I recently came across one beek's story about a disastrous winter. It was 2011 and there was not winter thaw that bees could take advantage of for a cleansing flight. Many beeks in the area lost 100% of their hives. Here is a link about winter survival and Warres that made a huge amount of sense to me:

http://www.thewarrestore.com/wintersurvival.htm

I'm looking forward to trying that kind of hive next year, if possible.

Peter Collins in Lower Michigan