textproduct: Western and Central Wyoming

KEY MESSAGES

- Light snow continues through the afternoon west of the Divide before snow chances (30-70%) shift east of the Divide this afternoon and evening. Snow accumulations across low elevations could be up to 1 inch (30-60% chance) with slightly higher amounts in the Casper area.

- Much colder temperatures today and Friday with highs in the 20s and 30s and Friday morning lows in single digits west of the Divide and in the teens east of the Divide.

- Warm, much above normal temperatures return Saturday with little to no precipitation chances Saturday through mid next week.

UPDATE

Issued at 1208 PM MST Thu Jan 8 2026

Noon/19Z satellite water vapor imagery shows a deep upper level trough axis roughly at the western Wyoming border. It's surface reflection, a cold front, is ahead of the trough axis and is bisecting the state from north to south. Behind the front, expect breezy northwesterly winds, especially across southern Wyoming. Across southern Wyoming northwesterly wind gusts of 25 to 30 mph will be common during the afternoon.

Across western Wyoming, light snow will linger through sunset until the upper level trough axis passes through and cuts off moisture. Brief instances of moderate snowfall rates will be possible through this time, resulting in reduced visibilities. Snow chances (30-70%) push east of the Divide as a 700mb boundary, associated with the upper trough, also shifts east this afternoon and evening. Snow will be focused along this 700mb boundary due to increased moisture, lift, and more favorable northerly flow. Expect snow to begin first across the Bighorn Basin around Noon, then across northern Johnson County and the eastern Wind River Basin as early as 2PM. Light snow chances push east to the central Wind River Basin (Riverton, Lander, and Shoshoni) between 4PM-6PM and the Casper area between 7PM-8PM tonight. Given the overall east shift of light snow showers, instances of reduced visibilities cannot be ruled out along I-90 from Buffalo to Casper starting around 3PM and along HWY20 from Shoshoni to Casper beginning around 5PM-6PM. Light snow showers will persist much of the evening and overnight in favorable northerly upslope locations, such as the Casper area, Lander area, from Red Canyon and along Beaver Rim, and along the Owl Creek and Bridger Mountains.

Similar to what will occur across western Wyoming, any light snow showers will quickly come to an end as the upper level trough axis passes through and cuts off moisture from west to east between 11PM and 2AM Friday. A brief push of 30 mph gusts are possible with the trough axis passage. Due to favorable upsloping in the Casper area, especially the south side and Casper Mountain, light snow could linger until 4AM. Snow amounts have largely not changed from the overnight forecast package with amounts less than an inch for most low elevation areas, 1-2 inches for the south side of Casper, and up to 6 inches for Casper Mountain. However, snow amounts have gone up to around 1 inch for the Lander area (50% chance) and 1 to 3 inches from Red Canyon and along Beaver Rim, and along the Owl Creek and Bridger Mountains (40% chance of 3 inches).

Strong northerly flow behind the trough will usher colder air into the entire area Friday morning. Expect lows Friday morning to be near 0 degrees Fahrenheit across western Wyoming and in single digits to teens elsewhere. Given these cold temperatures, some roads could be slick Friday morning.

DISCUSSION

Issued at 347 AM MST Thu Jan 8 2026

Radar and satellite imagery currently show a trough digging into the Great Basin. Moisture ahead of this continues to stream into western Wyoming early this morning within the southwesterly surface flow. Accordingly, snow will continue across the west today ahead of the approaching trough axis. Amounts will be lighter than previous days, however, as the leading shortwave that passed through yesterday cut off much of the available Pacific moisture. This initial wave also brought cooler air, and temperatures across western Wyoming are significantly colder this morning than this time yesterday. A stronger frontal surge is on the way later today. Snow accumulations for the western mountains will generally be under 4 inches today, with totals for the higher terrain of the Tetons near 8 inches. The valleys and basins west of the Divide will not see much, generally under an inch.

A cooler day is also expected east of the Divide where temperatures will drop to much more seasonable values (yet, still several degrees above normal for most). A mostly cloudy day in the morning will give way to light snow showers for most of the area as the trough axis passes through late this afternoon. This will induce a northerly surface flow after sunset, providing the best chance for light accumulations for northerly upslope favored locations. Accumulations this evening and overnight are expected to remain under an inch east of the Divide, with the Casper area (especially the south side) most favored to see accumulations over an inch (65% chance of at least 1 inch, 25% chance of at least 2 inches). Casper Mountain will be the exception to the low totals, with 3 to 6 inches expected tonight.

Snow will largely come to an end everywhere by sunrise Friday save for some light orographic snow across the northwest. With clouds mostly clearing, a colder morning is expected behind the front with highs ranging from around zero (west) to the teens (east). Friday will be fairly uneventful as a drier northwest flow takes over. It will be breezy as a surface pressure gradient builds, though gusts will generally stay under 30 mph.

Heights will rise through the weekend as a ridge begins to dominate the West Coast. A warming trend will begin on Saturday, with virtually no precipitation expected through at least early next week. By Monday, temperatures should return to well above-normal, generally in the upper 30s west and upper 40s to low 50s east. Further out, ensemble cluster guidance does not suggest much change; anomalously high 500 mb heights are favored to remain through much of the week, with hints at a potential ridge-breaker by late week.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1030 AM MST Thu Jan 8 2026

A broad low pressure system is passing through the forecast area today, continuing to bring complex weather conditions to the TAF sites. All sites will see periods of snow today and overnight, some more than others. General VFR conditions will drop to MVFR/IFR at times, especially KJAC and other sites west of the continental divide this afternoon and evening. Sites east of the divide will see a few hours of MVFR conditions and snow showers starting late this afternoon with KCOD and WRL, then pushing into KRIW/KLND/KCPR this evening. KCPR has a better opportunity for prolonged MVFR/IFR with snow as NNE winds push in for about 6+ hours overnight. Gusty north-northwest winds are expected at all sites this afternoon, and sometimes overnight with the frontal push. The higher terrain will continue to be obscured today, and occasionally obscured Friday.

A moist flow with gusty NNW winds will continue Friday in the post-storm system environment. Snow showers should remain over the northwest WY mountains, with stray showers possibly impacting KJAC Fri afternoon. This pattern continues into Friday evening when gusty NW winds decrease.

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

None.