textproduct: Cheyenne

KEY MESSAGES

- Gusty winds will continue through the early evening for much of southeast Wyoming.

- Strong winds may continue into Saturday for the wind prone areas, but confidence in speeds and timing is low.

- Isolated thunderstorms will be possible in Carbon County over the next several hours, bringing the potential for brief heavy rainfall and small hail.

- Snow showers will return to the mountains and adjacent valleys Friday night, spreading into portions of the High Plains Saturday night.

- A strong cold front Saturday night will bring more winter-like temperatures back to the area for Sunday and Monday.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 330 PM MST Thu Dec 25 2025

Highly anomalous weather continues across this area this Christmas Day. Several locations already broke daily record highs before 11AM this morning, though values were not quite as warm as yesterday due to increased cloud cover ahead of a subtle upper level shortwave. This feature is now apparent on GOES water vapor imagery, just crossing over into Nebraska. A dry slot is apparent right behind the axis, with improved moisture immediately behind. The upper level system is also helping to draw the east, resulting strong winds spreading into the I-25 corridor over the last few hours. Pressure gradients across the barrier should come down around 5PM, bringing at least a lull in the wind to most of the area. Meanwhile, a secondary surface trough currently straddles central Wyoming from southwest to the northeast. Convergence along the boundary is helping to produce some banded shower activity associated with low- level frontogenesis. This activity is located in an area of surprisingly high instability for this time of year. The latest mesoanalysis from the RAP indicates surface based CAPE exceeding 1000 J/kg along with bulk shear approaching 50 knots. Numerous lightning strikes have been observed in Sweetwater County, slowly moving off to the northeast. This will have the potential to produce small hail, gusty winds, and brief downpours across central and northern Carbon county through the early evening hours. Forcing for this activity should evaporate by around 8PM or so.

The break in the wind may be fairly short lived as parameters creep back to being marginally supportive for strong to high winds in the wind prone areas by around midnight. Cross-barrier height and pressure gradients are largely unimpressive, but 800-mb to 700-mb modeled winds consistently fluctuate between about 40 and 60 knots through Saturday morning. In addition, models show a good signal for descent in the immediate lee of our mountain ranges. Overall, these mixed signals produce a low confidence wind forecast for late this evening through Saturday morning. In-house model guidance is not particularly helpful either, with probabilities mostly between 30 and 50%. Will wait to make the decision until after expiring the current round of wind headlines at 5PM, but currently leaning towards a marginal High Wind Warning for Arlington/Elk Mountain and Bordeaux through mid afternoon Friday. There may be another window for strong winds (which could include the I-80 summit too) Friday evening into Saturday morning, but will probably wait to tackle that one later. Elsewhere across the area, Friday will bring another warm day, but not quite as warm as the last several days with 700-mb temperatures knocked down to around 0 to +2C behind today's shortwave. Forecast highs are still within a few degrees of daily records almost everywhere, but we probably won't have every climate site break records like we have seen the last several days.

Lastly, we will finally begin to see the weather pattern trend closer to a more typical wintertime pattern Friday night. An initial cold front during the overnight hours (ahead of a much stronger front Saturday night). Mid-level moisture will return to the southwest flow simultaneously, spreading snow showers back into Carbon County. This will be driven by a band of frontogenesis combined with orographic lift on west and southwest slopes. More about this system is described in the long term section below, but travel impacts may be present in Carbon County as early as late Friday evening.

LONG TERM /SATURDAY THROUGH THURSDAY/

Issued at 330 PM MST Thu Dec 25 2025

Friday night into Saturday morning an upper level trough will be pushing through the Intermountain West. As this trough pushes through the Intermountain west there will be some moisture and colder air associated will it. NAEFS Integrated Vapor transport (IVT) depicts IVT values to reach and remain in the 90- 98th percentile from late Friday night and throughout the day Saturday. The longer ran models of Hi-res guidance progs a frontogenetical band setting up somewhere near the Sierra Madres and Snowy ranges. The 15z RRFS and NAM-Nest have this band over the Mountains themselves and forecasting between 10 and 22 inches with the higher amounts over the Sierra Madres given the Southwest to westerly flow that favor the Sierras over the Snowy's. The Euro and GFS have the band of FGEN setting up a little more south over the WY/CO border. So the possible accumulations weren't as high but still gave around 7 inches with a 10:1 ratio. Given the atmosphere will be more like 15:1 or higher given the time, temperature, and moisture content of the air. A winter storm watch as snow accumulations between 13 to 20 inches were placed in the grids to match high-res guidance. It will be interesting to see how the HRRR handles the arctic front once its within the models resolution time. Temperatures will drop as the arctic front pushes through the region. The overnight temperatures look to drop into the teens and single digits (for some areas) as the colder air settles into the region. This will also bring colder but seasonable temperatures to the region Sunday with temperatures in the mid to upper 20's for majority of the CWA. However, these winter- like temperatures will be short lived as both model and ensemble guidance look to reach a consensus about another upper level ridge setting up and pushing into the region these last few days of December.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 440 PM MST Thu Dec 25 2025

The winds are gusting higher than expected this evening across the Wyoming terminals. Winds are expected to stay gusty overnight at the Wyoming Terminals. KLAR may have intermittent gusts due to the topographic bowl that they are in. Some showers are working their way east just north of KRWL once these showers dissipate the next wave of showers arent expected until 06z on the 27th. Low level wind shear will once again be a concern through the early morning hours after 06z or 11pm tonight. Westerly winds between 40 to 50 knots at 2,000ft is what the low level shear is forecasted to be at.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Warning until 5 PM MST this afternoon for WYZ101-106- 107-110-115-116. High Wind Watch from 8 PM MST this evening through Friday afternoon for WYZ106-117. Winter Storm Watch from late Friday night through late Saturday night for WYZ112. High Wind Warning until 8 PM MST this evening for WYZ117-118. NE...None.