Heavy snow fell in portions of the Tetons. The highest amount reported was 15 inches at the Jackson Hole Ski Resort.
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 RIW wrote it up.
Heavy snow fell in portions of the Tetons. The highest amount reported was 15 inches at the Jackson Hole Ski Resort.
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 26, 4:16 AM MST, 4 hours 44 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 416 AM MST Sat Dec 26 2020 .SHORT TERM...(Today through Sunday) Issued at 124 AM MST Sat Dec 26 2020 H5 ridge is getting pushed east this morning by the approaching shortwave, which will begin to impact the western mountains later this morning. As the trough passes, enough lift from the nearby jet will aid the orographic lift with snowfall production. Current forecast probabilities for snowfall note a high chance for greater than 8 inches for the Tetons, with a moderate chance for 12 inches for the highest elevations. As the jet shifts southward slightly this evening, snow chances increase for the Salt and Wyoming ranges, with a high chance for over 4 inches, and a moderate chance of reaching 8 inches. The pressure gradient ahead of this system will bring gusty winds again to the wind corridor from RKS to CPR this afternoon, with gusts near 50 mph possible during the afternoon. Temperatures for the Big Horn basin and the I-25 corridor will remain well above normal, reaching the mid to upper 40s. The shortwave exits quickly Sunday morning, with a brief respite for the western half of the state. Wind flow across the western mountains will be light from the northwest and north, which brings minimal snow chances through the day. Cooler temperatures are expected behind the Saturday wave, with highs Sunday near normal in the upper 20 to mid 30s. .LONG TERM...(Sunday night through Friday) Issued at 124 AM MST Sat Dec 26 2020 Quiet start to the beginning of term with dry northwest flow which will slowly transition to southwest flow Monday morning ahead of a broad central Pacific trough moving onshore. The main jet streak looks to remain far south of the region; however, the left exit region of the jet is progged to be close to the Wyoming/Colorado state line. This would place the the main snow shield of the associated low on a line from Sweetwater to Natrona Counties and areas east. Have kept snow potential across those locations including central and southern Fremont County. Recent models runs have the GFS and Euro departing from the consistency of previous shifts. The Euro and Canadian favor a further north track whereas the GFS has shifted a little south. Went with more middle track between the GFS and Euro/Canadian by using the NBM. Confidence has dropped a slightly with model divergence but still confident of accumulating snow across southern and central Wyoming. Still looking at potential snow totals but with lack of confidence in models won't be discussing that for another day or two. Winds also look to increase behind the departing low as a tight pressure gradient exists across the Wind Corridor. Model disagreement continues into Wednesday as the Euro is sticking to lingering snow showers behind the departing low whereas the GFS ejects the low rather quickly. Nonetheless, agreement on northwest flow sets up behind the low keeping the western mountains in the snow. However the snow potential for East of the Divide doesn't disappear because models are hinting at a decent shortwave slowly progressing through the upper-level flow bringing increased PoPs across the CWA Thursday through Saturday making the greatness of 2020 last a few more days into the new year. && .AVIATION...(For the 12Z TAFS through 12Z Sunday morning) Issued at 415 AM MST Sat Dec 26 2020 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals. Snow will occur over the far west today and tonight with MVFR to IFR conditions prevailing, including KJAC airport. In SW WY, scattered snow will occur with MVFR to IFR conditions at times, including KPNA and KBPI. KRKS will see VFR conditions through the period with an increasing west wind after 18Z, then keeping a gusty wind through 12Z Sunday. Mountains will be obscured at times. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals. VFR conditions will prevail at the terminal sites through the period. Scattered light snow with MVFR to IFR conditions will occur after 01Z and may impact some of the terminals by 06Z Sunday through 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 124 AM MST Sat Dec 26 2020 Only fire weather threats through early next week will be gusty winds today across zones 280 and 289, and 276 and 286. Wind gusts will reach around 40 mph during the afternoon. Much lighter winds expected through the middle of next week. Snowfall arrives for the western mountains today. A second system brings a chance for snow to southern and central WY on Monday. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 AM MST Sunday for WYZ001-013-023. Winter Storm Warning until 6 AM MST Sunday for WYZ012. && SHORT TERM...Straub LONG TERM...Vorst AVIATION...Straub FIRE WEATHER...Straub
Hazardous Weather Outlook National Weather Service Riverton WY 328 AM MST Sat Dec 26 2020 WYZ001>020-022>030-271030- 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- 328 AM MST Sat Dec 26 2020 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Significant snow returns to far western Wyoming. Please see the Winter Storm Warning and Winter Weather Advisories for details. .DAYS TWO THROUGH SEVEN...Sunday through Friday. A chance of snow is expected across portions of southern and central Wyoming Monday and Tuesday. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions.
The national radar mosaic for the moment the first event began.
1 winter storm. Local standard time, as filed.
At the top of the Jackson Hole Ski Resort in Teton county, Wyoming, 15 inches of new snow was measured.
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: 931694.