I posted a comment somewhere about an accident yesterday in NE OR. My facts were incorrect when I reported that the plane had tumbled through some trees. The story, as I have heard it (third person) is that the pilot was flying his 150 low and slow near the mountain. He was not attempting to land. It was about 7:30 pm and as he passed by a small canyon, he encountered a downdraft. He was unable to respond quickly enough to avoid coming in contact with the ground and running the plane into some brush. Pilot was not injured.

I've experienced similar downdrafts in the same area. Seems that every evening after the sun begins to set the cool air drains down the canyons and into the valley. With the combination of not much airspeed and not much altitude, not much can be done when a draft catches you from behind.