As a powerful storm system moves across the United States, millions are bracing for extreme weather, including catastrophic flooding, snow, and ice. The Eastern U.S. is experiencing severe flash floods stretching from the Tennessee Valley to Appalachians, while heavy rains have impacted Kentucky, Tennessee, and Virginia. In the Northeast, a weekend winter storm is expected to bring snow, sleet, and freezing rain, possibly evolving into a bomb cyclone with significant snowfall. Meanwhile, residents in the Midwest and Plains are facing frigid temperatures as well. A series of winter storms is likely to disrupt travel, with thousands of flights already canceled. Authorities are urging caution as hazardous conditions persist across 28 states.