textproduct: Cheyenne

KEY MESSAGES

- An unsettled weather pattern will continue into the weekend with daily chances for afternoon/evening showers and thunderstorms.

- Strong to severe thunderstorms could be possible Friday and into the beginning of next week.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 200 PM MDT Wed May 27 2026

The upper-level pattern remains stagnant with a 500 mb low spinning over California. The placement of this low will lead to a relatively stormy pattern over the next few days, with the CWA in southerly flow, allowing for access to Gulf moisture. The increased moisture will fuel storm activity, with stubborn vorticity maxes over the area triggering storm initiation. Current radar this afternoon shows a few light showers over the Snowy and Sierra Madre Ranges. These showers will continue for the western zones through the afternoon. There are also showers over the eastern plains of Colorado that are moving northward towards the Nebraska panhandle. Hi-Res guidance does show some of these showers and thunderstorms creeping into the Interstate 80 corridor between Cheyenne and Sidney this afternoon. Showers and storms will be short lived as the environment has very little shear to sustain storms. The environment is also not conducive for severe weather with only a few hundred joules of CAPE present across the CWA. For the most part, storms will be done by sunset, leading to a quiet overnight.

Thursday will be almost the same as Wednesday, with fairly spotty coverage of showers and storms. Hi-Res guidance does show some isolated storms developing in the far eastern Nebraska panhandle as well as the high terrain of southeast Wyoming. The environment looks a little better in terms of instability and shear, although likely still insufficient for any severe storm development. There will likely still be a good amount of CIN thanks to a stratus deck that will develop Wednesday night and stick around through much of the day Thursday. The stratus deck could limit storm development, depending on if/when clouds can clear out of the area. Although storms will be fairly isolated, coverage of storms will likely be a bit greater than Wednesday, with some lingering showers possible overnight.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Issued at 316 PM MDT Wed May 27 2026

An active, but very messy, pattern is in store for southeast Wyoming and western Nebraska through the mid-term and long-term forecast periods. Upper-level troughing will broadly be the dominant upper- level feature throughout the next week or so. Starting Friday, an upper-level trough and low will dig across Nevada and Utah, taking on a stout negative tilt by Friday afternoon with strong southerly flow throughout the atmosphere across the CWA. The NAM suggests between 2500 and 3200 J/kg of MUCAPE across western Nebraska late Friday afternoon into the early evening hours, but minimal to no shear to support the significant CAPE values. Therefore, organized storms may be difficult to reach. However, forecast soundings from the NAM across the southern Panhandle suggests Precipitable Water values of 1.2in, SBCAPE values of 3600 J/kg, and DCAPE values of 840 J/kg all suggest the potential for wet microbursts across western Nebraska, if storm initiation can occur. As of this forecast package, the biggest question for this set up will be whether there is enough forcing with the upper-level trough digging through and/or the 500mb vorticity lobes ejecting across the region, as well as the possibility of remaining capped all day due to low-level overcast cloud coverage. For now, a brief period of convection capable of producing wet microbursts is possible Friday afternoon into the evening hours before capping looks to return across the region. Uncertainty is fairly high at this time, due to the capping element as well as the uncertainty in sufficient lift across the region. However, there is a Marginal Risk (Level 1 of 5) for severe weather on Friday across far southeast Wyoming and western Nebraska.

The upper-level low will continue to impact the region through Saturday through Tuesday due to the messy evolution of this upper- level system. Both the GFS and ECMWF suggest the upper-level low closing off on Saturday and rotating northward along the Rocky Mountains before a secondary low pushes into the Pacific Northwest. This low will rotate across the region and head northward before a more defined trough develops Monday night into Tuesday and finally moves off to the east by early Thursday morning. With some version of troughing or upper-level lows across the CWA for multiple days, it is looking to be a fairly wet next several days with daily chances for afternoon showers and storms. Additionally, upper-level trough will keep surface temperatures quite comfortable with daily high temperatures Friday through Wednesday in the 70s and low-80s for all locations across the CWA. 700mb flow will largely see some for of troughing or 700mb lows throughout the next week or so, further supporting daily shower and storm chances.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 956 PM MDT Wed May 27 2026

Shower activity has largely waned, but a few light sprinkles may filter through the area, particularly around SNY, through the night. Southeast winds will be lighter overnight. Otherwise, watch for low CIGs around CYS, where the probability for IFR conditions is around 70% Thursday morning. This is also possible at SNY, but confidence was too low to add to the TAF.

Southeast winds will increase mid Thursday morning. Another round of isolated to widely scattered showers and thunderstorms is anticipated during the afternoon and early evening hours. Due to low coverage, this is handled with PROB30 groups at this time. More widespread low CIGs will begin to creep into the High Plains towards the end of the TAF period.

CYS WATCHES/WARNINGS/ADVISORIES

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