textproduct: Western and Central Wyoming

KEY MESSAGES

- A better chance for showers and thunderstorms returns Wednesday and Thursday. The main hazards will be large hail, strong gusty wind, and frequent lightning.

- A weather system has the potential to impact the area this weekend, producing below normal temperatures, a better chance of showers, and possibly high-elevation snow across the mountains of western Wyoming.

- Overnight low temperatures in the western valleys could fall below freezing both Saturday night and Sunday night.

UPDATE

Issued at 1200 PM MDT Tue Jun 23 2026

Not much to update regarding the forecast. A few isolated showers and thunderstorms remain possible this afternoon. The best chances (10-30%) are across portions of southern Fremont into southern Natrona Counties. A nearby shower or storm cannot be ruled out for Lander and Casper this afternoon. If these storms are able to develop and strengthen, the main concerns would be strong gusty winds, frequent lightning, and small hail. The focus turns to Wednesday and Thursday which remain rather unsettled with widespread chances for showers and thunderstorms. There is increasing confidence for some strong to severe storms to develop these days. CAM's have been showing two rounds of showers and storms Wednesday, with the first being in the early afternoon and a second arriving after sunset. A brief lull is expected Thursday morning with convection redeveloping by the late morning and early afternoon hours. Overall, the setup will continue to be monitored over the next <24 hours as there is the potential for widespread strong to possibly severe storms Wednesday and Thursday. If planning any outdoor activities either of these days, be sure to be prepared for the possibility of hazardous weather conditions.

DISCUSSION

Issued at 242 AM MDT Tue Jun 23 2026

It is shaping up to be a rather active several days across western and central Wyoming. June is usually our most active month for potentially severe thunderstorms, and much of the week will be no exception, as we will have a chance each of the next few days. We had a few yesterday, and more are possible, especially for the middle of the week. And at the end of the week, we may turn the clock back a few months. Read on for the details.

There should be a bit of a lull in the storms today. Ridging moving in from the west will provide some upper level convergence, which should stabilize the atmosphere somewhat, especially in northern and western portions of the area. However, we have one mesoscale feature that will be the driver today. Guidance is showing a subtle 700 millibar low this afternoon near Natrona and Carbon County this afternoon. And this feature will be the focus for any showers and thunderstorms this afternoon and evening. The main area of focus will be areas with northeast flow, where upslope flow should help with convective initiation. As a result, we have added POPS across Natrona as well as the southeastern half of Fremont County. This could be a later show though. As for threats, the main threat today will be strong wind gusts. This is especially the case further west where dew point depressions are larger and inverted V soundings are more defined. There is even a chance of a strong wind gust in a place like Rock Springs, but with the chance less than 1 out of 8 we left it out of the forecast. Some guidance has dew point depressions over 60 degrees though, so even a collapsing cumulus cloud could produce a gust over 50 mph. As for hail, the threat is more limited, generally from Jeffrey City and east where deeper moisture is located. And, with the low there will be some lower level shear from the low. As a result we can't rule out a brief tornado, although the chance is very small. Again, the best chance of this would be in southern Natrona County where there is more moisture and cloud bases would be a bit lower. Most convection should end by sunset with the overnight hours mainly dry. Otherwise, it will be a cooler day behind the cold front. Elevated fire weather will continue as well, especially in southern Wyoming where a gusty wind and humidity falling under 15 percent may bring rapid fire spread if one can start.

Things look to become more active on Wednesday. A shortwave will begin to top the ridge in the afternoon. At the same time, low level easterly flow will set up, bringing in deeper moisture, with precipitable water values climbing to around 160 percent of normal. Low level easterly flow will also help initiate upslope flow to help with convective initiation. There will also be some right rear quadrant jet energy to help with upper level divergence. The result could be a decent outbreak of severe weather. There is already a marginal risk across eastern portions of the area, and I could see this being upgraded by tomorrow morning. As for the main threats, this looks more like a large hail threat given the increased moisture, steep lapse rates and decent directional and speed shear. Natrona and southern Johnson County have a Conditional Intensity Group 1, indicating a chance of hail bigger than golf balls. We will also have the ubiquitous threat of strong wind gusts. And, with the good amount of shear, there will be the chance of a tornado or two, although once again, the chance is small. Most guidance is giving the best chance of this in the usual suspects, Natrona and Johnson Counties with a lessening chance further west. Again, most convection should end after sunset, although a few showers and storms may linger through the night.

It could be more of the same on Thursday, as another shortwave moves across the area. Many of the model soundings have more inverted V signatures on this day though, showing generally higher cloud bases. Lapse rates continue to be rather steep as well, over 9C/KM in the afternoon. This could be more of a high wind gust threat, but large hail will remain a possibility. We already have a marginal risk across eastern portions of the area, so again we will have to watch this.

Ridging should build across the area on Friday, bringing a warmer day and fewer showers and thunderstorms. The weekend forecast depends on what happens with an upper level low that will be dropping in from British Columbia. A few ensemble members show impacts as early as Friday night. However, models are usually too fast with these and most impacts would be Saturday or Sunday. And it is here where I bring up the famous Monty Python quote, "Now for something completely different". There is some cool air associated with this system. Later Saturday night and Sunday morning, some models show 700 millibar temperatures falling as low as minus 4, which could lower snow levels down to around 7000 feet. The National Blend of Models gives a greater than 1 in 2 chance of an 1 inch of snow above 8000 feet starting Saturday night to Sunday with some of the higher peaks having a greater than 1 in 3 chance of 4 inches or more. It would not even surprise me to see a few snowflakes in places like Jackson late Saturday night or Sunday morning. We are at the peak of tourist season so anyone heading to Yellowstone Park or the Tetons needs to watch for cold temperatures and snow this weekend. Travelers at this point have a greater than 1 in 2 chance of seeing some snow over Togwotee and Tetons Passes as well. The rest of the area will feature below normal temperatures with the main chance of showers shifting to northern Wyoming. So, as a conclude this rather lengthy discussion, we have a little bit of everything over this week, including a few different seasons.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 939 PM MDT Tue Jun 23 2026

Overnight tonight will see mainly VFR conditions for most locations. Only issues tonight will be a possible low cloud deck moving into KCPR from the east before sunrise. Models have been flipping back and forth on whether that deck will make it all the way into KCPR before dissipating in the morning. Solutions have been improving on this, so have kept bkn deck for later tonight. Other issue may be some smoke filtering into KRIW later tonight from a fire in western WY. Smoke has not bee thick as of yet, so not added to TAF, but will need to watch for some smoke settling in around sunrise.

Another round of showers and thunderstorms picks up tomorrow afternoon. Initial round will be isolated, with best chances being at KCPR/KLND/KRIW. With the isolated nature of these storms, have kept PROB30 for now.

After 00Z/25, the main push of showers and thunderstorms moves in from the south, with impacts at KRKS, KBPI/KPNA, KLND/KRIW and KCPR between 00Z and 06Z/25. Tue to low confidence on timing, have held to PROB30s for now. KJAC may be on the drier side of this system, so have a small chance for showers in the evening, with bkn midlevel clouds after 00Z. Showers will move north into the rest of the state near 06Z/25, with vcsh for KCOD/KWRL later tomorrow night.

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.