textproduct: Cheyenne

KEY MESSAGES

- A stormy weather pattern will setup later this week, continuing into the weekend with daily chances for afternoon/evening showers and thunderstorms.

- Strong to severe thunderstorms could be possible over the weekend into the beginning of next week.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 235 AM MDT Wed May 27 2026

Little to no change to the previous short term forecast with the best chance for showers and thunderstorms shifting east today towards the I-25 corridor and near the Nebraska border. Quiet this morning with evening shower activity finally dissipating around midnight. Skies will remain mostly cloudy through the early morning hours with relatively mild low temperatures in the 50s and low 60s across far eastern Wyoming and western Nebraska. Temperatures will briefly lower into the mid to upper 40s west of I-25 before sunrise.

For this afternoon and this evening, pretty much a carbon copy of Tuesday with the position and coverage of shower/thunderstorm activity being the only difference and shifted further east. all models show the upper level disturbance over northern Texas slowly retrograding westward as a Rex Block forms over the Great Plains, with a 586dm 500mb high centered over the Dakotas and Minnesota. This will allow the axis of moisture to shift further east and the best dynamic forcing, mostly upper level diffluence but some low to midlevel convergence, to shift into the I-25 corridor and possibly as far east as the Nebraska border. Kept the highest POP over this area from Laramie to Wheatland and Cheyenne...and into the southern Nebraska panhandle later this afternoon through this evening. Still not impressed with the convective environment, even though PWAT will be above the 95th percentile over the next few days. Thick cloud cover, hardly any notable shear, and MLCAPE between 300 to 600 j/kg at best will limit thunderstorm coverage and those that do form should be brief. It will also be a few degrees cooler today even though highs are still forecast to be slightly above average for May 27th. Strong to severe thunderstorm threat appears to be considerably less than 5% through the day. Will have to monitor how the upper level disturbance evolves Wednesday night, with a more stratiform rainfall possible for locations south of the North Platte River Valley.

Slightly better convective parameters for Thursday as the upper level disturbance moves overhead, mainly with increasing CAPE. Shear is better, but still not optimal (20 to maybe 30 knots later in the day). May see a better chance for frequent lightning and heavy rainfall into the evening hours with PWAT close to 99th percentile for this time of the year. A few model soundings show CAPE values approaching 800 to 1200 j/kg, but there is also a decent amount of CIN below 700mb. Kept POP below 30 percent with limited areal coverage expected and forecast cloud cover. But can see the need to raise POP further depending on the track of the disturbance and if cloud cover forecasts change. At this time, high res models are not impressed with the potential for deep convection and show minimal coverage at this time.

LONG TERM /FRIDAY THROUGH TUESDAY/

Issued at 300 PM MDT Tue May 26 2026

On Friday, the pesky closed low that has remained to our south and west throughout the week begins to get picked up by an 85-90 knot subtropical jet lifting north and east over the Baja Peninsula, gradually placing us in a region of stronger DCVA and therefore forcing for ascent. Again, the forcing at this time looks to be relatively weak, so no widespread rainfall is expected. Ensemble members are in good agreement that surface dewpoints along the Cheyenne Ridge will range from the upper 40s to the lower 50s under SSE upslope flow resulting in MUCAPE around 800 J/Kg. However thunderstorm coverage will depend on the amount of low-level cloud cover, which would ultimately keep us capped for most of the day. Regardless, effective bulk shear is expected to remain well below 20 knots, so severe thunderstorms are not expected. High temperatures will be near or slightly above climatology despite the potential for some low clouds.

Moving into the weekend, Saturday looks to be the most active day of the period, as the cutoff low transitions into an open wave and lifts over Wyoming and Nebraska. This will not only provide a greater source for lift, but flow aloft will also increase and effective bulk shear values are around 25-30 knots mainly over the Nebraska Panhandle. Forecast soundings indicate strong cap (MLCINH ~100 J/Kg) beneath a stout elevated mixed layer, however if storms can initiate in this environment with ~800 J/Kg of MLCAPE, they would have the potential to become severe. This will need to be monitored as we get closer to the weekend regarding the specific hazards, so stay tuned for future updates.

Sunday, the main wave departs our region and we remain in southwesterly flow aloft. This should result in the continuation of the ongoing moisture fetch, with ensemble guidance showing PWAT values near the 85th percentile of SE Wyoming and W Nebraska, allowing for additional chances for afternoon and evening thunderstorms through the remainder of the long term period. The ridge to our east begins to amplify resulting in 500 mb height rises, so can expect a brief warming trend towards the end of the weekend and into the work week.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 540 AM MDT Wed May 27 2026

Potent upper level disturbance will continue to slowly move northward out of Texas today. Increasing clouds are expected across the area with some showers and thunderstorms late this afternoon and this evening, mainly along the Interstate 80 corridor.

HAZARDS/WEATHER TRENDS: Low confidence forecast for the terminals along Interstate 80 due to uncertain coverage of shower and thunderstorm activity. Further north, expect VFR conditions to continue over the next 24 hours for KCDR, KAIA, and KBFF. Elected to add VCSH wording instead of PROB30/prevailing TSRA with high resolution models backing off on thunderstorm coverage later today. Models continue to hint at lowering CIGS and near IFR conditions later tonight for KCYS, and KSNY, so added lower CIGS after 09z Thursday.

CYS WATCHES/WARNINGS/ADVISORIES

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