A storm that was pounding California's Sierra Nevada with snow Tuesday took aim at the Colorado Rockies and could roll east and slam the Appalachians on Thanksgiving Day, bringing unsettled travel weather to millions of Americans hitting the skies and roads for the holiday weekend.

The National Weather Service has issued a series of winter weather advisories across the country as an estimated 80 million Americans are expected to travel at least 50 miles from their homes to celebrate Thanksgiving later this week.