A Pacific trough moved through northwestern Wyoming and brought heavy snow to northwestern Wyoming. Snowfall amounts of 1 to 2 feet were reported in portions of the Tetons and Yellowstone Park.
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The episode as NWS RIW wrote it up.
A Pacific trough moved through northwestern Wyoming and brought heavy snow to northwestern Wyoming. Snowfall amounts of 1 to 2 feet were reported in portions of the Tetons and Yellowstone Park.
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 6, 10:30 PM MST, 1 hour 30 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Riverton WY 1030 PM MST Wed Dec 6 2023 .KEY MESSAGES... - An active weather pattern will bring snow chances to western WY. The pattern will remain active through early next week. - Winter Storm Warnings and Winter Weather Advisories are in effect from tonight through Friday for western mountains and valleys. - Strong wind will develop late Thursday morning and persist through the afternoon across the area. A High Wind Warning goes into effect from 10 AM to 11 PM Thursday. && .DISCUSSION... Issued at 208 PM MST Wed Dec 6 2023 Two waves in the upper-level flow will slide through WY tonight through Friday. Conditions will be substantially different west of the Continental Divide compared to east of the Continental Divide, so let's call it a tale of two divide the next couple of days. The main difference will be where snow falls and where it does not. Western mountains, valleys, and YNP will have significant snowfall, whereas other locations will see little to no snow. The bighorn mountains will receive up to 10 inches above 9000 ft and less than 2 inches below 8000 ft. The Tetons and the Pitchstone Plateau in YNP will have strong upslope with this system, which will enhance snow totals there. Over 2 feet of snow is expected in those locations. Valleys will see Advisory amounts of 3 to 6 inches in the Jackson Valley and 3 to 10 inches in Star Valley. The area as a whole will have strong wind develop Thursday morning through Thursday afternoon as the first wave brings in a jet streak and tightens the pressure gradient through the area. The Cody Foothills are likely to have high wind and a High Wind warning has been issued from 10 AM to 11 PM Thursday. Travel conditions will be difficult on Thursday if travelling across western WY where the combinations of snow and wind will not be pleasant. The main issue will be blowing and drifting snow. The wind will decrease Thursday evening, with lesser impacts from blowing and drifting snow into Thursday night. The weaker wave with this system will pass through on Friday, with little to no break in snowfall across western WY. Snow will not be as heavy with this second wave. The wave then passes through Friday afternoon, with snow tapering off into the evening hours. Temperatures will be cooler on Friday behind this system. Highs will be about 10 to 15 degrees cooler on Friday compared to today. Lingering light snow is possible in western mountains on Saturday, but that will end Saturday night as a transient ridge races through the region. By Sunday morning the next system begins, but this doesn't appear to have much oomph with it. Light snow accumulations in western mountains looks possible with this system through Monday night. The pattern then become convoluted as models try to resolve a cut-off low developing in the desert southwest and a ridge from CA to Montana. Currently, it looks drier and cool from Tuesday and beyond. && .AVIATION...(For the 06Z TAFS through 06Z Thursday evening) Issued at 1030 PM MST Wed Dec 6 2023 West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals A weather system arrive early Thursday morning bringing snow chances to much of western WY. KJAC will likely see the most impacts with periods of MVFR and IFR conditions throughout the TAF period. Snow starts to develop at KJAC by 07Z Thursday with light snow expected to begin around 09Z. KBPI and KPNA will see lesser impacts with periods of light snow possible during the TAF period. The first chance for light snow showers will around 09-11Z Thursday morning. Precipitation looks to be to sporadic for any prevailing snow lines at either terminal. By the late morning KJAC, KBPI, and KPNA likely see precipitation come to an end as winds begin to increase. Winds may gust 25 to 35 knots at times during the early afternoon, with isolated gusts of 35+ knots possible. By Thursday evening winds diminish becoming light and variable. KRKS likely sees no impacts due to precipitation from this system. Winds would be the only concern as gusts of 30 to 40 knots will be possible by the late morning into the late afternoon Thursday. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts. East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals East of the Divide will see little to no precipitation from this approaching system. However, winds look to become gusty to even strong at times during the late morning and evening Thursday. KCOD and KCPR likely see the strongest winds. Sustained westerly winds of 25 to 40 knots will be possible, with gusts of 40 to 50 knots likely. Isolated stronger gusts of over 50 mph cannot be ruled out. KLND and KRIW will also see gusty winds but likely not as strong with gusts ranging between 25 to 35 knots. KWRL sees winds increase as well during this time period but gusts look to be weaker ranging between 15 to 25 knots. 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 Warning from 11 PM this evening to 11 PM MST Thursday for WYZ001. High Wind Warning from 10 AM to 11 PM MST Thursday for WYZ003. Winter Storm Warning from 11 PM this evening to 5 PM MST Friday for WYZ012. Winter Weather Advisory from 11 PM this evening to 5 PM MST Friday for WYZ013-014-023-024. && DISCUSSION...Rowe AVIATION...Hattings
Hazardous Weather Outlook National Weather Service Riverton WY 440 PM MST Wed Dec 6 2023 WYZ001>020-022>030-071400- 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- 440 PM MST Wed Dec 6 2023 ...A High Wind Warning is in Effect for the Cody Foothills Thursday... ...Winter Storm Warnings and Advisories Posted for Far West Wyoming through Friday... This Hazardous Weather Outlook is for Western and Central Wyoming. .DAY ONE...Tonight. Snow chances increase over the western mountains and valleys tonight. Moderate to heavy snow will impact Teton Pass for the Thursday morning commute. Occasional wind gusts of 60+ mph are possible between 2 AM and 6 AM Thursday around Red Canyon on Wyoming Highway 28 over South Pass and along Outer Drive on the south side of Casper. .DAYS TWO THROUGH SEVEN...Thursday through Tuesday. Thursday...Snow continues for the western mountains and valleys, with moderate snow amounts expected. Wind gusts of 45 to 55 mph will occur for many areas east of the Continental Divide and across southwest Wyoming from late Thursday morning through the afternoon. Stronger wind is expected in the Cody Foothills, with gusts of 55 to 65 mph late Thursday morning into the evening. Friday...Snow continues over the western mountains and valleys. The best chance for additional accumulations comes in the morning before the snow gradually diminishes in the afternoon. .SPOTTER INFORMATION STATEMENT... Weather spotters are encouraged to report snowfall totals.
The national radar mosaic for the moment the first event began.
2 winter storm. Local standard time, as filed.
Locally heavy snow fell in Yellowstone Park, especially in southwestern portions of the park. Amounts of 1 to 2 feet were commonplace.
Portions of the Tetons and Gros Ventre mountains reported 1 to 2 feet of new snow.
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: 1153380, 1153381.