textproduct: Cheyenne

KEY MESSAGES

- Chilly temperatures will continue for the next several days with patchy fog possible again Thursday morning.

- Isolated to scattered showers and a few thunderstorms will continue this evening. A more widespread round of showers and thunderstorms is expected Thursday into Friday.

- Slightly above average temperatures and pleasant weather is on track for the weekend.

SHORT TERM /THROUGH FRIDAY/

Issued at 250 PM MDT Wed May 20 2026

Some showers will be moving through this afternoon and evening mostly pushing in from Colorado. These showers are expected to be short lived and provide some light precip mostly for the southern corner of the Nebraska Panhandle. A shortwave trough will be pushing through the North Central Rocky Mountains tonight into early Thursday morning. The RAP model puts about 1,000 to 1,500 joules of CAPE east of the I-25 corridor. The increase synoptic lift of the trough and the semi weak but present jet dynamics will combine to give us some scattered thunderstorms for Thursday afternoon. SPC also upgraded eastern Laramie county and the southern half of the Nebraska Panhandle to a Marginal Risk of severe thunderstorms. The main concern will be hail sized up to quarters and some potential for gusty winds up to 60 mph. The scattered showers look to rough start in the afternoon as we become a little more unstable with better lapse rate due to diurnal heating on Thursday and continue through Friday morning. Most of the precipitation will come down as rain during the day but west of the I-25 corridor into the higher terrain, the precipitation should start to be more of a rain/snow mix by the late afternoon/early evening timeframe. The snow accumulations in the higher terrain look to be less than an inch with higher accumulations on the mountain peaks. By Friday afternoon the trough should be pushing into the Northern Plains and just east enough to be limiting the shower chances to mainly the Panhandle area then completely ending by the Friday evening.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/

Issued at 250 PM MDT Wed May 20 2026

The cool and unsettled weather pattern will come to a close this weekend as broad troughing is replaced by zonal flow on Saturday, followed by building ridging Sunday through Tuesday. Expect a pleasant day on Saturday with temperatures near seasonal averages. Typical diurnal cloud cover and winds can be expected with some mid- level cumulus and westerly breeziness developing in the afternoon. Isolated high based showers and a few thunderstorms will be possible, though the chance for appreciable rainfall is fairly low. A potent upper level ridge will build into the area Sunday into Monday, pushing temperatures above seasonal averages. 700-mb temperatures climb to around +8 to +12C, which will support highs around the climatological 90th percentile, but still several degrees shy of daily record highs. Chances for a few afternoon and evening high based showers and thunderstorms will continue Sunday and Monday, but again, rainfall potential will be limited. With westerly flow prevailing at the surface, dewpoints will remain stuck mostly in the 30s. Forecast soundings show decent moisture aloft, but fairly deep, dry, and well-mixed boundary layers. In addition, forcing for ascent looks limited. NBM PoPs are not really showing up for this period yet, but this is a fairly typical bias during warm and dry weather.

Tuesday will be another warm day, but hints of a more active pattern to come will begin to show up. The strong upper level ridge will shift eastward, setting up over the Plains and Midwest. Meanwhile, a closed upper level low will dive into the Pacific Northwest and then stall for several days as it inches eastward. Falling surface pressure over Montana associated with modest lee cyclogenesis will increase southerly flow Monday into Tuesday, which should allow low level moisture to recover. Forcing from the approaching upper level low will help ignite showers and thunderstorms in the place of modest instability and ample moisture. This should setup Tuesday as the best day for more widespread shower and thunderstorm activity. The upper level low will be very slow to move eastward, which may keep scattered to numerous showers and thunderstorms as a possibility for much of next week. NBM PoPs of generally 20 to 50% Tuesday and Wednesday afternoons appear appropriate at this time, considering we are still 6-7 days away.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 630 PM MDT Wed May 20 2026

A few lingering showers are possible this evening, but will dissipate in the coming hours. A low-level jet will persist over the Nebraska panhandle overnight, leading to wind gusts between 30 and 40 kts. Low CIGs will likely also move into portions of the Nebraska panhandle and KCYS overnight. MVFR to IFR CIGs are likely by morning. CIGs may lift at KCYS by the afternoon, but may persist in Nebraska for most of the day. Showers and thunderstorms will also return to the area by Thursday afternoon.

CYS WATCHES/WARNINGS/ADVISORIES

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