Why has it been such a mild winter so far in the Pittsburgh area?

PITTSBURGH — This winter has been anything but normal, with warm temperatures one day and cold temperatures the next.

Since December, our temperatures have averaged warmer than normal and we broke a 130-year-old record high temperature in January when the mercury hit 71 degrees.

We've also had fewer shots of brutal cold, like last year when the temperature dropped to a record breaking minus 5 degrees.

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Arctic air has stayed bottled up near the North Pole this year, thanks to a strong and stable polar vortex.

The polar vortex makes headlines when a real winter chill sets in -- and it’s always there, separated by the jet stream that’s almost like a wall holding it back.

When it's weak and wobbly, it stretches or splits, and cold air slides south. When it's strong and stable, winds keep the really cold air around the Arctic, and we stay mild.

A strong area of high pressure in the Atlantic has also been pumping warmer air our way this winter, so storms have been struggling to tap enough cold air to bring us heavy snow.