A powerful winter storm has been dumping deep snow in parts of the West. Much of the central U.S. has been unseasonably warm. And high winds have hiked fire risks in several states. Why is all this happening? The jet stream, El Niño and global warming. Jet stream winds keep warm air from the south trapped below cold air from the north. Global warming means average temperatures generally start higher. Also at play is a weather pattern called El Niño, which transports warm air from the Gulf of Mexico northward.
