COLUMBUS (WCMH) — The National Oceanic and Atmospheric Administration (NOAA) issued their annual winter outlook (Dec. 2020 to Feb. 2021) for the U.S.
Climate experts are predicting cooler than average temperatures across the Northwest and northern Plains, and a milder winter for the southern and eastern portions of the country, including the upper Ohio Valley.
Wetter than normal conditions are projected from the Pacific Northwest to the Great Lakes and middle Ohio Valley region.
The driving climate factor this season is La Nina, which indicates widespread cooler water in the eastern tropical Pacific Ocean, especially off the coast of South America in the vicinity of Peru.
In a typical La Nina winter, the polar jet stream shifts north around high pressure in the northeastern Pacific, and then dips south across the northern Rockies and Upper Midwest. Cold air masses are directed into the northern tier of states, but less likely to reach areas east of the Great Lakes with any frequency.
A main winter storm track in this climate pattern typically lies on the boundary from the central Plains and Mississippi Valley to the Great Lakes, which favors above-normal precipitation in the Ohio Valley, often a mixture of rain (south) and snow (north), depending on the storm’s exact path.
Snowfall tends to run a little below normal in a La Nina season. However, all La Nina winters are not alike. The winter of 2016-17 produced merely 9.7 inches in Columbus and was exceptionally mild. The following winter was a little snowier than average at 30.7 inches in 2017-18, with several bouts of harsh cold weather early in the season (late December to mid-January).
Winter precipitation depends on the prevailing storm track in response to multiple weather factors. There are additional factors such as solar activity, blocking Atlantic high pressure, and snow cover in northern Eurasia (Siberia) that also play a role in winter patterns.