A multi-day, multi-region potentially historic and destructive winter storm will unleash its fury beginning Monday and will last through Wednesday.
When everything is said and done, the storm may very well impact a third of the population of the United States; approximately 100 million people.
Update: Jeff Masters has more, and more technical detail:
Perhaps of greater concern is the potential for a major ice storm along a swath from Northwest Oklahoma to Massachusetts. Widespread freezing rain is expected to bring over 1/4″ of ice to many major cities, including St. Louis, Indianapolis, Columbus, Cleveland, and Pittsburgh. Some regions could see up to an inch of ice, and widespread power outages due to toppled power lines are likely for millions of people. Damages exceeding $1 billions are possible from this ice storm.