textproduct: Western and Central Wyoming

KEY MESSAGES

- High pressure will bring another warm and dry day today.

- Increasing wind and continued low humidity will bring elevated to critical fire weather to most of western and central Wyoming Friday afternoon.

- Increasing moisture and an approaching cold front will bring cooler and wetter weather starting Saturday and continuing into next week. Locally heavy rain is likely along with the first significant high elevation snowfall.

DISCUSSION

Issued at 133 AM MDT Thu Oct 8 2026

It certainly has been a very warm start to October, and this has been the theme for much of the year. Through the first seven days of the month, all of our major climate sites are ranked in at least the top 5 of all time warmest first seven days of October, with several ranking as the warmest. And we will have at least two more days of warm temperatures, with some locations having three more. However, we will get a slap across the face into reality as we have a greater than 9 in 10 chance of seeing much cooler temperatures, numerous rain showers and, for the higher elevations, the first good snow of the season.

We have no real issues today as ridging will continue to control the weather across the area today. All in all, it looks like another nice day, although feeling more like early September than early October with temperatures well above normal once again. Highs should be fairly close to what was seen yesterday. So if you can, get out and enjoy it.

The first signs of change will move in tomorrow. Not with temperatures, as highs will likely be a few degrees warmer than on Thursday. However, a cold front will be dropping out of Canada, the strongest front of the year. With the ridge beginning to flatten and the pressure gradient tightening, a gusty wind will develop across portions of the area. This will especially be the case in areas favored by southwest flow, especially from Rock Springs into southern Johnson County. The area with the current fire weather watch looks reasonable given the this is where the strongest wind will be and the mean lowest relative humidity is below 15 percent. The one additional area I considered was the Cody Foothills, but humidity may not be low enough. We will let the day shift take another look. We will continue the Fire Weather Watch as is for now as a result. There is a very small chance for a shower or thunderstorm in Sweetwater County with a bit of mid level moisture creeping northward, but the chance is less than 1 out of 6 for all locations.

The change really begins on Saturday. The aforementioned cold front approaches the state. At the same time, we will begin to see some moisture from Rachel, and I don't Jennifer Aniston's character from the 90s sitcom "Friends" that popularized the haircut of the same name. Moisture will be drawn northward between the ridge to the south and an upper level low over the Pacific northwest and channeled into the intermountain west. The main action here will be in western Wyoming, moving East of the Divide later in the day. At least during the day, any precipitation would fall as rain. This will bring another above normal temperature day across areas East of the Divide, although cooler than on Friday. Most guidance has also slowed the progress of the front a bit. Both the GFS and the European have the 700 millibar celsius line near the Montana-Wyoming Border by 12Z Sunday. As a result, snow levels should remain above pass level with the possible exception of Beartooth Pass.

At this point, the heaviest and steadiest precipitation looks to be on Sunday into Sunday night. The remnants of Rachel should be scooped up by and upper level low over California and moved rapidly northward. With the southwest flow, the heaviest precipitation would again fall in western Wyoming with the upslope flow, especially in places like the Wind River Range, the Tetons and the Absarokas. All areas will have a good chance of rain though. The NBM ensemble gives a greater than 1 out of 2 chance of a quarter of an inch of precipitation over the entire area, with a near 100 percent chance in western Wyoming. Much of western Wyoming, especially the mountains, has a greater than a 1 in 2 chance of an inch or more of QPF from Sunday through Sunday night. Precipitable water values are anomalously high at this time, topping out at around 0.85 inches, which is greater than 150 percent of normal. We do have a marginal risk of excessive rainfall over the area as well. One thing that may mitigate this threat is that with the cooler temperatures, it may be more stratiform than convective but we have to watch it.

The next question a lot of people are asking is, what about snow? Here is where there is a bit more uncertainty, at least for the lower elevations. We continue to have some differences in how cold it will get. There is as much as a 3 to 4 degree difference in the crucial 700 millibar temperatures. For example, the GFS keeps it warmer, which would hold snow levels at 8500 feet or higher. The European drops the temperature to minus 4, which lowers snow levels down to 6000 to 6500 feet across northern Wyoming. This implications for a place like Cody, where if precipitation is heavy enough it could bring enough evaporative cooling to change rain to snow. The NBM ensemble gives a greater than 4 out of 5 chance of an inch or more of snow here through Sunday night. Given the warm ground, impacts would be minimal but it could be a taste of winter. Elsewhere in the lower elevations, there could be some snow but accumulation would be unlikely. As for the mountains, above 8500 feet there is a greater than 1 in 2 chance of 6 inches or more of snow in the Wind River Range as well as the Absarokas. We will likely need the first winter weather highlights at some point over the next couple of days. I would lean more toward advisories at this point, since the heaviest snow should remain above pass level and over the highest elevations.

The deepest moisture from the remnants of Rachel should move away Monday morning. It still looks like we will remain unsettled through at least the middle of the week. However, details in timing and placement of the heavier precipitation are still highly uncertain. The two players here are the upper level low over California that will eventually be kicked east and moisture from another tropical system, soon to be Hurricane Stanley, that may reach the area. There is little agreement in the models this far out with details so we kept things generic for now. So, after a long stretch of dry, warm weather, we will transition to a cooler and more unsettled pattern with some much needed precipitation for this weekend and much of next week.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/

Issued at 1108 AM MDT Thu Oct 8 2026

VFR conditions will persist across all terminals through the TAF period. Skies are expected to remain SKC for mostly all terminals with some high level clouds possibly developing by the late afternoon. Winds are forecast to remain light with most seeing 5 to 10 knots at times. KCPR may see higher winds of 10 to 15 knots at times this afternoon before weakening by sunset. Winds begin to increase by the end of the TAF period with breezy winds developing across all terminals shortly after 18Z Friday.

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

FIRE WEATHER

Issued at 133 AM MDT Thu Oct 8 2026

Although humidity will drop under 15 percent at times today, wind should remain light to moderate for the most part. Increasing wind and continued low humidity on Friday will bring elevated to critical fire weather to most of western and central Wyoming on Friday afternoon. The area of greatest concern is from Rock Springs northeastward through southern Johnson County. Elevated fire weather may occur on Saturday as well but higher humidity should mitigate fire concerns somewhat.

RIW WATCHES/WARNINGS/ADVISORIES

Red Flag Warning from noon to 7 PM MDT Friday for WYZ279>281- 289.