The next in a series of Pacific troughs and ample moisture brought another round of heavy snow to portions of the western mountains and the Star Valley. The heaviest snow fell at the Jackson Hole Ski Resort where 30 inches of new snow fell.
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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.
The next in a series of Pacific troughs and ample moisture brought another round of heavy snow to portions of the western mountains and the Star Valley. The heaviest snow fell at the Jackson Hole Ski Resort where 30 inches of new snow fell. Amounts elsewhere were generally under 15 inches. In the Salt and Wyoming Range, 12 to 18 inches was common. In the lower elevations, in the Star Valley, amounts ranged from 7 to 14 inches.
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 Feb 15, 4:43 AM MST, 1 hour 17 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 443 AM MST Mon Feb 15 2021 .SHORT TERM...(Today through Tuesday) Issued at 221 AM MST Mon Feb 15 2021 Northwest flow continues to build across the region, with favorable direction for increased snowfall for the western mountains. Snow already starting to fall for the Tetons and Jackson Hole, which will spread into the southern WY mountains and the Green River basin during the day. Snow accumulations of 6 to 12 inches expected for higher elevations, with 3 to 5 inches for Jackson Hole and Star Valley. Models continue to note a piece of energy sweeping across southern WY late this afternoon and evening, bringing accumulations up to an inch across Sweetwater County and the lower elevations of Lincoln County. For areas east of the divide, the northwest flow will not bring precipitation, but will help shift the arctic airmass out of the region, with the beginning stages of more moderate winter temperatures. Highs today will still struggle out of the teens for most areas, but areas downwind from the Bighorn range may reach the upper 20s with some downsloping. Tonight and Tuesday, the northwest flow will become more dominant, bringing continued light snow to the western mountains, and increased snow chances for the Bighorn range. The northwest flow will continue to moderate temperatures, with most lower elevations reaching the lower 30s! .LONG TERM...(Tuesday night through Sunday) Issued at 221 AM MST Mon Feb 15 2021 Northwest flow will continue to be the dominant flow through the period. This means snow will be likely across the western mountains through the period as well. Models continue to show a small piece of energy dropping out of Canada late Wednesday; which could bring scattered snow showers east of the Divide. A weak ridge looks to build in briefly ahead of the next system late Thursday which will briefly turn off the snow machine in the west. Northwest flow associated with the ridge turns the snow back on in the west but the main story is the decent Pacific trough that is quickly on the heels of the departing ridge. As the trough dives toward the Desert Southwest, this will place the entire CWA in the most favorable location for widespread precipitation. First in the mountains then spreading east over the Divide by early Saturday morning before quickly departing late Saturday night. Models have been somewhat consistent with this system the last several runs which has raised confidence. However, confidence is lacking in overall timing and impacts. Nonetheless, this is a system worth watching over the next couple days. Along with this potential system, winds across the area will begin to increase with the highest winds happening late Sunday through late Monday in the wind prone areas. Mid-level temperatures appear to be favorable to those that aren't fans of frigid temperatures. These mid-level temps gradually warm through the period which has helped increase surface temperatures. Continued with long-term MOS guidance and agreed with the potential for low to mid-30s with the potential for a 40 or two in places toward the end of the term. These surface temps are still slightly below normal but long-term climate models suggest that there won't be any crazy subzero highs and lows for the foreseeable future. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 437 AM MST Mon Feb 15 2021 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals Snow has already begun to pick up around KJAC this morning, and will continue to impact flight operations through most of the next 24 hours. The snow will spread into the KBPI/KPNA vicinities around 18Z, continuing through around 06Z Tuesday. KRKS will see breezy southwest winds through the afternoon, with a few gusts near 20kts. A brief round of snow is expected late in the afternoon into the early evening. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals VFR conditions will prevail for the rest of the terminal sites through the period and ceilings have mostly scattered out. Ceilings will begin to develop again Monday at 4 to 7kft AGL as the next storm system moves in. A brief -shsn may reach KCOD late this afternoon, but chances are low and impacts would be minimal. 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 221 AM MST Mon Feb 15 2021 Snow returns to the western mountains today and tonight, with lighter snow continuing through midweek. Light snow will also return to the Bighorn range tonight and Tuesday. Gusty winds return to southern and central WY today with some gusts to 20mph expected. Breezy conditions continue for south WY Tuesday and Wednesday. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 AM MST Tuesday for WYZ012-013- 023-024. && SHORT TERM...Straub LONG TERM...Vorst AVIATION...Straub FIRE WEATHER...Straub
Hazardous Weather Outlook National Weather Service Riverton WY 326 AM MST Mon Feb 15 2021 WYZ001>020-022>030-161030- 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- 326 AM MST Mon Feb 15 2021 ...Winter Weather Advisories for parts of Western Wyoming today and tonight... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Monday and Monday night...Snow in the western mountains and the far west valleys. Please see the winter weather statement for more details. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Tuesday and Wednesday...Periods of light snow in the west. Friday and Saturday...A chance of snow over the west. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
The national radar mosaic for the moment the first event began.
3 winter storm. Local standard time, as filed.
Heavy snow fell in portions of the Tetons. At the top of the Jackson Hole Ski Resort, 30 inches of new snow fell. Amounts elsewhere were generally 15 inches or less.
New snowfall in the Star Valley generally ranged from 7 to 14 inches.
Heavy snow fell throughout the Salt and Wyoming Range, with many places receiving between 12 and 20 inches of new snow.
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, February 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: 940620, 940621, 940622.