textproduct: Western and Central Wyoming

KEY MESSAGES

- A widespread high wind event occurs Wednesday, with winds increasing early Wednesday morning. Widespread gusts over 40 mph are expected, with many locations over 55 mph.

- Snow is expected over the western mountains through Wednesday evening. A period of very heavy snow is likely (70%) Wednesday morning, from about 5am to noon, with snow rates near 2 inches per hour. Impacts to mountain pass travel expected.

- Another weather system is quick to follow, with gusty winds and western snow chances Tuesday afternoon and Friday.

UPDATE

Issued at 1204 PM MST Tue Dec 16 2025

No notable changes to the actual forecast with this update. Have expanded High Wind Warnings across the entire area, for widespread gusts 45 to 70 mph. Period of strongest winds will be late Wednesday morning through mid-afternoon, with gusts decreasing after sunset. Expect impacts to travel, with sudden westerly wind gusts. For the western mountain passes, moderate to heavy snow will create winter travel conditions, especially Wednesday morning into early afternoon. See the full discussion below for details.

DISCUSSION

Issued at 311 AM MST Tue Dec 16 2025

The theme of December so far has been warm well above normal temperatures, wet heavy mountain snow, below normal precipitation across lower elevations and widespread strong gusty winds. To no surprise that summarizes the weather for the remainder of the week pretty well. Near record breaking high temperatures are forecast for many locations east of the Divide today. Highs will range in the mid to upper 50s east of the Divide with slightly cooler temperatures over the west ranging in the low to mid 40s.

The setup for the upcoming stretch of active unsettled weather is fairly straight forward. A ridge that has been sitting over the region will be suppressed to the south. This will then allow for Pacific moisture to be gradually ushered into the region as a very potent disturbance treks across the far northern CONUS. Zonal flow will develop ahead of this disturbance which will create some chances (30-60%) for some light showers. Western WY looks to have the best chances for these showers due to developing and strengthening westerly flow. Winds start to gradually increase over the region Tuesday with the strongest gusts remaining over higher elevations and eastern slopes of the central WY mountains. Gusts of 40 to 50 mph will be common with gusts of 60 or more mph possible in locations such as the Upper Wind River Basin, Cody Foothills along with the Wind River and Absaroka Ranges. High Wind Warnings remain in effect for the Cody Foothills and Absarokas.

The main event arrives late Tuesday as a very potent jet moves into the region in association with the aforementioned disturbance. Strong gusty winds will be widespread along with wet/heavy snowfall across western mountains. Firstly, starting off with the snow, precipitation will begin to develop and become more widespread during the early morning hours on Wednesday. Strengthening westerly 700mb winds will enhance orographic dynamics during the morning and early afternoon Wednesday. This period will likely see the heaviest snowfall for western mountains with snowfall rates of 1 to even 2 inches possible. The heaviest snow is expected to be limited to the highest elevations above 8,500 feet due to warm temperatures. A nearing cold front and its passage will begin to cutoff for the heaviest precipitation over western WY. The timing looks to be in the late afternoon on Wednesday with it gradually spreading over central WY by the late evening Wednesday into the early morning hours Thursday. Storm total snowfall amounts have continued to gradually increase and that continues to be the case today. The higher elevations above 8,500 feet across the Tetons, Gros Ventre and Wind River Ranges currently look to see anywhere from 8 to 14 inches. Higher peaks may see amounts nearing 16 to 20 inches. Other locations such as the western Absarokas, the Salt River/Wyoming, and higher elevations of YNP can see amounts of 6 to 12 inches. Locally higher amounts of 14 to 20 inches are possible over southwestern YNP specifically Pitchstone Plateau. Warm temperatures will greatly limit snow accumulations across lower elevations and western valleys. Storm total amounts for these areas are low ranging from a wet slushy coating to an inch or two. No upgrades for Winter Storm Watches are planned at this time but an upgrade will likely occur during the afternoon.

The other aspect of this event will be widespread strong gusty winds. This is the result of a very potent jet that brings 700 mb winds of 60 to 80 knots over nearly all of the CWA. This would translate to surface wind gusts of 50 to 60 mph with stronger gusts of 70 to 80 mph not out of the realm of possibility. This wind event looks to begin early Wednesday morning, first across the higher elevations before gradually making its way to the lower elevations by the late morning. Probabilistic guidance supports a widespread strong wind event. Lower elevations of central and southern WY currently look to have a 50 to 80% for 60 mph or more wind gusts. This would include locations such as Sublette, portions of Lincoln, Sweetwater, Fremont, Natrona, and Johnson Counties. As a result of this High Wind Watches have been expanded to include the Lander Foothills, Wind River Basin, and northern Johnson County. Hi-res models have pinpointed the chance for a mountain wave to develop along the eastern slopes of the Wind River range and move into the Lander Foothills Wednesday morning. Guidance shows a 30 to 50% chance for 70 mph gusts within town and especially on the outskirts, including the lower portions of Sinks Canyon. Elsewhere strong gusty winds will begin to gradually decrease by the late afternoon into the evening on Wednesday. Gusty winds will persist into the overnight and Thursday morning but speeds are forecast to be much more tame. Hi-res models have begun to pick up on some showers making their way east of the Divide ahead of the cold front passage. The timing for these showers would be Wednesday morning into the early afternoon. Temperatures are looking too warm for any snow concerns so rain will likely be the main precipitation type associated with any showers over lower elevations.

Thursday will see a slight taste of cooler temperatures but still well above normal for this time of the year. Another disturbance takes aim at the state with very similar impacts as this current disturbance. Wet heavy snow looks increasingly likely for western mountains with widespread strong gusty winds returning to the area as well. Currently the timing for precipitation would be Thursday morning with winds gradually increasing through the day Thursday into Friday. The greatest impacts are likely to be limited to the western mountains and passes due to the combination of strong winds and heavy snow. This disturbance will be monitored over the next few days as a better idea of what to expect comes into view.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 425 PM MST Tue Dec 16 2025

Impactful aviation weather expected over the next 24 hours.

The going forecast remains on track. All locations, even those in tight western valleys (e.g. JAC, AFO) are likely to see strong and gusty winds tomorrow late morning into the afternoon. Wednesday daytime gusts on the order of 40 to 55 kt look likely (80% chance) in most locations, which is quite extreme even by Wyoming standards.

Of particular note, cross winds will be extreme for western Wyoming valleys, where runways and predominant winds are north- south, but after the cold front tomorrow afternoon, the strong west-northwesterly winds introduce a notable cross wind component.

West of the Continental Divide, morning snow and a rain-snow mix further complicate aviation operations. Precipitation moves eastward during the afternoon, causing a brief period of precipitation for sites east of the Divide. This will be rain for central Wyoming basins. The cold front will shift the winds to more northwesterly for the evening hours. Winds remain elevated after sunset, slowly decreasing in strength overnight into Thursday.

RIW WATCHES/WARNINGS/ADVISORIES

Winter Storm Warning from 1 AM to 11 PM MST Wednesday for WYZ001-002-012-014-015-024.

High Wind Warning until 1 AM MST Wednesday for WYZ002.

High Wind Warning until 5 PM MST Wednesday for WYZ003.

High Wind Warning from 11 AM to 5 PM MST Wednesday for WYZ004- 006-013-023.

High Wind Warning from 8 AM to 5 PM MST Wednesday for WYZ005- 007-010-011-017-018-025>029.

High Wind Warning from 8 AM to 11 PM MST Wednesday for WYZ008- 009-016-030.

High Wind Warning from 1 AM to 11 PM MST Wednesday for WYZ019- 020-022.