textproduct: Western and Central Wyoming

KEY MESSAGES

- Showers and storms are possible through this evening. Some could be strong with 50 to 70 mph wind gusts, hail, and moderate to 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.

UPDATE

Issued at 1124 AM MDT Tue Aug 18 2026

Lots of clouds across the area today, with showers and thunderstorms in various locations through the morning. Widespread chances (15-45%) continue through this afternoon. Latest hi-res models still have strong wind gusts up to around 70 mph possible with storms this afternoon and evening, mainly across the Bighorn Basin, Johnson County, and Natrona County. Some isolated stronger winds 50 to 60 mph could also occur over Teton/Park Counties and into the Wind River Basin, but chances are less than the aforementioned locations. Small hail is also possible for the stronger storms. This activity should quickly diminish this evening, with only a few lingering showers over central Wyoming through about midnight.

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 /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1107 AM MDT Tue Aug 18 2026

VFR conditions are expected to prevail across most terminals through much of the TAF period. Showers and thunderstorms continue to move through the state this afternoon. All terminals will have chances 20- 40% for a shower or thunderstorms this afternoon and evening. There may be brief periods of MVFR to even IFR conditions especially if any storms move overhead any terminals. The main concerns with any showers or storms today will be strong gusty outflow winds possibly in excess of 35 knots, frequent lightning, and moderate rainfall. Showers and thunderstorms are expected to linger into the late evening hours Tuesday mainly for terminals east of the Divide such as KWRL, KRIW, KLND, and KCPR. Winds are forecast to remain light through the overnight into Wednesday morning with speeds around 5 to 10 knots. Conditions should dry out by Wednesday morning with VFR conditions expected to prevail through the remainder of the TAF period. Mountains are likely to be obscured at times Tuesday with conditions improving through the overnight into Wednesday morning.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on icing and turbulence forecasts.

RIW WATCHES/WARNINGS/ADVISORIES

None.