textproduct: Western and Central Wyoming

KEY MESSAGES

- Another day of showers and thunderstorms today, with greater chance further east and somewhat less coverage in the western mountains.

- The chance of showers and thunderstorms continues through much of next week, with Tuesday through Thursday looking like the wettest days at this time.

- Above normal temperatures continue through Monday, with widespread highs in the 80s and 90s. Some highs above 100 are possible in the warmer locations on Sunday and Monday.

DISCUSSION

Issued at 238 AM MDT Sat Jul 18 2026

It you are of a certain age and attended a dance or wedding, especially around the turn of the millennium, you will probably remember a dance called the "Cha Cha Slide." And one of the instructions in the song is "Slide to the Left, Slide to The Right". That is what the plume of monsoonal moisture will be doing over the next several days, sliding to the east, sliding to the west, sliding to north and sliding to the south. I hate forecasting the monsoon as it is, this makes placing the expected convection a bit more difficult.

We continue to have some annoying showers out there tonight, but they are moving and not that heavy, keeping flooding concerns at this time to a minimum. And the monsoonal plume should, the quote the late, great DJ Casper, slide to the right, or move eastward somewhat. Northwestern portions of the area may see precipitable water values drop by as much as 30 percent, limiting the chance of convection today. However, it will increase to the east, rising to as much as 200 percent of normal in central Wyoming. The center of convection should continue to be in the Cody Foothills and the Absarokas with the favored low level easterly upslope flow. We will issue another flood watch for this afternoon and evening for this region. The difference today is that storms should be able to move a bit further east, possibly all the way to Natrona County and eastern Sweetwater County which have been dry the past few days. Like the past few days, most showers should end after sunset, but there will be a few annoying stragglers to may hang around most of the night.

There could be a lull on Sunday as the deepest moisture slides to the east a but and also to the south. Some models have very little coverage across the area, others have a bit more but it looks less than previous days. Not to say it will be dry, but precipitable waters are expected to drop another 20 percent or so. It is still 150 percent of normal but the flooding threat may drop again somewhat, especially in northern Wyoming where the drier air is expected to be.

Precipitable waters remain steady on Monday. The deterministic models have the minimum coverage during the day as a result. However, the monsoonal moisture will again begin to slide, this time to the north and west, and increase the chance of showers and storms across the area again on Monday night, although the time of arrival may limit coverage somewhat. The active conditions return on Tuesday as precipitable waters once again climb to 200 percent of normal across the area. As a result, the risk of flooding, which may drop somewhat Sunday and Monday will likely return on this day. A passing shortwave may also help enhance the storms, although exact timing of it is questionable this far out.

It is still looking like Wednesday will be the day to watch though. Most guidance is showing the deepest moisture moving over the area on this day. For example, the GFS is showing precipitable water values well over 200 percent of normal. At Riverton, for example, it is showing a precipitable water value of 1.5 inches. If this happens, it would be a record high for the station. (The old record is 1.41 inches). There could also be another shortwave moving in the help enhance convection as well, It there is a day to worry about more widespread flooding, this looks like the one. It is still 5 days out so timing might chance, but we have to watch this closely.

After this, it finally looks like moisture will begin to drop. It remains quite moist on Thursday across much of the area. Then the deeper moisture should begin to slide to the east and south, especially next weekend, and start to limit coverage of convection. But we have an active several days to get through before we get there.

We will still also be under control of the ridge, and that will keep temperatures quite warm over the next three days, with widespread highs in the lower elevations in the 80s and 90s. The warmest days look like Sunday and Monday, especially if the deeper moisture can get pushed to the south and east. Some of the warmer spots, like Greybull and Worland, could make a run at 100 on both days. Cooler, more seasonable temperatures then move in for the middle of next week as we get more cloud cover and showers. The coolest weather we have seen in a while, since before the heat wave of last weekend.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 413 AM MDT Sat Jul 18 2026

Largely VFR conditions are expected through 12Z Sunday. The main area of showers and thunderstorms will shift somewhat eastward today. As a result, we have only gone with vicinity showers near KJAC as most convection should be to the east. All other terminals have PROB30 groups with convection developing in the mountains around 17 to 19Z and moving off into the afternoon and evening. Brief MVFR and IFR conditions will be possible in and around any heavy shower or thunderstorms, along with wind gusts to around 35 knots. Most showers and thunderstorms should end after sunset, although a few will linger past midnight. Mountain obscurations are possible in and around any heavier shower or thunderstorm.

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

Flood Watch from noon MDT today through this evening for WYZ002-003.