What causes these things? I see these sporadic clusters of rampant branching with yellow needles on many trees (I think this is Douglas fir, Pseudotsuga menziesii) growing along the coast of a upper mountain lake.
A rust fungus; on Douglas-fir (yes, that's what yours is), either Melampsora medusae or Melampsora occidentalis. Other similar diseases occur on other Pinaceae genera.