Looking over the observation logs for CBI back to August, I identified
the following times where signatures of clouds were seen in total power:

Times are in UT.

11 Dec 00 : 0800  clouds seen in data
            0145       "

10 Dec 00 : 0135-0140 

 9 Dec 00 : 1600-1635  snow, clouds seen fringing on 1m baselines
            all daytime overcast, seen in total power with dome closed
            0200  seen in data

 6 Dec 00 : 0400-0500 

>From September to early December it was extremely clear and stable.
No events noted.

 5 Sep 00 : no observing, wind and light snow

30-31 Aug 00 : reports of clouds in data early-on

This should be good for a start (especially the December events which
I was there for).