A deep fetch of Pacific moisture from an atmospheric river and an Arctic Front dropping south combined to bring very heavy snow to much of western and central Wyoming. The heaviest snow fell across the western mountains, especially in the favored westerly flow upslope locations.
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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 deep fetch of Pacific moisture from an atmospheric river and an Arctic Front dropping south combined to bring very heavy snow to much of western and central Wyoming. The heaviest snow fell across the western mountains, especially in the favored westerly flow upslope locations. The highest snowfall amounts were in the Tetons, with the Jackson Hole Ski Resort reporting 47 inches of new snow. Portions of the Salt and Wyoming Range also picked up over 2 feet of new snow, with over a foot of new snow in the Bighorn Range and Wind River Range. In the lower elevations, over a foot of new snow fell in the Jackson Valley, Star Valley and Natrona County, with much of northern Wyoming seeing over 6 inches of new snow. The snow combined with gusty winds to produce widespread travel problems including the closure of several major roads for several days, disrupting commerce.
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 26, 4:16 AM MST, 5 hours 44 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 416 AM MST Thu Jan 26 2023 .DISCUSSION...(Today through Wednesday) Issued at 238 AM MST Thu Jan 26 2023 A lot to talk about today. We continue to have some light snow across the west but we are in a lull right now. Some snow showers will continue across then west today. In addition, a bit of jet energy will bring some snow to the east today but amounts look light with the best forcing remaining to the west of the County Warning Area. There is a bit of concern in Johnson County late today though as the HRRR shows some banding developing. The other models are drier so we will hold off on any highlights. Most other areas should have a mainly dry day with gusty winds around Casper and Buffalo for example. Better forcing and deeper moisture will reach the western mountains tonight and bring the start of some steadier snow once again. The heavier snowfall rates may hold off until Friday though when the area gets under the influence of some jet energy and a trough axis approaches the area. Meanwhile, East of the Divide, most of the day looks to remain dry as flow is largely of the downsloping variety. The exception will the Bighorn Range where favorable upslope flow will keep moderate to heavy snow going. We have hoisted a Winter Storm Watch for the Bighorn Range with the expected snow and there is a very good chance it will be upgraded sometime today. An Arctic Boundary will begin to press toward the area of Friday night into Saturday, and this will provide the lifting mechanism to bring snow in earnest to areas East of the Divide. Here, there is more uncertainty as to how much snow will fall. As with the passage of many Arctic Fronts, the snow will be of the banded variety and this far out, these bands are very difficult to nail down. And different models have different solutions as to there these will be. For now, few changes were made to amounts. However, these are likely to change over the next few days so stay tuned. Also, the Arctic air will drop into the area on Saturday East of the Divide with many areas seeing morning highs or falling temperatures through the day. The ending time is also uncertain, some deterministic models, like the GFS and some ensemble members show the snow ending for a time Saturday night. Others show the snow lingering through Saturday night. Meanwhile, on Sunday, additional snow may be possible, And upper level low moving across the Desert Southwest will try to feed some moisture northward to overrun the cold dome over the Cowboy State. The uncertainty is how far north will it get since we will be on the edge of it. For now, we kept it largely to south of the Owl Creek Range and kept amounts on the light side until there is more uncertainty. Almost all snow should end by Monday. Now we turn our attention to how low will the temperatures go. At this point, 700 millibar temperatures are not as cold the record setting outbreak we had in December, bottoming out around minus 25 as opposed to minus 30. In addition, there will likely be more cloud cover, especially through Monday that may but a lid of temperatures. The coldest night would likely be Monday night with the clouds breaking up and the lowest mid level temperatures. Widespread 40 below looks unlikely though. There could be some minus 30 temperatures East of the Divide though. Many areas probably won't rise above zero Monday or even Tuesday. Mainly dry weather should return for the middle of the week. There are differences in the models though with the European bringing ridging over the area through midweek, bringing strong inversions to the valleys and basins. The GFS has more of a northwest flow pattern with a couple of shortwaves moving through the west. Didn't take a real close look at this given the concerns closer to now though. So, to sum things up, we will have an active next few days with good chances for snow and frigid temperatures. The confidence is high in the following, very heavy snow in the west, likelihood of snow East of the Divide and frigid temperatures moving in this weekend and sticking around into the early next week. Confidence is still low on placement of the snow East of the Divide as well as timing of the ending of the snow. && .AVIATION...(For the 12Z TAFS through 12Z Friday morning) Issued at 414 AM MST Thu Jan 26 2023 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals. For KBPI, KPNA, and KRKS, VFR conditions prevail through most of the TAF period. Snow moving into the area begins to impact those sites after 03Z; have left it mainly as VCSH for now as confidence in exact timing is low. KJAC sees snow arrive sooner, with VCSH through the beginning of the period and a prevailing snow group by 18Z. Exact timing of heavier snow starting is a bit difficult at this time, but once snow begins at KJAC, it will continue through the TAF period and beyond. Gusty winds for all sites, except KJAC, Thursday afternoon, with 30 to 40 knot gusts. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals. VFR conditions to begin, with snow chances moving in for all sites, except KLND and KRIW, by around 17Z. Better snow chances begin for KLND and KRIW after the TAF period. Gusty winds for KCOD and KCPR Thursday morning and afternoon, with gusts up to 40 knots possible. 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 238 AM MST Thu Jan 26 2023 Snow showers will continue across the north today and west today but amounts should remain on the light side. Steadier snow will return to the west tonight and especially Friday and the spread East of the Divide later Friday into Friday night. A gusty wind will occur in the Lee of the Absarokas and in portions of Johnson, Sweetwater and Natrona Counties today. Relative humidity will remain above critical. && .RIW WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from this afternoon through Sunday morning for WYZ001-002-008-009-012-013-023-024. && DISCUSSION...Hattings AVIATION...Wittmann FIRE WEATHER...Hattings
Hazardous Weather Outlook National Weather Service Riverton WY 248 AM MST Thu Jan 26 2023 WYZ001>020-022>030-271400- 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- 248 AM MST Thu Jan 26 2023 ...Numerous Winter Storm Watches in effect for Western Wyoming and the Bighorn Range from tonight through Sunday Morning... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Snow likely over the northern and western mountains. Snow possible in Johnson County. Gusty winds at times over southern portions, Johnson and Natrona counties, the Cody Foothills and the Upper Wind River Basin. .DAYS TWO THROUGH SEVEN...Friday through Wednesday. Friday through Monday...Snow will continue over northern and northwestern portions Friday, becoming widespread across the area Saturday. This activity will remain possible through Monday. Much colder temperatures starting Saturday. High temperatures Monday and Tuesday may remain below zero East of the Continental Divide. All areas will see temperatures 20 to 30 degrees below normal. .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.
18 winter storm. Local standard time, as filed.
Heavy snow fell in the western Bighorn mountains, with a maximum amount of 21 inches.
Up to 13 inches of new snow fell in the eastern Bighorn Range.
Over a foot of snow fell in the higher elevations of Yellowstone Park, with a maximum amount of 19 inches near the east entrance of the park.
Very heavy snow fell in portions of the Tetons. All observation sites reported over a foot of new snow. The highest amount was measured at the summit of the Jackson Hole Ski Resort where 47 inches of new snow was reported.
Snowfall amounts around the Jackson Valley generally ranged from 7 inches in the town of Jackson to 16 inches at Moose.
Snowfall amounts around northern Johnson County ranged from 7 to 11 inches. The heavy snow and gusty wind brought the closure of Interstates 25 and 90.
New snowfall amounts around the Star Valley ranged from 9 inches at Afton to 23 inches near Thayne.
Most reporting sites in the Salt and Wyoming Range reported over a foot of new snow, with a maximum of 28 inches of new snow at Blind Bull Summit.
Snowfall amounts of 4 to 6 inches around Dubois, with gusty winds causing blowing and drifting snow.
Heavy snow and gusty wind brought the closure of Interstate 25.
Heavy snow fell in portions of the Absarokas, with a maximum amount of 20 inches of new snow to the west of Sunlight Basin.
New snowfall amounts in the western Wind River Range generally ranged from 12 to 16 inches.
Snowfall amounts ranged from 6 inches around Pinedale to around a foot near Bondurant.
The SNOTEL sites on Casper Mountain reported 12 to 15 inches of new snow.
Heavy snow fell across much of Natrona County, with the highest amounts in the foothills of Casper Mountain where 17 inches of snow fell. Snowfall amounts generally decreased to the north and west of Casper. The heavy snow resulted in the closure of Interstate 25 and US 20 26 for several hours.
A trained spotter reported 6 inches of snow near Meeteetse.
A trained spotter reported 11 inches of new snow north of Ten Sleep. Snowfall amounts dropped to under 6 inches further west.
A trained spotter reported 8.5 inches of new snow near Lucerne. Six inches of snow was reported in Thermopolis.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2023Every state in 2023This day in weather historyWarnings in Wyoming, January 2023
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: 1078166, 1078169, 1078180, 1078188, 1078189, 1078167, 1078171, 1078172, 1078768, 1078226, 1078183, 1078184, 1078186, 1078176, 1078174, 1078228, 1078190, 1078229.