An LED light fixture including a plurality of upwardly-protruding elongate fins extending therealong from distal fin-ends to proximal fin-ends adjacent to upward-flow openings through the fixture, the fins defining horizontal between-fin channels open at the distal fin-ends, and a plurality of flow-interrupters between adjacent fins changing air flow along the channels. The flow-interrupters may be less than half the heights of their respective between-fin channels and may be mounting bosses to serve the further purpose of facilitating assembly of the fixture.