A Pacific trough and cold front brought heavy snow to the northwestern mountains. This was a warmer system with most snow falling above 8000 feet in elevation.
Every event with a place to put it; 5 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 Pacific trough and cold front brought heavy snow to the northwestern mountains. This was a warmer system with most snow falling above 8000 feet in elevation. The most snow fell in the Tetons, with 20 inches of new snow at the Jackson Hole Ski Resort. Other notable amounts included 19 inches at the Lewis Lake Divide SNOTEL site in Yellowstone Park and 14 inches at the Beartooth Lake SNOTEL site in the Absarokas. In the Lander Foothills, strong downslope winds developed. The maximum gust reported was 68 mph at the Lander 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 20, 10:29 PM MST, 31 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Riverton WY 1029 PM MST Sat Dec 20 2025 .KEY MESSAGES... - Snow returns to western portions tonight, as the start of a multi-day heavy snow event. Snowfall amounts of 18 to 36 inches are expected through Monday night. - Winds of 30 to 40 mph can be expected Sunday and Sunday night, adding to the already difficult travel conditions over Teton and Togwotee Passes. - Snow is expected in the western valleys at times, but will change over to rain by Sunday afternoon. - Above normal, possibly record high, temperatures, and windy conditions Monday through Christmas Eve. && .UPDATE... Issued at 1230 PM MST Sat Dec 20 2025 Winds have been relatively tame compared to the past few days, with the only higher gusts noted along I-80. Most areas should see limited wind activity through the rest of the day, with higher gusts limited to the wind corridor from Rock Springs to Casper. The atmospheric river tap of moisture begins to surge into the western mountains tonight, with a good 24 to 36 hours of snow for the western mountains. Totals have remained consistent, so have hoisted Winter Storm Warnings for the western ranges tonight through around sunrise Monday. The lower valleys will see snow tonight, with an inch or two for Star Valley and Jackson Hole through Sunday morning. These areas will switch over to rain by noontime Sunday, and will remain rain through the duration. With a total liquid precip over an inch at Jackson through Monday, some ponding is possible around the region, and temperatures near freezing Sunday night will bring some icy conditions to wet areas. Still looks like the mountains will wring out all the moisture from this atmospheric river, so areas east of the Divide, along with Sweetwater County, will not see precip from this episode. && .DISCUSSION... Issued at 210 AM MST Sat Dec 20 2025 As of 07Z, the cold front has reached Casper and Riverton and is expected to reach the Divide in the next few hours. Temperatures at these locations have dropped below freezing, with bands of snow occurring over southern portions of the Bighorn Basin and Johnson County, Natrona County along the US-20/26 Corridor and off the southern end of the Wind River Mountains. Snow will also continue to fall over the Salt River/Wyoming Ranges and the Wind River Mountains through the morning hours with an additional 2 to 4 inches expected. Most of this will fall before sunrise. Rain showers are also expected along the I-80 Corridor shortly, pushing south of the Interstate by 10Z. Temperatures are currently in the upper 30s/lower 40s and are not expected to drop below freezing until 12Z. Winds continue to decrease behind the front, with gusts of 25 to 45 mph continuing across southern portions. These winds will gradually decrease by sunrise this morning, with the east slopes of the Wind River Mountains continuing to gust 45 to 55 mph. This will be a brief lull, as west-northwest winds increase to gusts of 25 to 45 mph by midday. These winds will occur for most areas, except eastern portions of the Bighorn Basin and northern Johnson County. Temperatures will be closer to seasonal levels, but still slightly above normal for this time of December. Precipitation chances will increase over western portions after 06Z Sunday (11pm tonight), as a plume of Pacific moisture moves over the region. This will be part of an Atmospheric River moving onshore over northern CA today and be a multi-day event. Precipitation will likely start as snow in the Jackson/Star Valleys tonight, changing over to rain by the afternoon. Snow levels will range between 7000 and 8000 ft over the western mountains by 18Z Sunday, with moderate to heavy snow through the day and Sunday night. Precipitable water values will be close to record values with this event. This, coupled with favorable west-southwest upslope flow, will lead to snowfall amounts of 18 to 36 inches through Monday night. The bulk of this will occur through Sunday night, with snow becoming light during the day Monday. Wind gusts up to 30 mph will also occur with the snow, adding to the travel hazard over Teton and Togwotee Passes. One of the challenges with the forecast will be if temperatures drop below freezing in the western valleys Sunday night. Elsewhere, it will be a windy day again Sunday with southwest winds gusting 25 to 35 mph across southern portions and the Wind Corridor. Exceptions will be portions of Natrona County and southern Fremont County, where gusts of 35 to 45 mph will be common. Locally higher gusts up to 60 mph will be possible over South Pass and Hwy 258 on the south side of Casper. There is a possibility for high wind Sunday night into Monday, as 700mb winds increase to 50kt over the Cody Foothills, South Pass and Natrona County. A cold front will move over areas east of the Divide Monday. No precipitation is expected either ahead or behind the front. The impacts from the Atmospheric River will continue to wane Tuesday, as a ridge begins to build over the region. This will lead to another day of above normal temperatures (possibly record high temps), with highs in the 40s and 50s. Any precipitation will be confined to far northwestern portions, as the ridge shunts most of the moisture to the north and west. Dry, warm and windy conditions are likely Christmas Eve. Another storm system will impact the CWA on Christmas, with western portions having the best chance for a White Christmas. There is the potential that this will be another windy day, as the flow aloft will be southwesterly. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 1029 PM MST Sat Dec 20 2025 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals. The next weather system is quickly approaching western Wyoming. KJAC is expected to see MVFR to IFR impacts starting by 11Z. KBPI and KPNA will follow by 14Z as snow moves east. These conditions should last through the morning before snow gradually makes a transition to a rain/snow mix and then potentially all rain. This should lead to a slight improvement in ceilings and visibility, though confidence is low on totally breaking out of IFR, especially at KJAC. KRKS is not expected to see precipitation impacts. Gusty winds will be seen with this system, especially in the afternoon. This will be most notable at KJAC which will first see strong southwest wind above the surface before surface gusts reach 30 knots after 00z Monday. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals. Precipitation will largely be confined west of the Divide. VFR conditions are expected through tonight, with wind beginning to pick up at KCPR by 16Z. KCOD and KLND will have the best chance of seeing at least brief precipitation impacts coming off of the mountains through the afternoon; KLND will carry a PROB30 group to account for this potential. There is also the potential for strong winds at KLND after 16Z as a mountain wave develops, though low confidence precludes prevailing this wind for now. Wind shear at KLND is much more certain during this period. KCPR is expected to see southwesterly gusts to 40 knots after 00Z Monday. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning until 5 AM MST Monday for WYZ001-002-012- 014-015-024. && UPDATE...Straub DISCUSSION...LaVoie AVIATION...Myers
Hazardous Weather Outlook National Weather Service Riverton WY 1229 PM MST Sat Dec 20 2025 WYZ001>020-022>030-212330- Yellowstone National Park-Absaroka Mountains-Cody Foothills- North Bighorn Basin-Southwest Bighorn Basin-Southeast Bighorn 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- 1229 PM MST Sat Dec 20 2025 ...WINTER STORM WARNING IN EFFECT FROM 11 PM THIS EVENING TO 5 AM MST MONDAY FOR THE MOUNTAINS OF WESTERN WYOMING... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...This afternoon and tonight. Wind gusts of 25 to 45 mph will return across much of the area this afternoon. Snow develops over western portions tonight. This will be the start of a multi-day event that will continue through Monday night. .DAYS TWO THROUGH SEVEN...Sunday through Friday. Sunday through Monday Night...Periods of moderate to heavy snowfall will occur across the higher elevations of western WY. Snow levels will rise to 7000 to 8000 ft by midday Sunday, so any precipitation will likely fall as rain in the Jackson/Star Valleys. Snowfall amounts of 18 to 36 inches expected during this time. Wind gusts up to 30 mph will occur Sunday afternoon, increasing to 40 mph Sunday night. Wind gusts up to 60 mph will be possible over South Pass and the south side of Casper Sunday and Sunday night. Christmas Eve and Christmas Day...Early indications for the potential of another round of snow mainly across western WY. Temperatures may be cold enough to support snow over lower elevations, but at this time confidence remains low. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report significant weather conditions according to Standard Operating Procedures.
The national radar mosaic for the moment the first event began.
3 winter storm, 2 high wind. Local standard time, as filed.
Heavy snow fell in southwestern Yellowstone Park, with a maximum amount of 19 inches at Lewis Lake Divide.
Heavy snow fell in portions of the Absarokas, including 14 inches at Beartooth Lake and 13 inches at Blackwater.
Heavy snow fell in the higher elevations of the Tetons, with a maximum of 29 inches at the top of the Jackson Hole Ski Resort.
A WYDOT sensor above Red Canyon near South Pass recorded a wind gust of 107 mph.
A maximum wind gust of 68 mph occurred at the Lander airport.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2025Every state in 2025This day in weather historyWarnings in Wyoming, December 2025
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: 1306375, 1306376, 1306377, 1309523, 1307715.