textproduct: Cheyenne

KEY MESSAGES

- Record breaking warmth is expected to continue through at least Thursday.

- Brief high winds possible on both Christmas Eve and Christmas with gusts up to 65 MPH. Strong winds continue into Friday.

- Brief taste of winter expected Sunday into Monday.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 232 AM MST Wed Dec 24 2025

Warm and windy weather will continue today for much of the CWA as broad upper-level ridging remains in place. 700mb height gradients have begun increasing early this morning and the Arlington/Elk Mountain zone has started gusting over 58mph. This period of high winds will be fairly short-lived, with winds decreasing by around 11AM this morning. A brief lull is expected this afternoon into the early evening hours before winds start to increase once again. Winds turn southwesterly aloft as a shortwave trough pushes through the flow to the northwest of the CWA. 700mb height gradients will strengthen as the shortwave moves through, leading to a strong southwesterly 700mb jet around 55 to 60kts across western portions of the CWA. Strong downward omega values in the GFS suggest that these strong winds will mix down to the surface, likely resulting in wind gusts up to 65mph across much of Carbon County. As a result, went ahead and issued another High Wind Warning for most of Carbon County from 7PM this evening through 11AM Thursday and for the Arlington/Elk Mountain zone from 11PM tonight through 2PM Thursday.

700mb wind slowly turn from southwesterly to westerly during the late morning and early afternoon hours on Thursday. As a result, a westerly 700mb jet will kick up along the Laramie Range early Thursday afternoon, with a jet maximum of around 55 to 60kts. Maxed out downward omega values are expected to develop along with this jet, leading to increasing wind concerns for I-25, especially the Bordeaux wind prone zone. Around a 4mb surface pressure gradient sets up west to east along the Laramie Range, further increasing the potential for high winds. A downstream 700mb trough is expected to form just east of the Laramie Range and strengthen. AS this strengthens, the 700mb jet along the southern Laramie Range will kick up to 50 to 55kts by late Thursday night. With downward omegas forecast to maxed out at this time too, wind gusts at the surface in the I-80 Summit and Foothills zones could gust up to 60 to 65mph. With this setup acting as a second, separate event from the High Wind Warning, decided to issue a High Wind Watch for the Bordeaux, I- 80 Summit, and South Laramie Range Foothills zones from 2PM Thursday through 2PM Friday. Central Laramie County has the potential to also reach high wind criteria, however, this period is slight delay from about 11PM Thursday night through 11AM Friday morning. Therefore, kept central Laramie County out of the Watch for now, but will let later shifts take another look at the setup.

Record warmth is expected again today and tomorrow, as 700mb temperatures remain above the 95th percentile for most of the region. High temperatures today look to max out in the mid-50s to low-60s west of the Laramie Range and mid-60s to low-70s east of the Laramie Range, where downslope warming will promoted higher temperatures. Similarly, Thursday boasts highs west of the Laramie Range in the low- to mid-50s with highs east of the Laramie Range in the low- to upper-60s. 700mb temperatures will remain above the 95th percentile Thursday as well.

In addition to record warmth, the remnants of the atmospheric river currently impacting the western coast will start to move in to the CWA late this evening throughout the day Thursday. NAEFS Mean IVT suggests IVT values above the 99.5th percentile across the higher elevations. As a result, mountain snow chances begin to pick up this evening throughout the day Thursday. The Sierra Madres may see anywhere between 3 to 5 inches of snow, with less in the Snowies due to the shadowing effect. The best chance for mountain snow exists early Friday morning throughout the day were the mountains could see between 6 and 12 inches of snow.

LONG TERM /FRIDAY THROUGH TUESDAY/

Issued at 232 AM MST Wed Dec 24 2025

No major chances for the long term forecast. See previous discussion for more details...

The main focus of the long term forecast is the sprawling, disorganized storm system that will slowly move through the area this weekend. Picking up Thursday night, the synoptic pattern will remain dominated by a broad ridge over the central CONUS with southwest flow aloft. Remnant moisture from the west coast storm system will stream into the area, continuing mountain snow shower activity through Saturday. Southwest flow will favor the Sierra Madre range while the Snowy Range will receive less. Expect mixed rain and snow showers to spill into the neighboring valleys of Carbon and Albany counties through Friday, but this should become mostly or all snow Friday night into Saturday as colder air moves in and snow levels drop. Elsewhere, Friday will bring one more day of well above average temperatures, although it should be several degrees cooler than the earlier part of this week. Highs will "only" be 15-20F above average. These will still be within a few degrees of daily record highs, with Chadron and Alliance currently most likely to match their daily records. Breezy to windy conditions will also continue over most of the area ahead of the surface cold front. Pressure and height gradients across the area are unimpressive, but most guidance has 700-mb winds around 40 knots covering much of the area. High wind probabilities are around 25% for Arlington/Elk Mountain, and near 50% the I-25 corridor wind prone areas and the I- 80 summit. Winds were nudged towards the NBM 75th percentile for this period.

Gusty winds may carry into friday night or early Saturday, but a break in the windy pattern is expected by Saturday afternoon or evening. A strong upper level low will pass well to our north this weekend, but a potent surface high will dive down the eastern side of the Rockies in its wake. Expect temperatures to drop quickly behind this front, ushering in colder air by Sunday. Currently, this system looks to be unsurprisingly moisture starved. However, almost all of these weak arctic fronts this season have managed to over perform with fairly widespread light snow showers. Therefore, decided to bump PoPs up ever so slightly over the High Plains to get a mention of a slight chance for snow Saturday night. 700-mb temperatures will bottom out around -10C Sunday morning. While this appears in some aspects to be a dramatic cold front, this is not likely to be a substantial cold air outbreak at this time. Forecast highs for Sunday are generally in the 30s, which is near average west of I-25 and a few degrees cooler than average to the east.

This taste of winter will be short-lived as models are now in excellent agreement showing another very strong upper level ridge building in early next week. There is some discrepancy in timing of the return to above average temperatures, but expect a warming trend to resume in the early part of next week. During this phase of the warmth, the jet stream looks to be pushed well to the north, so we are not expecting the widespread strong winds we have seen the last two weeks. Occasional marginal wind prone area wind events will still be possible, but widespread wind events look fairly unlikely for the last few days of 2025.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1042 AM MST Wed Dec 24 2025

Mid to high based clouds will be pushing through the forecast area over the next 24-36 hours. VFR conditions are expected through the TAF period. Winds are expected to be between light or calm for terminals east of I-25 to include KCYS and the all the Nebraska terminals. Winds look to remain rather gusty for KRWL but are expected to drop off overnight and become gusty again for KLAR around 15z.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Warning from 7 PM this evening to 11 AM MST Thursday for WYZ104-109. High Wind Watch from Thursday afternoon through Friday afternoon for WYZ106-116-117. High Wind Warning until 11 AM MST this morning for WYZ110. High Wind Warning from 11 PM this evening to 2 PM MST Thursday for WYZ110. NE...None.