textproduct: Cheyenne

KEY MESSAGES

- Near average temperatures through Wednesday, with a slight warming trend late this week and into the weekend.

- A few thunderstorms Tuesday and Wednesday may produce strong gusty winds, marginally large hail, and very heavy rainfall.

- Daily precipitation chances expected Friday onwards.

- Strong winds possible Friday and Saturday, but high winds are not anticipated at this time.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 200 AM MDT Tue Aug 25 2026

Yesterday's thunderstorm activity still lingering across the northern and central Nebraska Panhandle at this hour as a line of strong thunderstorms pushed across the eastern high plains late last night, produce widespread wind gusts of 45 to 55 MPH. Current KCYS radar loop shows this line of storms weakening and pushing into central Nebraska this hour with a few trailing rain showers. Surface analysis shows the surface cold front has moved south into the I-80 corridor and the Colorado border, likely aided by the outflow from the line of thunderstorms to the north. Expect this front to stall and be the focus for convection initiation Tuesday afternoon.

Models continue to show the next potent shortwave trough, embedded in northwest flow aloft, digging southeast across the I-25 corridor and the eastern plains this afternoon. 0-6km shear has ticked up a bit compared to yesterday, with MLCAPE around 600 to 1200 j/kg...locally higher (near 2000 j/kg) over the southern panhandle based on model soundings. Environment not as favor further north away from the stalled front, with a more stable boundary layer and lower CAPE. Thankfully, the lowest 0-6 km shear is colocated with the highest CAPE, so not expecting a super active day. However, a few thunderstorms will likely become severe or marginally severe with strong gusty winds, large hail, and very heavy rainfall. A Marginal Risk for excessive rain continues today (and Wednesday) along the I-80 corridor and as far north as the North Platte River Valley. Continued to increase POP between 40 to 60 percent for scattered/numerous showers and scattered thunderstorms. Will have to watch the position of the front, since this is where thunderstorms may train over the same area.

Similar conditions on Wednesday as another transitory shortwave moves southeast across the same area. Higher boundary layer moisture as well with PWATS approaching the 95th percentile. However, models are showing a bit more CIN below 700mb as the front lifts north as a warm front and stalls. High resolution models are showing a limited coverage of showers and thunderstorms due to low clouds and maybe some fog in the morning. Will have to keep an eye on this trend since Wednesday was looking like the best potential for excessive rainfall and some flooding. Kept POP as is but did lower them slightly further east into western Nebraska. Convective variables look good, with the exception of the low stratus seen on model soundings. Believe high res guidance is underplaying the potential, since good surface convergence is expected with easterly winds east of the Mountains, and a continuation of west to northwest winds across Carbon and Albany counties. Will also need to keep an eye on severe thunderstorms since 0-6km shear will be higher with models indicating MLCAPE of 1000 to 2000 j/kg across the eastern plains.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 159 AM MDT Tue Aug 25 2026

Upper-level ridging will continue to dominate the early portion of the long term forecast period until it starts to breakdown Friday into Saturday. This ridge will start to intensify on Thursday with northwesterly flow moving in aloft. With northwesterly flow also anticipated at 500mb, multiple vorticity maxima will move around the 500mb high over the Four Corners and push across the region from the northwest. This will induce some forcing for ascent across the CWA. The 700mb flow will be messy at best on Thursday with ridging to start the day before a shortwave pushes through and turns winds out of the south and southeast for locations east of the Laramie Range. Modest 700mb warm air advection will be possible as the shortwave pushes into the CWA, with the strongest WAA possible in and around the South Laramie Range from Laramie to Cheyenne. 700mb temperatures will warm into the 13 to 15C range Thursday afternoon, with southeasterly winds east of the Laramie Range favoring upslope development of the South Laramie Range. Despite warming 700mb temperatures, surface temperatures are anticipated to remain in the low-80s to low-90s Thursday afternoon, with moisture starting to funnel in from the south due to the southerly flow. GFS soundings suggest modest CAPE possible, though potentially capped, in the afternoons, around 1000 J/kg. Soundings also suggest decent turning with height, and around 35 to 40 kts of 0-6km shear. This would be enough to get a few isolated strong storms, if they can overcome the cap.

A similar setup is expected for Friday as the upper-level ridge remains overhead, but starts to flatten out Friday night into Saturday morning. Westerly flow is expected at 500mb as the ridge weakens with the peak starting to flatten out. A few lobes of 500mb vorticity look to advect through the 500mb flow and into the region, though the strength looks much weaker than the lobes passing through on Thursday, but the overall coverage increases a touch. Therefore, more widespread, weak, synoptic forcing for ascent should develop across much of the region Friday afternoon. Westerly 700mb flow is also expected as the shortwave moves across the region ahead of the next incoming shortwave expected for Saturday. 700mb height gradients will increase, leading to a stronger, westerly jet around 35kts by Friday evening. WAA will increase Friday evening as downsloping along the Laramie Range increases with the 700mb jet overhead. Surface temperatures on Friday are anticipated to be hot once more, with highs in the mid-80s to upper-90s across much of the area. Despite synoptic forcing for ascent and increasing 700mb temperatures, precipitation will be hard to get, largely due to downslope drying off the Laramie Range and out into the Plains. Kept low PoPs due to some uncertainty in exactly how much precipitation will be possible, but organized convection appears unlikely at this time.

Saturday onwards becomes much more active across the region as an upper-level trough starts to dig south out of Canada into Montana and North Dakota. Strong, southwesterly flow will develop between the trough to the north and the ridge to the south, placing the CWA in a region of strong, southwesterly flow aloft. The 500mb high over the Four Corners Region will push southeastward as the ridge begins to interact with the incoming trough, leading to west-southwesterly flow at 500mb Saturday through the start of the week. Multiple lobes of 500mb vorticity will push through daily across the region, favoring increased precipitation chances throughout the weekend into the early half of the work week. Looking down at 700mb, a shortwave is progged to push through the region Saturday. 700mb height gradients increase and result in a jet around 40kts through the early morning into the midday timeframe. A surface low develops Saturday morning and pushes off to the northeast, increasing surface pressure gradients across the region. GFS downward omega values along the Laramie Range will be quite high, leading to increased concern for strong, downsloping winds Saturday morning. High Winds are not anticipated at this time, but the setup looks favorable and will continue to be monitored. The remainder of the long term will see daily precipitation chances and seasonable temperatures across the region.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 540 AM MDT Tue Aug 25 2026

A surface cold front will gradually move south across Wyoming and the eastern high plains today. Another round of showers and thunderstorms will develop this afternoon and push into the eastern plains this evening.

HAZARDS/WEATHER TRENDS: VFR conditions expected to prevail over the next 24 hours. Main Aviation concern is another round of showers and thunderstorms for most terminals after 20z. Kept PROB30 groups for most terminals with the exception of KRWL and KCDR, where the coverage of any activity will be low enough to keep out of the TAF. Strong gusty winds up to 50 knots and locally heavy rainfall may result in brief IFR conditions...mainly for KCYS, KBFF, KSNY, and KAIA.

CYS WATCHES/WARNINGS/ADVISORIES

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