textproduct: Cheyenne

KEY MESSAGES

- There is a Marginal Risk (Level 1 of 5) of severe weather for the Nebraska Panhandle today.

- There is another Marginal Risk (Level 1 of 5) for Tuesday afternoon covering the majority of the forecast area.

- Seasonable temperatures and chances for scattered PM showers and thunderstorms continue through Wednesday.

- Warmer and drier weather will return to the area Thursday and Friday.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 155 PM MDT Mon Aug 17 2026

As the upper-level ridge attempts to strengthen throughout the day, a low pressure system will be moving across the Canadian Providences. The trough created by the system will be moving the Intermountain west Monday and Tuesday. For today our westerly flow will continue to dry out the lower levels along and east of the I-25 corridor severely limiting todays shower potential for Southeast Wyoming. The Nebraska Panhandle will be slightly capped through the morning allowing for enhanced moisture retention compared to Wyoming. As the dryline pushes eastward, it will lead to forcing for western Nebraska. With residual moisture and support from 500mb vorticity maxima, showers and storms are anticipated to develop this afternoon. MLCAPE values increase this afternoon to around 1000 to 1500 J/kg in western Nebraska. Forecast soundings from the RAP suggest stout Inverted-V signatures west of the dryline across southeast Wyoming, with more favorable severe soundings in western Nebraska, though still will substantial DCAPE values. The Storm Prediction Center (SPC) has covered much of the Nebraska Panhandle in a Marginal Risk (level 1 of 5) mostly for severe wind and the possibility of hail greater than 1 inch. Multiple lobes of 500mb vorticity continue to trek across the region Tuesday afternoon into the overnight hours, due to increased vorticity from the proximity of the upper-level trough. The slightly compressed height gradient will lead to more shear across the region, with strong 700mb warm air advection allowing increased forcing. The terrain-induced dryline will retreat westward Tuesday afternoon, allowing stronger moisture advection along and east of the Laramie Range, setting up another day with increased precipitation chances. With stronger forcing, increased moisture, and increased shear in the region, storms will have a better chance of becoming severe on Tuesday, with large hail and damaging winds possible once more. SPC has expanded the Marginal risk (level 1 out of 5) to include majority of the forecast area.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Issued at 155 PM MDT Mon Aug 17 2026

Global model guidance has trended faster in amplifying the upper level ridge over the western CONUS and transitioning our area to a northwest flow pattern. As a result of this trend, the shortwave trough riding on the back edge of the zonal flow pattern has accelerated from a Wednesday PM arrival to a Wednesday AM arrival. Drier air and more subsidence in the wake of this feature has modified the forecast for Wednesday somewhat by pushing the moisture out faster. What looked like a potentially potent severe weather setup yesterday has now been nudged further to the southeast, such that storm chances are reduced for the majority of the area. There is still the potential for a few isolated strong to severe storms in the eastern and southeastern portions of the forecast area, but look for a drier day than previously anticipated along and west of a Cheyenne to Harrison line.

This also accelerates the onset of the next round of hot temperatures as ridging builds in to our west. Expect highs to climb a few degrees above average on Wednesday, then 5 to 10 degrees above for Thursday through Saturday. We probably won't be totally dry on Thursday and Friday, but expect PM convection to be much more limited and likely confined to areas in or near the higher terrain of southern Wyoming. Attention will shift back to fire weather during this period as well. Westerly winds moving into the area behind Wednesday's shortwave trough will lead to at least elevated, if not critical, fire weather conditions along and west of the Laramie Range. The winds appear a little lighter for Thursday and Friday, but model guidance has been consistently too low on winds in Carbon and Albany counties lately.

The upper level ridge will very gradually shift eastward over the course of the week, sliding east of the Four Corners by the weekend. This will allow a fresh tap of monsoon moisture to be pulled northward into the Great Basin and Four Corners states, eventually working its way over the top of the ridge and into our area. As a result, look for increased coverage of PM shower and thunderstorm activity for the weekend with temperatures remaining about 5 to 10 degrees above seasonal averages.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1210 PM MDT Mon Aug 17 2026

A few isolated showers and thunderstorms will be possible once again this afternoon and evening, but overall coverage will be lower than the last several days. The main concern today will be gusty outflow winds, though a brief VIS drop in heavy rainfall remains possible. PROB30 groups are introduced for most terminals as confidence remains low in timing and exact location of this activity.

Overnight winds will be all over the place as large-scale flow remains week, but outflow boundaries from distant showers and thunderstorms may travel far away from their source and reach our area. There is low confidence in the direction, and several sites may go variable. A few stronger gusts are possible depending on the aforementioned outflows, but confidence was too low to add to the TAF.

CYS WATCHES/WARNINGS/ADVISORIES

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