textproduct: Western and Central Wyoming

KEY MESSAGES

- Another warm day across the area today. A gusty wind and low humidity will bring elevated to critical fire weather to most of the area this afternoon.

- Increased moisture and a couple of weather systems will bring rounds of showers and occasional thunderstorms from Saturday through the middle of the week. The most numerous showers are expected on Sunday.

- Cooler temperatures move in this weekend. Snow is likely for the higher elevations, with around a 1 in 3 chance of some accumulating snow across some of the lower elevations of northern Wyoming.

DISCUSSION

Issued at 158 AM MDT Fri Oct 9 2026

For those of us that like warm weather, this has been a very enjoyable past couple of weeks. The area has received very little rain over the past couple of weeks, and temperatures have been nice and warm, but not hot. And still comfortably cool at night as well. However, all good things must come to an end, and it looks like this will occur over the weekend as we transition into a cooler and wetter pattern. We do need the rain though.

We will have one more very warm day today. Most locations below 5500 feet should see high temperatures into the 80s today. The difference today is that there will be breezy to windy conditions developing across much of the area ahead of a strong cold front approaching the area from the north. With the pressure gradient tightening ahead of the front, almost the entire area has at least a 1 out of 2 chance of wind gusts over 30 mph. The limiting factor will be humidity. The mean low humidity on the NBM ensemble less than 15 percent covers the northeastern half of the area as well as eastern Sweetwater County. With this, we have expanded the Red Flag Warning to cover the Big Horn Basin, Cody Foothills, the Owl Creek and Bridger range as well as the southern Bighorn Range. However, all areas will have at least elevated fire weather this afternoon.

The transition day will be Saturday. We have the same three players that will impact the weather: the cold front approaching from the north, an upper level low over the Pacific Northwest and the remnants of Hurricane Rachel that will be drawn northward into the area. Shower and thunderstorm development will increase on Saturday, especially in the afternoon and evening as deeper moisture gets drawn into the area. Some guidance shows precipitable water rising as high as 0.80 inches by Sunday morning. This is more than 200 percent of the climatological mean and would be a record for the date. The core of any forcing should remain south of the area though, so shower coverage would be more scattered, with the greatest coverage in the western mountains. There will be one more warm day East of the Divide, although somewhat cooler with increased cloud cover across the area. Shower coverage may increase at night when deeper moisture moves toward the area and what ever is left of the circulation from Rachel approaches the area.

Sunday still looks like the wettest day across the area, as the deepest moisture from Rachel makes it's closest approach. There has been some change though. The most recent guidance takes the deepest moisture and best forcing further to the west, which may lower precipitation amounts across portions of the area, especially East of the Divide. And, with cooler temperatures and more extensive cloud cover, the precipitation may be more stratiform and not convective. The Weather Prediction Center did cut back the marginal risk of Excessive Rainfall somewhat as a result, confining it largely to far western Wyoming. There is fair agreement in showing the wettest period from Sunday afternoon through Sunday evening, when the circulation makes it's closest approach and we get additional jet dynamics from the right rear quadrant of a jet streak moving across the Montana / Wyoming border. As for snow, there will be some. I will discuss this later in the discussion.

Following this, uncertainty ramps up across in the forecast. The X factor is how fast will the upper level low now located over the Pacific Northwest move through the area. As for the deterministic models, the European is around 18 to 24 hours faster than the GFS. For example, the European keeps showers going through Monday night into Tuesday, while the GFS is largely dry. The GFS also lingers showers longer, into Wednesday night, while the European dries things out faster. It does look unsettled through Wednesday, but details in precipitation amounts, placement of the heaviest precipitation and timing remain highly uncertain for this time frame at this time.

As for total rainfall amounts, most areas should have a decent chance of rain. I will only discuss amounts through 6 am Monday, as uncertainty really increases past that. All areas across western and central Wyoming have at least a 1 in 2 chance of having at least a quarter of an inch or QPF through Monday morning, with the highest chance in western Wyoming. As for an inch of QPF, the area north and west of a Cokeville to Dubois to Clark line has at least a 1 in 2 chance of this, with rapidly decreasing chances further east. The real epicenters of the heaviest QPF at this time look to be the favored southwest flow areas like the Wind River Range, Tetons and Yellowstone Park. Some of the highest elevations here have a 1 in 2 chance of 2 inches or more of QPF. As for the risk of flooding, it is there. There are some mitigating factors. For one, it has been very dry lately and there is room in the soil. In addition, a lot of the rain is more of the stratiform variety, not convective, so it rates may be less. And finally, some will fall in the form of snow, which we will talk about now.

The time of greatest concern for snow will be Sunday into Sunday night, when the coolest air and heaviest precipitation will move in. Guidance has trended a bit warmer this morning though, with most guidance holding the 700 millibar 0 celsius line close to the Wyoming-Montana border, putting snow levels at 8000 feet or higher. This still looks like a good snowfall for areas above 9000 to 10000 feet, with several inches of snow possible. There is a greater than 1 in 2 chance of 6 inches of snow across the higher elevations of the Absarokas and Wind River Range and even the Bighorns. We may need our first winter highlights of the year but I would lean toward advisories. The peaks above 12000 feet, especially in the Wind River Range, have the potential of seeing over a foot of new snow, but impacts here would be minimal. Temperatures may cool some more on Monday, but there is more uncertainty on amounts with uncertainty if things will dry out. But, there is one more thing on my mind.

That is the potential for snow in the lower elevations. Most guidance keeps thing too warm for most. However, call it a gut feeling, it could turn out to be cooler. That is, if precipitation rates are heavy enough there could be enough cooling to turn rain to snow. The main area of concern here would be in northern Wyoming, where a few models and a few ensemble members show a brief period of 700 millibar temperatures falling to around minus 5 celsius, which could lower snow levels down to 5500 to 6000 feet. The main area of concern would be in the Cody Foothills from Meeteetse to Cody and northward toward Clark. Some models also show this area in the right, rear quadrant of a 90 knot jet streak, and this is a known pattern for potential snow across northern Wyoming. If things set up right, there could be a few inches of heavy, wet snow in this vicinity, with later Sunday afternoon into Sunday evening the time of concern. The chance of this happening is small, generally less than 1 out of 3, but I wanted to mention it in case things trend colder again. So, after a stretch of fairly quiet weather, things will turn rather active once again this weekend and into much of next week.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 404 AM MDT Fri Oct 9 2026

VFR conditions should continue through 12Z Saturday. Mainly clear skies will give way to some mid and high level clouds through the day. Wind will begin to increase after 18Z and peak around 21Z before decreasing after sunset for most TAF sites. Wind gusts of 20 to 25 knots will be possible at all TAF sites with the strongest gusts in vicinity of KCPR where wind gusts over 30 knots will be possible this afternoon. Any lower ceilings are showers from the moisture moving northward from the remnants of Rachel should hold off until after 12Z Saturday.

FIRE WEATHER

Issued at 158 AM MDT Fri Oct 9 2026

An approaching cold front will bring a gusty west to southwest wind today. With relative humidity falling into the teens, much of the area East of the Continental Divide will see critical fire weather this afternoon. Elsewhere, elevated fire weather is likely although humidity should remain above critical levels. Fire weather concerns should ease somewhat on Saturday as higher humidity moves into the area.

RIW WATCHES/WARNINGS/ADVISORIES

Red Flag Warning from noon today to 7 PM MDT this evening for WYZ275-276-279>282-285-287-289.