A Remarkable Sky

I like a storm that starts like this one.  Check out the view from the Avenues this evening.  The Wasatch are obscured (which means it is snowing) and the Salt Lake Valley is filled with mammatus clouds.

Click to enlarge

Numerous mechanisms have been proposed to explain the formation of these clouds.  Here in Utah, they seem to be frequent visitors when moisture moves in at mid levels above a dry low-level airmass.  There's a good discussion, and even more fantastic pictures of these clouds, at wikipedia, which draws heavily from an excellent review article by Schultz et al. (2006).