MISSION, Kan. (AP) — Thousands of flights were canceled and homeless shelters are overflowing amid one of the most treacherous holiday travel seasons the U.S. has seen in decades. Some places have experienced temperatures plummeting 50 degrees Fahrenheit within a matter of hours. Forecasters expect a bomb cyclone to develop late Thursday into Friday near the Great Lakes. That occurs when atmospheric pressure drops quickly in a strong storm.They warn of an impending “bomb cyclone” that could pack blizzard conditions. President Joe Biden has warned Americans to take the storm seriously. He said Thursday in the Oval Office that “this is not like a snow day when you were a kid.”