A persistent moist flow of Pacific moisture, the passage of several shortwaves and favorable jet dynamics brought heavy snow to much of Teton County. The heaviest snow fell at the Jackson Hole Ski Resort where three day amounts ranged from 19 inches at the base to 38 inches at the summit.
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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.
A persistent moist flow of Pacific moisture, the passage of several shortwaves and favorable jet dynamics brought heavy snow to much of Teton County. The heaviest snow fell at the Jackson Hole Ski Resort where three day amounts ranged from 19 inches at the base to 38 inches at the summit. Heavy snow fell in the Jackson Valley as well with amounts anywhere from 9 to 16 inches commonplace.
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 27, 10:42 AM MST, 2 hours 18 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1042 AM MST Wed Jan 27 2021 .SHORT TERM...(Today through Thursday) Issued at 256 AM MST Wed Jan 27 2021 An approaching trough will bring two issues concerning the short term forecast. First up will be strong winds across the Wind Corridor beginning this morning as the southwest flow gets established. While locally high wind criteria gusts look possible this afternoon, we expect the more widespread hazard to be blowing snow. While only 1 to 3 inches of snow fell recently across that area, it should be primed to blow as temperatures have stayed well below freezing, keeping it from glazing over. We will be issuing a Winter Weather Advisory for blowing snow across these areas through this evening. Meanwhile, the moist flow will bring snow to the west starting this afternoon. Snow should be light to moderate most of the time, lasting overnight and through Thursday. With southwest flow, the most snow will likely fall over the Winds, Tetons, and southern portions of Yellowstone; have issued a Winter Weather Advisory for these areas and Jackson Hole through Thursday evening. Elsewhere, locations will mainly remain dry, with warmer highs on Thursday as warmer air advects into the area. The gusty southwest wind will remain across the Wind Corridor through the period, but expect the highest winds today. .LONG TERM...(Thursday night through Tuesday) Issued at 256 AM MST Wed Jan 27 2021 Strong southwest flow aloft will occur Thursday night through Friday ahead of a major trough. The trough is expected to split and push across the Rockies Friday night and Saturday with the strongest energy pushing across the southern Rockies. The GFS continues to keep snow over the west, albeit lighter, continuing Thursday night and Friday. On the other hand, the NAM and ECMWF are much drier during this time frame. Models are in agreement with snow returning across the west with the frontal passage Friday night with some lingering snow into Saturday. There could be some aided lift over the west associated with a right-entrance of an upper jet as pulls away from the area late Friday into Friday night. Will probably need highlights for portions of the west with this wave of snowfall. Areas east of the Divide will remain dry through Friday with the central wind corridor remaining breezy. With the frontal passage, areas east of the Divide could see some light snow Friday night and Saturday. Ridging is expected Sunday into Monday with dry conditions expected with seasonal to slightly below average temperatures. Medium range models are in decent agreement with a trough pulling into the Pacific Northwest/N. California Monday night. Models then begin to diverge in the details, but show the general trough pulling into the Rockies Tuesday night and Wednesday. The associated cold front looks to pull across the area Tuesday night/Wednesday morning. Good chances of snow over the west Tuesday. Current model data shows decent chances of snow east of the Divide in the Tuesday night/Wednesday time frame. However this is of course 7 days out. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 1036 AM MST Wed Jan 27 2021 Pesky FZFG at KRIW lifting and shifting more away from the airport currently. KBPI FZFG also starting to lift, and will be clear of the airport within the hour. Cigs and VIS should be VFR for the remainder of the day for all remaining sites. Winds starting to pick up at KCPR, with gusty winds up to 40kts expected this afternoon. Some blowing snow may reduce vis locally through this evening. && .FIRE WEATHER... Issued AT 256 AM MST Wed Jan 27 2021 Snow chances will increase across western Wyoming this afternoon and evening and last through the weekend. Southwest winds will become strong this afternoon along the Wind Corridor from Rock Springs to Natrona County. Also expect gusty winds along higher elevations in the mountains. Smoke dispersal will be poor to fair this afternoon, with some areas of good in windier areas. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 10 PM MST this evening for WYZ019- 020-022. Winter Weather Advisory from 2 PM this afternoon to 8 PM MST Thursday for WYZ001-012>014. && SHORT TERM...Myers LONG TERM...Murrell AVIATION...Straub FIRE WEATHER...Myers
Hazardous Weather Outlook National Weather Service Riverton WY 526 AM MST Wed Jan 27 2021 WYZ001>020-022>030-281230- 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- 526 AM MST Wed Jan 27 2021 ...Winter Weather Advisory for Blowing Snow across southeast Fremont and Natrona counties thru this evening... ...Winter Weather Advisory for Significant Snow across the northwest this afternoon thru Thursday evening... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Significant blowing snow over southeast Fremont and Natrona counties through this evening. Significant snow expected over the northwest late this afternoon into Thursday. Please see the winter weather statement for more details. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Thursday...Significant snow continues over the northwest. Friday night and Saturday...Significant snow possible over the west. .SPOTTER INFORMATION STATEMENT... Spotters are encouraged to report any snow amounts.
The national radar mosaic for the moment the first event began.
2 winter weather. Local standard time, as filed.
Heavy snow fell in the Tetons. The highest 3 day total was 38 inches at the top of the Jackson Hole Ski Resort.
Heavy snow fell throughout the Jackson Valley over a 3 day period. Amounts generally ranged from 9 to 15 inches.
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: 935882, 935883.