.. seems to be the word of the day: graupel, aka granular snow pellets, also known as soft hail. There seems to be an emerging consensus that that's what we had falling in different neighborhoods today.
So, we're willing to call that we had snow in Altadena on Feb. 26, 2011. Yes, it didn't look like a picture frame from Currier and Ives, and there probably wasn't enough to build a decent sized snowman, but there seems to be no argument that we were snowed on today.
Our proof: reader Robert sent this picture -- and you can make a decent size snowball from the stuff, and that's good enough for us!