The above photo was taken about 4:30 in Brighton by Michele Faust while some menacing looking clouds moved through the area. Strange, wasn’t it, that the rain followed after these clouds seemed to be gone.
UPDATE 6:48 p.m. Steve Davis at the NWS informs me, after looking at Michele’s photo, that it shows a shelf cloud. Wikipedia says a shelf cloud is a type of arcus cloud, “a low, horizontal cloud formation associated with the leading edge of thunderstorm outflow, or occasionally with a cold front even in the absence of thunderstorms.” Makes sense with what I saw today.