The race is on to get the federal insurance website HealthCare.gov working smoothly by the end of November. And it's not just because that's what federal officials have promised. December could see a surge in demand for health insurance. "There is an avalanche coming," says Bryce Williams, managing director for exchange solutions at the benefits consulting firm Towers Winston. Williams says the firm knows from years of experience with open enrollment for Medicare patients, that the Monday after Thanksgiving is always the single busiest day for business.