textproduct: Western and Central Wyoming

KEY MESSAGES

- There will be a lull in the number of showers and thunderstorms for the next two days, reducing the chance of local flooding.

- Very moist conditions return by Tuesday with an increased chance of thunderstorms and possible flooding. Wednesday at this point looks to be most impactful day for heavy rain.

- Temperatures remain above normal through Monday, with 100 degree highs in the warmer spots. Somewhat cooler temperatures move in for midweek with the increase in cloud cover.

DISCUSSION

Issued at 155 AM MDT Sun Jul 19 2026

Like last night, we continue to have some annoying little showers lingering, although nothing heavy at this time. The monsoonal pattern looks like it will continue for several days, but there will be ups and downs with it through the next week. And that is the main challenge with the forecast today, as it has been for past few days.

We should be entering a less active period for the next 36 to 48 hours or so. Most guidance shows the monsoonal plume pushing to the east and south today, dropping precipitable water values by around 20 to 30 percent across the area. They will still be above normal, but only 130 to 150 percent versus 175 to 200 percent yesterday. The result will be fewer showers and storms and less chance for flooding, although the chance is not zero. As for where the thunderstorms will be, the best chance is across the south where the deeper moisture will be, and the far north where a weak short will be passing through. However, since the models have been nothing short of hot garbage with the placement and timing of the storms the past few days, I have gone with around a 15 percent chance across most areas except for the far west, where the chance is less than 1 out of 10. The other story will be the continued very warm temperatures, even warmer than yesterday. The warmer spots in the Bighorn Basin, like Worland and Greybull, have around a 1 in 2 chance of reaching 100 degrees. Highs in the 90s will be fairly widespread below 6300 feet as well.

Activity also looks fairly sparse on Monday as well. The Weather Prediction Center has removed all of our area from the Excessive Rainfall Outlook on this day. Moisture does increase with precipitable waters rising again but now it looks to be more at night than during the day when instability would be limited so the threat of flooding would be reduced. Coverage looks to be largely across southwestern Wyoming with mainly dry conditions further north and east. Most areas will probably not see a shower or thunderstorm on this day, although most areas should have at least a 1 in 10 chance. Again, no confidence in locations of daytime convection except in the favored mountain areas like the Absarokas. And it will be another hot day, high temperatures look similar to Sunday, with warmer areas of the Bighorn Basin having around a 1 in 2 chance of high temperatures of 100 or higher.

The monsoonal moisture really makes it's return on Tuesday, as we see values again climb to an average of 175 to 200 percent of normal once again. And the expected result will be a return to a bigger coverage of showers and thunderstorms, with most guidance showing the southwestern portions of the area the favored location. This is roughly the area that has a marginal chance of Excessive Rainfall as well. And like previous nights, most coverage will during the day, but more showers and even a few thunderstorms should linger through the night. In addition, with the increased cloud cover from the increased moisture should allow for cooler temperatures across the area.

The main event still looks to be on Wednesday. The models have been fairly consistent in bringing some very deep moisture into western and central Wyoming on this day. The mean precipitable water at our office continues to be around 1.50 inches, which would be the highest in station history (the all time high is 1.41 inches) and around 250 percent of normal. At the same time, a shortwave will be approaching the area, bringing some additional lift in the afternoon and evening. As for the excessive rainfall outlook, it was upgraded to a slight risk. We don't see that much around here on Day 4. If we have a day with a more widespread flooding risk, this would be the day for it. We will have to watch it closely.

Starting Thursday, the core of the monsoonal moisture should shift east of the area, with precipitable waters falling back more toward 175 percent of normal. This is still plenty for another good coverage of showers and thunderstorms though. Moisture remains above average through next weekend as well, before drier air may begin to move in for the start of next week, possibly shutting off the monsoon. However, we have several days to get through so be alert for heavy rain and possibly flooding and make sure to turn around, don't drown if you encounter flooding.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 400 AM MDT Sun Jul 19 2026

The day should start off dry for all TAF sites and largely VFR conditions are expected through 12Z Monday. Most terminals will have a small chance of a shower or thunderstorm, but with most at 15 percent or less, not enough confidence to include in the TAFs at this time. The exceptions are at KCOD and KRKS where PROB30 groups were included or added for this afternoon and evening. Brief MVFR conditions are possible if a shower or thunderstorm moves over a TAF site. Wind should remain under 11 knots except in vicinity of any shower or thunderstorm.

RIW WATCHES/WARNINGS/ADVISORIES

None.