textproduct: Western and Central Wyoming

KEY MESSAGES

- A warmer day for most today. Increasing moisture will bring isolated to scattered thunderstorms, mainly in southern and western Wyoming.

- Deeper monsoonal moisture spreads over the area Thursday through Saturday, with a greater chance of showers and storms. At this point, Friday looks like the day for the most widespread showers and storms.

- Temperatures remain near to above normal through Friday, with cooler temperatures for the weekend. Dry weather may return by Sunday.

DISCUSSION

Issued at 216 AM MDT Wed Sep 16 2026

Have you ever had someone that overstayed their welcome, be it at a party or staying at your house? Well, the weather is doing that again. Our friend the monsoon (which those of you who read my discussions know I love so much, note sarcasm) has returned. And will be around for a few more days.

We do have some shower and isolated thunderstorms around as I write this, but nothing strong and the storms are moving. Monsoonal moisture will continue to push northward today and increase the coverage of showers and storms across the area. Coverage still looks scattered at best though (at most a 1 out of 3 chance). There is decent model consensus in keeping a vast majority if the showers and storms along and west of the Continental Divide and also near Casper. We can't rule a shower or storm out anywhere, but the chance is only around 1 in 10 or less. As for potential flooding, probably not through Wednesday night. The core of the deepest moisture should remain south of Wyoming today. There is also some steering flow, about 15 to 20 knots worth, which should keep the showers and storms of the moving and not of the stationary variety. As for temperatures, this looks to be the warmest day of the week with flow turning to south and still some sunshine. Some of the warmer spots will likely see highs around or over 80 degrees.

Coverage should increase on Thursday. An upper level low will slowly approach from the Pacific Northwest. At the same time, a strong ridge over the southeast will begin to retrograde to the west and direct deeper moisture into the area, as much as 175 percent of normal. At the same time, a weak shortwave will be pivoting around the upper level low giving a bit more lift. However, there is a limiting factor. It is that with the moisture in the atmosphere, much of the day may end up being fairly cloudy. This may limit instability somewhat, especially since it is now mid September and not July, limiting daytime instability. Nevertheless, there will be an increased chance of showers, especially across western Wyoming. With the increased cloud cover, temperatures will also be cooler, generally by about 5 to 10 degrees compared to Wednesday.

The upper level low will begin to make a closer approach by Friday. Of all the days, this looks like the most active day across the area with almost all areas having at least a 1 in 3 chance of convection during Friday and Friday evening. I have one more concern about this day as well. Most guidance is showing a 20 percent drop in precipitable water. However, this could lead to a fairly sunny morning that could bring more instability and a greater chance of convection, especially East of the Divide. If there could be local flooding, this could the most likely day. The one mitigating factor continued to be steering flow though, as much as 40 knots at times. So the storms will be moving. And with more sun, temperatures will be warmer, but likely not as warm as today.

The low will passing close to the area on Saturday,turning flow more to the northwest. This should result in a noticable cooler day across the area. There will still be enough wrap around moisture for some showers and isolated thunderstorms to continue. However, most guidance shows precipitable water values much lower on this day, so the threat of heavy rain looks less. Uncertainty then increases from Sunday into early next week. as a lot depends on the movement of the upper low. Some guidance moves it far enough east for drier weather to move in for Sunday, other guidance keeps showers around through Sunday night. Confidence is not high in specifics as the models have had different solutions in regards to speed and track of the upper level low for the past few days. However, we do have high confidence of unsettled weather through at least Saturday. Somewhat drier and warmer weather may then return for early next week.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 1006 PM MDT Tue Sep 15 2026

Midlevel clouds will continue to sweep northeast across the state tonight into tomorrow morning. This initial push will bring a chance for showers into KRKS overnight tonight, with best chances before 12Z. Chances decrease 12-18Z, but high clouds will continue for all sites. Thunderstorm chances increase during peak heating again for KRKS, and into KBPI/KPNA and KLND/KRIW. Any showers will be more isolated and have higher cloud bases, so chances remain lower, so PROB30 wording remains. This chance for showers has trended southward in latest runs, with KJAC chances decreasing, so have removed PROB30 for the time being.

KCOD/KWRL hold onto light north winds through the day, with minimal flight concerns. KCPR starts with southwest breezes and high clouds. The north wind push will sweep in around 00Z/17, with gusts around 25kts through 06Z/17.

RIW WATCHES/WARNINGS/ADVISORIES

None.