textproduct: Western and Central Wyoming

KEY MESSAGES

- Somewhat drier air moving into the area will bring less coverage of showers and thunderstorms today through Monday.

- Increased moisture should bring another more active day on Tuesday with more numerous showers and thunderstorms.

- Drier air returns Wednesday into Friday with only isolated thunderstorms expected. Above normal temperatures return Friday into the weekend with highs in the 90s East of the Continental Divide.

DISCUSSION

Issued at 157 AM MDT Sun Aug 16 2026

I have stated a few times before how much I hate forecasting the monsoon. The models do not handle it well, especially in weakly forced situations. An example is tonight where continue to have some showers and embedded thunder in western Wyoming and stretching into southern Idaho. No guidance had this last night, and nighttime is where it really struggles. In this case, as has been the case much of the previous several weeks, having as much vision of it as Helen Keller or Stevie Wonder. So, although my confidence in the trend of the coverage of the monsoon is fairly high, placement and timing of any convection, especially at night, is very low.

The general trend of the showers is down, but some will linger all night. Most guidance does show drier is moving into the area, especially across eastern and southern Wyoming. Precipitable water values drop another 20 percent or so, and dew points should average 5 to 10 degrees less than yesterday. This means a lesser coverage of showers and storms (generally no more than a 1 in 3 chance at any point, and less then 1 in 5 at most places), and also less of a chance of heavy rain that could lead to local flooding. For now, we confined most POPs to the northwestern half of the state, and I have higher confidence during the day since there has been better model performance during this time frame. And, with more sunshine, temperatures should be somewhat warmer. As for tonight, most convection should end after sunset. However, my confidence in dry overnight period is low given the terrible performance of the models over the past few weeks with the monsoon during the nighttime hours. I just don't have the confidence to pinpoint an area at this time.

Monday at this point looks fairly similar to Sunday, with mainly isolated convection and largely across northern and western Wyoming with less activity to the south and east. Temperatures should run fairly similar to Sunday. Some guidance is giving a surge of moisture at night and possible increase in activity but guidance is split. This, plus the models weakness in nighttime monsoon convection, confidence is low. With precipitable waters around 125 to 150 percent of normal on Tuesday, this also looks like a more active day with temperatures close to seasonal averages.

There has been a bit of a change for Wednesday, and there is decent model agreement on this. It is that most show drier air moving in from the southwest and lessening the chance of showers and thunderstorms, with the best chance across eastern Wyoming. The drier pattern looks to hold at least into Friday with near normal precipitable water across the area and high pressure building northward out of the desert southwest. The forecast for Friday is probably the wettest it would be. Monsoonal moisture may increase again for next weekend, but timing this far out is uncertain. And with the ridge building northward again, temperatures will be on the rise again. Highs will begin to rise again on Thursday. By Friday and into next weekend, highs in the 90s look fairly commonplace East of the Divide and in the 80s West of the Divide.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 425 AM MDT Sun Aug 16 2026

A few showers will be around this morning until around 15Z in western Wyoming, and may get close to KJAC. Otherwise, VFR conditions are expected through most of the TAF period. The one exception will be in and around any shower or thunderstorm where brief MVFR conditions are possible in and around any heavier shower or thunderstorm. Showers and storms will be less numerous than the past couple of days with moisture decreasing somewhat. It will also be mainly across northern Wyoming so we continued the mainly dry forecast in vicinity of KRKS and KCPR. Wind should remain below 15 knots or less except in and around any shower or thunderstorm. Patchy fog may form around KJAC this morning but not enough confidence to continue at this time.

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.