textproduct: Cheyenne

KEY MESSAGES

- Cooler this weekend with temperatures around 5 to 10 degrees below normal.

- Widespread rain and mountain snowfall expected Sunday and Monday as a central Pacific system lifts northeast across the region. - Near normal temperatures and a bit warmer by Tuesday through Thursday, but the next Pacific system will be approaching from the eastern Pacific later in the week.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 150 AM MDT Sun Oct 25 2026

An active beginning to the forecast period, as a vigorous closed upper-level low continues to churn over the Desert Southwest. A considerable moist conveyor belt associated with this system is evident on GOES mid-level water vapor imagery, with numerous shower streaming up from the south and west out of Colorado. Heading through the overnight period and into Sunday morning, these showers are expected to impact mainly the eastern portion of the Nebraska Panhandle as an axis of weak isentropic ascent gradually lifts to the north and east. Decided to increase PoPs through the morning hours across the Panhandle for this reason, although the bulk of the forcing for ascent will remain well to the south and west of our area until late Sunday into Monday as the closed low lifts to the north and east. QPF looks to remain spotty and light for areas across the Panhandle overnight into Sunday morning, with most areas seeing under a tenth of an inch. Areas further west across SE Wyoming should stay mostly dry through the rest of the morning, although patchy dense fog will impact much of the region under the moist, southeasterly upslope flow behind yesterday's FROPA. Decided to go ahead and issue a Dense Fog Advisory for the I-80 summit until 10AM MDT on Sunday for this reason, with WYDOT cameras and sensors showing visibilities under 1/4 mile.

During the day on Sunday, the closed low to our south and west will transition into an open wave as it lifts north and east closer to our area. Expect a relatively gloomy and brisk day, as areas east of the Laramie Range will remain under weak ESE upslope, resulting in a cold air damming setup. Highs east of the I-25 corridor tomorrow will likely be stuck in the 40s given lots of low cloud cover, with locations west of the Laramie Range expected to see highs in the 50s.

Sunday night into Monday morning is when the most active (and wet) weather is expected as the strongest DCVA impacts mainly the Nebraska Panhandle as the wave translates across our area. Deterministic guidance is showing very strong isentropic ascent over the Panhandle counties into Monday morning, with forecast soundings illustrating strong low-level veering/warm advection. Combined with overall favorable kinematics, NAEFS guidance shows PWAT at or above the 99th percentile relative to climatology, translating to over 0.80" of PWAT (!!), which is truly a feat for late October. ECMWF ensemble guidance showing as much as 0.7" of QPF for this event. Wouldn't be surprised to see some locally higher totals up to 1.0" given the anomalous deep-layer moisture and some very weak elevated instability atop the warm nose, with MUCAPE up to 100 J/Kg, allowing for at least some isolated weak convection. Locations east of the Laramie Range across SE Wyoming will likely also expected to see some decent rainfall, however not as impressive as areas further east where the strongest forcing for ascent is expected. Gradually decreased PoPs from west to east throughout the day on Monday to reflect this trend.

Now, the question everyone has been waiting for...Will it snow? Unlikely, but not out of the question is the answer. Latest trends from high resolution ensemble guidance have trended slightly cooler with 700 mb temperatures along the I-25 corridor down to -2C across SE Wyoming. While unlikely to see any accumulating snow across the High Plains of SE Wyoming, this will have to be monitored as any increase in the magnitude of ascent as the system ejects over our area could result in additional cooling of the column. This may allow for a brief transition to snow or a rain/snow mix across SE Wyoming Monday morning, with the latest HREF showing snow probabilities for Cheyenne Monday morning of around 35%. No impactful accumulation is expected at this time, but is worth mentioning due to the current cooling trend.

Precipitation will gradually end from west to east on Monday, with another chilly day expected with highs mainly in the 40s east of the I-25 corridor, and perhaps a few 50s to the west. Chadron and locations north of the Pine Ridge may actually struggle to get out of the 30s for highs on Monday, as weak NE surface flow will keep cool, moist air banked up against the ridge, keeping the areas socked in with stratus. Can expect a seasonably chilly night Monday night into Tuesday with lows primarily in the 30s. Can expect some lingering fog mainly east of the Laramie Range overnight as winds will be rather light, with just a few clouds.

LONG TERM /TUESDAY THROUGH SATURDAY/

Issued at 150 AM MDT Sun Oct 25 2026

Medium to long range models in reasonable agreement through late week, with a period of quiet weather expected for southeast Wyoming and western Nebraska during the middle of the week. Models show moderate southwesterly flow across the area with the polar jet staying north of the Front Range, and the subtropical jet staying well to the south over Texas and northern Mexico. We're kind of in- between these two separate storm tracks for most of the week with mostly quiet weather expected and near or slightly above average temperatures. A pair of potent Pacific shortwave troughs are forecast to impact the area late this weekend and early next week, with the second one likely missing southern Wyoming and remaining north of the area Tuesday. Models show a surface "cold front" rapidly moving east and clipping the forecast area to the north. However, all this front will do is shift low to midlevel winds into the west and increase wind speeds on Tuesday and Tuesday night...producing somewhat warmer downslope winds for a bulk of the area, including the high plains. Will need to watch for High Wind criteria for the typical wind prone areas of southeast Wyoming since most models show 700mb winds increasing over 45 knots by Tuesday morning and remaining elevated through Tuesday night with a decent surface pressure gradient and some hint of brief mountain wave activity. At this time, in-house wind guidance shows probability of wind gusts over 55 MPH around 20% to 45% for Arlington, Bordeaux, and even some of the sub wind prone areas along Interstate 25 near Douglas. For now, increase wind speeds up to criteria but did not increase wind gusts over 60 MPH quite yet. Event should be pretty brief and not too widespread, and peak mid Tuesday morning. Models have backed off on winds Tuesday night/early Wednesday with a slight downward trend, so kept those winds lower for now.

Downslope winds should result in relatively mild temperatures for this time of the year Tuesday through Thursday, but not quite as warm as it has been prior to this weekend. Kept high temperatures in the upper 50s to upper 60s, warmest of the eastern plains below 5000 feet and coolest temperatures across Carbon and Albany counties. Peak temperatures should occur later in the week with highs approaching 70 degrees over the western Nebraska panhandle as an upper level ridge axis across the southern United States and the Gulf amplifies ahead of the next Pacific storm system. Model solutions begin to diverge at this time, which is to be expected nearly 7 days out, as potential long wave trough attempts to settle across the eastern Pacific Ocean with a potent storm system pushing inland and into the Great Basin Region by late next Saturday and into next Sunday. Will have to keep an eye on this storm later in the forecast period as some model solutions and ensembles show a decent amount of colder air along with a subtropical moisture tap from the central Pacific. This pattern typically favors lee-side low pressure systems and an active weather pattern for the Front Range.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1149 PM MDT Sat Oct 24 2026

The main aviation concern overnight will be increasing clouds with the threat of MVFR and IFR CIGs. South to southeast flow across the area tonight will moisten the low-levels, leading to the development of low stratus across a large portion of the area. MVFR/IFR CIGs are most likely east of the Laramie Range. Cannot rule out fog developing as well with light winds across the area. Low CIGs are less likely west of the Laramie Range, but did trend ceilings down as the HREF did show low probabilities of MVFR conditions occurring. Most areas east of the Laramie Range will be socked in clouds throughout the day tomorrow with precipitation chances increasing during the evening hours.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Dense Fog Advisory until 10 AM MDT this morning for WYZ116. NE...None.