textproduct: Western and Central Wyoming

KEY MESSAGES

- Monsoonal moisture hangs around again today with more scattered showers and thunderstorms, and another risk for heavy rainfall and local flooding.

- A few storms may become strong to severe, with wind gusts to 60 mph or over the main threat.

- Monsoonal moisture will linger much of the week, with a chance of showers and thunderstorms each day. Temperatures will average above normal through the period, but not overly hot.

DISCUSSION

Issued at 226 AM MDT Sun Aug 23 2026

It was a typical monsoon day yesterday, with some areas, mainly in southwest and in Johnson and Natrona Counties getting a LOT of rain, causing some local flooding. Other areas saw nothing. And we continue to have some showers and embedded thunder around late tonight, although intensity is significantly less. And these will continue through the night, gradually becoming weaker and less numerous.

We will have another round of showers and storms today. There are some differences. For one, precipitable water values are less today by about 20 percent in most locations. This should bring less coverage and somewhat lesser rainfall rates. The other difference is that there will be more steering flow today, generally about 10 to 15 knots at 700 millibars and 25 to 35 knots at 500 millibars. So storms should have more movement. This should decrease the chance of flooding somewhat. We still have an excessive rainfall outlook across most ares West of the Divide though, so the threat is still there. There is also the risk of strong to severe thunderstorms. Most of the area is under a marginal risk of severe weather today. There could be some small hail, but this not the main risk. The main risk looks to be strong wind gusts. Roughly north and west of a Buffalo to Riverton to Lyman line has a Conditional 1 outlook for wind, or possible convective wind gusts to 75 mph. Soundings do show some inverted V profiles, especially across northwestern Wyoming where the surface will be drier, with low and mid level lapse rates close to 9 C/Km. This could lead to some strong downburst winds later today. Again, the best chance would be across the northwest but most areas will have a chance. And, like previous nights, most convection should end after sunset but a few showers and storms will likely linger through the night. As for temperatures, they should be a few degrees warmer than yesterday with more sunshine expected.

The rest of the week looks like more of the same as the annoying monsoonal moisture will hang around the area through at least Thursday and possibly into Friday as well. The models continue to have different ideas on which day will be more active with no real well defined shortwaves with changes from day to day. Precipitable water generally average about 125 to 150 percent of normal through the period though. So, at this point we went with a generic solution of mainly diurnal showers and storms each afternoon. Temperatures should remain fairly similar through the period, not very hot but averaging around 4 to 8 degrees above normal on average, with the possibility of a cooler day if there is more cloud cover than expected. Drier air may then work in for next weekend and bring a return to drier weather but uncertainty remains high on the exact timing. So, all in all, it continues to look like more of the same as the summer of the monsoon lives on in western and central Wyoming.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 416 AM MDT Sun Aug 23 2026

A few showers will linger early this morning in vicinity of KCPR and KRKS until around 13Z to 14Z, followed by a clearing sky. Today will be another day of scattered showers and thunderstorms, with the best chance of a shower or thunderstorm after 20Z until around 04Z Monday. The best chance is across the northwestern terminals, especially in vicinity of KJAC which has the highest chance. Most other terminals have around a 20 to 25 percent chance, and PROB30 groups were included for those. The smallest chance is at KCPR, with the chance less than 20 percent so we left thunder out of the forecast for now. However, confidence is low in timing individual showers and storms. A gusty wind will increase in vicinity of KRKS and KCPR this afternoon, with gusts of 20 to 25 knots.

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.