From Weather.com:
More than 100 trees fell in an area on the north side of Lake Quinault on the Olympic Peninsula just after midnight on Jan. 27. Cliff Mass, a Seattle meteorologist and professor of atmospheric sciences at the University of Washington, is trying to figure out why.
According to a two-part post he wrote for his blog, Cliff Mass Weather and Climate, early reports seemed to indicate that a microburst was responsible for the tree fall. Mass became skeptical that winds from a microburst would be sufficient to topple the large trees, particularly since some fell while others were snapped at the base of the tree.