textproduct: Cheyenne

KEY MESSAGES

- Cool but seasonable temperatures will continue through mid- week, with a warming trend expected for the weekend.

- Increasing coverage of showers and thunderstorms expected through Thursday as a subtropical disturbance lifts northward over the area, then a brief drying trend for the weekend.

SHORT TERM /THROUGH FRIDAY/

Issued at 200 AM MDT Wed Sep 23 2026

Current KCYS radar loop shows several bands of rain showers and embedded thunderstorms across the area, with the main cluster moving northeast and weakening across the northern NE panhandle, and a secondary band over the mountains and moving into the high plains near I-25 early this morning. A bit higher coverage than what was previously expected since the upper level trough seems to be initializing further east than what models were showing yesterday, but forecast generally remains on track this morning with some minor tweaks to precip coverage through sunrise. Did add some patchy fog to portions of the high plains of southeast Wyoming and western Nebraska since a few places did receive some decent rainfall amounts from the thunderstorm activity yesterday evening. Expect showers to become more isolated around sunrise as the upper level trough lifts northeast into the Dakotas with some drier air temporarily moving into southeast Wyoming for Wednesday afternoon.

Models are starting to come into better agreement for today and Thursday with rainfall and thunderstorm chances, although confidence is still limited. The northern Front Range will be in-between systems today as we'll be watching the next subtropical disturbance lifting northward out of New Mexico. This is the same system that is aiding in the development of excessive rainfall and flooding across far western Texas and southern New Mexico over the last 24 hours. This disturbance is forecast to lift northward slowly today and gradually into southern Colorado by tonight. For today, expect near average temperatures in the 70s to near 80, warmest north of Interstate 80. Since we're in-between weather systems, shortwave ridging will temporarily limit convection today. Kept POP between 20 to 40 percent for most of western Nebraska, where the best moisture profiles will be located, and across far southern Wyoming where some moisture advection and instability is noted as we head into the afternoon hours. High res models do show widely scattered to scattered showers and thunderstorms moving eastward across the high plains, generally along and east of the Laramie Range. Some gusty winds and brief heavy rainfall possible, but strong to severe thunderstorms are not expected.

Models have trended less aggressive on Thursday regarding the subtropical upper level disturbance, mainly because models have trended slower with the vort max/midlevel energy. The 00z GFS still shows a southwest to northeast trajectory of the system with limited impacts over the forecast area. The Canadian and ECMWF show the disturbance lifting northward very slowly into Wyoming Thursday night instead of Thursday afternoon. Generally, there will be less instability and limited forcing to work with. Although there is still a good chance for widespread rainfall, lighter amounts are expected with moderate amounts in and near thunderstorms. QPF amounts have been adjusted lower with the highest amounts between a quarter inch to maybe a half inch from the I-80 corridor towards the lower North Platte River Valley through Thursday night. However, will continue to monitor the timing of this disturbance, since NAEFS continue to show PWATs/low to midlevel moisture above the 99th percentile if climatology for late September and early October.

All models show drier air moving into the region on Friday as low to midlevel winds shift into the west and dewpoints lower into the 30s and low 40s across most of southeast Wyoming. Surface moisture will remain over western Nebraska, but limited forcing and instability should greatly inhibit convection this time of the year. Kept POP below 25 percent with a lower coverage of showers and thunderstorms expected, mainly over the northern Panhandle of NE and the mountains of southeast Wyoming. Temperatures will begin to rebound after a relatively cool Thursday with high temperatures back into the 70s to near 80, warmest below elevations of 4500 feet.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

Issued at 220 PM MDT Tue Sep 22 2026

Saturday...Pleasant early autumnal weather continues with dry westerly flow aloft and relatively low precipitable water values, PWAT. 700 mb temperatures near 13 Celsius suggest mild late September maximum temperatures.

Sunday...Outdoor enthusiasts that like mild early Autumn like weather will be pleasantly surprised under dry southwest flow aloft and weak low level southeast winds. Continued mild with 700 mb temperatures near 11 Celsius.

Monday...Another moisture plume develops from Arizona and New Mexico, northeastward to southern Wyoming and western Colorado on strengthening southwest flow aloft. With a low level surface trough developing from western South Dakota to eastern New Mexico, and a series of shortwave troughs aloft moving overhead, expect to see an increase in areal afternoon and evening shower and thunderstorm coverage, especially across our Snowy and Sierra Madre Ranges due to orographic lift on moist southwest flow aloft.

Tuesday...Confidence in synoptic pattern is low to moderate as this is, after all, day seven. However, it looks like some form of troughiness aloft will reside across Wyoming and Colorado with the moisture plume extending from western Colorado to western Nebraska, and daytime heating and low level convergence is likely to set off at least widely scattered to scattered showers and thunderstorms in the afternoon and evening, and we may need to see POPS boosted if model trends continue.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1105 PM MDT Tue Sep 22 2026

A tricky TAF forecast for this period with a variety of weather, leading to differing flight categories over the next 12 hours. With ample moisture in place across the Nebraska Panhandle, kept the TEMPO groups for KSNY and KAIA for BR and IFR CIGs; however, KBFF may be included at a later time, will watch trends and AMD if needed. Showers and thunderstorms are rolling through the Nebraska Panhandle, impacting KBFF currently and moving towards KAIA in the next hour or so. The main aviation hazard with these storms will be gusty and erratic winds up to 35 knots. The storm activity should end by 07Z this evening, with a return of light winds generally less than 10 knots.

CYS WATCHES/WARNINGS/ADVISORIES

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