textproduct: Western and Central Wyoming

KEY MESSAGES

- Cool today. Isolated showers (15-30% chances) occur across southern Wyoming. Chances (25-40%) linger overnight across far eastern Sweetwater County to around Casper.

- A quick-moving weather system brings strong winds to the area late Monday night through Tuesday. The strongest winds occur over the mountains and from South Pass to Casper, which will be gusting in excess of 50 mph.

- Western mountain snow occurs Monday night into early Tuesday morning. A few inches of snow is possible over Teton and Togwotee Passes, which could bring minor impacts to travel through Tuesday morning.

UPDATE

Issued at 1237 PM MDT Sun Oct 25 2026

A quick system brings light showers to portions of southern Wyoming today and possibly up to around Natrona and Johnson Counties overnight. Overall chances are about 15 to 30 percent, with slightly better odds around Casper. Any accumulations would be light, under 0.1 inches.

The focus remains on the larger system Monday night through Tuesday. Latest guidance leaves confidence high enough that a High Wind Watch has been hoisted for the the Wind Corridor, from about South Pass to Casper. Wind gusts should start increasing just ahead of the front, around 4am Tuesday, with the strongest winds expected through about 11am as the front tracks eastwards. Though it remains windy, the trend will be decreasing winds Tuesday afternoon. Outside the watch zone, it will still be windy, mainly around the mountains. Gusts over 30 mph will be common and could be stronger as the front passes. For snow, amounts have not changed much from the full discussion below. Main impacts would be for any early Tuesday morning commutes along Teton and Togwotee Passes. This system is quick-moving, so the duration of snowfall is limited, maybe to about a 6 hour period between about 11pm Monday night and 5am Tuesday.

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 County as well as eastern portions of Fremont and Sweetwater Counties tonight. All showers should end by or shortly after sunrise Monday. It will be another cool day as well, with high temperatures similar to highs on Saturday.

The second, and more significant system, impacts the area from Monday night through Tuesday. This will be a quick low moving into the Pacific Northwest tonight and 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 Ranges 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 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 Monday evening through sunrise on Tuesday.

But the main question everyone is wondering about is 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 Monday night through sunrise Tuesday, when 700 millibar temperatures fall as low as minus 5C to minus 6C, 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 potentially 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 work week, 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 /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1050 AM MDT Sun Oct 25 2026

Low clouds/fog in the Jackson/Star Valleys is starting to dissipate and expected to clear out by 19Z.

An area of clouds extends from the southwestern corner of the state to the Bighorns as part of an area of low pressure over the Uintas. These clouds, SCT-OVC FL050-100, will shift to the north-northwest through the afternoon as the center of the low moves toward the northeast. There remains a 30% chance for light showers to occur over KRKS from 21Z to 01Z as a result. MVFR ceilings will develop at KCPR by 06Z, quickly dropping to IFR/LIFR by 08Z. Light showers will be possible by this time with the already lowering ceilings being the bigger threat. Mountain obscurations will become more widespread across the area after 06Z as well.

Clouds will scatter out across the area with SKC skies over the central basins toward the end of the TAF period, as the main storm system begins to move over the NE Panhandle. Winds will continue to be light (11kt or less) through the TAF period.

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

RIW WATCHES/WARNINGS/ADVISORIES

High Wind Watch from late Monday night through Tuesday afternoon for WYZ019-020.