textproduct: Cheyenne

KEY MESSAGES

- Dry conditions and above average temperatures will continue through the work week.

-Critical fire weather conditions are possible Friday afternoon into the early evening.

-A pattern change Sunday into Monday will drop temperatures back to near seasonal normals, and bring renewed chances for rainfall primarily in Carbon and Converse counties.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 255 PM MDT Wed Oct 7 2026

A slightly cooler day today despite high temperatures still remaining 10 to 15 degrees above average for this time of year and even a few record highs possible west of the Laramie Range. The longwave ridge that has been responsible for the record warmth over SE Wyoming and W Nebraska these past few days has started to dampen, partially as a response to slight cooling of 700 mb temperatures. Temperatures this afternoon across SE Wyoming have again soared into the mid to upper-70s, with Rawlins already having broken their daily record of 76F set back in 2020 and 1979, whereas Laramie is currently just shy of breaking their daily record of 77F set in 2020 and 1956. Although those in the Panhandle are not shattering records, locations are still well above average with temperatures reaching the upper 70s to low 80s.

Current visible satellite imagery is showing some cumulus development, primarily over the Snowy and Sierra Madre Ranges, which is similar to what we saw yesterday. Due to the lack of any large- scale forcing for ascent and negligible instability, decided to keep PoPs below 15% even for our southern most areas as any deeper cumulus cloud would struggle to produce rainfall reaching the surface as dewpoints are currently in the mid to upper 20s thanks to strong heating and mixing. Tonight, we can expect another mild night (at least relative to climatology), with locations east of the I-25 corridor only dipping into the upper 40s to low 50s, and locations west of the Laramie Range falling into the upper 30s to lower 40s. Locations west of I-25 were adjusted downward from NBM guidance as winds are generally expected to be light under mostly clear skies.

Heading into Thursday, temperatures will again be on the toasty side, with highs 15-20 degrees above climatology as we remain under an anomalous ridge characterized by 500 mb heights nearing +2 sigma relative to climatology. Again, a few locations west of the Laramie Range (i.e. Laramie) are at risk of breaking daily record highs. Locations in the Panhandle will also be very warm, though likely just shy of record highs, with forecast temperatures mainly in the low 80s and dry conditions. Afternoon RH values are just critical thresholds, however wind gusts are expected to remain below critical thresholds, so no fire highlights have been introduced at this time. Expect another mild and dry night again underneath the ridge and overall tranquil conditions.

The general flow pattern will become more WSW on Friday as the ridge axis shifts to our east. Strong lee cyclogenesis is expected to occur well to our north over the Canadian Prairies ahead of a rather broad shortwave trough digging into the Pacific Northwest. Despite a moisture surge embedded in the WSW flow with LREF guidance showing PWAT above the 75th percentile relative to climatology, mostly dry conditions are expected due to the lack of any large-scale forcing for ascent. Ensemble guidance does hint at a few weak embedded shortwave trough, so PoPs may have to be adjusted as we get closer in range, but for now no widespread precipitation is expected. The main concern will be critical fire weather conditions, as we will experience a notable uptick in our wind speeds due to strengthening gradient flow in response to lee cyclogenesis occurring to our north. With a more favorable downsloping pattern in place and lee troughing east of the higher terrain, gusty WSW winds will result in critical fire weather conditions, primarily for portions of SE Wyoming and the extreme northern Nebraska Panhandle. A Fire Weather Watch has been issued for Friday afternoon and early evening for these areas as daytime RH values below 15% are expected with gusty winds as high as 40 mph. Red Flag conditions will need to be monitored as we get closer to this time frame as details become more apparent. High temperatures will continue to be well-above seasonal values, with many of our Nebraska sites approaching record daily high temperatures in the mid to upper 80s, to perhaps even 90 degrees north of the Pine Ridge.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Issued at 255 PM MDT Wed Oct 7 2026

After a quiet start to October, the weather pattern will turn more active this weekend into much of next week. After the ridge moves off to the east at the end of this week, southwest flow aloft will pull in improved mid to upper level moisture into our area. By Saturday afternoon, precipitable water exceeds the 99th percentile of climatology per the NAEFS mean over much of Wyoming. Elevated moisture will gradually mix into the boundary layer during this time. While we will still be somewhat dry, the added moisture should be enough to keep RH from dropping below critical values Saturday afternoon. While we will remain breezy under the continued southwest flow, critical fire weather conditions are unlikely. Instead, increased moisture aloft should support the development of a few afternoon/evening showers and possibly some thunder. Saturday's temperatures will still be 10-15+ degrees above seasonal averages, but should be a touch cooler than Friday as the ridge moves off to the east and cloud cover increases.

The stubborn western ridge pattern will finally break down on Sunday as a powerful Pacific trough dives into the western US. Ensembles have converged onto a solution in which the upper level low closes off over the west coast and the parent trough stalls to our west. The ridge, over the central US by this time, remains firmly in place and prevents the trough from progressing eastward. Meanwhile, southwest flow ahead of the closing off upper level low will absorb the remnant moisture from Hurricane Rachel in the eastern Pacific ocean. Closer to home, a surface high will push into the area Sunday morning behind a more subtle northern branch trough. The result of this will be a frontal boundary stalled across the state of Wyoming from northwest to southeast Sunday into Monday. Expect much cooler temperatures across the entire area Sunday. Highs will fall about 10F from Saturday's values along I-80 from Cheyenne to Rawlins, but 24-hour temperature drops could be 15 to 25F or even 30F around the Douglas to Chadron corridor due to combined impacts of the cooler airmass and increased cloud cover. By Sunday night, precipitable water looks to surge up to between the climatological 99th percentile, just short of seasonal maximums. Positive theta-e advection overrunning stalled frontogenesis will lead to more widespread showers across Wyoming Sunday into Sunday night. However, models have trended further west with the location of the most favorable lift, now focusing on central and western Wyoming. Therefore, the probability for beneficial rainfall has decreased for much of the high plains, but further north and west has better odds. NBM probabilities of exceeding 0.25" of rainfall exceed 50% for areas around Saratoga towards Douglas and further west. Probabilities are only around 5 to 20% for Laramie, Cheyenne, Scottsbluff, etc. Due to the tropical nature of this moisture influx, temperatures will be rather warm relative to typical precipitation events this time of year. Current forecasts for snow level are hovering around 10-12 kft, meaning that precipitation should fall as rain for all but the peaks of the Snowy and Sierra Madre ranges.

Forcing for lift largely comes to an end by around midday Monday, but plentiful moisture and unsettled weather will remain over much of the western CONUS for days afterwards. The northern branch trough is expected to pull away, but leave the closed upper level low over or near California. Upper level south to southwest flow ahead of this system will continue to advect improved moisture into the Four Corners states, and possibly as far north as our area. Temperatures will be close to seasonal norms Monday onward, which will probably feel chilly coming on the heels of weeks of near record warmth. Overnight lows will probably still be on the mild side due to higher dewpoints. As such, we may kick off the first freeze of the year towards one of the latest on record for several areas of the High Plains. Freeze probabilities are only around 20% for early next week around Cheyenne and Scottsbluff. The next window for more appreciable precipitation appears to be the middle to latter part of next week when the closed low finally makes its exit off to the east. Several moving parts make this a fairly uncertain forecast. This includes potential for another remnant tropical system getting pulled out of the East Pacific, combined with an uncertain track for a closed upper level a week out. Most of the area has about a 50% chance for 0.25" of QPF or more in the Wednesday-Thursday time period, but also about a 20% for 1.0" or more. The second phase of this event has a relatively high ceiling on precipitation amounts, if all of the pieces come together perfectly, which as always, is relatively unlikely.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1100 PM MDT Wed Oct 7 2026

VFR conditions will dominate across all the terminals for the duration of this TAF period. No other aviation weather concerns as winds, in general, will remain light, 10 knots or less, and variable across all sites except KRWL and KLAR. These two locations will see westerly winds ramp up around 16/17Z with gusts near 20 knots for the afternoon hours.

CYS WATCHES/WARNINGS/ADVISORIES

WY...Fire Weather Watch from Friday afternoon through Friday evening for WYZ417>422-425-427-432. NE...Fire Weather Watch from Friday afternoon through Friday evening for NEZ434.