Bicyclist hit by bus mirror (lightly)

Monday, I was riding northbound on N Williams, hugging the left side of the bike lane, as I normally do when passing parked cars [in order to avoid the door zone]. At about NE Thompson, I was startled by a light "thwack" on the left side of my helmet. My instant thought was "tree branch", but my startling carried on as a TriMet bus passed me within an elbow's reach.
I realized my helmet had been grazed by the bus's side mirror.
Story here!