textproduct: Western and Central Wyoming

KEY MESSAGES

- A cold front brings snow to much of the area late tonight through early Saturday morning. Wind and falling snow may impact travel, especially over Johnson and Natrona Counties.

- The coldest air of the season moves in tonight through the weekend, with some locations seeing below zero low temperatures Saturday night.

- A cold and wet pattern looks likely for much of next week.

UPDATE

Issued at 1128 AM MST Fri Nov 28 2025

The overall message with this update remains the same, with only minor changes to snow amounts and winds with the latest hi- res models. The main change to the forecast is the addition of a Winter Weather Advisory for the lower elevations of Natrona County, including Casper and portions of I-25. Given amounts near 3 inches, gusty winds with the front, and it being a holiday weekend, an advisory covers the overall travel impacts expected. Greatest impacts for this area occurs between about 6pm and 3am MST when the heaviest snow and greatest winds occur. Snow banding may bring brief and localized greater impacts and snow amounts. Snow amounts should also increase further south in Casper town as upsloping aids in snow production. Some impacts may linger into early Saturday morning, but snow and wind should be on a decreasing trend.

DISCUSSION

Issued at 206 AM MST Fri Nov 28 2025

As I've said before, I'm getting old. And the weather pattern now reminded me of something that many people do on Thanksgiving, watch football, assuming they haven't passed out from the tryptophan in the turkey. The first color commentator I remember was on Monday Night Football, the late, great Don Meredith. And one of his famous lines when a victory was certain, was "Turn Out The Lights, The Party's Over". And that is what will happen to the unbelievably nice weather we have had through November (if you like mild weather). Many locations are averaging 10 or more degrees above normal, with some having the warmest November so far in station history. However, this will come to a crashing halt tonight and through the rest of the week.

It has also been snow free for a lot of locations. That will change late today and especially tonight, as the first accumulating snow arrives to most areas east of the Divide. We will have one more mild day today though, with some locations approaching 50 degrees. A few showers will move through this afternoon, but the main impacts will be after sunset tonight.

A cold front will drop into northern Wyoming late this afternoon and then move southward through the night, ushering much colder air. It will also bring in the aforementioned snow of the anafrontal variety. The system is a quick mover and does not have a lot of moisture to work with, and this should keep snow amounts down somewhat. Probabilistic guidance is giving around a 1 in 2 chance of 6 inches or more snow only across the higher elevations of the Tetons and southern Bighorns where impacts will be few. As for the lower elevations, advisory amounts are generally 3 inches or more. And chances are generally 1 out of 4 for the most part. There are a couple of exceptions. With the north-northwest flow behind the front, the favored orographically enhanced areas around Ten Sleep and east of Thermopolis have around a 2 in 5 chance of 3 inches or more, as well as some portions of Casper to the south of Wyoming Boulevard. We have held off on advisories here though, since this is a small part of those zones. There are a couple of other factors though. There will be an 110 knot jet streak moving over the area later tonight to help enhance lift. This could also increase the chance of snowbands, which could locally increase snowfall amounts. It will also bring gusty, and in some locations, strong winds. This will especially be the case in the favored cold advection / northwest flow areas like Johnson County and the northern Bighorn Basin. Some gusts to 50 mph could occur with the snow and cause travel problems. Snowfall amounts look fairly limited in the northern Bighorn Basin, but a little heavier in Johnson County. With this, along with the area having two Interstates, we have decided to issue a Winter Weather Advisory for Johnson County, mainly for blowing snow and travel impacts than for snowfall amounts. As for timing, the greatest impact would be from around 8 pm tonight through around 4 am Saturday morning. Following that, snow should come to an end as the front moves away to the south and east.

The main concern then shifts to cold temperatures, the coldest of the season so far. Northern locations will likely stay in the teens for highs on Saturday. Most locations east of the Divide will have at least a 4 in 5 chance of low temperatures in the single digits Saturday night as 700 millibar temperatures fall as low as minus 18C. Johnson and Natrona County have around a 2 in 5 chance of the below zero low temperatures. Chances decrease further west though, as cloud cover may keep temperatures a bit warmer.

And the reason the clouds will increase is another fast moving wave diving in from the northwest. This is another fast mover and has even less moisture to work with than tonight's front. It will bring some light snow to roughly the southwestern half of the area on Sunday. However, the best forcing should remain to the south and west. The chance of advisory level snow is basically zero at this point.

Following that, we will be in a progressive, northwest flow pattern. Monday at this point looks to be a dry day with moderating temperatures. Another system will approach the area with the next chance of snow for midweek, although this does not look like a large storm at this point. Details are still hard to nail down this far out.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1019 AM MST Fri Nov 28 2025

Cold front will come racing across the state this afternoon and evening, north to south. KCOD/KWRL and KJAC will be first, roughly 20Z-21Z, central WY around 00Z, and into KRKS around 05Z. Confidence is higher for most locations for a period of snow, so have brought in more predominant groups, with low cigs, vis and -sn through the evening. Northern sites should be done with -sn around 06Z with gradual clearing starting by 12Z. Central WY will see snow farther into the overnight hours, with low clouds continuing into the day Saturday. Any -sn and low cigs at KRKS will be brief around 06Z. All sites will also see strong north winds when the front arrives, which stay gusty into the morning Saturday.

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 from 5 PM this afternoon to 8 AM MST Saturday for WYZ010-011-020.