textproduct: Western and Central Wyoming

KEY MESSAGES

- Another cool day today with isolated (15-25%) showers, mainly in the southern half of Wyoming.

- An approaching weather system brings mountain snow and strong wind Monday night into Tuesday.

- Drier weather returns later in the week with near to above normal temperatures.

DISCUSSION

Issued at 135 AM MDT Sun Oct 25 2026

It was quite bright this evening when driving to work from my house to the humble Riverton weather abode to the west of town. This is courtesy of the almost full Hunters Moon, which peaks tomorrow night around midnight or so. Most areas would have a better chance of seeing it tonight though, as there will be a couple of systems impacting the area over the next couple of days.

The first system is an upper level low over Arizona that will lift northeast over the next couple of days. This system looks much more like a glancing blow as it will be weakening and the best forcing will remain to the south and east of the area. The best chance of showers will be from later this afternoon into tonight and especially from south of a Rock Springs to Casper line. This looks more like a minor nuisance system. All areas with the exception of the highest elevations of Casper Mountain and the Wind River Range have less than a 1 in 2 chance of a tenth of an inch of precipitation. Many locations will see nothing. The best chance of showers will be in southern Wyoming today, shifting toward Natrona as well as eastern portions of Fremont and Sweetwater Counties tonight. All showers should end by or shortly after sunrise Monday. It will another cool day as well, with high temperatures similar to highs on Saturday.

The second, and more impactful system impacts the area from Monday night through Tuesday. This will be a fast moving low moving into the Pacific Northwest tonight and moving across the northern Rockies Monday night into Tuesday. This will set up the typical fall / winter westerly flow situation across the area, with most precipitation falling in western Wyoming with favorable orographics and wind being the main impact East of the Divide. With this being the heart of football season, we will tackle each of these threats individually, but hopefully not be penalized for being wrong.

We will start with the precipitation, which includes some accumulating snow, maybe even for the lower elevations. Most of the western mountains have a nearly 100 percent chance of a tenth of an inch of QPF or more from Monday night through Tuesday. The area with a greater than 1 in 2 chance of a third of an inch of QPF or greater is where you would expect it with a west to southwest flow, mainly from the northern Salt and Wyoming Range through the Tetons and southwestern Yellowstone Park. Amounts have increased somewhat from yesterday, with a decent amount of the aforementioned area having a greater than 1 in 2 chance of a half an inch or more. There will be some decent upper level forcing with this system, with an 100 to 110 knot jet streak moving over the area, enhancing precipitation rates. The limiting factor will be the speed of the system, with most of the precipitation falling in a period from later Sunday evening through sunrise on Monday.

But the main question everyone is wondering about it the potential for snow. One factor will be how fast a cold front can move through and lower snow levels. Through most of Monday evening, 700 millibar temperatures would likely remain at 0 celsius or higher, keeping snow levels at 8500 feet or higher. The main time of snow accumulation would be from midnight Sunday night through sunrise Monday, when 700 millibar temperatures fall as low as minus 5 to minus 6, which would lower snow levels to valley floors. Most locations, including portions of the Jackson and Star Valleys have at least a 1 in 2 chance of an inch of snow or more. As for the chance of 3 inches, the 1 in 2 probability is generally around 7500 feet or higher, which includes places like Teton and Togwotee Passes. The mountain advisory amount is 6 inches, and the chance of this is mainly above 10000 feet where impacts are minimal. However, with the jet overhead, there will be a fair amount of wind that could bring some blowing snow. As for potential highlights, the chance is around 2 out of 5 for advisories, probably from Monday night into midday Tuesday. We won't issue any yet but future shifts will have to take a closer look. Most lower elevation areas would have few impacts, but there could be a small accumulation of snow in places like Big Piney, Pinedale or Dubois later Monday night or Tuesday morning.

In areas East of the Divide, the main concern shifts to strong to potential high wind. The pressure gradient will tighten ahead of the cold front. And, with a combination of the jet overhead and 700 millibar winds climbing as high as 55 knots, things will get quite blustery. A large portion of areas East of the Divide have at least a 1 in 2 chance of wind gusts over 40 mph. The core of the highest wind is where you would expect it in this pattern, from Muddy Gap through Casper, where there is a greater than 1 in 2 chance of wind gusts past 55 mph. The current forecast has borderline high wind, and the National Blend of Models tends to not capture wind well in this area. We may need some high wind highlights, with the chance around 1 out of 2 at this time. With the main threat not until Tuesday, we will not issue right now, but will consider for future shifts.

Ridging should then build over the area through most of the remainder of the workweek, bringing locally breezy conditions and near to above normal temperatures. A couple of weak disturbances may bring a few showers to the west, but amounts look small. The next more widespread precipitation chance may move in next weekend as a system approaches from the southwest but details are difficult to hash out this far out.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 402 AM MDT Sun Oct 25 2026

A weather system will move northeastward toward the area and spread thickening clouds across roughly the southern two thirds of the area. Most locations will see VFR conditions through 12Z Monday. Deeper moisture will bring around a 30 percent chance of a shower in vicinity of KBPI, KPNA and KRKS this afternoon and evening, so PROB30 groups have been added to those sites. In vicinity of KCPR, there is a 50 percent chance of MVFR conditions after 04Z tonight with around a 40 percent chance of showers after 04Z tonight. A shower can't be ruled out later this afternoon in vicinity of KRIW and KLND, but with the chance less than 20 percent we left it out of the TAFs for now.

RIW WATCHES/WARNINGS/ADVISORIES

None.