Area Forecast Discussion

KEY MESSAGES

- A few showers are possible (less than a 1 in 3 chance) in western Wyoming today, but most areas will have a dry and mild end to the workweek.

- More numerous showers spread into the area Friday night into Saturday, with the most numerous in western Wyoming. There should be a lull in activity Saturday evening.

- A more potent weather system moves through the area Sunday and Monday, bring areas of rain and higher elevation snow.

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 /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 451 AM MDT Fri Oct 30 2026

VFR conditions should continue through around 06Z Saturday. Dry conditions are expected at the TAF sites through sunset, although there is around a 20 percent chance of a shower in the mountains in vicinity of KJAC, KPNA and KBPI. Otherwise, expect a mix of sunshine and mid to high level clouds. Moisture and an approaching weather system from the southwest will lower ceilings and bring MVFR ceilings after 06Z tonight in vicinity of KBPI, KPNA and KJAC with rain. A PROB30 groups was added in vicinity of KRKS with the moisture. Most TAF sites East of the Continental Divide should remain precipitation free through 12Z (less than a 15 percent chance), although ceilings will lower and we did add VCSH to KLND toward the end of the TAF period. Occasional mountain obscurations will be possible after 21Z across western Wyoming.

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

None.