textproduct: Western and Central Wyoming

KEY MESSAGES

- Scattered showers and thunderstorms become more widespread through Wednesday evening and overnight as a weather system moves into the state from Utah. These showers and storms continue to move east through the forecast area Thursday morning.

- Gusty outflow wind 40 to 50 mph, brief heavy rain, and small hail will be the primary hazards associated with Wednesday night and Thursday morning showers and thunderstorms.

- Another round of showers and thunderstorms crosses the region Thursday afternoon with gusty wind and small hail the main hazards.

- A weather system moves into the Pacific Northwest Friday and heads toward Wyoming over the weekend. This leads to gusty southwest wind Friday, which elevates fire weather conditions, followed by cooler temperatures, precipitation chances, and possibly some high elevation mountain snow over the weekend.

UPDATE

Issued at 1152 AM MDT Wed Jun 24 2026

A few adjustments with the daytime forecast update. Firstly, strong to severe thunderstorms remain possible this afternoon and evening. The Storm Prediction Center has nudged an area of marginal and slight risks further into central WY. The latest convective outlook now includes Riverton, Thermopolis, and Worland with the main hazard being large hail. Southwestern WY has also seen an adjustment in the marginal risk. Rock Springs has now been included with the main concern being dry thunderstorms which could produce strong gusty winds in excess of 55 mph. Otherwise, not much of the forecast has changed. Similar to the previous discussion the area with the greatest chances of seeing a strong to severe storm remains east of the Divide. CAMs have highlighted an area from the southern Bighorn Basin to the Wind River Basin and into Natrona County. As mentioned in the previous discussion the timing for the strongest storm development looks to be in the mid afternoon. The second round of showers and thunderstorms pushes across central and southern WY after 6 MDT. There remains a chance for an isolated strong to severe storm with this second push but chances will quickly decrease after sunset.

Thursday continues to look like another active day with widespread showers and thunderstorms. Similar to the previous discussion, morning cloud cover will be the main caveat. Currently, it is looking like there should be some clearing during the mid to late morning especially across central and eastern WY. This window is quite limited with likely only a few hours of scattered to broken cloud cover. However, this may be enough to aid in fueling storms as they begin developing by the late morning and early afternoon. The main hazards with any of these storms will be strong gusty winds, frequent lightning and large hail. Friday is looking active as well with another round of showers and thunderstorms possible during the afternoon and evening. A few strong to severe storms cannot be ruled out Friday afternoon and evening. For the weekend and past, the previous discussion remains on track with not much additional information to add.

DISCUSSION

Issued at 212 AM MDT Wed Jun 24 2026

Things are still shaping up to be rather active across the area over the next several days. And in true Wyoming fashion, we may pass through a few seasons over the next few days.

The main concern today will be thunderstorms as a shortwave moves across the area, and some of them have the potential to be severe. There will be some storms around in the afternoon, but a bulk of the activity may end up being in the evening and even overnight hours. The risk of stronger storms would likely be before sunset though, when instability will be the greatest. Our partners at the Storm Prediction Center have largely kept the Marginal Risk status quo, running largely east of the Worland to Hiland line, and covering Johnson, Natrona and eastern Washakie Counties. The area of most concern is Natrona County, where a slight risk is in effect. This makes sense given CAPE is maximized here (as high as 1500 J/Kg) as well as lifted indices (as low as minus 4). The strongest storms at this point should remain East of the the area over Eastern Wyoming, but it is a bit too close for comfort. And there is another area of concern, this one across southwestern Wyoming, although the main and probably only threat here would be strong wind gusts. We will now discuss the individual threats with the storms: large hail, strong wind, tornadoes and heavy rain.

Large Hail...The main threat of this looks to be in our eastern counties, mainly Johnson and Natrona Counties. This chance maximizes in southern Johnson and Natrona Counties though. Conditions are good for this as model Skew Ts show as much as 50 knots of 0 to 6 kilometer shear with large lapse rates of almost 9C / Km. There will be a cap on the atmosphere initially though, so this looks like a later show, with most worst possibly in the evening. This area also has a Conditional Instability Group Level 1, meaning hail up to golf ball size or higher. However, there is Conditional Instability Group 2 just to the east of the Casper, which means the chance of baseball sized hail. Chances of large hail do drop further west, but almost any storm to the East of the Divide could have small hail. The greatest threat of this should end around midnight as the we lose the heating of the day and instability.

Strong Wind Gusts...As usual, this will be a threat with just about any shower or thunderstorm, this is Wyoming after all. There are two main areas of concern. The first is in the area similar to the large hail threat, and this area has the most instability. There is another area of concern though. And this is across southwestern Wyoming. This is more of a little green blob scenario as the shortwave approaches this evening, with soundings showing very well defined inverted V soundings resulting in some high based showers and thunderstorms. Lapse rates are very steep (as much as 9C/km) with dew point depressions over 50 degrees in some locations. The result will likely be some wind gusts over 55 mph at times in any thunderstorm, shower or even cumulus cloud when it collapses. The main threat of this will be in the afternoon and evening, then decreasing later in the evening as the atmosphere cools.

Tornadoes...This again is by far the least threat, but it is not zero. There are things going for it, mainly the deep directional and speed shear. In addition, cloud bases will be lowering into the evening as the moisture increases. The main factor against it is that with slow 700 millibar flow, there may be more storm interactions and not as many stand alone supercells. The best chance of this would be in eastern Natrona County, but even here the chance is only 2 percent, with chances decreasing further west.

Heavy Rain...Most storms, but especially the ones East of the Divide will have the potential of this. Precipitable water values rise two over an inch in some locations Wednesday evening, and this gets my attention as this is 200 percent of our climatological value. Dew points will also get fairly high for these parts, rising into the 50s in our eastern counties. Flow will also be easterly up to around 700 millibars, bringing in additional moisture. One mitigating factor is that there will be decent flow at 500 millibars, anywhere from 20 to 30 knots, so the storms should have some movement. It is also been very dry across most of the area, so there is room in the soil to soak up some moisture. There will still be the chance for some localized flooding, but it should not be widespread. The best chance would be East of the Divide, where upslope flow and the greatest moisture will be found.

More strong storms will be possible on Thursday. However, there will be more uncertainty here. Another shortwave will be moving across the area. The limiting factor may be cloud cover and showers that will linger across the area during the morning hours. This may limit surface heating and instability somewhat and decrease the chance of stronger storms. There will still be a decent amount of shear present though. So, if there can be some clearing, we could see another round of strong to severe storms. This will again be in areas similar to today, largely East of a Greybull to Worland to Hiland line. But the chance of stronger storms looks less than today at this time.

Looking further out, Friday should be a lull with shortwave ridging over the area and less storms. Attention then turns to an upper level low that will be moving onshore in the Pacific Northwest Friday night and moving into the northern Rockies this weekend. Recent model trends have weakened the system a bit and also shifted to low a bit further to the west. This has decreased the QPF across the area. The system has also trended a bit warmer, so potential snowfall amounts in the west look less. The 700 millibar temperatures now look to bottom out around minus 1 or so, which would put snow levels around 8000 feet later Saturday night and Sunday. Nevertheless, locations above 9000 feet will likely see a light accumulation of snow during this time. This includes anyone going over Togwotee Pass as well, although most snow would melt on roads. So, the active weather pattern will continue across western and central Wyoming for the next several days.

AVIATION /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 524 PM MDT Wed Jun 24 2026

Showers and thunderstorms will continue to increase in coverage across Wyoming, and potentially impact all terminals through the evening and overnight. Storm coverage is expected to increase from southwest to east/northeast, so the first terminal to potentially see showers or thunderstorms is KRKS followed by all other terminals. PROB30s have been maintained where confidence in timing and/or direct impacts is more uncertain. Strong to severe thunderstorms - mainly due to outflow wind gusts - are possible, mainly prior to 06Z at KCPR, KRKS, KRIW, KLND, and KWRL, with frequent lightning, gusty 50kt winds, and hail being the main hazards. Another round of showers and thunderstorms is forecast again on Thursday at most terminals. KJAC is expected to see showers or thunderstorms first around 14Z. Showers and thunderstorms then increase in coverage through Thursday morning and early afternoon. Any thunderstorms on Thursday could have gusty 40kts to 50kt winds and small hail.

Outside of shower and thunderstorm activity, most terminals will remain VFR this TAF period. KCPR is the exception terminal, where MVFR clouds are forecast with prevailing light rain followed by MVFR ceilings persist through 16Z/Thursday. Breezy winds between 10kts and 15kts are expected through 03Z/Thursday. KRKS, KRIW, KPNA, and KBPI are forecast to have frequent 20kt to 30kt wind gusts the remainder of 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

None.