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 into Wednesday, but the next Pacific system will be approaching from the Pacific Northwest by the middle of the week.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 212 PM MDT Sat Oct 24 2026

A pretty quiet afternoon ahead as stable conditions engulf the region behind a cold front that swept across CWA earlier today. This will keep high temperatures this afternoon slightly cooler than average, with highs west of I-25 topping out around 50 degrees and lower to mid 50s east of the corridor. Blustery northerly winds behind the front will taper off through the afternoon hours. Switching gears a bit and taking a look at the upper levels, initially we have a cut- off low over the Desert Southwest while we sit under a southwesterly flow regime with a ridge to our east across the Mississippi Valley. As we progress in the short term period, the cut off low will lift northeast and as it does so, the flow aloft over the CWA will become difluent, this combined with a plume of moisture in the southwest flow will support increased precipitation chances across the CWA this weekend. It will take a bit for us to see impacts here locally as a stable airmass over us will hold firm for most of today, so the impacts will not start until this evening as the atmosphere become saturated. But, before that, we may see returns on radar, with the dry layer at the lower levels of the atmosphere, any precipitation will struggle to hit the surface through at least the afternoon hours. As the atmosphere saturates, look for showers to become more widespread and persist throughout most of Sunday.

Lets take a closer look at Sunday, the low over the Southwest will continue to lift northeast closer to our CWA. Guidance indicates a surge of moisture ahead of this system, with ensemble members having PWATs above the 90th to 98th percentile. With adequate forcing with the aforementioned system, moderate rainfall looks to be a possibility. So, with ingredients in place, this looks like a scenario where up to 0.3" of rainfall, locally higher amounts, looks to be a possibility across the CWA, with lower amounts west of the Laramie Range. As the best dynamics sets up across the Nebraska Panhandle, many locations there have the best chances of seeing 1.0" of precipitation. To keep the forecast consistent, kept PoPs above 60 percent, mainly outside of Carbon County. Lower elevations should see all rain while the mountains will see sub advisory snowfall, with amounts on the order of 5.0" or less. Expect slightly cooler temperatures for Sunday as highs will only top out mid to upper 40s across the region as lows Sunday night tank to near freezing by Monday morning.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 115 AM MDT Sat Oct 24 2026

No major changes in the long term period, please see previous discussion...

The work week will begin unsettled as a weak, inverted lee trough will be located to our south and east over the Central High Plains. This feature is associated with a rather broad mid-level shortwave trough, placing much of the Nebraska Panhandle at the inflection point between a weak downstream ridge located over the Upper Midwest, resulting in upper-level ageostrophic divergence and the formation of a weak surface low to our east. The strongest forcing for ascent at this time looks to set up over the Nebraska Panhandle and points further east, bringing chances for precipitation primarily east of the I-25 corridor during the day on Monday. Ensembles at this time have trended down from previous runs, with ECMWF ensemble means having 0.15-0.2" of QPF for Cheyenne, with locations in the Panhandle seeing upwards of 0.5", which would certainly help out with our drought conditions. Ensemble guidance suggests PWAT at or above the 95th percentile relative to climatology (~0.7") in the Panhandle, so heavy rain will be a threat especially if we see any convective elements over the area despite the main instability axis progged to remain well to the south and east over Kansas and Central Nebraska.

In terms of precipitation type, temperatures at this time look to be too warm for any snow (generally below 8000-9000 feet), as LREF guidance keeps 25th percentile minimum temperatures mainly in the mid to upper 30s east of the I-25 corridor, with low to mid-30s Monday morning for locations west of the Laramie Range. Places like Rawlins and Laramie will be away from the bulk of the forcing for ascent at this time, so will likely stay dry despite seeing slightly cooler temperatures. A weak cold front is progged to move through SE Wyoming and the NE Panhandle sometime late Monday into early Tuesday, which will result in slightly cooler overnight lows Tuesday morning, with locations west of I-25 waking up to temperatures at or slightly below freezing, and mid to upper 30s to the east. The shortwave trough ejects off to the north and east during the day Tuesday, placing us under a SW flow regime on the southern periphery of a rather amplified negatively-tilted shortwave trough lifting over Idaho and the Northern Great Basin. The strongest forcing for ascent looks to remain well to our north over Northern Wyoming and the Dakotas, so conditions for us look to remain mostly dry, with the exception of the Snowy and Sierra Madre Ranges which may manage to pick up some light snowfall, though ensemble guidance keeps totals under 1-2" and confined to the higher peaks. High temperatures on Tuesday are expected to be at or slightly above climatology with highs in the low 60s east of the Laramie Range, and low 50s to the west.

Wednesday, anticyclonic wave breaking over Northern British Columbia will serve to strengthen the geopotential height gradient associated with a closed low located off the coast of the Pacific Northwest. This, combined with an additional secondary shortwave trough located off the Oregon coast will serve to increase southwesterly 700-500 mb flow up to 50-60 knots, introducing the possibility for a high wind event, primarily for our wind-prone areas of Arlington and Bordeaux (tis' the season!). Model cross-sections along the I-80 corridor show mountain wave signatures that are reflective in the omega fields, however a mountain-top stable layer is lacking, which may be a limiting factor for a more high-end and widespread high wind event. As it stands, in-house random forecast guidance has around 40% probabilities of Arlington experiencing high wind conditions Wednesday morning, with Bordeaux at around 20%, so while it may be gusty, stay tuned for potential high wind highlights as we get closer to this timeframe. Given gusty, downsloping conditions, high temperatures on Wednesday will continue to remain mild, with highs slightly above climatology in the low 60s east of the I-25 corridor, and 50s to the west.

Heading towards the end of the work week, a negtaively-tilted ridge will begin to amplify, with the ridge axis located mainly to the east of our area, placing us under southwesterly flow. As 500 mb height anomalies increase to +1-2 sigma relative to climatology, can expect dry conditions and a slight warming trend.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1122 AM MDT Sat Oct 24 2026

Mainly dry conditions are expected for most of today with low CIGs that have been plaguing several terminals continuing to lift and break over the next few hours. Gusty northerly winds at KCYS, KRWL, and KSNY will continue then diminish by early this afternoon. After 00Z, coverage of -SHRA will increase across the Nebraska Panhandle sites, which may bring IFR to LIFR CIGs primarily after 03Z when more widespread showers may begin.

CYS WATCHES/WARNINGS/ADVISORIES

WY...None. NE...None.