watch from Wednesday afternoon through Wednesday evening for WYZ004. Winter Weather Advisory from 5 PM this afternoon to 11 PM MST Wednesday for WYZ012. && SHORT TERM...McDonald LONG TERM...Clayton AVIATION...AR FIRE WEATHER...McDonald
Hazardous Weather Outlook National Weather Service Riverton WY 235 PM MST Tue Jan 12 2021 WYZ001>020-022>030-131200- 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- 235 PM MST Tue Jan 12 2021 ...Winter Weather Advisory for the Teton Mountains Tonight through Wednesday... ...High Wind Watches across Northern and Central Wyoming for Wednesday morning through Thursday morning... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...This Afternoon and Tonight. Tonight...Light snow will begin and become more widespread across northwest Wyoming. Breezy to windy conditions will continue overnight in some areas .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Wednesday...Snow across the west becomes heavier and more widespread. Heaviest snow will fall during the day Wednesday. Accumulations could reach 5 to 10 inches in the mountains of Teton County and the south half of Yellowstone National Park. The lower elevations could see 1 to 3 inches as well. Gusty west to southwest wind of 30 to 45 mph with higher gusts expected in central Wyoming and portions of I-80. Wind gusts of 40 to 60 mph are also possible around the Cody area starting Wednesday morning, and in the Wind River Basin and northeast Bighorn Basin late Wednesday afternoon and evening. Wednesday Night and Thursday...Very gusty northwest wind will increase over most areas east of the Continental Divide. The strongest winds are expected over northern Johnson County where gusts of 50 mph are quite possible along I-90 and I-25. Saturday through Monday...More chances for snow across the region, but confidence is low at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today or tonight, but will be needed for snow amounts and high wind speeds Wednesday into Thursday. McDonald
Special Weather Statement National Weather Service Riverton WY 521 PM MST Tue Jan 12 2021 WYZ005>009-131300- Southwest Big Horn Basin-Southeast Big Horn Basin- Owl Creek and Bridger Mountains-Bighorn Mountains West- Bighorn Mountains Southeast- Including the cities of Thermopolis, Ten Sleep, and Worland 521 PM MST Tue Jan 12 2021 ...Very Windy Conditions Expected Wednesday Evening into Thursday Morning... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Northwest wind 25 to 35 mph with gusts 45 to 50 mph. Wind gusts in the mountains will be over 50 mph. * WHERE...Big Horn Basin, Bighorn Mountains, Owl Creek and Bridger Mountains. * WHEN...Wednesday Evening through early Thursday Morning. * ADDITIONAL DETAILS...As a cold front blasts south through northern Wyoming Wednesday evening, a period of very gusty wind will occur. Snow in the Bighorn mountains will be 1 to 3 inches with much blowing and drifting snow. Powder River and Granite Passes will be impacted with near blizzard conditions at times. WYZ001-002-131300- Yellowstone National Park-Absaroka Mountains- Including the cities of Lake, Mammoth, and Old Faithful 521 PM MST Tue Jan 12 2021 ...Winter Weather Returns through Wednesday Night... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Periods of snow. Snowfall of 3 to 6 inches. Higher snow amounts will occur at the higher elevations and in the southwest portion of Yellowstone National Park. Much blowing and drifting snow will occur in open areas as wind speeds of 30 to 40 mph will be common late tonight and Wednesday. * WHERE...Yellowstone National Park and the Absaroka mountains. * WHEN...Tonight through Wednesday night. * ADDITIONAL DETAILS...Snow will cause roads to become slick. Blowing snow will reduce visibility. WYZ014-024-131300- Wind River Mountains West-Salt River and Wyoming Ranges- 521 PM MST Tue Jan 12 2021 ...Winter Weather Returns through Wednesday Evening... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Periods of snow. Snowfall of 3 to 6 inches. Higher snow amounts will occur at the higher elevations. Much blowing and drifting snow will occur in open areas as wind speeds of 30 to 40 mph will be common. * WHERE...West Slopes of the Wind River Mountains and the Salt River and Wyoming Ranges. * WHEN...Late Tonight through Wednesday evening. * ADDITIONAL DETAILS...Snow will cause roads to become slick. Blowing snow will reduce visibility. WYZ013-131300- Jackson Hole- Including the city of Jackson 521 PM MST Tue Jan 12 2021 ...Winter Weather Returns through Wednesday Evening... This is a special weather statement from the National Weather Service Office in Riverton. * WHAT...Periods of snow. Snowfall of 2 to 4 inches. Higher snow amounts from Moose to Moran Junction where 6 inches may occur. Blowing and drifting snow will occur north of Jackson to Moran Junction where wind speeds of 20 to 30 mph will be common on Wednesday. * WHERE...Jackson Hole Valley. * WHEN...Tonight through Wednesday evening. * ADDITIONAL DETAILS...Snow will cause roads to become slick. Blowing snow will reduce visibility.
The national radar mosaic for the moment the first event began.
14 high wind. Local standard time, as filed.
High winds occurred in the Cody Foothills. The highest wind gust reported was 74 mph in the west side of Cody, Wyoming.
High winds occurred through many of the lower elevations of Natrona County. The strongest wind gust reported was 79 mph along Wyoming Boulevard south of Casper, Wyoming.
High winds occurred in the Absarokas. A maximum wind gust of 83 mph was reported along the Chief Joseph Highway.
A maximum wind gust of 74 mph was measured in Sink Canyon State Park. The Lander, Wyoming airport had a wind gusts as high as 63 mph.
High winds occurred in the Upper Wind River Basin. The strongest wind gusts reported was 60 mph at Crowheart, Wyoming.
A period of hurricane force winds occurred in the Wind River Mountains. A maximum wind gust of 101 mph was recorded at Red Canyon.
High winds occurred in much of Johnson County, Wyoming. The highest gust was 70 mph in Johnson County. The high winds flipped over an outbuilding along Muddy Creek Road.
A maximum wind gust of 64 mph was reported at the Jackson Hole airport.
A maximum wind gust of 65 mph was reported in Thermopolis, Wyoming.
A maximum wind gust of 59 mph was reported at the Worland Airport.
Wind gusts as high as 62 mph were recorded along Interstate 80.
A maximum wind gust of 76 mph was reported along Interstate 25 north of Kaycee, Wyoming.
High winds occurred through much of the Wind River Basin. The strongest gust reported was 68 mph at the Riverton airport.
High winds occurred in the higher elevations of the Green and Rattlesnake Range. The highest wind gust reported was 81 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, January 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: 935778, 935793, 935777, 935789, 935785, 935784, 935781, 935783, 935779, 935780, 935794, 935782, 935786, 935791.