CNN  —  Holiday travelers returning home this weekend could contend with more delays at airports as severe thunderstorms intensify in the South and a parade of atmospheric river-fueled storms slams the West. More flight delays and cancellations could be on the horizon this busy holiday weekend after nearly 18,000 flights into, out of or within the United States were delayed or canceled Thursday and Friday, according to FlightAware.com. Another 359 US flights have already been delayed Saturday