textproduct: Cheyenne

KEY MESSAGES

- A High Wind Warning has been issued for the wind prone areas of southeast Wyoming beginning Monday evening and continuing through noon Tuesday. - Long term remains active with multiple systems promoting prolonged periods of high winds alongside mountain snow and chances of lower elevation snow as well.

- Temperatures will remain very cold through mid-week, before a weak warming trend arrives Wednesday onwards.

SHORT TERM /THROUGH TUESDAY/

Issued at 255 AM MST Mon Dec 1 2025

Current IR Satellite loop shows the upper level trough responsible for the light snow on Sunday moving eastward with the trough axis near the Colorado/Wyoming/Nebraska border at this hour. Light snow has either ended or tapered to brief snow flurries early this morning with no additional snow accumulation expected. Therefore, cancelled the Winter Weather Advisory for the mountains with most locations showing between 4 to 7 inches. Very cold temperatures remain over the area with readings in the single digits to low teens for most places. A few below zero readings are starting to show up, but temperatures will likely not fall too much more with increasing westerly winds and some patchy fog in the more sheltered valleys. Once the upper level system ejects eastward, it should pull most of the arctic airmass with it as 700mb temperatures increase above -10c. High temperatures today will likely climb above freezing for some areas, especially far southeast Wyoming and western Nebraska.

Main forecast concern over the next 36 hours is locally strong winds over the wind prone areas...bringing some concern for blowing snow in addition to wind gusts around 70 MPH. Models show another disturbance quickly digging south into the Pacific NW, Idaho, and Montana late this afternoon and tonight. This system will include a strengthening upper level as it moves southeast as the arctic airmass retreats eastward. All models show low to midlevel pressure gradients quickly responding with increasing 700mb subsidence along the spine of the mountains. The GFS, NAM, and Canadian continue to show 700mb winds increasing to 65 knots by early Tuesday morning. Models appear to have leveled off with these winds speeds with very little chance from 24 hours ago. In-house wind guidance continues the upward trend with probabilities...now nearing 90% to 95%. Guidance is also showing higher probs for the central and southern Laramie Range...up to 70%. With growing confidence, upgraded the High Wind Watch to a Warning. Decided to start the Arlington/Elk Mountain zone early and closer to 2 PM with most models showing an earlier trend for gusts over 50 MPH during the day. Smaller timing window for Bordeaux and the I-80 Summit, but after looking at recent data, may need to extend the I-80 Summit through Tuesday afternoon. Will let the next shift(s) take another look at it though before making any adjustments.

Otherwise, kept blowing snow in the forecast for portions of I-80. However, won't have any current surface snow depth observations for another 4 hours, so confidence is limited at this time. With the increasing winds, and breezy conditions outside the wind prone areas, temperatures tonight won't be as cold with lows generally in the teens to low 20s.

For Tuesday, strong winds will continue for the wind prone areas with breezy conditions elsewhere as the upper level disturbance across the PAC northwest becomes a broad upper level trough as it digs southeast into Wyoming and Utah. With increasing westerly downslope winds and "warmish" air out ahead of the trough, expect temperatures to respond with a brief warming trend as highs return to the mid 30s (west) to mid 40s (east). This will help settle the snowpack with diminishing blowing snow concerns once we get into late Tuesday morning.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Issued at 300 AM MST Mon Dec 1 2025

Long term forecast remains on track. Edited previous discussion to take out mention of Tuesday's high wind event (see short term discussion). Otherwise, another light snow event, similar to the previous two this past weekend, is still on track for Tuesday night and Wednesday. Models have trended a little further south with this system, but the I-25 corridor and areas west of I-25 still look like they'll receive another few inches of snow with this system. The 00z ECMWF has backed off on the slower solution, but 33% of it's ensemble members still show 0.20+ QPF. Otherwise, a progressive northwesterly flow pattern is expected past midweek...which typically leads to increasing winds across the area, several chances for mountain snow, and even some low elevation snow...especially across southeast Wyoming Friday night and Saturday.

Previous discussion... Issued at 339 PM MST Sun Nov 30 2025

Long term remains active thanks to multiple systems bringing rounds of precipitation alongside long durations of high winds, with temperatures steadily warming during the later part of the week to bring us back to near normal by the weekend.

Meanwhile a few models have shown some increased QPF which would lead to higher snowfall late Tuesday and into Wednesday, but the majority of ensembles and the NBM are keeping QPF in the mountains and to our south, so the expectation remains we'll see amounts high enough to warrant products, at least advisories, in the mountains, with around 1-3 inches in the lower terrain thanks to shadowing effects.

Moving into Wednesday and Thursday, both days should be relatively calm and dry as the ridge tries to build in, but our winds will once again begin increasing on Thursday in response to the next approaching system as pressure gradients tighten and the 700mb jet begins to re-establish and remain firmly planted over the CWA through the weekend. In house guidance continues to highlight this period and with such consistency there is moderate to high confidence in a multi-day high wind event once again for our wind prone regions. Meanwhile models expect that this flow should allow for more chances of mountain snowfall with some of this able to spill over into the adjacent high plains, but once again shadowing effects are likely going to limit how much accumulation we can produce outside of the high terrain. Finally our temperatures start off near normal on Tuesday with highs in the 30's to 40's, dropping notably on Wednesday thanks to the passage of the front with the first system and highs not making it out of freezing, but as the ridge tries to take control through the weekend a modest warming trend should bring us back to the 30's and 40's by Saturday.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1012 PM MST Sun Nov 30 2025

Snow showers are slowly tapering off across southeast Wyoming and western Nebraska. IFR ceilings have remained behind at KCYS, with MVFR to near-IFR ceilings possible at KLAR in the next few hours. Ceilings remain at VFR status in the Panhandle, though visibility will fluctuate with remaining snow shower activity across KBFF, KSNY, and KAIA for the next 1 to 3 hours. Clouds slowly clear out overnight with light winds. Gusty conditions return for the afternoon hours with clear skies expected at most terminals.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Warning from 8 PM this evening to noon MST Tuesday for WYZ106-116-117. High Wind Warning from 2 PM this afternoon to 8 PM MST Tuesday for WYZ110. NE...None.