I knew once the upstairs had no water (2 days ago) to open the faucets and pray. When I heard some weird popping sounds, I knew I had to wait until a thaw for the rush of water to cascade into the basement. Hit the shutoff valve asap but there really was no way to tell where the split (s) were until later. All the pipes were concealed and along exterior walls.
I hate having to do this by myself--this is when I miss my father, who was an engineer and contractor /plumber in the old days.