While models predict climate change will plunge California and the Southwest deeper into drought, what awaits Washington and Oregon is less clear. The Pacific Northwest will get warmer. That much is certain. But in terms of the rain that places like Seattle and Portland are known for, things get fuzzier.
The bulk of it, Voisin said, is expected to come from atmospheric rivers streaming overhead between fall and spring, with rivers running low in late summer as the snow and ice in the mountains that rim the region melt ever earlier and no longer keep the waters as high as they historically have.
It’s important to remember that some dams act as flood control and smooth out the river discharge for various benefits. Typically in monsoon style areas, not sure how many others. We might see that role come up if we have fewer but more severe rains.