I was over at a friend's home for the evening, and was getting ready to leave. the sky was a lot clearer than i'd expected, being on the oregon coast. there were a few scattered high clouds, and a bit of haze. we spent some time looking at jupiter, which was clearly visible. i was still looking up at the sky and saw a momentary bright flash of light, much brighter than jupiter (still visible) or venus. it was also brighter than a plane's lights would have been. i did, at first, think it might have been a plane but kept watching the same area, which was adjacent to a small 'clump' of thicker cloud, but no lights 'reappeared' on any of the edges of the cloud, nor did another flash appear in the same place. the location of the flash was approximately at the vertex of an equilateral triangle pointing westwards, with a line drawn between arcturus and jupiter as the base of the triangle. unfortunately, my friend was not looking up, and so did not see the flash.