A cold front swept across Wyoming and brought heavy snow and high wind to portions of central Wyoming. Most areas saw only light snow.
Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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 cold front swept across Wyoming and brought heavy snow and high wind to portions of central Wyoming. Most areas saw only light snow. However, upslope flow brought heavy snow to much of the Lander Foothills, with widespread reports of 6 to 11 inches of snow. High wind occurred across portions of Johnson and Big Horn Counties following the passage of the cold front. The maximum wind gust reported was 61 mph at the Johnson County airport near Buffalo.
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 23, 11:28 AM MST, 2 hours 5 minutes earlier.
Area Forecast Discussion National Weather Service Riverton WY 1128 AM MST Sat Dec 23 2023 .DISCUSSION...Today through Friday Issued at 230 AM MST Sat Dec 23 2023 The next 24 to 30 hours will be the most active period of the forecast. Things are quiet right now, but radar is showing snow moving toward western Wyoming and this will spread into the western mountains before sunrise. All in all, the reasoning in the forecast remains the same as yesterday. Most models show Wyoming being under the influence of a northern stream Pacific trough and cold front with the phasing with the upper level low that is moving through the Desert Southwest far enough to the east to keep the heaviest precipitation to the east. Most areas should see most of the snow fall in around a 6 hour period, generally progressing from northwest to southeast. The highest amounts look to fall in the favored northerly upslope area, mainly areas like Lander, the south side of Casper as well as Thermopolis and the southwestern portions of Park County. Amounts came in slightly higher than continuity though. So we added the Green and Rattlesnake Mountains to the advisory this morning. As for timing, the heaviest snow looks to fall in the Bighorn Basin this afternoon, and the Wind River Basin, Lander Foothills and Casper area this evening, possibly lingering a bit longer around Casper. There is a small chance (10 to 15 percent) of some local warning amounts if banding persists, but this should be localized. We will also issue some special weather statements this morning, mainly for the northwestern mountains, Sweetwater County and Casper Mountain to account for some accumulation. The other concern is for strong wind. A tight pressure gradient will develop, and with decent cold advection behind the front, strong winds are possible in areas favored by this. These areas are the northern Bighorn Basin and Johnson County. Gusts over 40 mph look likely (70 to 80 percent) with gusts past 50 mph possible (around 40 percent). Snow amounts should remain sub advisory in these areas, although the wind will create reduced visibility and falling temperatures will lead to icy roadways and possibly a flash freeze in some areas. Wind will remain strong into the night, before subsiding Sunday morning. Quiet weather then returns as only leftover snow showers are expected Sunday, ending in the afternoon. Quieter weather then moves in for next week, as ridging returns to the Northern Rockies. One weak shortwave may bring a few showers to the west Tuesday, but nothing of consequence. Another Pacific system, this one maybe stronger, may approach later in the week, but there are large model differences so uncertainty is high. Given more pressing concerns in the short range, we didn't look at it too closely. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1128 AM MST Sat Dec 23 2023 Expect winter weather impacts to terminals over the next 24 hours, as a winter storm moves through the region today and tonight. Conditions should return to prevailing VFR towards the end of the period (18Z Sunday) for most, if not all terminals. West of the Divide terminals (KBPI, KJAC, KPNA, KRKS) expect some improvements this afternoon, as the first wave of snow exits. Then, late tonight, cigs drop again due to the second wave of precipitation and fog/low clouds. East of the Divide Terminals (KCOD, KCPR, KLND, KRIW, and KWRL) will see a cold front move southward through the afternoon hours. A northerly wind shift (gusts 20 to 30kts) will be the first indication of the front, followed by low clouds, followed by precipitation (which may begin as rain briefly then quickly change to snow). Cigs will slowly improve from northwest to southeast Sunday morning. Expect widespread mountain obscurations across the region through the entire TAF period. See below for detailed Terminal specific discussions: KJAC Terminal...Occasional snow showers this afternoon are expected with cig/vsby oscillating between VFR/MVFR. Have left a TEMPO through 22Z to account for uncertainty in cigs. Mid-level stratus are expected to begin to break up late this evening. Enough clearing is expected to result in radiational cooling and thus fog development overnight. Have gone with prevailing VCFG for much of the night and morning , with prevailing IFR during the hours with the most confidence in cig/vsby reductions due to fog. Confidence is moderate (50 to 60% chance) in fog development, but still low (20 to 30%) on LIFR conditions. Fog/Low stratus should scatter out towards the end of the period. KBPI and KPNA Terminals...TEMPO groups cover chances for snow showers and associated low clouds and reduced vsby from the initial wave of this storm system early in the period. Prevailing mid-level stratus and VFR should occur, however, through the first 6-10 hours of the forecast. After 06Z, snow showers will pour over top of the Wind River Mountains, impacting KPNA. KBPI may also see some occasional snow showers, but confidence is lower (30 to 40% chance). However, both terminals will see IFR to LIFR cigs at times through the night, with improvements by the end of the TAF period. KRKS Terminal...The initial wave of this storm system has brought low cigs to KRKS. Expect these to continue through much of the afternoon. Winds will increase late in the afternoon, which will help to erode the low cloud deck briefly, but the next wave of precipitation will likely (70 to 80% chance) bring the low cigs with accompanying -SN and reduced vsby back to the terminal overnight. Low cigs will likely linger through much of the rest of the TAF period. East of the Divide Terminals (KCOD, KCPR, KLND, KRIW, and KWRL)... KCOD Has already seen the frontal passage with snow with accompanying IFR conditions behind it. KWRL Will see the frontal passage around 19Z, with lagging by 1 to 2 hours behind the initial frontal passage. KWRL and KCOD will see slow cig improvements overnight, with prevailing VFR conditions after 03Z. KCPR, KLND, and KRIW will see the frontal passage between 22Z and 00Z this afternoon with precipitation following within an hour or so behind the front. KRIW may take a little longer for precipitation to fill in. The aforementioned three terminals will struggle to see cig improvements before day break Sunday, and could (40 to 50% chance) hold onto MVFR cigs through the end of the period. 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 Weather Advisory until 5 AM MST Sunday for WYZ003>006-017- 018. Winter Weather Advisory until 8 AM MST Sunday for WYZ010-011-019- 020. && DISCUSSION...Hattings AVIATION...Hensley
Hazardous Weather Outlook National Weather Service Riverton WY 235 AM MST Sat Dec 23 2023 WYZ001>020-022>030-241400- 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- 235 AM MST Sat Dec 23 2023 ...Winter Weather Advisory for portions of northern and central Wyoming today into tomorrow morning... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. A winter storm will bring light to moderate snow to much of the area. Strong wind is likely across northern Wyoming this afternoon into tonight. See the latest forecasts and Winter Weather Products for more details. .DAYS TWO THROUGH SEVEN...Sunday through Friday. Sunday...Snow showers ending. .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.
2 high wind, 1 winter storm. Local standard time, as filed.
A maximum wind gust of 59 mph was reported a the Greybull airport.
Snowfall amounts around the Lander Foothills ranged from 6 to 11 inches.
A 61 mph wind gust was reported at the Johnson County airport near Buffalo.
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: 1153384, 1153382, 1153383.