textproduct: Western and Central Wyoming

KEY MESSAGES

- Another cool and damp day for much of the area, although dry conditions will return to northwestern Wyoming.

- The most numerous showers and mountain snow will be across central and southern Wyoming, with the most numerous showers through this evening. Gusty to strong is likely (a 3 out of 4 chance across much of the area tonight).

- A clear sky and lighter wind brings a very good chance (a 4 out of 5 chance) of a freeze across most of the area later Thursday night.

DISCUSSION

Issued at 233 AM MDT Wed Oct 14 2026

The main driver in the forecast this morning remains me of one of the better movies of the mid 1990s, Leaving Las Vegas. It is because the upper level low that has brought the clouds and showers of the past few days that was centered near Las Vegas is now leaving and will be making a turn toward to the northeast, crossing Colorado through tonight before moving into the central Plains states for the end of the week. And it will continue be the main driver in the weather for about the next 24 to 36 hours.

Satellite imagery shows some more enhanced cloud tops heading toward Wyoming, with showers across much of the southern two thirds of the area. There remains some uncertainty this morning in regards to how widespread the showers will be today though. Some ensemble members, as well as the operational GFS, keep the low further south, keeping more of the area mainly dry, with showers confined largely south and west of a Buffalo to Riverton to Green River line. Other members, as well as the operational European model, bring the low closer and keep showers across most of the southern two thirds of the area through this evening. There is some agreement in showers starting to end from northwest to southeast starting after midnight tonight, with all showers finally over by noon on Thursday.

Now we turn to precipitation amounts. Far northwestern Wyoming should be done with showers. As for an additional quarter of an inch starting at 6 am this morning, the 1 out of 2 chance of an additional quarter inch or more runs roughly south and east of a Kaycee to east of Riverton to Rock Springs line. However, precipitation has been underperforming in most locations. The heaviest amounts, with around a 2 out of 5 chance of three quarter inches of rain are mainly in Natrona, southeastern Fremont and southern Sweetwater Counties.

And finally, we talk about snow. Amounts over the passes have been rather small so far. Snow levels will reach the lowest point early this morning. With 700 millibar temperatures generally dropping to between minus 2 to minus 3, which would lower snow levels to around 7000 to 7500 feet. This would keep the lower elevations largely rain, although there could be some wet snowflakes from time to time, especially if precipitation is heavier. As for an additional inch starting at 6 am this morning, it mainly across the Wind River Range, the Green and Rattlesnake Ranges and also Casper Mountain where there is a greater than 1 in 2 chance of 1 inch or greater. When we bump it up to 3 inches, it is again mainly above 8500 feet. However, the NBM ensemble has a couple of interesting things. It still has a greater than 2 out of 5 chance of 3 inches over the higher elevations of South Pass. I am giving some thought to possibly extending the Winter Weather Advisory another 6 hours or so, when snow levels should rise another 1000 feet or so. This will likely be a gametime decision based on road conditions when we get closer to expiration, which is at 6 am. Other locations that could see over 3 inches include Casper Mountain, but all guidance keeps the chance of over 6 inches to less than 1 out of 5. The other location is the Green and Rattlesnake Range, but this would be the higher elevations with no impacts. Snow should really taper off after midnight with just about all areas done by Thursday morning.

And you think we are done, but wait, there's more! And that will be the strong wind tonight. The upper level will initiate some lee cyclogenesis over Colorado and tighten the pressure gradient as the low deepens. This will be mainly after midnight tonight and into Thursday morning, although it will linger longer over Johnson County. Most areas East of the Divide as well as eastern Sweetwater County have at least a 3 out of 5 chance of wind gusts past 30 mph. The areas prone to the cold advection / north flow pattern, like Johnson County and portions of the Big Horn Basin have at least a 1 in 2 chance of gusts past 40 mph. High wind looks unlikely, as 700 millibar wind looks to top out at around 40 knots, and I would likely to see 50 knots for that. Wind should decrease Thursday afternoon as the low moves into the Plains states.

And this brings us to the last main concern, a possibly killing freeze. Yes, most locations are a few weeks past the average first freeze, so we have been living on borrowed time. But many areas will have a good chance Thursday night as the wind decreases and the sky the sky clears as the low moves away. Thursday night there is a very good chance of that killing freeze. Just about the entire area has at least a 2 out of 3 chance of temperatures of 28 degrees or below. Freeze warnings will likely be needed, but we will let future shifts issue these as we still have rain and snow to deal with.

Following that, it looks like some pleasant fall weather should return for several days as ridging builds back into the area. This means a mainly clear sky and temperatures near to somewhat above normal from Friday through the weekend and into early next week. The next chance for decent precipitation looks to hold off until the middle of next week when the next Pacific system approaches the area.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1106 PM MDT Tue Oct 13 2026

A system continues to bring moisture and precipitation to the area through the period. This will be most widespread east of the Divide, where MVFR to IFR conditions are expected for terminals through most of the period. Terminals across western and northern Wyoming will be less likely to see longer term impacts (namely KJAC and KCOD). KCPR, KLND, and KRIW are expected to see the most persistent rain showers, especially before 18Z. Lower clouds linger at terminals but begin to lift late in the period. KCPR will be a notable exception, with IFR ceilings through Wednesday evening.

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

Winter Weather Advisory until 6 AM MDT early this morning for WYZ014-015.