textproduct: Cheyenne

KEY MESSAGES

- A few isolated showers and storms are anticipated Sunday afternoon.

- Widely scattered strong to severe thunderstorms are possible again on Monday, with large hail and strong winds as the primary hazard.

- Daily chances for showers and thunderstorms will continue through much of the week ahead with temperatures near average west of I-25 and cooler than average east of I-25.

SHORT TERM /THROUGH TONIGHT/

Issued at 202 AM MDT Mon Jun 22 2026

Another day and another shot of severe weather, more on that in a bit. With an abundance of low-level moisture in place, low ceilings and areas of fog are possible for many location east of the I-25 corridor through the early morning hours, with most of it eroding by noon as model solutions depict. Then, attention shifts to the possibility of severe weather once again for this afternoon primarily east of the Laramie Range into the Nebraska Panhandle. This is where storms will initiate and drift off to the east, sometime between 1-3PM. The severity of the storms are always on our minds and what are the possibilities of tornadoes. Well, there will be ample instability in place along with enough shear, enough to produce strong winds and large hail, at the start. As we progress through the afternoon hours, the low-level jet should ramp up, this will increase vertical shear and with ample instability in place, this may supper the development of supercells. These supercells will have the capability to produce very large hail and perhaps a tornado or two into the evening hours. All this is shown with in-house hi- res guidance, the development of discrete supercells developing near the I-25 corridor and trekking east into the Nebraska Panhandle during the late afternoon/early evening hours. Some of the thunderstorm activity, most likely less in severity, may last into the overnight hours as an upper level low to our north supports additional synoptic lift. When all the activity ends late tonight, the added moisture will once again bring another round of patchy fog and low celings across the High Plains through Tuesday morning. One other thing, highs today will top out into the low to mid 80s while lows tonight (Monday night) dip into the low to mid 50s.

LONG TERM /TUESDAY THROUGH SUNDAY/

Issued at 130 PM MDT Sun Jun 21 2026

The long-term period will begin under zonal flow aloft underneath a flat longwave ridge with numerous embedded vorticity maxima propagating across SE Wyoming into Western Nebraska. High temperatures on Tuesday will be cooler than the previous day thanks to a cold frontal passage during the morning hours which will shift our surface winds to NNE. Moist, post-frontal upslope flow will increase our surface dewpoints across SE Wyoming and the Nebraska Panhandle into the mid to upper 50s combined with 40-50 knot 500 mb flow and an associated shear-induced vorticity maximum moving across the area which will set the stage for convective initiation on Tuesday afternoon. Forecast soundings continue to indicate effective bulk shear values in excess of 45 knots, so there will be the potential for a few severe thunderstorms with the addition of 500- 1000 J/Kg of MLCAPE confined to areas east of the I-25 corridor where the greatest low-level moisture will exist. This lines up with the Day 3 SPC Convective Outlook which places Cheyenne and other locations along and south of the I-80 corridor in a marginal risk for severe weather. Despite sufficient deep-layer shear for supercells, low and mid-level flow is progged to be quite weak, lower than 10-15 knots, yielding little to no low-level curvature in the hodograph. This should limit the overall tornado threat with any storms, leaving large hail and damaging winds as the main threats with any supercells. With the cooler post-frontal air mass and lingering low-level moisture, forecast highs on Tuesday are expected to be near or slightly below climatology in the mid to upper 70s mainly east of the Laramie Range, with upper 70s to low 80s to the west.

The pattern remains active into Wednesday as another shortwave trough embedded in the zonal flow regime progresses across our area, providing another source for forcing for ascent. Surface winds turn to more SE, which will allow for additional theta-e advection and low-level moistening throughout the day. It is too far out to get into specifics, but the combination of a lifting mechanism, progged dewpoints in the mid 50s (resulting in surface-based instability), and effective bulk shear values greater than 50 knots, there will be a threat for severe weather on Wednesday as well. SPC has placed much of SE Wyoming and the Panhandle in a Day 4 risk for severe weather, so future forecasts will have to be monitored. High temperatures will again be slightly below climatology mainly in the low to mid 70s.

Much of the same for Thursday as embedded disturbances continue to move across our region and consistent signals from ensemble guidance that low-level moisture will remain in place east of the Laramie Range. Forecast soundings and medium-range ensembles continue to show sufficient deep-layer shear and flow aloft for organized convection, with primary hazards to be ironed out in the coming days. As we finish off the work week and head into the weekend, the synoptic-scale flow pattern will become southwesterly downstream of a rather high-amplitude trough centered over British Columbia and the Pacific Northwest. PWAT is progged to be at or above the 80th percentile on Friday, so there will be the possibility for an additional round of late day afternoon showers and storms. Severe potential looks low at this time given the lack of shear. A warming trend will continue into the weekend with mostly dry conditions and temperatures near or slightly above climatology.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 525 AM MDT Mon Jun 22 2026

Thunderstorms are expected around 21Z, with Nebraska terminals having the highest PROBs of being impacted, hence the PROB30 groups. Confidence decreases and therefore, Wyoming sites have no mention of TS at the issuance of the 12Z TAFs. BR and/or FG along with low CIGs may continue to impact KCDR, KAIA, and KSNY for the next several hours before burning off by 18Z. With the TS threat, large hail and gusty and erratic winds are likely if a storm goes over or comes close to one of the Nebraska terminals through 04Z Tuesday.

CYS WATCHES/WARNINGS/ADVISORIES

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