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 on Saturday. Storms may produce damaging winds and large hail.

SHORT TERM /THROUGH SATURDAY NIGHT/

Issued at 231 PM MDT Fri May 29 2026

Much of the low-level moisture we woke up to this morning has mixed out, as dewpoints across SE Wyoming have dropped into the 40s east of the Laramie Range thanks to heating/insolation. At the time of this discussion, sites across the Nebraska Panhandle are seeing surface dewpoints in the mid-50s and are beginning to see shallow cumulus develop based on visible satellite imagery. SPC Mesoanalysis currently shows MLCAPE of 500-1000 J/Kg east of the I-25 corridor with some deeper reflectivity returns along and just north of the Cheyenne Ridge. However with effective bulk shear of around 20 knots, supercells today are unlikely and storms are expected to be rather short-lived. With plenty of near-surface vorticity combined with 0-3 km lapse rates of 9.5 degC/km (nearly dry adiabatic), would not be surprised to see a landspout tornado occur if a developing updraft manages to sit atop a localized, terrain-induced boundary under prevailing SE flow in the lee of the Cheyenne Ridge. Otherwise, the main hazards with any stronger thunderstorms will be gusty winds of 50-60 knots, small hail, and frequent lightning. We should see most of the shower and thunderstorm activity move east of Wyoming and the Nebraska Panhandle by 06Z as any rain-cooled air and nocturnal cooling after sunset should erode most of our instability.

GOES-19 mid-level water vapor imagery is showing a robust negatively- tilted shortwave trough located over the Desert Southwest that is ejecting north and east and will become the main feature of interest on Saturday, particularly for the Nebraska Panhandle, hence the Storm Prediction Center placing much of Dawes County in a Day 2 slight risk for severe weather. A 45 knot 500 mb speed maximum is expected to pivot around the base of the wave located over SE Wyoming and Western Nebraska on Saturday afternoon, providing a source for deep-layer vertical wind shear and the potential for organized deep convection. Low-level theta-e advection will take place during the day across the eastern Nebraska Panhandle ahead of a weak dryline, with the strongest isodrosothermal gradient located south of the Kansas-Nebraska border. In the warm sector, surface dewpoints are expected to remain in the mid-50s per high resolution ensemble guidance with temperatures expected to reach the upper 70s to low 80s. The upstream shortwave trough is expected to initiate showers and thunderstorms over the higher terrain around 18-20Z before moving NE over lower elevations. With an effective bulk wind difference of 25-30 knots combined with 1500-2000 J/Kg MLCAPE in the warm sector, supercells remain possible across the Nebraska Panhandle late afternoon into the evening hours. Forecast soundings indicate LCLs around 1500m across the northern Nebraska Panhandle, which is well within the realm (near the 50th percentile) of tornado climatology. The main failure mode for tornadoes tomorrow will be the lack of low-level shear, as 850 mb flow remains weak around 10- 15 knots before gradually ramping up to 20 knots after 03Z with the onset of a weak low-level jet, however storms look to be elevated at this time, therefore limiting the tornado threat. The main threats tomorrow will be large hail and damaging winds, especially with any sustained rotating updrafts where hail has a longer residence time within the cloud (to allow for maximum accretion and growth). Storms should begin to exit the Nebraska Panhandle after 06Z Sunday.

Focus shifts to high winds for our wind-prone areas of Wyoming late Saturday night into Sunday morning. 700 mb cross-barrier flow increases to 50 knots overnight, with in-house guidance continuing to show Arlington with 65% probabilities of exceeding high wind criteria into Sunday morning, with Bordeaux at about 40%. Model cross-sections show a mountain-top stable layer with strong downward omega signatures in the lee of the Snowy and Laramie Ranges, so these probabilities for high winds seem appropriate at this time.

LONG TERM /SUNDAY THROUGH FRIDAY/

Issued at 231 PM MDT Fri May 29 2026

The long term will remain as unsettled as the short term with near daily chances of precipitation through at least mid-week. With the upper-level trough responsible for Saturday's storm expected to eject northeastward out if the area Sunday, precipitation chances on Sunday will be rather slim. Lingering showers could be possible for the northern Wyoming and Nebraska zones of the forecast area as the system ejects into the Dakotas, but even these chances look rather slim.

Precipitation chances will increase for the start of the work week as the upper-level trough/low begins to retrograde back towards the northwest. The rough location of the low over the Montana/Canada border, will allow the CWA to once again tap into moisture from the Gulf. Moisture-rich mid-level southerly flow will usher in the necessary humidity to fuel storm develop during the afternoon and evening. Lift will come in the form of vorticity maxes streaming through the area from the trough to the north, as well as another trough the enters the picture during the middle of next week. At this point, global models seem fairly consistent on showing daily storm chances east of the Laramie Range Monday through Thursday. A quick look at model soundings for areas east of the Laramie Range show moderate amounts of CAPE each afternoon as well as decent shear most days. As a result, severe weather cannot be ruled out each afternoon.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1105 PM MDT Fri May 29 2026

Isolated showers are slowly coming to an end tonight across southeast Wyoming and western Nebraska. KCDR and KBFF will likely see showers and storms in the vicinity for the next 1 to 2 hours, while showers periodically move through KRWL and KLAR over the next few hours. Gusty winds are anticipated in and around any shower or storm that is ongoing. Once storms pass, lighter winds return to most terminals, with low ceilings likely moving in to KBFF, KSNY, and KAIA for the overnight hours. Isolated to scattered showers and thunderstorms return for the afternoon, with another round of gusty winds and large hail possible.

CYS WATCHES/WARNINGS/ADVISORIES

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