Wavy jet stream

A wavy jet stream seems to be getting to be a habit.

http://www.weather.com/forecast/national/news/mild-midwest-warm-west-record-highs#/1

By Nick Wiltgen
Published Jan 26 2015

Record-breaking warmth has arrived in parts of the West and Midwest, and more records may be broken Tuesday and Wednesday. By late in the week, the warmth will continue in the West while the Midwest sees a cooldown.

The most remarkable record thus far 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, tying its all-time record high for the month of January.

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On Monday, Rapid City, South Dakota topped its daily record high soon after midday, surging into the upper 60s by mid-afternoon. Oklahoma City surged to at least 78 degrees, shattering its daily record of 71 and marking its warmest day since 1997.

Several dozen daily record highs were set across the West and Plains Sunday. Monterey, California, reached 84 to tie its second-highest temperature on record in the month of January.

Bismarck, North Dakota, did not set a record high – but its Sunday low of 33 degrees was the first time Bismarck has stayed above freezing for an entire January day since 2001, and only the 16th such day in 140 years of records there.

On Saturday, Redding, California, reached 80 degrees to tie the city's all-time record high set Jan. 15-16, 2014. Daily record highs were set in several other California cities as well as parts of Oregon, Washington, Idaho and Nevada.

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But there are also downsides. In the Midwest, the persistent warmth will likely cause ice to grow thinner on lakes and ponds, making it more dangerous to venture out onto the ice for fishing or other recreational activities. In fact, a man and his son died Sunday near Oshkosh, Wisconsin, when the man's vehicle plunged through ice on Lake Winnebago according to WISN-TV.

In the West, the warm weather will likely aggravate the ongoing drought in California, especially as it continues to eat away at what little snowpack there is in the Sierra Nevada.

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Why is all of this warm weather happening?

As usual, a sharp northward bulge in the upper-atmospheric jet stream – known technically as a "ridge" – will play a role in the upcoming pattern. The first northward bulge has 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. As that already mild air blows down the slopes of the Rockies it will warm even more as it spreads across the Canadian Prairies and southeastward into the Northern Plains and Upper Midwest.

A second bulge in the jet stream will arrive on the West Coast this weekend, bringing an even warmer air mass into the western U.S. and potentially setting the stage for the widespread record warmth next week.

On top of the atmospheric pattern, the ongoing California drought and relatively sparse snow cover in the Sierra Nevada will further allow temperatures to warm up. The daytime temperatures we feel at ground level on a daily basis are strongly influenced by the sun's ability to heat the ground; wet ground warms up more slowly than dry ground, and snow-covered ground reflects most of the sun's energy back to outer space, preventing it from reaching the ground underneath.

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http://www.weather.com/storms/winter/news/5-things-to-know-about-winter-storm-juno

5 Things You Should Know About Winter Storm Juno

By Chris Dolce
Published Jan 26 2015

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5.) Juno's Making the West Warm

The deep dip in the jet stream providing the dynamic energy for Juno to intensify has sent the jet stream into an equally amplified, but opposite, configuration in the western United States.

Typically when the jet stream jogs southward in the East, this results in it building northward across the West. The outcome is widespread warmth, and that's what we are seeing from the Great Plains to the West Coast.

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