A large trough of low pressure is sitting over the western United States. It will bring periodic clouds and isolated shower and thundershowers to western Montana. However, nothing well organized is expected, and thus most of the time will be dry. The best chance for isolated showers will be Wednesday evening and again Thursday afternoon. Otherwise, variable cloudiness with lows in the upper 30s to mid 40s and highs Thursday in the 60s.
A better organized system will bring a better chance of widespread rain to southwest Montana, around Butte and Bozeman, on Friday. Elsewhere, a few showers are possible. Highs in the upper 50s and 60s.
For the Memorial Day weekend, a few showers Saturday, mainly across southwest Montana around Butte and Bozeman, and Sunday mainly across northwest Montana around Kalispell.
A stronger storm system will bring the best chance of widespread rain area wide on Monday, Memorial Day. Highs in the 50s and 60s.