A stream of Pacific moisture a moved into the area and brought locally heavy snow to portions of western Wyoming. A band of heavy snow set up in Lincoln County were the highest snow amounts were reported.
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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 stream of Pacific moisture a moved into the area and brought locally heavy snow to portions of western Wyoming. A band of heavy snow set up in Lincoln County were the highest snow amounts were reported. The Star Valley was the hardest hit, with widespread amounts over 6 inches. The foothills had widespread amounts over 1 foot with over 20 inches reported to the east of Thayne and Smoot. Locally heavy amounts of snow fell in the Jackson Valley as well, with 9 inches of new snow reported near Wilson.
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 1, 10:04 AM MST, 1 hour 56 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1004 AM MST Fri Dec 1 2023 .DISCUSSION...(Today through Thursday) Issued at 154 AM MST Fri Dec 1 2023 Key Messages: -The first wave of a winter storm impacts western Wyoming today, bringing snow, mainly to the mountains. -The more impactful part of the winter storm brings higher snowfall rates Saturday afternoon through early Monday. A couple feet of snow is possible for western mountains in this time, with 8 to 14 inches possible for the western valleys. -Strong winds begin Saturday afternoon and continue through Monday. The strongest winds will be Saturday afternoon through Sunday morning. Gusts 30 to 50 mph are possible for a large portion of the area. Discussion: Happy December! The first part of a prolonged winter storm has begun to move in to western Wyoming in the form of a shortwave ahead of the main system. This shortwave brings light, continuous snow over the western mountains and valleys through the day. Snow rates pick up this afternoon and continue through early Saturday morning. In this timeframe, 4 to 9 inches are possible over the western mountains. The highest totals are favored for the Tetons, where near a foot is possible. The lower elevation valleys could pick up an inch to maybe two for more favored locations in the westerly flow. Continuing the discussion from the previous shift, will continue with no highlights for the snow today as to not confuse anyone with the the Winter Storm Watches issued for the latter part of the storm (discussed shortly). HREF snow accumulations show good confidence in these snow totals as well, with fairly tight ranges for the 25th to 75th percentiles. It also highlights mainly the mountains for snow accumulations. Temperatures today will be similar to that of yesterday. Increased cloud cover could keep temperatures a few degrees cooler, however. The Wind River Basin continues to see cold temperatures, and have adjusted the temperatures once again as models struggle to accurately depict snowcover. The focus then shifts to Saturday through Monday, where the main weather system moves through. Snow rates decrease a bit Saturday morning as the shortwave moves out and the main push has yet to impact western Wyoming. By midday Saturday, the jet stream begins to shift eastward, bringing more ideal dynamics, moisture, and winds (discussed later). Snow rates increase over the west as a result, with the highest values favored for southwest Yellowstone, the Tetons, and the Salt/Wyoming Ranges, thanks to west/northwest flow. Winter Storm Watches have been issued from 18Z Saturday to 18Z Monday to cover this main round of snow over the west. Snow totals of 1 to 2 feet are looking possible for most of the western mountains. The aforementioned favored locations of the Tetons, Salt/Wyoming Ranges could see a foot or two more over the highest elevations. Confidence of these amounts are fairly good. The Extreme Forecast Index (EFI) and Shift of Tails (SOT) continues to highlight the Tetons down through the Salt/Wyoming Ranges as a place of significant snowfall. The lower elevation valleys (Jackson and Star Valleys) could see 8 to 13 inches as snow totals by midday Monday. The more northwest flow of this system could mean a bit lower ends for the town of Jackson and southern Star Valley, including Afton. One point of lower confidence is the northern Star Valley area. Given the flow from the northwest, the northern half Star Valley could see the higher ends of that snow range to potentially even more snow. This would effect Alpine down to around Bedford and Turnerville. This will be something to keep an eye on when more high-resolution models come into play. The EFI and SOT are also highlighting Star Valley for impactful snow amounts. The other aspect of this storm will be the wind, which will occur over most of the area. A strong west to northwest wind develops across the area Saturday, and especially Saturday afternoon. Strong winds gusting 30 to 50 mph will be common across the western mountains, the Central Wind Corridor from Sweetwater County through Natrona County, and eventually the Bighorn Mountains. There are hints of 50 knot winds at 700 mb for the Central Wind Corridor, indicating potential for high winds (gusts greater than 58 mph). This will have to be watched for consistency in these indications. In either case, however, expect and plan for strong winds across the area Saturday afternoon through Sunday morning. One interesting feature noted as more high-resolution models come into play is strong downsloping air on the lee side of central mountains from Clark down to South Pass between 06Z and 12Z. A warmer and drier airmass appears on models, indication of a strong downslope wind. This could manifest as 60 mph winds near Clark, with 50 mph or so for locations east of the central mountains down to South Pass. This is yet another feature to track over the next day to see if confidence builds for this event. If it were to occur, this could be a good event to push the colder air out of the Wind River Basin; the FV3 has a strong wind over the northern basin in that 06Z to 12Z timeframe. If it doesn't occur, cold temperatures would remain. Snow rates over the west really start to decrease Monday morning. By the afternoon, northwest flow may keep weak snow going over the northwest portion of the state, but elsewhere will be dry. Ridging builds in for Tuesday, bringing more mild conditions and dry weather. Flow turns more zonal Wednesday and Thursday ahead of the next weather system. Models are vastly different at this point, so Friday and beyond is a bit of a mystery at this time. && .AVIATION...(For the 18Z TAFS through 18Z Saturday morning) Issued at 1004 AM MST Fri Dec 1 2023 A winter weather system will bring snow to western WY through the period. Snow will continue at KJAC, with MVFR to IFR conditionsat times through this evening. Light snow showers will also develop at KPNA, with MVFR conditions by 13Z. Wind gusts of 15-25 knots will occur at most terminals this afternoon and will decrease around sunset. Breezy conditions persist at KRKS through tonight. Fog will continue to dissipate in vicinity of KRIW. Wind will remain elevated at KCPR through Saturday. Light snow showers, with MVFR conditions prevail at KRKS beginning 01Z. 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 Watch from Saturday morning through Monday morning for WYZ001-002-012-013-023>025. && DISCUSSION...Wittmann AVIATION...Hattings
Hazardous Weather Outlook National Weather Service Riverton WY 253 AM MST Fri Dec 1 2023 WYZ001>020-022>030-021400- 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- 253 AM MST Fri Dec 1 2023 This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and tonight. Areas of fog possible, mainly for portions of central Wyoming through the morning. Light snow begins over western Wyoming this morning, with increasing snow rates this afternoon and evening. Light accumulations expected for western valleys, with moderate mountain accumulations. .DAYS TWO THROUGH SEVEN...Saturday through Thursday. Saturday through Monday...Continuous moderate snowfall over western Wyoming. Significant mountain snow accumulations, with impactful accumulations for western valleys. Strong winds develop Saturday afternoon and continue into Sunday. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
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 Star Valley; especially the eastern Foothills. Amounts around 20 inches were reported to the east of Thayne and Smoot.
Snowfall amounts of 1 to 2 feet were reported across much of the Salt and Wyoming Range.
A trained spotter reported 9 inches of the snow to the southwest of Wilson.
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, December 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: 1153377, 1153378, 1153379.