textproduct: Western and Central Wyoming

KEY MESSAGES

- Chances for showers and storms increase today, and peak on Tuesday. The best chance for showers and storms will be across northern Wyoming.

- Drier air returns starting Wednesday and lasts through Friday, with only isolated convection, mainly in and near the mountains.

- Above normal temperatures return by Wednesday and last through at least Saturday, with widespread highs in the 90s East of the Divide Thursday, Friday and possibly through the weekend.

DISCUSSION

Issued at 1246 AM MDT Mon Aug 17 2026

The monsoon continues today and, like last night, the models did another horrible job with the night time convection. There are less than last night though with the air mass being drier. But, what I wouldn't give for a nice, strong cold front to push through and vanquish the monsoon until next summer. But, we have to play the hand we are dealt so here we go.

Moisture will increase across the area today, but not dramatically. Precipitable water values today look to generally run anywhere from 100 to 140 percent of normal, not excessively high. The result will be a somewhat greater coverage of showers and storms that yesterday. Most guidance is also fairly consistent in keeping the most numerous storms across the northern half of the area, with mainly dry conditions persisting in southern Wyoming. Not saying there won't be any there, but the chance is only around 1 out of 10. The best chance looks to be across the northern border where the chance is around 1 out of 3. As for hazards, dew point depressions are over 40 degrees so there could be some strong wind gusts. There could also be some locally heavy rain but there is steering flow today and that should help mitigate the flooding threat; it is not zero but it is low. With somewhat higher thicknesses, temperatures should be a couple of degrees warmer than yesterday, fairly close to what is normal for mid August. Some convection lingers into as well, but placement is uncertain given the poor model performance with the monsoon.

Tuesday looks like the most active day for this round of the monsoon. The highest precipitable water values are not the highest, again topping out around 140 percent of normal. However, it is the most widespread. As a result, just about all locations will have at least a 1 in 5 chance of a shower or thunderstorm. Just about everything else looks similar to today, the main threat would be strong wind gusts, with a lesser chance of minor flooding with decent steering flow mitigating that threat somewhat. A few showers may linger into Tuesday night as well, but probably fewer than on Monday night. Temperatures should also run fairly similar to Tuesday.

Drier air will then overspread most of the area for Wednesday and Thursday. Precipitable water values fall back to below normal levels for most of the area on Wednesday and even into Thursday as the moisture gets suppressed to the south. The chance of convection on these days is very small, less than 1 out 10 for all locations. There is a slightly better chance of a shower or storm on Thursday, but it would likely be restricted to the mountains. With the associated ridge building northward, temperatures will be on the rise as well. The forecasted temperatures may be a few degrees too cool as well. Most of the lower elevations East of the Divide will probably see high temperatures into the 90s possibly as early as Wednesday and almost definitely from Thursday through at least Saturday. Some of the warmer spots could be in the upper 90s Friday or Saturday.

The chance of showers and storms also begins to rise on Friday as monsoonal moisture moves back into the area. Most activity would be confined to in and near the mountains on Friday though. Saturday may be a day that needs to be watched. Some guidance shows precipitable water values climbing to over 150 percent of normal, possibly approaching 200 percent of normal. There is steering flow, so this should mitigate the flooding threat somewhat. I would not be surprised to some sort of Excessive Rainfall Outlook for this day though. Above normal moisture also looks to persist into Sunday and early next week, keeping the chance of showers and thunderstorms in the forecast.

AVIATION /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 347 AM MDT Mon Aug 17 2026

VFR conditions are generally expected through the period. A few showers will be ongoing across northern Wyoming but the only terminal that may be impacted is KCOD. For the most part, we have continued the PROB30 groups for mainly the northern terminals, but confidence in timing of the storms remains low. Brief heavy rain could lead to occasional MVFR conditions, but the more likely impact will be outflow wind gusts of 30 to 40 knots. Most convection should end after sunset, but a few showers will linger through the night, mainly across northern Wyoming but confidence in the placement of the showers tonight remains very poor.

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

None.