Forecasters at the National Oceanic & Atmospheric Administration's (NOAA) Climate Prediction Center issued the "U.S. Winter Outlook" on Oct. 20 and said La Nina weather patterns are expected to influence winter conditions this year.
The Climate Prediction Center issued a La Nina watch this month, predicting that the climate phenomenon is likely to develop in late fall or early winter. La Nina favors drier, warmer winters in the southern U.S and wetter, cooler conditions in the northern U.S. If La Nina conditions materialize, forecasters say it should be weak and potentially short-lived.
“This climate outlook provides the most likely outcome for the upcoming winter season, but it also provides the public with a good reminder that winter is just up ahead and it’s a good time to prepare for typical winter hazards, such as extreme cold and snowstorms,” said Mike Halpert, deputy director of the NOAA Climate Prediction Center. “Regardless of the outlook, there is always some chance for extreme winter weather, so prepare now for what might come later this winter.”
Other factors that often play a role in the winter weather include the Arctic Oscillation, which influences the number of arctic air masses that penetrate into the South and create "nor'easters" on the East Coast, and the Madden-Julian Oscillation, which can affect the number of heavy rain events in the Pacific Northwest.
Specifically, NOAA said the U.S. outlook for the winter (December 2016 through February 2017) includes:
* Precipitation — Wetter-than-normal conditions are most likely in the northern Rockies, around the Great Lakes, in Hawaii and in western Alaska. Drier-than-normal conditions are most likely across the entire southern U.S. and southern Alaska.
* Temperature — Warmer-than-normal conditions are most likely across the southern U.S. and extending northward through the central Rockies, as well as in Hawaii, western and northern Alaska and northern New England. Cooler conditions are most likely across the northern tier from Montana to western Michigan.
The rest of the country falls into the “equal chance” category, meaning there is not a strong enough climate signal in these areas to shift the odds, so they have an equal chance for temperatures and/or precipitation to be above, near or below normal.
* Drought — Drought will likely persist through the winter in many regions currently experiencing drought, including much of California and the Southwest. Drought is expected to persist and spread in the southeastern U.S. and develop in the southern Plains. New England will see a mixed bag, with improvement in the western parts and persistence to the east. Drought improvement is anticipated in northern California, the northern Rockies, the northern Plains and parts of the Ohio Valley.
NOAA explained that this seasonal outlook does not project where and when snowstorms may hit or provide total seasonal snowfall accumulations. Snow forecasts are dependent upon the strength and track of winter storms, which are generally not predictable more than a week in advance. However, NOAA said La Nina winters tend to favor above-average snowfall around the Great Lakes and in the northern Rockies and below-average snowfall in the mid-Atlantic.
NOAA produces seasonal outlooks to help communities prepare for what conditions are likely to come in the next few months and minimize the impacts of the weather on lives and livelihoods.
A video of NOAA's 2016 winter outlook is available here.