Wyoming Department of Transportation sensor at Arlington measured a brief few hour window of high sustained winds above 40 mph. Highest hourly average was 42 mph.
Every event with a place to put it; 1 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 CYS wrote it up.
Wyoming Department of Transportation sensor at Arlington measured a brief few hour window of high sustained winds above 40 mph. Highest hourly average was 42 mph.
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 Cheyenne, WY wrote its last area forecast discussion before the first event at Dec 13, 4:16 PM MST, 2 minutes earlier.
Area Forecast Discussion National Weather Service Cheyenne WY 416 PM MST Sun Dec 13 2020 .SHORT TERM...(Late this afternoon through Monday) Issued at 220 PM MST Sun Dec 13 2020 The upper low pressure system that produced the snow over southeast WY and southern NE Panhandle Saturday was moving east along the Red River Valley of OK/TX. Visible satellite imagery showed high clouds spreading west to east over WY/CO. Surface ridges of high pressure were located over eastern MT/western ND and eastern ID into western NM. Filtered sunshine and fresh snow cover have kept a lid on high temperatures thus far with readings in the 20s over southeast WY. Elsewhere, temperatures were in the low to mid 30s. Westerly winds averaged 20-35 mph with gusts to 55 mph across portions of I-80 along the Summit, and between Laramie and Rawlins. Peak gusts thus far were 55 mph at Arlington and 57 mph at County Road 402. There were patches of blowing snow seen on WYDOT webcams in these areas. Periods of strong and gusty winds will continue along the I-80 corridor between Cheyenne and Rawlins through late afternoon, subsiding briefly early this evening before increasing once again later this evening. The CAG-CPR/CAG-ARL 850mb gradients remain between 50 and 60 meters through 09Z Monday then gradually decrease. 700mb winds will hold between 40 and 50 kt through 15Z Monday, taper off thereafter. The High Wind Warning for WY Zone 110 (North Snowy Range Foothills) will remain in effect through 8 AM Monday. Low temperatures tonight will be in the single digits and teens. Pacific moisture will begin spreading into southern WY late tonight, and much of southeast WY in advance of the next upper low pressure trough. Light snow will develop across Carbon County by 12Z Monday, Laramie Range by midday, and east to a Lusk-Wheatland-Cheyenne line by mid- afternoon Monday. Accumulations will vary between a half inch and two inches along and west of the Laramie Range, with less than a half inch east by late Monday afternoon. High temperatures Monday will range from the mid 20s to mid 30s. .LONG TERM...(Monday night through Sunday) Issued at 255 AM MST Sun Dec 13 2020 Long range models continue to show a more unsettled weather pattern compared to the past few weeks across southeast Wyoming and western Nebraska. However, progressive northwest flow with fast moving Pacific energy will result in limited snowfall amounts every couple of days. It does appear windy most days, especially Tuesday/Wednesday and next weekend. Models indicate the first poorly organized upper level trough will push across the region late Monday and Tuesday with some light snow across southeast Wyoming and the southern Nebraska Panhandle. Accumulations look light, even in the mountains. Colder air will keep temperatures below normal through Wednesday due to northwest flow. Once the trough exits the area to the east, another round of strong gusty winds are expected for the wind prone locations along I-80 and I-25 in southeast Wyoming. Wind analysis shows this event should be primarily confined to the wind prone areas with little chance of the strongest winds developing across the high plains and high valleys. However, some low level mixing will result in gusty winds through Wednesday for the areas outside the wind prone zones. Another round of strong winds, likely localized to the wind prone areas, possible Thursday night ahead of the next Pacific upper level trough. Cold front passage will likely bring some light snow to the mountains and adjacent high valleys/plains of southeast Wyoming, before winds increase once again behind the trough axis for the weekend. Westerly downslope winds may actually serve to increase temperatures across the eastern plains for the weekend. Adjust POP to reflect a better chance of accumulating snowfall across east central Wyoming and along the more favorable ridges. && .AVIATION...(For the 00Z TAFS through 00Z Monday afternoon) Issued at 416 PM MST Sun Dec 13 2020 VFR conditions expected to persist through the period at all sites except KRWL where some MVFR cigs and vsbys possible by 18Z Monday along with areas of light snow. Winds light overall though some gusts around 20 knots expected in the KRWL area Monday afternoon. && .FIRE WEATHER... Issued at 145 PM MST Sun Dec 13 2020 Seasonably cold temperatures, high humidities and periods of light snow will preclude fire weather concerns through early next week. Breezy to windy conditions are forecast much of this week. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...High Wind Warning until 8 AM MST Monday for WYZ110. NE...None. && SHORT TERM...MAJ LONG TERM...TJT AVIATION...RE FIRE WEATHER...MAJ
Hazardous Weather Outlook National Weather Service Cheyenne WY 321 AM MST Sun Dec 13 2020 WYZ110-141030- North Snowy Range Foothills- 321 AM MST Sun Dec 13 2020 This hazardous weather outlook is for portions of south central Wyoming. .DAY ONE...TONIGHT Strong winds are expected to develop in the Arlington and Elk Mountain area later this morning, and continue through early Monday morning. A High Wind Warning is in effect for wind gusts to 60 mph. Blowing and drifting snow is also expected. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Snow showers expected Monday into Tuesday with 1 to 2 inches of accumulation possible. A prolonged period of high winds is expected from Wednesday through Friday. .Spotter information statement... Spotter activation will not be needed. WYZ106-116-117-141030- Central Laramie Range and Southwest Platte County- South Laramie Range-South Laramie Range Foothills- 321 AM MST Sun Dec 13 2020 This hazardous weather outlook is for portions of southeast Wyoming. .DAY ONE...TONIGHT Gusty winds with blowing and drifting snow expected today. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Snow showers expected late Monday into Tuesday with 1 to 2 inches of accumulation possible. A prolonged period of high winds is expected from Wednesday through Friday. .Spotter information statement... Spotter activation will not be needed. WYZ103>105-109-111>115-141030- North Laramie Range-Ferris/Seminoe/Shirley Mountains- Shirley Basin-Central Carbon County-Southwest Carbon County- Sierra Madre Range-Upper North Platte River Basin-Snowy Range- Laramie Valley- 321 AM MST Sun Dec 13 2020 This hazardous weather outlook is for portions of south central Wyoming and southeast Wyoming. .DAY ONE...TONIGHT Gusty winds with blowing and drifting snow possible today. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Snow showers expected Monday into Tuesday with 1 to 2 inches of accumulation possible. Higher elevations could see 2 to 4 inches of snowfall. A prolonged period of elevated to high winds is expected from Wednesday through Friday. .Spotter information statement... Spotter activation will not be needed. WYZ107-108-118-119-141030- East Platte County-Goshen County-Central Laramie County- East Laramie County- 321 AM MST Sun Dec 13 2020 This hazardous weather outlook is for portions of southeast Wyoming. .DAY ONE...TONIGHT Gusty winds with blowing and drifting snow possible today. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Snow showers possible late Monday into Tuesday with up to 1 inch of accumulation possible. Gusty winds possible mid-to-late week. .Spotter information statement... Spotter activation will not be needed. NEZ002-003-019>021-054-055-095-096-WYZ101-102-141030- Dawes County-Box Butte County-Scotts Bluff County-Banner County- Morrill County-Kimball County-Cheyenne County- Northern Sioux County-Southern Sioux County- Converse County Lower Elevations-Niobrara County- 321 AM MST Sun Dec 13 2020 This hazardous weather outlook is for portions of panhandle Nebraska and east central Wyoming. .DAY ONE...TONIGHT No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY Snow showers possible late Monday into Tuesday with up to 1 inch of accumulation possible. Gusty winds possible mid-to-late week. .Spotter information statement... Spotter activation will not be needed.
The national radar mosaic for the moment the first event began.
1 high wind. Local standard time, as filed.
Wyoming Department of Transportation sensor at Arlington measured the reported max sustained wind.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2020Every state in 2020This day in weather historyWarnings in Wyoming, December 2020
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: 927390.