textproduct: Cheyenne

KEY MESSAGES

- Above average temperatures and chances for gusty showers and some isolated storms through Sunday.

- A pattern change will bring a gradual cool down and increased chances for precipitation next week.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 330 PM MDT Sat Oct 10 2026

Areas of showers and an isolated storm or two are making their way across the region this afternoon. While all deterministic guidance absolutely failed on where this precipitation is occurring and how far east it's spreading, high resolution guidance has been much more helpful in determining where convection will occur. Made large and sweeping changes to precipitation, spreading it across all of southeast Wyoming and through the upper 2/3's of the Nebraska Panhandle to account for this activity. Looking at mesoanalysis for thunderstorm potential, most favorable instability lies just to our south and west, which is allowing a storm or two to lift up into the region, mainly Carbon County, before weakening into shower activity as it continues to progress. Likely expecting this to continue, but not going to rule out an isolated lightning strike or two in any heavier showers, and definitely expecting gusty winds as has been seen this afternoon with many of the showers thanks to favorable sounding profiles.

Overnight into tomorrow, showers and storms should recede across the region, though occasional lingering precipitation for Carbon County expected through the night. Looking at a largely similar precipitation spread for tomorrow though shower chances should be a bit higher across the region overall. This will be thanks to a larger influx of PWATs, as values 200% of normal are expected (0.8-1.0 inch on average). Similar to today, CAPE values will be strongest just to our southwest, but a few values in excess of 500 J/kg may move into Carbon County. We may see a stronger storm or two possible, even bordering into marginally severe, but otherwise forecast profiles are still favoring gusty showers with isolated lightning. Looking at the remainder of the forecast, the overspreading cloud cover and cool front moving into the region will help promote temperatures a few degrees cooler than today. While still notably warmer than average, we should see most locations finally dropping below 80 degrees for the day, though the southern panhandle and perhaps Torrington may still peak at just around 80 for the day. While winds will be generally breezy under an enhanced pressure gradient, a jet streak will push across during the nighttime hours into Monday, fueling some stronger winds for our western zones. These could be borderline high wind warning level, and in house guidance favors a 25-30% chance of winds exceeding 58 mph, but overall confidence is still too low to consider even a watch at this time. That being said much like today, don't be surprised if we do achieve several gusts in the 50-60 mph range between gusty shower activity and the aforementioned enhanced winds. Overall it will be an active weekend, and at least the beginning of the end to October feeling more like summer.

LONG TERM /MONDAY THROUGH SATURDAY/

Issued at 330 PM MDT Sat Oct 10 2026

The exceptionally warm weather pattern for this time of year will finally break down this week, as the weather will actually feel like October by the middle of the week. One more day of unusual warmth is anticipated for Monday. While the sprawling upper level low will remain to our west, the subtle short-wave providing forcing for the earlier shower activity will lift to our northeast. Synoptic descent will push in behind along with a drier airmass dropping precipitable water closer to seasonal averages. While some shower activity driven by SSW upslope flow will likely persist in Carbon County, expect a lull in the shower chances for much of the area Monday morning. High temperatures will still be around 10F above seasonal averages. We will still have enough moisture lingering to support high-based showers in the late afternoon and evening, but appreciable rainfall is unlikely.

The warm pattern will finally break on Tuesday, with nearly all ensemble members in agreement. A northern branch shortwave trough passing well to our north apart from the stalled upper level low to our west will support a modest surface high pressure center over the northern Plains. This feature will push a cool front through the area Monday night, leading to a cooler day Tuesday. The frontal boundary is expected to stall against the Laramie range once again. So, while areas along and east of I-25 should be a good 10F or even 15F cooler than Monday, Laramie and Rawlins may only drop a few degrees. As the front pushes in overnight, models are more consistently showing isentropic lift on the east side of the approaching upper level low developing over much of the area. Thus, expect to see shower coverage increasing Monday night into early Tuesday morning. Still, rainfall rates and amounts look light during this window. Look for another lull during the daytime hours on Tuesday as the forcing weakens temporarily. A few showers will probably linger across the area, but with much more limited coverage. Models are in good agreement now showing very strong isentropic lift and positive theta-e advection kicking up again Tuesday evening and lasting into Wednesday. This looks like the best window for beneficial rainfall for most of our area due to the more potent forcing. Snow levels will start around 10 kft and drop to 8500 or even 8000 ft into Wednesday morning. Thus, snow is likely in the Snowy and Sierra Madre, and possible as low as the I-80 summit and Arlington/Elk Mountain areas. However, relatively few ensembles (10% or so) have the temperatures cold enough to support snow levels dropping to populated areas of southeast Wyoming, at least during the Tuesday night to Thursday morning period.

Ensemble agreement falls apart completely Wednesday night and beyond. Models have diverged into two distinct camps with starkly different outcomes for our area. The primary piece of the puzzle driving this uncertainty is the track of a powerful and cold upper level low dropping out of Canada mid to late week. In one camp, the western ridge recovers quickly enough to deflect this trough to the east, pushing it into the Great Lakes area. In this case, the upper level closed low would get abandoned underneath the re-amplifying ridge, keeping unsettled weather but generally light winds and warmer temperatures, in place over our area. In the other scenario, the upper level low plunges into the US much further west, possibly as far as down the eastern front of the Rockies. This would first allow the the closed low to eject off to the northeast, and then bring a potent surge of cold air to the area on Friday. In this scenario, there would be potential for high winds across the plains on Thursday, followed by widespread freezing temperatures Friday. About 20% of total ensemble members push the trough far enough west to bring another round of upslope precipitation to the area, which would have much lower snow levels (likely snow down to at least 5000 ft, if this scenario were to play out). Ensembles are split nearly exactly 50/50 right now, so there is not much insight into which is favored at this time. The official forecast straddles the middle between them at this time.

While this week will provide improved chances for beneficial precipitation for much of the area, exact amounts are still quite uncertain. While ensemble means are fairly high, it is worth mentioning that there are a small number (10 to 15%) of extreme high end outlier scenarios that might be skewing the average. Ensemble median QPF generally ranges around 0.5 to 0.75" in southeast Wyoming, and 0.3 to 0.6" in western Nebraska. The NBM distribution appears somewhat inexplicably higher than the ECMWF ensemble median and even the aggressive GEFS median. In addition, AI ensembles are considerably drier than the conventional NWP systems. The ECMWF AIFS median is around 0.25 to 0.5" for the High Plains, while the GEFS AI is even lower, around 0.1" to 0.4". This will be another interesting test on conventional NWP versus newer AI ensemble systems as we see how this plays out.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/

Issued at 515 PM MDT Sat Oct 10 2026

Isolated, gusty showers continue to drift across southeast Wyoming and western Nebraska this evening with occasional gusts over 40mph possible. Breeziness at KLAR, KRWL, KCDR, and KAIA will continue for the next 1 to 2 hours with an isolated thunderstorm possible for the Nebraska terminals. Calmer winds expected overnight at most terminals. Isolated showers will continue overnight near KLAR as showers develop along the mountains. Skies start to clear in the mid-morning hours tomorrow as winds shift northerly across western Nebraska.

CYS WATCHES/WARNINGS/ADVISORIES

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