textproduct: Western and Central Wyoming

KEY MESSAGES

- Warm and dry weather continues through Friday, with more record high temperatures possible.

- Low humidity and a gusty southwest wind will bring near critical to critical fire weather to areas east of the Divide.

- Next system this weekend will bring mountain snow, valley rain, and cooler temperatures back to seasonable to even below for this time of year.

DISCUSSION

Issued at 149 AM MDT Wed Oct 7 2026

Classic rock was on the docket for tonight's shift, and I heard two songs that describe my feelings about the upcoming weather over the next several days and what will happen. With the nice autumn weather we have had over the past several days that I have been really enjoy, my feelings were related to the song "Don't Change" by INXS, especially the line "Don't Change a Thing". However, reality will be related to the other song I heard, "Changes" by the late, great David Bowie, as we will have a major change in the pattern coming this weekend and early next week.

It will be more of the same through Friday though. Ridging will continue to hold fairly strong through this time, with 700 millibar temperatures remaining at 10 celsius or higher through this period, resulting in a continuation of well above normal temperatures. Most locations at 5500 feet or lower have at least a 1 in 2 chance of high temperatures over 80 degrees each afternoon, through this period. There is another concern for Friday though, fire weather. An approaching cold front, the one that will likely change the pattern, will be toward Montana. This will tighten the pressure gradient across the area, with the strongest wind gust in the favored southwest flow areas, like from Rock Springs through Casper. A large portions of the area has at least a 1 in 2 chance of wind gusts past 30 mph, with the windier areas having at least a 3 out of 4 chance of gusts past 40 mph. The limiting factor will be humidity though. As of now, the portions of the Bighorn Basin as well as Johnson and Natrona Counties have a mean low relative humidity of 15 percent or lower. If we need fire weather highlights, this is where they would likely be. However, at least elevated fire weather will be possible across most of the area. This also looks like the warmest day with the downsloping flow, with some areas possibly seeing highs over 85 degrees. As for precipitation, we can't completely rule out a stray shower or storm over southern Sweetwater County. However, with the chance generally 1 out of 10 or less, the forecast was left dry for the most part.

Saturday looks like the transition day as we enter a wetter and a rather complicated pattern as we head through the weekend and even into next week. We have three main players with this. The first is the cold front, the strongest so far this season by far, that will be dropping toward Wyoming. The second is an upper level low moving in from the northwest. And the third will be some tropical moisture moving toward the area from Tropical Cyclone Rachel. How these interact and when the interact will ultimately determine where the heaviest precipitation will fall, when it will fall and what type of precipitation will fall. There are some details on each one in the following paragraphs.

Uncertainty #1: How fast and how far will the colder air move into Wyoming. It should remain north of Wyoming for most of Saturday, bringing another warm day although a bit cooler than on Friday. Sunday is where there is a decent amount of model divergence with how cold it will get. For example, the European model is a more aggressive and pushes the front down to the Continental Divide, with 700 millibar temperatures much lower on Sunday. The 0 celsius line makes it down to the Divide, which would lower snow levels down to around 8500 feet. Northern portions of the state would get as low as minus 6, which could bring some snow into areas like Cody Sunday into Sunday night. Meanwhile, the GFS is much warmer, keeping snow levels anywhere from 1000 to 2000 feet higher, which would be mainly in the mountains. So, there is still a ton of uncertainty in regards to this.

Uncertainty #2: The exact track of the moisture plume from the remnants of Rachel as it interacts with the upper level low and the cold front. Recent trends have pulled things a bit further west, with the highest amounts in the western mountains, especially in areas prone to southwest flow, like the Wind River Range. There is decent agreement in Sunday afternoon and night when the heaviest precipitation moves across the area though. But, with it being several days out, this is subject to change. Precipitable water values do rise to over 150 percent of normal at times, so some heavier precipitation is possible at times.

Uncertainty #3: How fast the system move out of the area. Guidance is all over the place with a trailing upper level low that could bring some additional showers next week. The guidance is all over the place in regards to this but unsettled weather could linger into the middle of next week as well.

Now for the question a lot of people are wondering about, how much snow? First, a major disclaimer as this is still several days out and VERY SUBJECT to change. But, this is the first guess. For the chance of advisory level snow, the main likelihood is in the Absarokas and Bighorns where the coldest air will be found, as well as the Wind River Range where upslope flow would be maximized. Areas above 8000 to 9000 feet have at last 1 in 2 chance of 6 inches of snow or more. Chances of a foot or more are largely above pass level, over 10000 feet. Nevertheless, there could be some travel concerns over the higher passes, especially Beartooth, Granite and Togwotee Passes. As for the lower elevations, the best chance would again be in northern Wyoming. The NBM ensemble shows at least a 1 in 2 chance of some snowflakes in this area. As for accumulating snow, the further north you are, the better. The area from Meeteetse northward toward Cody is the most interesting given the higher elevations and closer proximity to the colder air. This morning's NBM ensemble gives a 3 out of 5 chance of an inch or more in Cody, with a 1 in 6 chance of 6 inches or more. Now, given the very warm ground a lot of this would melt on contact. However, this looks interesting and we will have to watch it. However, this ties back into uncertainty number 1. So, it will be quite active. However, there is still a lot of uncertainty with the details that will hopefully resolve themselves over the next few days.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1128 AM MDT Wed Oct 7 2026

VFR conditions expected through the next 24 hours, with nearly clear skies and winds remaining under 10kts. No aviation concerns through 18Z Thursday.

Please see the Aviation Weather Center and/or CWSU ZLC and ZDV for the latest information on smoke, icing, and turbulence forecasts.

RIW WATCHES/WARNINGS/ADVISORIES

None.