CNN  —  Storms across both the w estern and southern United States threaten flight delays as millions of holiday travelers prepare to close out the year. On what is expected to be one of the busiest travel weekends of the year, another round of severe thunderstorms is expected to hit the South Saturday with strong tornadoes, damaging winds and large hail from Louisiana to Alabama, according to the National Weather Service . Elsewhere in the country, a series of Pacific storm systems will