textproduct: Cheyenne

KEY MESSAGES

- Much colder temperatures today with well-below average temperatures expected through early Monday morning with low temperatures in the single digits possible.

- Gradual warming trend Monday through Wednesday with periods of very windy conditions across the wind prone areas of southeast Wyoming.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 250 AM MST Sun Dec 28 2025

Current observations across the region show that the arctic front has progressed south and west through most of southeast Wyoming and all of western Nebraska early this morning with temperatures currently in the teens and wind chill readings below zero at this hour. Arctic front responsible for the very cold airmass is now pushing south across Colorado and central Nebraska/western Kansas. The upper level trough axis and secondary disturbance have not exited the region quite yet and will likely take its time ejecting eastward. The main vort max/disturbance is expected to briefly enhance snowfall rates for a few hours this morning with IR Satellite showing some cooling cloud tops over southern Wyoming at this hour. With this in mind, increased POP from Carbon county eastward into Laramie County and the far southwestern part of the Nebraska Panhandle. High res guidance continues to show another band of light to moderate snow moving along the I-80 corridor through sunrise. May see another half inch of snow from this early this morning, but impacts should be limited. Let most of the Winter Weather Advisory expire for the lower elevations of Carbon County. However, the northern Snowy Range foothills, including Arlington and Elk Mountain, continue to show visibility down to 1/2 mile in periods of snow. Extended this portion of the Advisory until 800 AM with Webcams in that area showing snow covered and icy roadways and difficult travel conditions. For the mountains, the Snowy Range was a bit of a surprise in this event with SNOTEL sites showing over 2 feet of snow in a few places...and a minimum of 10 inches. Therefore, upgraded the Advisory to a Winter Storm Warning this morning as that previously mentioned band of moderate snow moves into the area shortly, resulting in another 3 to 6 inches of snow.

Cold day is still expected today (Sunday) as the snowfall will gradually come to an end by the afternoon. Can't rule out some occasional flurries across southeast Wyoming this afternoon, but no additional accumulations are expected. Another very cold night expected tonight with single digit temperatures and low teens for lows. Added some below zero readings due to models trending a bit colder across the western Nebraska panhandle...mainly near Alliance and Chadron Nebraska.

The only other concern today will be winds and the potential for additional blowing snow in the wind prone areas. Models have trended a little more aggressive with strong gusty winds across a few of the wind prone areas this afternoon and this evening as a lee-side inverted trough forms near the mountains in response to the arctic front becoming a stationary front later today and slowly moving east over the next 24 hours. 00z GFS and Canadian shows increasing 700mb winds for a time late this morning through this afternoon with winds as high as 60 knots. Upgraded the High Wind Watch to a Warning for the I-80 Summit due to high confidence in WNW winds as high as 65 MPH. Can't rule out Arlington either, so added the northern Snowy Range foothills to the High Wind Watch. Not completely confident in warning criteria, but the zone tends to do well in this pattern; in- house wind guidance confirms this with probabilities around 60 percent. The southern Laramie Range foothills have been tricky this year, so kept them in a Watch for now.

Slow warming trend begins on Monday as an upper level ridge builds into the area from the eastern Pacific and 700mb temperatures climb above -5c. Still expect a near or slightly below average day for temperatures with highs in the 30s to low 40s. Will continue to monitor wind potential for the Wind Prone areas late Monday night, but models have backed off on the magnitude of low level subsidence and weaker 700mb winds compared to the last several models runs.

LONG TERM /TUESDAY THROUGH SATURDAY/

Issued at 312 PM MST Sat Dec 27 2025

Not much to talk about as conditions across the CWA will be pleasant under ridging that will slide in and dominate weather conditions for most of the long term period. So, lets dive in a bit deeper, at the start of this forecast period, a robust upper-level high at 500mb sits off of the California Coast while a deep low is parked over the Great Lakes region, this keeps dry northwest flow pouring into our CWA. As we progress, the low over the Great Lakes slides east while the high and associated ridge pushes across the Intermountain West into our region by Wednesday afternoon. This continues dominates our weather here locally on Thursday and most of Friday. Then, some things begin to change with a shortwave diving south late Friday afternoon. In-house guidance has a few differences in solutions, primarily with placement and timing of this shortwave, but this is something to watch heading into next weekend due to the possible pattern change. At the surface, not much to write home about with high pressure dominating, keeping weather conditions across the CWA benign for a large chunk of this long term period. As mentioned previously, with the shortwave aloft diving south late Friday, this may increase chances of precipitation for next weekend. So, in the meantime, expect these abnormal conditions to continue, especially with high temperatures, as they soar back into the 40s and 50s, some locations may top out in the low 60s, with the warmest temperatures east of I-25, along with minimal to no precipitation chances. Winds, which have been hammering our known wind prone areas over the previous several weeks, we will get a reprieve from any major events through next weekend.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1030 AM MST Sun Dec 28 2025

With the passage of an arctic cold front earlier this morning, precipitation has ended and skies are clearing. So, VFR conditions will prevail for the duration of this TAF period across all terminals. Winds will be the only aviation concern for this forecast, west to northwest gusts will be ramping up into the 30-45 knot range through 03Z Monday. In addition, LLWS for KCYS is possible from 04Z Monday to 12Z Monday.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Warning until 8 PM MST this evening for WYZ110. High Wind Warning until 8 PM MST this evening for WYZ116. High Wind Watch until 8 PM MST this evening for WYZ117. NE...None.