textproduct: Western and Central Wyoming

KEY MESSAGES

- An active monsoon today will bring more numerous showers and storms. Some could be strong with strong wind gusts, hail and heavy rain.

- Drier Wednesday through Friday with any isolated convection confined largely the mountains. Hot temperatures return with many locations having highs in the 90s Thursday through Saturday.

- Deeper moisture returns for the weekend and early next week with another increased chance of showers and thunderstorms.

DISCUSSION

Issued at 145 AM MDT Tue Aug 18 2026

Over the past six weeks or so, the main weather story has been one of two things: heat, some record breaking; and the monsoonal moisture which as stuck around a long time and is wearing out its welcome like an house guest that won't leave. Some days it was one or the other, other days it was both. And the next seven days will be no exception.

Today looks rather active. Dew points are rising across the area as another plume of the moisture moves into the area. One difference today is we will have a subtle shortwave moving across the area, providing some additional lift. Just about everyone will have a chance of a shower or thunderstorms today, but, much like many of the previous days, not everyone will see one. As for threats, there could be heavy rain with any storm, with precipitable water values rising close to an inch in some locations, which approaches 175 percent of normal. However, we do have decent wind at the mid levels, approaching 40 knots in some areas. So these storms will have movement, and this should mitigate the threat of flooding somewhat. However, we do have some other possible threats today. We do have a marginal risk of severe weather roughly along and east of a Cody to Shoshoni to Rawlins and eastward. The main threat looks to be strong wind. Dew point depressions are not all that large (generally 30 to 40 degrees), however lapse rates are rather steep (over 8C/Km). Sounding also have somewhat of an inverted V signature. Hodographs are also largely straight with wind fairly well aligned. With the moist atmosphere, I also can't rule out some hail, but the threat of this smaller. Western portions of state look to have the most storms during the afternoon, with the greatest coverage shifting to the east in the evening. And a few storms could linger well into the afternoon before ending after midnight. As for temperatures, they should run fairly similar to yesterday, fairly close to seasonal averages.

Then, for the next three days or so, the main concern shifts toward temperatures. Almost all guidance shows the monsoonal moisture getting suppressed to the south and east as high pressure over the desert southwest builds northward. This will lead to temperatures going up and the chances of showers and storms dropping. At this point, Wednesday looks like the driest day as we finally get a day of below normal precipitable water across most of the area. We can't completely rule out a stray shower or thunderstorm across far southern Sweetwater County, but even here the chance is less than 1 out of 6. With the ridge building back northward, 700 millibar temperatures will be climbing again, likely peaking on Friday when some areas each 20 celsius. This will lead to a period of above normal temperatures starting on Wednesday and peaking on Friday. Most areas East of the Divide will likely see highs in the 90s starting on Thursday and lasting through at least Saturday. Friday looks to be peak of the heat with most locations with elevations less than 5000 feet having at least a 1 in 2 chance of highs of 95 or over. A bit more moisture may return on Thursday or Friday, but almost all convection on these days will be confined to the western mountains and chances will be rather low, generally less than 1 out of 4 each afternoon at any particular location.

Concerns then shift to a another return of the monsoon for the weekend and into next week. Recent models have slowed the return of the moisture a bit for Saturday, with precipitable water values generally 20 percent less than yesterday. The current forecast for Friday night is likely too wet, the deepest moisture looks to return Saturday and into Sunday and early next week. There is some disagreement in the guidance in regards to the details of the most active day of the monsoon as well as placement of the most numerous convection, as would be expected this far out. However, precipitable water values look to remain above normal for much of next week. Temperatures should also lower somewhat with more cloud cover, but will likely remain near to somewhat above normal through the period. So, if I could sum up how the next week has compared to much of the summer, it would be more of the same.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 422 AM MDT Tue Aug 18 2026

Mainly VFR conditions are expected through 12Z, with exception of around showers or thunderstorms. A weak shortwave moving through the area will bring some showers this morning and a around of thunderstorms this afternoon. High resolution models continue to struggle with placement and timing of showers, so confidence of the PROB30 groups remains low and will likely need more tweaks. Showers and thunderstorms should end across western Wyoming by sunset, but will linger East of the Divide until after midnight, especially in vicinity of KCPR. The main threat from any thunderstorms will be wind gusts in excess of 40 knots, although brief MVFR conditions from heavy rain are also possible. Patchy fog may be possibly in western terminals after 07Z Wednesday that get rain, but not enough confidence to include in the TAFs at this time.

RIW WATCHES/WARNINGS/ADVISORIES

None.