textproduct: Cheyenne

KEY MESSAGES

- On and off high winds continue for the wind prone areas, with the next round on track for Thursday night into Friday.

- Accumulating snow is expected in the Snowy and Sierra Madre Ranges through Friday. Winter Weather Advisories are in effect.

- Above average temperatures, breezy conditions and a chance of precipitation primarily in the mountains expected through early next week, with a pattern change possible late.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 300 PM MST Thu Jan 1 2026

Mild temperatures continue across the area today with the broad ridge remaining stuck over the western United States. Meanwhile, an expansive closed low is undercutting the ridge aloft, spreading moisture and cloud cover across most of the region. The upper level low center is still well to our west in central California, but an elongated band of vorticity aloft stretches out ahead of it, all the way from the Pacific northwest down to western Texas. Despite mostly cloudy skies over the area, temperatures are still surging to values well above average for the first of January, with the early part of 2026 picking up just how 2025 ended. Ample moisture advection continues out of the southwest, with the column beginning to approach saturation in our western zones. Orographic lift will increase snowfall in the higher elevations through this evening. The vort-max aloft will also provide some overrunning isentropic lift which will fill in elevated shower activity over valleys and the High Plains. It will take some time to saturate the lower atmosphere, but expect improved low level moisture to migrate slowly eastward through the evening. Rawlins has already seen humidity improve to 75% as improved moisture mixes into the boundary layer. While we can expect to see some radar echoes developing over the next few hours over the High Plains, anything reaching the ground is more in question. For example, Cheyenne is currently sitting at a dewpoint of 11F, supporting an RH of 15%. It will take quite a bit of time to saturate this very dry boundary with moisture injected from aloft, but expect to see dewpoints back into the 30s during the evening hours. Once low-level moisture improves after dark, we should see some light rain/snow showers spread into the valley and plains portions of the area, but impacts will be limited outside of the mountains.

For the higher elevations, we have precipitable water exceeding the 99th percentile with southwest to westerly flow aloft. The extremely warm temperatures are making it a little easier to hit these impressive PW values, but IVT still remains around the 90th percentile of climatology. This should promote light to moderate snowfall through the night and into the daytime on Friday. As discussed previously, we are pretty close to needing to upgrade the Winter Weather Advisory to a Winter Storm Warning, but decided to hold off again with this forecast package. We still may see above 12" in portions of our mountain zones, but this should be confined to the higher peaks, generally above 9 kft in the Sierra Madre Range and above 10 kft in the Snowy Range. In addition, the disorganized nature of this system reduces confidence somewhat. GOES water vapor imagery shows a significant dry slot currently moving across central Utah that would be on track to arrive in our mountain zones in about 5-6 hours or so. This may reduce snowfall rates or even shut off snow entirely from about mid evening through early Friday morning, although most hi-res models show snowfall continuing unabated through this period. This kept confidence too low to upgrade on this shift, but if the dry-slot or potential lull fails to materialize by about 8PM or so, an upgrade may still be needed for the Sierra Madre range. Regardless, expect snow to continue for the higher elevations on and off through the day Friday and taper off during the afternoon or evening hours.

The other primary concern in the near term will be the continued on and off marginal high wind threat for our wind prone areas. Southwest flow aloft this evening will support lee cyclogenesis in the form of an elongated surface trough stretching nearly the entire extend of the Rockies from Alberta into northeast New Mexico. As the pressure gradient tightens, we will see the wind threat increasing once again. Craig to Casper height gradients are marginal but sufficiently supportive of high winds, reaching 55 to 60 meters late this evening into Friday. 700-mb winds also creep up, with LREF mean values exceeding 50 knots Friday morning. This increased gradient will be associated with a secondary upper level shortwave currently visible as a kink on the upper level height contours moving across Idaho just behind the elongated band of vorticity. Confidence is sufficient for reaching high wind criteria in the I-80 wind prone areas, with probabilities around 70%. For I-25, there is a bit more uncertainty. During the period of the best gradients overnight and early Friday morning, most models show a pretty consistent signal for ascent along most of I-25 in Platte and Laramie Counties with the surface trough west of the highway. However, once the upper level shortwave trough axis passes over the area around sunrise Friday, it should pull the surface trough to the southeast as a low pressure center wraps up. This will draw winds eastward into the High Plains Friday morning, but we will be past the best forcing aloft at this time, so it may be difficult to reach high wind criteria. As a result, probabilities are around 30% for the wind prone areas of I-25. Confidence was too low for a Warning, but this should still warrant some messaging, so decided to opt for a High Wind Watch.

For the rest of the area, expect this low passing through to knock down temperatures by several degrees. We will be generally 5-10F cooler than today over the High Plains with breezy conditions across the area. In addition, the passage of the shortwave will nudge the stalled arctic frontal boundary currently well to our northeast slightly to the southwest. This may sneak into the Chadron area on Friday, which could keep highs considerably cooler than the rest of the area.

LONG TERM /SATURDAY THROUGH THURSDAY/

Issued at 300 PM MST Thu Jan 1 2026

A quick moving system from off of California will continue to disrupt the upper level ridge pattern into the the weekend, helping to bring a bit more breeziness and mountain precipitation to the region.

Models show the upper level ridge to be over the region with the axis just to the west of the CWA. A disturbance will make its way around the ridge Sunday bringing some mountain precipitation and windy conditions. Mostly dry conditions will persist through the long term with in-house calculations showing temperatures to be well above seasonal average by between 15 to nearly 25 degrees decreasing to 10-15 degrees above average by the end of the period. Temperatures Saturday through Monday for everywhere east of the Laramie Range will be in the mid to upper 50s with some isolated locations seeing low 60s (70-90% confidence).

Models show a disturbance will shift the ridge to a more around the pattern Sunday bringing heightened winds and mountain snow back Sunday afternoon. A relatively strong 700 mb jet with winds between 65-75 kts will align with the North Laramie Range with a decent downsloping signal reaching portions of the lower elevations off the range. In-house wind probabilities have Bordeaux seeing 60-65% probabilities of seeing gusts over 58 mph. There is also a weaker 700 mb jet aligning with the Snowy Range with in-house wind probabilities showing Arlington seeing gusts to over 58 mph as well with 60% probabilities. As for the precipitation expected Sunday afternoon through Monday morning is going to be between 7500-8000 feet with accumulations beginning at 0.2-0.5, 8000 ft an above 1-3 inches with 40-70% probabilities.

Not much has changed from the previous forecast beginning Monday. Models show the back end of the upper level ridge to be breaking down as an upper level low digs in from the PacNW. South-west flow aloft will allow for some moisture advection to infiltrate the western portion of the CWA bringing in some mountain snow. In-house calculations show the ridgetops of the Sierra Madre Range has 60-80% probability of seeing 4-6 inches of snow accumulating between Monday and Tuesday. The Snow Range has 40-50% probabilities of seeing 1-2 inches. Areas between 7000-8000 feet will see between 0.2-0.8 inches while elsewhere will remain dry. Winds associated with this disturbance will also increase Monday into Tuesday with the ridgetops seeing gusts of 35-34 mph (50-70%) while the lower elevations will see 25-30 mph gusts.

AVIATION /06Z TAFS THROUGH 06Z SATURDAY/

Issued at 1040 PM MST Thu Jan 1 2026

KRWL looks to likely stay MVFR through the morning unless that clear spot to the southwest moves Northeast faster. There is a current hole in the clouds near KLAR but expecting to stay VFR for the rest of the TAF period. The line of heavier showers seem to have stalled out to the southwest of KBFF so its uncertain if any showers will make it to KAIA or KCDR. After 18z the sky will start to clear out with SCT to FEW clouds by 03z.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Watch from 2 AM MST Friday through Friday evening for WYZ106-117. High Wind Warning until 8 PM MST Friday for WYZ110. Winter Weather Advisory until 5 PM MST Friday for WYZ112-114. High Wind Warning until 8 PM MST Friday for WYZ116. NE...None.