textproduct: Cheyenne

KEY MESSAGES

- Cold front early this morning will result in much cooler temperatures this weekend with temperatures around 5 to 10 degrees below normal.

- Widespread rainfall and mountain snowfall expected Sunday and Monday as a central Pacific system lifts northeast across the Front Range. - Near normal temperatures and a bit warmer by Tuesday into Wednesday, but next Pacific system will be approaching from the Pacific Northwest by the middle of the week.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 230 AM MDT Sat Oct 24 2026

Pretty quiet early this morning as a (mostly) dry cold front has pushed southeast across the area with winds shifting into the north. The actual colder airmass still remains to our north across central Wyoming, but expect this to move south into the I-80 corridor over the next few hours with temperatures likely dropping into the upper 20s to mid 30s. Once this front moves southward and stalls near the mountains, some low clouds are expected...but not expecting any fog at this time through early Saturday morning. KCYS radar shows some returns over Platte and Niobrara county (near the front), but it is unlikely any of this rainfall is reaching the ground. Mostly post-frontal stable conditions for Saturday with little, if any, forcing and cooler than average temperatures in the mid 40s to mid 50s, warmest over western Nebraska. Impacts from the upper level low to our southwest will likely hold off until this evening.

Models show the next Pacific storm system, responsible for the flooding concerns across the Desert Southwest, slowly lifting northeast later today and Saturday night. Models indicate decent moisture advection ahead of this system, with PWATs above the 90th to 98th percentile for late October. Forcing looks sufficient with this system, at least enough to produce some moderate rainfall amounts due to a negatively tilted trough as the upper low becomes an open wave on Sunday. Upper level diffluence is strongest near the Wyoming/Nebraska border and is colocated with decent upslope easterly flow and additional low level convergence near the 700mb low and the surface low to our south. Looks like a good case of widespread 0.20-0.50 inch of rainfall across the region, lowest amounts west of the Laramie Range. Some amounts across western Nebraska may approach 1.00 inch of rain Sunday night as the base of the trough axis slowly lifts northeast over the region. Kept POP above 60 percent for most of the area outside of Carbon County. Snow accumulations are forecast for the mountains, but this will also be the lowest QPF region to the west of the best dynamics, so snow amounts should generally be less than 5 inches, even above 10,000 feet. Cool temperatures will continue on Sunday with lows near freezing early Monday morning.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 114 AM MDT Sat Oct 24 2026

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 /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 509 AM MDT Sat Oct 24 2026

Winds have shifted to northerly across SE Wyoming and the Nebraska Panhandle ahead of a cold front that is currently draped from SW to NE just north of Cheyenne. Current RH values behind the front are ranging from 80-90% at this time, so will leave MVFR CIGs in for KCDR and KCYS based on timing of the FROPA and current satellite trends.

Expect mostly dry conditions during the day today with primarily northerly flow of 15-20 knots east of the I-25 corridor with peak gusts of 35-40 knots mainly from 12-18Z especially for KSNY and KAIA. KLAR may see a diurnal uptick in SW winds with gusts up to 30 knots from 18Z-00Z. -SHRA coverage increases after 00Z for the Panhandle terminals, which brings moderate confidence in IFR to LIFR CIGs primarily after 03Z when the onset of widespread showers is expected to occur. KCYS may see MVFR CIGs after 03Z, although confidence is low at this time as most precipitation is expected to be to the east.

CYS WATCHES/WARNINGS/ADVISORIES

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