The Cascade Mountains, like most mountain ranges, pull moisture out of the prevailing winds. In this case the westwardly winds off the Pacific Ocean. The rains that fall favour the growth of Western Red Cedar, Douglas Fir, various Maples and Cottonwoods.
A shutter speed of 2 seconds was needed for this photograph. Most of the image is tack sharp but the ends of the longer branches had moved in the slight breeze.