After a mild and dry start to the month, a Pacific weather system brought heavy snow to portions of western Wyoming and high wind to portions of central Wyoming. The heaviest snow fell in the Tetons with the high amount of 22 inches at the Jackson Hole Ski Resort.
Every event with a place to put it; 5 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.
After a mild and dry start to the month, a Pacific weather system brought heavy snow to portions of western Wyoming and high wind to portions of central Wyoming. The heaviest snow fell in the Tetons with the high amount of 22 inches at the Jackson Hole Ski Resort. Over a foot of snow also fell in the western slopes of the Wind River Range and the Salt and Wyoming Range. In the western valleys, up to 9 inches fell in the Jackson Valley and up to 11 inches in the Star Valley. High wind occurred in some of the favored locations East of the Divide as well. The highest wind gust reported was 86 mph at Red Canyon along South Pass. Numerous locations of the south side of Casper had wind gusts over 60 mph as well.
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 14, 3:45 AM MST, 4 hours 15 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Riverton WY 345 AM MST Sat Dec 14 2024 .KEY MESSAGES... - Heavy snow across the western mountains tonight through Sunday. Expect hazardous travel across mountain passes. - Strong to high wind across portions of the Wind Corridor tonight. - Another weaker trough will bring snow to the west and strong winds to the Wind Corridor Monday night into Tuesday. - Strong area of high pressure builds by late-week and looks to dominate the weather pattern through Christmas. && .DISCUSSION... Issued at 335 AM MST Sat Dec 14 2024 A longwave trough will push into western WY by Noon today, bringing heavy snow to the west and strong winds to the Wind Corridor. Because of the varying impacts and locations, will split this portion of the discussion into two parts: Snow and Wind. Snow will begin across the western mountains between 10 AM and Noon today with the onset of the trough. Snow will be fairly steady across the Tetons through tonight, with snowfall rates generally 0.5 to 1 inch per hour. Confidence is high (>95%) in Warning amounts (12+ inches) across the Tetons and southwest Yellowstone Park (Pitchstone Plateau). Confidence is a bit lower in the Jackson Valley, however. Let me explain why. With the onset of the trough, winds will be southwesterly, which can help to funnel snow into the valley, and upslope conditions along the terrain features throughout the valley are possible. The lower confidence stems from the duration of this southwest flow. Winds will shift and become more westerly (downsloping off the Tetons) at some point this evening. When this occurs, snowfall rates across the valley will drop and will increase across the west slopes of the Tetons. Snowfall amounts of 1 to 2 feet will be common across the Tetons, with locally up to 30 inches across favored peaks (90% confidence). Other western mountain ranges including the west slopes of the Wind River Mountains towards Togwotee Pass, and the Salt and Wyoming Ranges will see generally 8 to 16 inches (80% confidence). Across Yellowstone, highest amounts will be in the southwest (Pitchstone Plateau) with up to 18 to 24 inches possible (90% confidence). Across the rest of the Park, amounts will generally increase from north to south with 1 to 3 inches around Mammoth to 6 to 10 around Old Faithful (80% confidence). Looking at the Jackson Hole Valley specifically, the 25th to 75th percentile range is 4 to 6 inches. However, extending the period of southwest flow or SLRs slightly higher than expected could result in much higher amounts. For Jackson itself, there is a 20% chance of 8+ inches and a 5% chance of 10+ inches with this event. There is less spread on the lower end of the range, with a >95% probability of >3 inches. That means there is a better chance of over 10 inches than there is less than 3 inches for Jackson. I do not want to move on from the snow discussion without mentioning a few other locations that could see snow with this event. The upper Green River Basin (Pinedale, Bondurant) could see 3 to 6 inches, locally higher in the foothills due to upslope effects. Towards Big Piney and Farson, a few rounds of snow showers could bring 1 to 2 inches. Star Valley will generally see amounts 2 to 4 inches, with higher amounts (locally up to 6 or 8 inches if upslope effects in SW flow sets up for a longer period of time) towards the northern part of the valley (Alpine) (40% confidence). As the trough moves across areas east of the Divide on Sunday, the Bighorns will get their chance at some snow, with 4 to 6 inches across most of the range, up to 6 to 12 in northern portions of the western slopes possible (60% confidence). A few lower elevations on the west side of the Bighorn Basin (near Tensleep) and portions of Johnson and western Natrona Counties could see some light snow Sunday afternoon and evening, but amounts should stay under 1 inch. The other part of this event will be the wind. With the approaching trough, the gradient will tighten significantly today and tonight. Coupled with the tightening gradient, we also will get the jet overhead (though better jet energy will stay to the south over northern CO). This will push 40-50kts down to 700mb, and likely to the surface overnight. We have >90% confidence that Casper, and even better confidence on the south side of Casper (Outer Drive), will see 60+ mph winds for at least several hours tonight, and thus have upgraded the High Wind Watch to a Warning. With the tight gradient, even though winds will shift from southwest to less favorable westerly flow during the day Sunday, it is expected that wind gusts will remain in the 50 to 55 mph range, up to 60 mph gusts, so have extended the Warning to 00Z Monday (5 PM Sunday evening). Muddy Gap, Fales Rock, and other favored areas along that zone could also see 50 to 60 mph gusts tonight through much of the day Sunday. There is less confidence in high wind around South Pass, however, several high-res models, namely the HIRESWFV3 and HRRR, indicate a period of possible downsloping winds for South Pass, but also the Lander Foothills between 10 PM and 3 AM tonight. This is further evidenced in the NAM 700mb wind during that time period, as there seems to be a 50 to 55kt feature in the 700 mph flow setting up along the southern Wind River range during that time. Did not have enough confidence (30%) to issue any high wind highlights, but certainly will be something to watch over the next few high-res model runs. As soon as winds become westerly (rather than southwesterly) this feature looks to quickly cut off and winds will drop off quickly. The trough will exit the region pretty quickly by Sunday evening with winds decreasing and snow ending around sunset. A shortwave ridge will build for Monday, but another trough will be close on the heels of today's trough. The next trough, similarly to this one will be progressive with westerly flow, but also similarly to this one, does look to bring a quick shot of moderate to heavy snow to the west and strong winds along the wind corridor with some jet energy and tight gradient enhancing the winds. There is not as much moisture with this next trough, however, and jet influence/gradient do not look to be as strong. At this time, expecting similar set-up but lesser impacts compared to the trough this weekend. After that trough exits Tuesday night, all extended range models build high pressure across the west. This ridge looks to be strong for this time of year, and will keep quiet weather across the region through next weekend, and likely (50% confidence) through Christmas. With the ridge, expect much above normal temperatures to return by the end of next week and stick around with minimal to no precip chances. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 345 AM MST Sat Dec 14 2024 VFR conditions at all TAF sites to begin the period. Mid level ceilings west of the Divide as winds remain light less than 10kts. Light snow will push in to JAC by 18Z, and 20Z for RKS/BPI/PNA. MVFR ceilings and visibility expected with snow on station as a prevailing through much of the remainder of the period. LAMP data indicates possible IFR conditions at PNA/BPI after 00Z. Dry conditions expected east of the Divide with mid level ceilings around 10kft. Winds look to increase by 02-05Z as the gradient strengthens ahead of FROPA towards the end of the period. CPR will be strongest with warning level winds up to 50kts as LND will see downsloping gusts between 05-08Z up to 40kts. Otherwise, gusts up to 25kts at all other locations likely during this time frame east of the Divide. JAC will see the increased gusts towards the end of the period after 10Z. 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 from 11 AM this morning to 5 PM MST Sunday for WYZ001-013. Winter Storm Warning from 11 AM this morning to 5 PM MST Sunday for WYZ012-014-024. High Wind Warning from 7 PM this evening to 5 PM MST Sunday for WYZ020. && DISCUSSION...Hensley AVIATION...Lowe
Hazardous Weather Outlook National Weather Service Riverton WY 202 AM MST Sat Dec 14 2024 WYZ001>020-022>030-151315- 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- 202 AM MST Sat Dec 14 2024 ...Winter Storm Warnings and Advisories are in effect for western WY mountains and the Jackson Valley 11 AM Saturday through 5 PM Sunday... ...HIGH WIND WARNING IN EFFECT FROM 7 PM THIS EVENING TO 5 PM MST SUNDAY for Natrona County... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Today and Tonight. Moderate to heavy snow in western Wyoming begins this afternoon and continues through tonight. Travel across mountain passes will be difficult to impossible. Strong wind likely in the southwestern wind corridor. Southwest winds gusting to 50 to 60 mph are expected around Casper tonight. Elsewhere, west to southwest winds will gust 20 to 40 mph. .DAYS TWO THROUGH SEVEN...Sunday through Friday. Sunday...Winds and snow gradually decrease through the day. Travel will remain difficult across western mountain passes through much of the day. High winds continue in the Casper area through the afternoon, decreasing by sunset. Monday night and Tuesday...Light snow across the west and gusty winds across the Wind Corridor. .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.
3 winter storm, 2 high wind. Local standard time, as filed.
Heavy snow fell throughout the Tetons. The highest amount was 22 inches at the top of the Jackson Hole Ski Resort.
The Blind Bull Summit SNOTEL site picked up 12 inches of new snow, with 12 inches falling at Commissary Ridge as well.
At the Kendall Ranger Station SNOTEL site, 14 inches of new snow fell.
Wind gusts were commonplace on the south side of Casper. The highest wind gust recorded was 73 mph along Wyoming Boulevard.
Wind gusts as high as 86 mph occurred along South Pass in the eastern Wind River Mountains.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2024Every state in 2024This day in weather historyWarnings in Wyoming, December 2024
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: 1226538, 1226539, 1226540, 1226542, 1226541.