I don’t know of any Washington based sites dedicated to high lake fishing. There are some individuals in other states. There is a fellow who posts here as giantbrookie that has a website dedicated to high lake fishing in California.
Useful information can be found at NW Hikers or WTA but they aren’t specifically fishing sites. And don’t forget to check out the links page on this site for other pages with high lake info or other info that might be of interest to high lake anglers.