Second Half of January Brings Record Warm Tempatures

The second half of January created a warm air mass around mostly the west region. The most remarkable record happened in a place famous for recording the world's official record high temperature back in July 1913. Death Valley, California, reached 87 degrees on Sunday, Jan. 25, tying its all-time record high for the month of January. States like Kansas, Nebraska, and South Dakota all reached all time high in their temperatures for this January.

So why did this weather shift happen in the end of January? As usual, a sharp northward bulge in the upper-atmospheric jet stream – known technically as a "ridge" – played a role in the pattern. The first northward bulge last week sent the jet stream as far north as the Yukon in northwest Canada, bringing a rush of mild Pacific air into western Canada, then east across the Rockies.A second bulge in the jet stream arrived on the West Coast over the weekend, bringing an even warmer air mass into the western U.S. and setting the stage for the widespread record warmth in recent days.

Link:http://www.weather.com/forecast/national/news/mild-midwest-warm-west-record-highs