textproduct: Cheyenne

KEY MESSAGES

- Chances for light and brief showers with temporary strong wind gusts possible this evening.

- A temporary drying trend begins Tuesday and possibly continuing through the end of the week.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 1213 PM MDT Tue Sep 8 2026

A slightly cooler, but much drier day today as the longwave ridge to our south begins to elongate, transitioning the flow regime to more zonal. This will shunt off our main supply of monsoonal moisture from the southwest, which was responsible for providing us with the scattered showers and thunderstorms that we saw yesterday afternoon and evening. These managed to squeeze out anywhere from a quarter to four tenths of an inch of rainfall, however they were moving fast enough to limit any flooding threat. We will take what we can get before we begin the stretch of mostly dry weather through the work week.

Mid-level water vapor imagery shows another disturbance digging south and east across Eastern Oregon and Western Idaho, which is expected to lift north and east, well to the north of our area. As a result, the bulk of the forcing for ascent is anticipated to remain over Montana and the Dakotas. A much drier air mass is in place today behind a weak, stalled front that has essentially washed out somewhere in the vicinity of NE Colorado, as denoted by a surface pressure trough based on current mesoanalysis. With the lack of any synoptic-scale forcing, any convection will be driven by differential heating of the higher terrain. PWAT is well under an inch across all of SE Wyoming and Western Nebraska, with surface dewpoints in the 30s and 40s across the region. Any showers and thunderstorms that do manage to drift off the higher terrain will produce far more wind than rain (in other words, the Wyoming Special aka gusty showers). CAMs and high-resolution ensemble guidance are hinting at widely isolated high-based showers later this afternoon and evening mainly along and south of I-80, however confidence isn't high enough at this time to increase PoPs beyond 20% given such a dry air mass in a relatively stagnant pattern. Temperatures today are expected to peak in the low to mid 80s east of the I-25 corridor, with mid to upper 70s further west.

Red flag conditions are also in place today mainly across northern and western portions of our Wyoming counties as median minimum RH values are expected to range from 10-15%, with winds gusts peaking from 20-25 mph out of the west. Dry lightning from showers that produce little to no rain, but gusty and erratic winds will exacerbate our fire concerns, hence the Red Flag Warning that is in effect until 8PM this evening.

Overnight tonight, a secondary front will slide down across the area bringing another surge of cooler and drier air. We may actually wake up to some more "fall-like" temperatures tomorrow morning, especially in the typical cool spots such as Laramie, where HREF guidance has median low temperatures in the low to mid 40s, and Cheyenne dipping to around 50 degrees by sunrise. Perhaps the most notable change overnight into the morning will be the increase in our winds (it is getting to be that time of year again!), mainly for our Nebraksa counties, which should begin to wind down by the lunch hour.

Attention then shifts to more fire weather concerns tomorrow afternoon over areas along and west of I-25, with westerly winds increasing to 15-20 knots during the day, and minimum RH values ranging from 10-15%. Tomorrow will also feature cooler temperatures behind the front, with temperatures primarily in the 70s tomorrow afternoon and dry conditions as the zonal flow shunts off any moisture from the south and west. Can expect another seasonably cool night tomorrow across the region with light and variable winds and lack of cloud cover, allowing for efficient radiative cooling.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 1213 PM MDT Tue Sep 8 2026

Heading towards the end of the work week, a warming trend will take place as flow remains primarily out of the west, resulting in downsloping. High temperatures on Thursday and Friday are expected to peak in the mid 80s to around 90 degrees east of the Laramie Range, with mid 70s to the west. With the gusty, downslope flow and minimum RH values of 10-20%, fire weather will again be a concern given the lack of any moisture, especially as much of our area is currently in severe to extreme drought. A cold front is expected to move through sometime late Friday into Saturday as lee cyclogenesis occurs over the Dakotas. This will drop high temperatures by 5-10 degrees heading into the weekend, with the potential for some more active weather after a dry and breezy week.

On Saturday and Sunday, a vigorous closed low is expected to dig across the Pacific Northwest, shifting our mid-level flow to more southwesterly, thus allowing for another influx of monsoonal moisture. Long range ensemble guidance has PWAT above the 75th percentile over Southeastern Wyoming and Western Nebraska during this time, which provides some optimism in terms of beneficial moisture. With the main bulk of the forcing lifting off to the north and east over Montana and Dakotas, widespread precipitation isn't expected at this time. Thus, most shower and thunderstorm coverage will likely be highest over the higher terrain and activity over lower elevations will be dependent on if these storms can survive with rather poor low-level moisture expected (dewpoints in the low to mid 40s). Temperatures will also be cooler over the weekend with increased cloud cover thanks to increasing mid and upper-level moisture and the post-frontal air mass. The flow again becomes more zonal on Monday, with a lobe of vorticity moving through the area, continuing the chance for scattered showers and thunderstorms, though nothing appears to be widespread at this time.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1122 AM MDT Tue Sep 8 2026

A few isolated showers, possibly a rumble of thunder, may come in the VC of KCYS, KBFF, and KSNY this afternoon. The main aviation hazard with this activity will be the gusty and erratic winds that accompany any shower, with speeds up to 20 knots. Otherwise, for the remainder of the terminals, VFR conditions will prevail for the duration of this TAF period. Winds, in general, should remain 10 knots of less across all sites except KCYS and KLAR where breezier conditions will continue into the early afternoon hours.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Red Flag Warning until 8 PM MDT this evening for WYZ417>423- 427-428. NE...None.