We can look into all sort of diagnostics: rear brake lines, stuck brake pistons, prop valve, saggy suspension, the lot. But at the end of the day it all boils down to tyres, well mostly for sure at this time of year.
Listen to what @hash4u said: over inflated tyres, hard rubber, cold temperatures- when the rubber cannot get warm enough, causing lack of traction- that's your problem. So just drive carefully and maintain a safe distance.
Good luck bleeding the living days out of it, it won't get you any where.