textproduct: Western and Central Wyoming

KEY MESSAGES

- Shower potential increases for areas west and southwest Wyoming late this afternoon and overnight. Precipitation (20% to 40% chance) pushes into northern and central Wyoming early Saturday morning.

- Shower activity is forecast to be more isolated Saturday afternoon and evening, with overall dry conditions for trick- or-treating activities!

- A potent weather system reaches western Wyoming early Sunday morning and shifts east Sunday afternoon into Monday. Most low elevations are expected to see rain whereas snow will be confined to the higher elevations.

- Temperatures through Sunday are forecast to be in the upper 40s to 50s each afternoon. Widespread cooler temperatures arrive Monday with highs in the 40s for most.

UPDATE

Issued at 1220 PM MDT Fri Oct 30 2026

The forecast remains largely on track with a round of showers today into Saturday and more widespread precipitation Sunday into Monday. Today's precipitation potential begins to increase across southwest and western Wyoming in the 5PM to 6PM time frame as a shortwave treks across the area. Any given location across the aforementioned areas have a 40% to 80% chance of showers from 5PM/6PM until at least sunrise Saturday. As the shortwave progresses east, shower chances (20% to 40%) also push into northern and central Wyoming by Saturday morning. Snow levels are now forecast to be 8,000 feet or higher, thus any snow accumulations will still be confined to higher elevations of west and southwest Wyoming. Liquid precipitation amounts through Saturday are similar to slightly higher compared to this morning's forecast, with the greatest amounts over the western mountains. Regardless, accumulating snow will be confined to the locations 9,000 feet or higher. If you will be traveling over Togwotee Pass on Saturday do not be frightened if you see 1 or 2 inches of new snow!

Lingering moisture combined with favorable orographic lift brings a 50% to 80% chance of showers for much of Teton County, Yellowstone National Park, and the western mountains throughout the daylight hours on Saturday. As mentioned in the morning discussion, most will remain dry elsewhere across the area on Saturday. However, a few isolated showers cannot be ruled out across southern Wyoming on Saturday afternoon. These showers must be scared of all the trick-or- treaters because by Saturday evening the shower chances drop to 15% or less across the entire area. Otherwise, the remainder of the forecast is on track with a more potent weather system bringing widespread precipitation early Sunday through Monday. The liquid precipitation amounts have remained consistent with the morning forecast, so no changes have been made at this time.

DISCUSSION

Issued at 230 AM MDT Fri Oct 30 2026

It is now October 30th. Where I grew up, in southern New England, this was know as Mischief Night. This was a night when young people did mostly harmless pranks, like shaving cream on a car or toilet paper one someones house or trees. We do have a couple of systems that will be moving through over the next few days, so it looks like the weather could cause some mischief as well.

We are dry right now. However, deeper moisture is noted over Nevada and Utah. And this moisture will ride northeastward, along with a shortwave that will start to bring some showers. However, today should be dry for most areas, especially East of the Divide. For most here, the day looks like a decent one with a mix of clouds and sun and above normal temperatures. There will be a bit of breeze at times as well in the wind prone areas from Rock Springs to Casper as flow will be southwest. Any showers today should be confined to western Wyoming, but even here chances are generally 1 out of 3 or less with most locations remaining dry.

The deeper moisture from this wave should arrive tonight into Saturday and bring a better chance of showers. The main area of showers will be West of the Divide. Almost all locations East of the Divide have a 1 in 3 chance or less of a tenth of an inch of rain from Friday night through the day on Saturday. The only areas with a greater than 1 in 2 chance of a quarter of an inch or more are the western mountains. And, with the southwest flow, this will be a warmer event. The 700 millibar temperatures are expected to remain at 0 celsius or higher, with the warmest temperatures further east. This would keep snow levels above 8500 feet with any snow accumulation limited to above 10000 feet in the western mountains. So, travel problems are not expected through this timeframe. And there is some good news for trick or treating or holiday parties. It looks like most of the area will be in between systems for most of Saturday evening and even late at night, so most areas should be rain free. There is a small chance of showers in far western Wyoming but the chance is less than 1 out of 3 until after around 3 am.

The main show still looks to be from Sunday into Monday, and this is where some mischief in the weather would most likely be found. The players remain the same as yesterday, with a longwave trough and upper level low moving eastward and another low with a feed of Pacific moisture moving in from the southwest. All in all, reasoning looks the same as yesterday at this time. The systems are expected to phase. The heaviest precipitation should remain to the south of Wyoming. Most of the area, with the exception of portions of the Big Horn Basin, Wind River Basin and southern Green River Basin have at least a 1 in 2 chance of a quarter of an inch of precipitation or more. The greater than 1 in 2 chance of 0.75 inches of liquid is generally restricted to the mountains. In the lower elevations, the best chance would be in areas favored by northerly upslope flow, places like Casper, Lander and south of Worland. Buffalo may also see more, where there could be wrap around precipitation as the low moves to the east. Timing is coming more into focus as well. The steadiest precipitation in western Wyoming looks to be from midday Sunday through Sunday evening. East of the Divide, the steadiest would be Sunday night into Monday morning. All precipitation should end Monday night as the low moves into the Plains States.

The next question is, what about snow and how much? Somewhat cooler air will move into western Wyoming during the day on Sunday, but will really spread across the entire area Sunday night into Monday. At this time, the lower elevations look to be largely rain. The colder air in most locations doesn't get deep enough until most of the moisture is east of the area. Snow levels look to be around 6000 feet by Monday morning. Places like Dubois may see some snow, and some lower elevations may see some flakes in the air Monday morning, but accumulation looks slim to none. The western valleys will likely see some snow, but again, accumulations at this time look like a coating at the most. The mountains obviously look more interesting. Most locations above 10000 feet have at least a 1 in 2 chance of 6 inches of snow or more, but the chance of a foot or more is generally restricted to above 11500 feet. It could get slick over some of the higher passes though, especially Togwotee and Granite Passes, and possibly Powder River or Teton Passes. We may need some advisories for the higher elevations (greater than a 1 in 2 chance). However, since the main impacts are still more than 48 hours away, we will hold off for now.

Following this, ridging should build over the area and bring mainly dry conditions Tuesday and Wednesday. A weak system may bring a few showers later in the week. However, as of now, no major systems are expected past Monday for most of the next week.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1100 AM MDT Fri Oct 30 2026

West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals.

High clouds continue to increase today with the approach of the next weather system. Shower chances will be on the increase after 00Z, with more confidence in precipitation beginning in the 02Z to 06Z time frame. Have nudged the timing of the showers forward a bit and increased likelihood of precip at all sites tonight into Saturday. Expect a mix of rain and snow later tonight into Saturday morning, which will draw down some of the visibilities. MVFR ceilings will accompany precipitation, with KJAC approaching IFR flight conditions around 10Z, which will continue through most of the morning Saturday. Frequent mountain obscurations can be expected.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals.

High clouds continue to increase today with the approach of the next weather system. The greater precipitation chances exist across western Wyoming, but there is generally a 30 percent chance of rain showers at most East of the Divide terminals after 08Z Saturday. MVFR ceilings are forecast to accompany any precipitation. PROB30 groups have been added to reflect the precipitation chances. Confidence is much lower (around 15 percent) at KCPR, so opted to not mention in TAF at this time. Mountain obscurations are possible after 08Z Saturday.

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

RIW WATCHES/WARNINGS/ADVISORIES

None.