textproduct: Cheyenne

KEY MESSAGES

- Monday & Tuesday bring another chance for strong to severe thunderstorms in the afternoon and evening. There is a slight risk (level 2 of 5) across the eastern high plains on both days. Large hail, severe wind, and an isolated tornado possible.

- A warming and slight drying trend appears likely after Wednesday with temperatures climbing into the 80s by later in the week and during next weekend.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 1230 PM MDT Mon Jun 1 2026

After some morning showers and thunderstorms that produced hail, storminess will continue into the afternoon as daytime heating begins to further destabilize the atmosphere. A stagnant upper-level low over the Montana/Canada border will allow the CWA to tap into moisture from the Gulf. Moisture-rich low-level southerly flow will usher in the necessary humidity needed to fuel storm development during the afternoon and evening. Lift will come in the form of vorticity maxes streaming through the area from the trough to the north. Moderate instability this afternoon with MUCAPE values around 1500 J/kg will create an environment capable of producing severe storms east of the Laramie Range. Hi-Res guidance shows initially discrete cells, with effective shear and steep mid-level lapse rates supporting a large hail threat. As the afternoon progresses into evening, more outflow dominant storms will lead to a severe wind threat. Storms will move out of the Nebraska panhandle rather quickly this evening, with most storms expected to be out of the area by 9 PM. A few lingering storms could be possible overnight, but the severe threat will be long gone by then.

With the upper-level low still stuck over the Montana/Canada border, a similar set up is forecast for Tuesday. The environment remains largely the same, although with a few small, but important changes. Model soundings show a lot more instability in the Nebraska panhandle Tuesday afternoon with MUCAPE values of 2500 J/kg and higher. However, shear values are rather unimpressive with weak low- level and effective shear. On top of that, a strong capping inversion seems to persist through most of the afternoon. Hi-Res guidance shows storms forming off the high terrain per usual, but not necessarily strengthening as they enter the more favorable environment. They are likely also catching onto the cap that may be in place. Soundings do show the cap eroding by the evening hours. This is also when the HRRR shows another round of convection developing off the high terrain and pushing eastward into the Wyoming high plains, and into the Nebraska panhandle overnight. These storms do appear stronger, as instability will persist into the overnight hours. As a result, cannot rule out severe nocturnal convection from about 8 PM Tuesday through 1 AM Wednesday. Primary hazards will once again be large hail in initial discrete cells, transitioning to more of a wind threat as convection becomes a bit more organized.

LONG TERM /WEDNESDAY THROUGH MONDAY/

Issued at 150 PM MDT Sun May 31 2026

We remain under SW flow aloft upstream of a high amplitude positively-tilted ridge centered over Ontario and the Great Lakes region, resulting in mostly dry and above-average temperatures heading into the second half of the week. Thanks to trajectories stemming from the Gulf of Mexico, PWAT over SE Wyoming and W Nebraska will be in the 80th-90th percentile relative to climatology. This will allow for daily chances of showers and thunderstorms despite the absence of any large-scale forcing for ascent. Despite anomalously high PWAT, long range ensemble forecast soundings continue to show large dewpoint depressions at the surface and inverted-V profiles, so any showers or storms will likely produce far more wind than any beneficial moisture. The threat for any severe weather looks to remain low towards the end of the week as deep-layer shear is weak due to the lack of mid and upper level flow. Going into the weekend, high temperatures are expected to push 80 degrees west of the I-25 corridor, with even a few 90s for our Nebraska counties as we remain under longwave ridging through the end of the long term period.

AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 530 PM MDT Mon Jun 1 2026

Thunderstorms will continue through sunset near or over Nebraska panhandle TAF sites (namely, BFF, CDR, SNY, and AIA). Strong winds up to 50 kt, hail, and heavy rain causing ponding of water are all threats with these strong storms. Brief IFR conditions are also possible as storm cores move overhead with heavy rain, thus reducing visibility.

After storms have exited the region to the east after 02/0600Z, low clouds may develop, especially for locations that received rainfall this evening. The most likely timeframe for low clouds and fog is during the early AM hours, shortly before sunrise (02/0900Z) and lasting until mid-morning (02/1500Z). After this time, increasing mixing should help dissipate low clouds. Storms will again develop Tuesday afternoon, with PROB30 groups used to indicate the locations and timing in the the favored areas.

CYS WATCHES/WARNINGS/ADVISORIES

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