We had two other 2009 falcons (Ty from the Radisson and Luck from Brandon) up until maybe a week ago. Luck might still be around actually, haven't been by the site for a few days.
And don't worry about Sandy, she was here last fall at about this time before heading out just before the weather turned. Lots of food for her (just watched her devour a pigeon she had cached in the nestbox) and this weather ain't nothing. Madame, Princess' predecessor, was here from 1990 to 2005 (maybe a bit longer) all year round.
No reason that Sandy wouldn't migrate, no mate (Ty seemed to be interested and she seemed to be interested in him) staying with her, she hasn't nested at this site so no reason for her to be territorial about it (and she wasn't when Dennis and I visited her a few days ago) and from what I know of her genetics, she doesn't have a whack of non-migratory peregrine subspecies genes (like Madame).
Suspect she will wait out the rain before leaving - could leave as soon as Thursday (when the rain/snow is suppose to break) or hang around until the weather shifts again ...