For the second winter in a row, La Niña will be in the driver’s seat.  on

Thursday morning, declaring that La Niña conditions were now in place in

both the atmosphere and ocean. NOAA gives odds of around 65-75% that La

Niña conditions will extend at least through the upcoming Northern

Hemisphere winter of 2017-18.

 

La Niña's U.S. signature:  frequent ups and downs, active storm track

 

 

The atmospheric rearrangements triggered by La Niña often lead to a

consolidated jet stream over North America and an active, progressive storm

track. Typically, this leads to periods of roller-coaster weather, with

frequent ups and downs in temperature. For the season as a whole, La Niña

winters tend to end up colder than average toward the north central and

northwest U.S. and warmer than average toward the south and southeast. On

top of this is the overall warming influence from human-produced greenhouse

gases, which can help reinforce the southern warmth and blunt the northern

cold.