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.

- A Winter Weather Advisory has been issued for the Sierra-Madre and Snowy ranges for Tuesday morning through Wednesday morning. - 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 308 PM MST Mon Dec 1 2025

We're already beginning to see winds increase along the I-80 corridor with speeds gusting in the 50 mph range. This should continue through Tuesday as the low level begins to set in with speeds in the 50-65 knot range and favorable downward omega values, alongside strong cross pressure gradients. In house guidance also shows a high probability of high winds for our usual wind prone locations, with high (80%) confidence overall we'll achieve high winds for our warned locations (Arlington, Bordeaux, and Laramie Summit regions). Have increased confidence in higher winds lingering across at least Bordeaux but possibly the Summit as well, and have therefore extended these warnings through 5 PM on Tuesday. Meanwhile as we see the current trough push through the region and a second upper level system dig in and strengthen across the Western US and then into the Four Corners region, snow is expected to begin increasing for our mountain zones beginning Tuesday morning and persist through Wednesday morning. High res ensemble guidance paints a moderate to high (60-70%) probability of snowfall amounts 6+ inches for these zones, leading to good confidence in at least advisory level accumulations, and a Winter Weather Advisory has been issued from 5 AM Tuesday through 11 AM Wednesday for this. And while snow is expected to spill over into the adjacent zones and some of the high plains, shadowing should keep the bulk of this from being impactful, with only a dusting to around 1-2 inches for adjacent zones primarily along the I-80 corridor. Finally, the fresh incoming snow alongside already fallen amounts with the breezy winds will bring a threat of blowing snow, and have continued this in the grids impacting mountain and adjacent zones including into the I-80 area.

Otherwise look for a slight warmup on Tuesday as temperatures reach closer to near normal for this time of year, but a cold airmass with the second system will help to drop us right back down with highs stuck below freezing again on Wednesday.

LONG TERM /TUESDAY NIGHT THROUGH MONDAY/

Issued at 308 PM MST Mon Dec 1 2025

Mean northwest flow aloft looks to persist through the period with hints of shortwave ridging intermittently putting a damper on what seems to be near daily snow chances across the Snowy and Sierra Madre ranges. Current ensembles and clusters paint this picture well with a shortwave ridge both on Thursday and Monday passing within the vicinity of the forecast area though slight variations exist in the amplitude and track that could impact the nightly radiational cooling potential (Thursday AM lows in the single digits to teens). After a chilly Thursday morning highs climb back near freezing in the afternoon.

High winds look to return Friday after a quiet few days wind-wise Wednesday/Thursday with the in house guidance showing a greater than 60 percent chance for high wind criteria in the typically wind prone areas. This is expected to be a long duration event with the 700mb jet between 45-55kts per clusters and a tightening pressure gradient working to get these winds to the surface. At the same time things look to turn wintry once again by Friday afternoon in the mountains with several inches likely in the Snowy and Sierra Madres through Sunday as more shortwave activity brings moist flow to the higher elevations. However once again shadowing effects are likely going to limit how much accumulation we can produce outside of the high terrain. Near average temperatures continue into the weekend as we feel the impact of ridging (and the embedded shortwave activity on its eastern periphery producing the snow) keeping highs in the 30s and 40s through the weekend.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 424 PM MST Mon Dec 1 2025

VFR conditions will prevail across most terminals for nearly the entire duration of this TAF period. The one exception, KRWL, snow chances increase Tuesday morning which may reduce VIS down to MVFR. At the tail end of this TAF period, light snow may spread across terminals in southeast Wyoming. Gusty winds will impact many terminals, with gusts generally in the 25 to 30 knot range, while KRWL may gust up to 35 knots. In addition to the gusty surface winds, wind shear may affect KCYS and KBFF through 18Z and 15Z, respectfully.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Warning from 8 PM this evening to 5 PM MST Tuesday for WYZ106-116-117. High Wind Warning until 8 PM MST Tuesday for WYZ110. Winter Weather Advisory from 5 AM Tuesday to 11 AM MST Wednesday for WYZ112-114. NE...None.