textproduct: Western and Central Wyoming

KEY MESSAGES

- A hot day today with isolated afternoon and evening thunderstorms in northwestern Wyoming (a 1 in 5 chance). Any shower or storm could have strong wind gusts.

- An increased chance of showers and thunderstorm Monday through Wednesday, with the most numerous storms expected on Tuesday.

- The hottest temperatures of the year are likely Friday and especially next weekend with some record high temperatures possible.

DISCUSSION

Issued at 136 AM MDT Sun Jul 5 2026

We have now reached the end of the holiday weekend. All in all, the fourth of July was pretty nice, with warm temperatures, no convection and lots of sunshine. All that except for a new fire start southeast of Lander. But, we don't want to talk about the past, let's talk about the future, this is a forecast after all.

There will be two changes. The first will be warmer temperatures as flow turns southwest ahead of a weak cold front. Temperatures should average around 5 degrees warmer than yesterday, making this the hottest day for quite a while, possibly the hottest so far this year. This is looking like the day when we will see the first 100 degree high temperatures of the year, with much of the eastern and southern Bighorn Basin having around a 1 in 2 chance of seeing highs at or over the century mark. Just about all locations East of the Divide in the lower elevations will see highs in the 90s, with some 80s to low 90s West of the Divide. The second change is the chance for convection returns. The atmosphere remains rather dry (precipitable water values are below normal). However, there is enough mid level moisture for some isolated showers and thunderstorms across northwestern Wyoming, largely west and north of a Frannie to Alpine line. The only hazard would be strong wind gusts. There are very steep low level lapse rates (greater than 9C/km) along with very large dew point depressions (up to 60 degrees). All this adds up to the threat of microbursts, even from small showers (the infamous "Little Green Blobs)." Coverage will be small, generally less than 1 out of 5 in the impacted area though. Most of these showers should end shortly after sunset with dry conditions through Monday morning. Elsewhere, elevated fire weather is likely with humidity falling into the single digits at times. Largely light wind though should keep conditions from becoming critical.

A cold front (or a reasonable facsimile of one) then slips into northern Wyoming, getting close to continental Divide by Monday morning. This should knock high temperatures down around 5 to 10 degrees compared to today. The other difference will be an increase in moisture as low pressure passes to the southeast of Wyoming and turns low level flow to the south and southeast. Precipitable water values rise to around 125 to 150 percent of normal by 00Z Tuesday. This means an increase in convection across the area, and maybe some needed rain. Most guidance favors northern Wyoming, where greatest instability will be found (up to around 500 J/Kg of CAPE). Most soundings show a decent cap initially though, so this favored to be a later show, mainly in the evening with some convection lingering into the overnight hours. Guidance is fairly consistent in having the highest chance (up to a 1 out of 2 chance) across northern Wyoming, with decreasing POPs further south, with little chance in southeastern Sweetwater County. Most storms should not reach severe limits, but there could be a few.

Storm coverage should peak on Tuesday. A more defined shortwave will be moving through the area. Precipitable water values also reach a maximum on this day, with many locations seeing greater than 150 percent of normal and some locations reaching values over an inch. The atmosphere is also the most unstable on this day, with negative lifted indices across the entire area. As for stronger storms, again the most favored location would be across the north where the greatest CAPE (>1000 J/Kg) and lifted indices (down to minus 4 will be found). Locally heavy rain is also possible with moist atmosphere. There will be some movement with the storms and with the recent dry weather there is room in the soil so this should mitigate the flooding threat somewhat. More cloud cover should also keep temperatures cooler on this day. The current highs are probably the warmest it would be, it may turn up being cooler. Most of these storms should end after sunset.

Starting on Wednesday, we will have what is called an inverse relationship. A very strong ridge will begin building across the southwest and will be expanding northward into the late next week and especially into next weekend. The inverse relationship will be temperatures going up, and chances of convection going down. On Wednesday, there will still be enough lingering moisture for a decent coverage of storms, but more scattered. Drier air really surges into the area starting Thursday, any storms would be restricted to eastern portions of the area on this day. Temperatures really begin climbing on Friday and especially into the weekend. Many runs of the ensembles center the ridge on or very close to Wyoming, with 500 millibar heights as high as 6000 meters. THis is the classic definition of a death ridge, bringing very hot temperatures and little to no chance of rain. Ensemble forecasts start giving at least a 2 out of 5 chance of highs over 100 once again in the typically warm locations by Friday. But the weekend is where the heat may really hit. On both Saturday and Sunday, the NBM ensemble gives a greater than 3 out of 5 chance of triple digit highs both days below 5500 feet. Some of the typically warmer spots, like Greybull and Worland have a 2 out of 5 chance of highs over 105. A word of caution, this is still a week out and things can change. However, we do have the chance of one of the more notable heatwaves we have seen in a while.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 942 PM MDT Sat Jul 4 2026

VFR conditions prevail through the TAF period. Scattered rain showers and isolated thunderstorms will develop Sunday afternoon, mainly across northwest Wyoming. Little to no precipitation will reach the ground with these showers and storms. Main concern is strong to very strong downdraft wind. Gusts could reach as high as 50 knots with the strongest showers/storms. The only terminals with a high enough chance for impacts to mention in the TAFs are KJAC and KCOD with PROB30 groups for Sunday afternoon. There is a low chance (15%) of a shower or storm at KWRL late Sunday afternoon into Sunday evening.

A very weak cold front will drop into northern Wyoming Sunday evening into Sunday night, with wind becoming northerly behind the front. In general wind will remain 10 knots or less through the TAF period.

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.