In southeastern Grand Teton National Park, four skiers were caught in an avalanche in the Olive Oil section of the park. One man was able to call 911.
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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.
In southeastern Grand Teton National Park, four skiers were caught in an avalanche in the Olive Oil section of the park. One man was able to call 911. One man suffered a leg injury and was transported to a local hospital. The other three were able ski out with rescuers.
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 31, 1:43 PM MST, 42 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 143 PM MST Sun Jan 31 2021 .SHORT TERM...(This evening through Monday night) Issued at 121 PM MST Sun Jan 31 2021 Tranquil weather continues through the next 36 hours, as the H5 trough remains steady across the Rockies. Lack of distinct surface pressure centers in the vicinity will keep winds low for most areas, except for the central WY wind corridor due to the southwesterly surface flow. These areas will continue to see gusts of 25 to 35 the remainder of today, and during the day Monday. .LONG TERM...(Tuesday through Sunday) Issued at 121 PM MST Sun Jan 31 2021 The ridge that has been in place the last several days will gradually breakdown and shift eastward ahead of southwest flow associated with a trough moving onshore. This trough has undergone various changes with each run of long-term models. The split flow nature of this system has diminished as models bring a shallow, digging trough and associated jet streak through the Great Basin toward NM/TX before the trough flattens out early Thursday. Models are still struggling with the timing of the event as the GFS is faster with the onset of snow in the western mountains by late Tuesday night. The ECMWF lags behind by a few hours and pushes it into the region early Wednesday morning. This looks to be a mainly West of the Divide event before snow gradually spills over the Divide by Wednesday afternoon. Snow sticks around East of the Divide through the night before departing early Thursday morning. Confidence is still low to medium with respect to timing and impacts of this storm. Temperatures are a big factor as model guidance has surface temperatures in the upper-30s to low-40s through the day before dropping them Wednesday evening. This temperature predicament could allow for a rain/snow mix thus decreasing overall snow accumulations East of the Divide. As the storm approaches, the tightened gradient could increase winds across the Wind Corridor ahead of the trough on Tuesday. By the departure of Wednesday's storm, northwest flow will usher in cold, Arctic air which in turn will drop temperatures across the region. Both guidance and probabilistic models are suggesting a 20 to 25 degree drop in temperatures from Wednesday to Friday and even the potential for colder air through next weekend. However, to get that reinforcing shot of colder air, another system will cross the region. Models are in agreement for a long duration event that begins impacting the northwest Friday evening and keeping widespread snow in the region through early Sunday morning. Behind this system, that reinforcing shot of Arctic air will set in bringing below average temperatures to Wyoming to end the period. Nonetheless, models continue to suggest an active but cold pattern to set up across the area well into the second week of February. && .AVIATION...(For the 18Z TAFS through 18Z Monday) Issued at 1008 AM MST Sun Jan 31 2021 VFR conditions will prevail across all TAF sites through the period as skies begin to clear and precipitation dissipates across the area. Wind will continue to plague site KCPR as winds gust to over 30 knots to start the period. Winds slightly diminish after 00Z but pick up again to end the period. All remaining sites will see light and variable winds through the term. && .FIRE WEATHER... Issued AT 121 PM MST Sun Jan 31 2021 Dry weather is in the forecast today through Monday night. Breezy to windy in the central wind corridor of zones 280 and 289, today through Monday night. Smoke dispersal will be poor for most places today and Monday with fair dispersal in the windy areas. && .RIW WATCHES/WARNINGS/ADVISORIES... NONE. && SHORT TERM...Straub LONG TERM...Vorst AVIATION...Vorst FIRE WEATHER...Straub
Hazardous Weather Outlook National Weather Service Riverton WY 306 AM MST Sun Jan 31 2021 WYZ001>020-022>030-011200- 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- 306 AM MST Sun Jan 31 2021 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. No hazardous weather is expected at this time. .DAYS TWO THROUGH SEVEN...Monday through Saturday. Tuesday night and Wednesday...A chance of snow in the west. A chance of snow east of the divide Wednesday into Wednesday night. Friday and Friday night...A chance of snow for most of the area. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today or tonight.
The national radar mosaic for the moment the first event began.
1 avalanche. Local standard time, as filed.
Please see narrative for description.
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: 935884.