October 20, 2011
High Resolution (Credit: NOAA)
The Southern Plains should prepare for continued drier and warmer than average weather, while the Pacific Northwest is likely to be colder and wetter than average from December through February, according to the annual Winter Outlook released today by NOAA.
For the second winter in a row, La Niña will influence weather patterns across the country, but as usual, it’s not the only climate factor at play. The ‘wild card’ is the lesser-known and less predictable Arctic Oscillation that could produce dramatic short-term swings in temperatures this winter.
NOAA expects La Niña, which returned in August, to gradually strengthen and continue through the upcoming winter. It is associated with cooler than normal water temperatures in the tropical Pacific Ocean and influences weather throughout the world.
“The evolving La Niña will shape this winter,” said Mike Halpert, deputy director of NOAA’s Climate Prediction Center. “There is a wild card, though. The erratic Arctic Oscillation can generate strong shifts in the climate patterns that could overwhelm or amplify La Niña’s typical impacts.”
The Arctic Oscillation is always present and fluctuates between positive and negative phases. The negative phase of the Arctic Oscillation pushes cold air into the U.S. from Canada. The Arctic Oscillation went strongly negative at times the last two winters, causing outbreaks of cold and snowy conditions in the U.S. such as the “Snowmaggedon” storm of 2009. Strong Arctic Oscillation episodes typically last a few weeks and are difficult to predict more than one to two weeks in advance.
High Resolution (Credit: NOAA)
With La Niña in place Texas, Oklahoma, New Mexico and parts of surrounding states are unlikely to get enough rain to alleviate the ongoing drought. Texas, the epicenter of the drought, experienced its driest 12-month period on record from October 2010 through September 2011.
Stormy periods can occur anytime during the winter season. To improve the ability to predict and track winter storms, NOAA implemented a more accurate weather forecast model on Oct.18. Data gathered from the model will support local weather forecast office efforts to prepare for and protect the public from weather events. This service is helping the country to become a Weather-Ready Nation at a time when extreme weather is on the rise.
According to the U.S. Winter Outlook (December through February) odds tilt in favor of:
This seasonal outlook does not project where and when snowstorms may hit or provide total seasonal snowfall accumulations. Snow forecasts are dependent upon winter storms, which are generally not predictable more than a week in advance.
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