textproduct: Cheyenne

KEY MESSAGES

- Another round of high winds will be possible on Monday, with High Wind Watches in effect for Bordeaux, Platte County, and the South Laramie Range and foothills.

- Mountain snow is expected across the Sierra Madre and Snowy Ranges Sunday night into Monday. A Winter Weather Advisory is in place.

SHORT TERM /THROUGH TUESDAY/

Issued at 259 PM MST Sun Jan 4 2026

Strong winds continue this afternoon as subsidence drives 55 kts winds down to the surface. Winds will quickly dissipate this evening below Warning thresholds, however, a breezy overnight is still expected across the area as another weak shortwave moves into the area. This shortwave will also bring another round of mountain snow starting tonight and continuing into the day Monday. Ample mid- level moisture combined with orographic lift will lead to accumulating mountain snow, primarily in the Sierra Madre Range. A Winter Weather Advisory has been issued for this range, starting tonight and continuing through Monday evening. Some snow showers could spill over into lower elevation areas of Carbon County.

Temperatures will be a few degrees cooler on Monday as the shortwave ushers in cooler temperatures aloft. Temperatures will still be on the mild side with highs out west in the 40s, and highs east of the Laramie Range in the 50s and 60s. Although these highs will still be anywhere from 10 to 20 degrees above average, Monday will mark the start of a gradual cooling trend through the rest of the week. The shortwave will cause mountain snow to continue through the day. Model soundings show about 500 J/kg of surface CAPE around Rawlins and Carbon County, which could lead to heavy snow and high snowfall rates at times. Hi-Res guidance like the HRRR does show convective showers popping up throughout the day west of the Laramie Range. With the amount of instability present, cannot rule out a few rumbles of thunder in both snow and rain showers. The 250 mb jet will also be positioned over the CWA, leading to yet another windy day. Lee-side troughing will increase pressure gradients over the Laramie Range, with winds aloft strengthening up to 55 kts. Strong subsidence could drive these winds down to the surface, with in-house guidance showing 40 to 50 percent probabilities of high winds for the Laramie Range wind prones. As a result, issued High Wind Warnings for Platte County, including Bordeaux, and the South Laramie Range and foothills. Wind will ease Monday evening, leading to a brief break in high winds.

High winds will likely return on Tuesday as the CWA sits under zonal flow. Winds aloft will crank up to 65 kts by the afternoon hours with strong downward omegas. By the afternoon wind prones and wind prone adjacent areas could be affected by high winds. High winds will continue into Tuesday night. Under zonal flow, conditions will be drier with mostly sunny skies. High temperatures will range from the 40s to the 50s.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Issued at 259 PM MST Sun Jan 4 2026

The long term will be characterized as active. The period will start with weak northwest flow over the region with a shortwave disturbance embedded within it which will bring windy conditions Tuesday evening through Wednesday as well as light mountain snow. By Wednesday night into Thursday morning, the southwest flow will have shifted farther to the east with slight chances (<10%) of low elevation light snow.

Primary concern through the long term will be the high winds that will accompany the disturbance that will cross the region late Tuesday evening and persisting through Wednesday morning. Surface wind guidance also shows strong low level winds and in-house guidance shows Bordeaux seeing nearly 80-90% probabilities of sustained between 38-48 kts (43-55 mph) Tuesday evening into Wednesday morning with gusts between 55-63 kts (63-72 mph). 700 mb deterministic guidance shows another strong 700 mb jet lining up along the ridge lines and out across some of the lower terrains with peak gusts of 72-78 kts (82-89 mph) Tuesday night which signals high probabilities the winds will mix down to the surface with 80-90% confidence. All this leads to higher confidence (90-100%) that there will be a high wind event occurring Tuesday evening through Wednesday morning.

Tuesday evening models are in firm agreement with the upper level flow aloft being slightly northwest. This will dampen the amount of snowfall expected along the ranges. 72 totals have dropped significantly between the last runs with models now showing less QPF over the region. Tuesday night into Wednesday morning there is no accumulation expected. However, by Wednesday morning, models show the flow aloft to shift to the southwest. This will allow for some moisture advection into the region. Deterministic guidance does show some precipitation coming in over the mountains, but QPF amounts have dropped and the Sierra Madres are only looking at up to inches between Wednesday and Thursday with 60-70% confidence, while the Snowy Range will see 55-65% confidence in 0.5-1 inch. Thursday to Friday there is 50-70% confidence in the Sierra Madres seeing an additional 3 inches and the Snowys seeing 1 inch. By Friday, models become a bit more diverged and snow accumulations drop off to little to no accumulations.

Lastly, while clusters show a bit of divergence in the models with the incoming trough with regards to positioning and timing, models do agree on at least there being southwest flow aloft through the period. As the southwest flow aloft continues to build, temperatures will begin reflecting the cooler temperatures and by Thursday, temperatures east of Laramie Range will see highs below 50. These temperatures Thursday are still averaging nearly 10 degrees above normal, however, the trend in the long term is downward through the early weekend before another possible swing in the warming direction may return.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1110 PM MST Sun Jan 4 2026

Another Pacific disturbance aloft will move across the region over the next 12 to 18 hours, producing some light rain/snow across central Wyoming. Otherwise, breezy or windy conditions will continue across most of the area with BKN-OVC high cloudiness.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail for most terminals, the only exception will be KRWL, which has the best chance of seeing some rain/snow shower activity tonight through Monday morning. MVFR conditions are possible (30% to 50% chance), so added a TEMPO and prevailing groups accordingly until 19z for MVFR CIGS. Low confidence with VIS impacts due to snow, so kept VCSH for now. Otherwise, windy conditions expected for KLAR and KCYS after 15z with some LLWS possible between 06z and 15z Monday morning.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Warning until 5 PM MST this afternoon for WYZ106-110- 116. High Wind Watch from late tonight through Monday afternoon for WYZ106-107-116-117. Winter Weather Advisory from 11 PM this evening to 11 PM MST Monday for WYZ112. NE...None.