Why Is It So Cold in the Southwest?

Known for hot temperatures, Southern California and the rest of the Southwest United States are undergoing a cold snap that has set records in many areas throughout the region.

Los Angeles set a record daily low of 34 degrees Fahrenheit (1 degree Celsius) this morning (Jan. 14), the coldest it's been in 22 years, according to the National Weather Service. Water pipes also froze and busted in Las Vegas, where the mercury dropped to nearly 17 F (minus 8 C), according to news reports.

So what's bringing all this chilly air to the area?

The low temperatures are due to an extremely cold, dry mass of air originating off the Arctic sea ice in the Canadian Arctic, said Jeff Weber, a scientist with the University Corporation for Atmospheric Research in Boulder, Colo. This mass of air has been pushed southward by a warmer, high-pressure system that moved north and east toward Alaska from the Pacific, Weber told OurAmazingPlanet. This helps explain why it's unseasonably warm in Alaska, while Angelinos are searching for sweaters. [The World's Weirdest Weather]

This flip-flopping of hot and cold is caused by a buckling of the jet stream, the current of air that normally ferries air in a relatively straight line from west to east across the United States and out into the Atlantic Ocean. However, due to higher-than-usual temperatures near Greenland, the stream is backed up. This heat and associated high pressure have slowed down the North Atlantic Oscillation, a climate pattern that pulls weather patterns eastward across the country.

read more: http://www.livescience.com/26260-record-southwest-cold-explained.html