textproduct: Cheyenne

KEY MESSAGES

- Hot temperatures will persist through the end of the work week.

- Precipitation chances return by this weekend, with the possibility of widespread rain on Saturday.

- Daily shower and storm chances continue Monday through the end of the week with slightly above average temperature expected until Thursday.

SHORT TERM /THROUGH SUNDAY/

Issued at 210 AM MDT Fri Aug 21 2026

Quiet weather early this morning with clearing skies after some isolated convection late yesterday evening. Surface observations show pretty light winds across the area with south to southeast Winds across most of the eastern high plains, and northeast winds over the far northern Nebraska Panhandle and portions of east central Wyoming. A weak stationary cold front will remain in this area for much of the day, and will need to be monitored for afternoon convection initiation. Otherwise, high resolution models not showing much in this area today, but do show scattered rain showers and isolated thunder developing across southeast Wyoming with activity moving southeast through the afternoon over the eastern plains. High res models are showing a little better consistency with this convection over the last few runs. In addition, models indicate a subtle shortwave digging southeast across the area on the northeast periphery of the upper level ridge axis. Believe this feature will be enough to trigger widely scattered convection...but not totally convinced we'll see scattered thunderstorms due to the strength of the upper level ridge and associated midlevel subsidence. Increased POP up to 25 percent, but kept a slight chance mention of thunderstorms for now. SPC as added a marginal and slight risk of severe weather to the far eastern portion of our western Nebraska zones. Going to message this lightly since models are showing poor run to run consistency on deep convection getting going. Can't rule this out though with a stationary front in the area, however. One or two storms may produce gusty winds up to 70 MPH and hail around the size of quarters, mainly east of Highway 71 over western Nebraska. Pretty hot today with highs in the 90s pretty much everywhere, with reading in the mid to upper 90s over the lower elevations of western Nebraska and far eastern Wyoming.

As we head into the weekend, pretty typical late August weather pattern over the western United States with strong upper level high pressure near the four corners region...drifting to the southeast by Sunday. Southeast Wyoming and western Nebraska will be in the "ring of fire" around the northern periphery of the upper level high. All models show a plume of monsoon moisture (sitting over Arizona/southern Calif at this hour) lifting north and eventually east around the upper level high on Saturday. In addition, surface winds will shift into the southeast across the plains as a potent upper level shortwave moves over the area Saturday afternoon. NAEFS shows a quick jump in PWATs across the area with 1.00 inches as far west as Rawlins and Laramie...and closer to 1.25 to 1.50 across the eastern plains. These values are around the 97th to 99th percentile for this time of the year. Ensembles are also starting to hint at the potential of heavier rainfall across the region, mainly on Saturday. Increased POP between 40 to 70 percent for scattered to numerous thunderstorms. Some strong to marginally severe storms are possible. May need to monitor for excessive rainfall/localized flooding, especially further south along the I-80 corridor and lower North Platte River valley. A slight cooling trend expected this weekend due to plentiful cloud cover and expected rainfall, with highs in the 80s to low 90s.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Issued at 240 PM MDT Thu Aug 20 2026

Monday...Coverage of afternoon and evening showers and thunderstorms increases somewhat by an increase in pseudo monsoonal moisture and lowering 700 mb temperatures providing less convective inhibition, CIN, compared to Sunday. As is this type of pattern, afternoon convection will be over and near the mountains due to differential heating and orographic effects, with the activity spreading across the rest of the forecast area before dissipation by late evening. Warmer temperatures compared to the previous day due to less cloud cover and convective coverage.

Tuesday...Similar pattern synoptically to Monday with minor perturbations in the flow aloft aiding in lift of pseudo monsoonal moisture to produce widely scattered to scattered afternoon convection over and near our Snowy, Sierra Madre and northern Laramie Ranges, with the activity spreading eastward across the rest of the forecast area in the evening. Some lowering of mid level temperatures suggests daytime maximum temperatures will be a little cooler.

Wednesday...The primary change compared to Tuesday, will be a reinforcement of the ridge aloft axis over Wyoming, inducing a return to upslope mechanical lift aiding the areal increase of showers and thunderstorms, especially east of the mountains and along the I-25 corridor and eastward. Slight warming trend with 700 mb temperatures near 13 Celsius yielding high temperatures in the 80s.

Thursday...Monsoonal moisture becomes a bit more scant with decent westerly flow aloft and with warm temperatures aloft producing more convective inhibition, CIN, to limit development. A slight warming trend continues based on mid level, 700 mb temperature trends.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1132 AM MDT Fri Aug 21 2026

Ridging aloft will prevail across western Wyoming and western Colorado. Aside from isolated showers and thunderstorms across southeast Wyoming this afternoon, and over western Nebraska this evening, mostly clear skies will prevail.

Wyoming TAFS...High confidence in VFR prevailing. The HRRR shows isolated showers and thunderstorms propagating to the southeast, from 20Z to 02Z. Coverage will be so isolated, that it may be best to just go with VCSH at KLAR and KCYS. Scattered high based cumulus through sunset.Winds gusting to 25 knots through sunset.

Nebraska TAFs...VFR prevails, with high confidence. Scattered high based cumulus through sunset. HRRR shows isolated showers and thunderstorms from around 01Z to 06Z, so continued with VCSH at KBFF. Winds gusting to 25 knots through sunset. Boundary layer progs suggest that MVFR ceilings due to fog and low clouds will occur from around 07Z to 14Z.

CYS WATCHES/WARNINGS/ADVISORIES

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