textproduct: Cheyenne

KEY MESSAGES

- Drier and warmer, but windier conditions are expected Tuesday into Wednesday with a low potential for High Wind criteria being met for the wind-prone areas along the I-80 corridor. - Quieter weather to end the week, but multiple systems are taking shape for the weekend into the start of next week. At this time, model agreement is poor so confidence is low.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 202 AM MDT Tue Oct 27 2026

The system that brought SE Wyoming and the Nebraska Panhandle some beneficial moisture earlier today has since moved off to the north and east, leaving us in a much calmer pattern over the next few days. Gauge observations along with MRMS QPE shows totals as high as 0.75" across mainly the southern portion of the Panhandle, with lighter amounts up to 0.25" across SE Wyoming.

Surface observations at this hour continue to show weak low-level upslope flow in a rather moist air mass, resulting in areas of dense fog mainly east of the Laramie Range. Have decided to issue a Dense Fog Advisory until 9AM MDT for the I-80 corridor including the summit and points east, in addition to the I-25 corridor where visibilities less than 1/4 mile have been observed. Low-level moisture is expected to mix out sometime mid-morning thanks to an increase in our winds (i.e. mechanical turbulence), and any lingering fog should dissipate. Tuesday will feature dry conditions and warmer temperatures relative today ahead of an amplifying wave located off the Pacific Northwest, placing us under WSW flow aloft. Expect highs to be around 5-10 degrees above average east of the I- 25, mainly in the low to mid 60s, with slightly cooler 50s to the west of the Laramie Range. Aside from the notable warming and clearing relative to the previous couple of days, most will also notice an uptick in our winds. This will occur as a deeper closed low phases with a weaker shortwave trough to our north and west, increasing the height gradient and therefore our mid-level flow. Westerly 700 mb flow is expected to ramp up to 45-50 knots through Tuesday morning, with a strong mountain wave signature showing up on the omega fields, mainly across the Snowy Range and to a lesser extent the Laramie Range. One limiting factor that will make this more of a marginal high wind event, rather than a slam dunk, will be the lack of a mountain top stable layer, as model cross-sections aren't showing a tight vertical isentropic gradient (i.e lack of static stability) at mountain top. In-house random forest guidance currently has Arlington with a 40% probability of high wind conditions sometime mid-morning, with Bordeaux at around 20%. Due to the somewhat marginal high wind setup and relatively low confidence, decided to keep the High Wind Watch going until 12PM MDT for the wind-prone areas of the Snowy Range, along with northern portions of Converse County. Decided to nudge up the wind speeds through Tuesday morning from the NBM by going with a blend of the NBM 90th percentile combined with CONS MOS to match the more probable wind gusts up to 50-55 mph for Arlington and other wind-prone areas along the I-80 corridor.

Expect a seasonably chilly, but dry night Tuesday into Wednesday with lows mainly in the 30s and breezy conditions west of the Laramie Range. With much lighter winds to the east of the I-25 corridor, along with high-resolution ensemble guidance having median RH values above 90% in the Panhandle, areas of fog into Wednesday morning are also possible, especially with the recent increase in soil moisture from the past system.

The warming trend will continue into Wednesday as upper-level ridging gradually builds across the eastern half of the country. Under subsidence, cross-barrier flow (albeit weaker than Tuesday), and downsloping, can expect another day with above-average temperatures with highs mainly in the 60s east of the I-25 corridor, and 50s to the west. Conditions will also be breezy across SE Wyoming, although most likely below high wind criteria as surface gradient flow weakens and a rather weak surface low translates to the north and east over the Dakotas. Overnight Wednesday will be much like Tuesday night, although perhaps slightly cooler with a lack of low clouds and light winds. Most locations should hover just above freezing waking up on Thursday, although the usual cool spots of Laramie and Alliance dip down to or slightly below the freezing mark.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 202 AM MDT Tue Oct 27 2026

Mostly quiet weather expected to start the long term forecast as upper-level flow turns west-southwesterly and weakens for Thursday. The next upper-level trough will start to become more amplified off the coast of the Pacific Northwest throughout the day Thursday, while a shortwave develops off the coast of central California. Expecting a nice day on Thursday with highs in the upper-50s to upper-60s across the region with sunny skies turning partly cloudy into the overnight hours. The aforementioned upper-level shortwave will move quickly to the northeast Thursday into Friday as it moves inland with long range models currently suggesting it will impact the region late Friday evening into the overnight hours. However, there is some model disagreement on how quick this shortwave ejects northward. The GFS suggests the shortwave moving through between 06 and 18Z on Saturday, while the ECMWF suggest delayed impact between 18 Saturday and 06Z Sunday. Precipitation chances are anticipated with the passage of the shortwave, with isolated showers possible across the Panhandle as early as 18Z Friday, but a delayed shortwave would delay the increasing precipitation chances across the region. Clouds will accompany this shortwave, with mostly cloudy skies expected throughout the day Friday as the shortwave approaches the region. Friday will be mild with temperatures in the low- to mid-60s everywhere.

While the longer range models had some significant timing differences with the upper-level shortwave moving through, the GFS and ECMWF are in good agreement with the progression of the incoming upper-level trough. This trough is currently progged to move inland Saturday evening, strengthening as it does so. The CWA is progged to be caught between the Sub-Tropical jet across the southern half of the CONUS and the incoming Polar Jet across the northern half of the CWA. As a result, a brief period of zonal flow is anticipated early Sunday morning before upper-level winds turn southwesterly with the approaching system. Monday onwards, long range models start to diverge once again with the GFS suggesting the upper-level low diving southward into northern New Mexico. The ECMWF on the other hand broadens the low and advects it directly overhead, before elongating the trough southward Tuesday morning. Both evolutions would bring widespread precipitation into the region Monday and Tuesday, but the ECMWF evolution would keep precipitation around longer, likely leading to higher accumulation values. Another glaring difference between the GFS and the ECMWF is the 700mb temperatures associated with this system. The ECMWF is much warmer than the GFS, keeping 700mb temperatures around -4 to -2C range, with a brief period of -5C. The GFS, however, suggests a cold system with a longer duration of -5C temperatures across southern portions of the region. Both long range models suggest that some snow would be likely, especially in the overnight hours, with this system, but the GFS evolution would likely produce more snow, given the longer duration of colder temperatures. This evolution will continue to be monitored over the upcoming model runs, to start getting a better idea of storm evolution and precipitation totals. Despite this, cooler temperatures are expected to return for much of next week.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1139 PM MDT Mon Oct 26 2026

Low stratus and fog are expected tonight, mainly for terminals east of the Laramie Range. South to southeast winds overnight will keep low stratus persistent across the area. MVFR to IFR CIGs are expected at western Nebraska terminals and KCYS. Fog is also expected to develop later tonight from light winds and ample surface moisture from rain and snow that fell during the day. Fog and low CIGs will continue into Tuesday morning, with conditions gradually improving as the day progresses.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Dense Fog Advisory until 9 AM MDT this morning for WYZ101-103- 106>108-116>119. High Wind Watch until noon MDT today for WYZ101-110. NE...Dense Fog Advisory until 9 AM MDT this morning for NEZ054-055.