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 will develop this afternoon for areas east of the I-25 corridor. If severe thunderstorms develop all hazards are possible; large hail, damaging winds, and tornadoes are possible.

SHORT TERM /THROUGH SUNDAY/

Issued at 600 AM MDT Sat May 30 2026

A negatively tilted trough will push into the Southeastern corner of Wyoming this afternoon. A 45 knot 500 mb speed maximum is expected to pivot around the base of the wave located over SE Wyoming and Western Nebraska, providing a source for deep-layer vertical wind shear and the potential for organized deep convection. SPC issued a slight risk with a 2 percent chance for Tornadoes over the Nebraska Panhandle. 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. 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. As the low pressure begins to lift and head north, winds will turn westerly and high winds will be possible as the 700mb jet develops and wind speeds begin to ramp up to around 60 knots. Strong downward omegas develop over the wind prone areas allowing for those faster winds to mix down to the surface. In- house guidance continues to show Arlington with 65% probabilities of exceeding high wind criteria into Sunday morning, with Bordeaux at about 40% adding confidence in the high wind scenario. The strong 700mb jet doesn't last very long at the wind speeds needed to produce high winds so a High wind watch was issued for the usual wind prone areas along with the Summit and Foothills area between Laramie and Cheyenne along I-80. The winds will gradually decrease in the afternoon and evening hours on Sunday. THe high wind watch goes from 9pm tonight to 3 pm Sunday.

LONG TERM /SUNDAY NIGHT 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 /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 600 AM MDT Sat May 30 2026

A low pressure system will push into the Intermountain West this afternoon. Thunderstorm look likely to develop as early as 18z for the Wyoming terminals and 00z for the Nebraska Airports. All storm activity should quit by 06z. Looking at the observations in Northern Wyoming, ceilings are going to be between 6,000 and 8,000ft for areas not under thunderstorm activity. Ceilings look to drop as low as 1,000ft for the some of the areas under thunderstorms. Gusty winds look to develop overnight into Sunday morning before starting to die down by the afternoon to evening hours on Sunday.

CYS WATCHES/WARNINGS/ADVISORIES

WY...High Wind Watch from this evening through Sunday afternoon for WYZ106-110-116-117. NE...None.