Brace yourself: Early outlook says it'll be a snowy, wet winter

A snowier, wetter winter may be in the cards for the Chicago region, according to the latest seasonal outlook from the National Weather Service's Climate Prediction Center.

The forecast shows that — along with a wide swath of the Midwest, including Indiana and much of Ohio — Illinois could see more precipitation than normal, while temperatures are predicted to remain near average levels.

One of the strongest indicators of a wet Chicago winter is the earth is in its third year of the naturally occurring weather phenomenon known as La Niña, which brings cooler-than-normal sea surface temperatures in the tropical Pacific Ocean.

Its counterpart, El Niño, refers to warmer tropical Pacific sea surface temperatures.

Meteorologist Matthew Rosencrans said current forecasts are “very reflective” of past La Niña winters, which typically have favored above average precipitation for the Great Lakes region.

“On a year-to-year basis, El Niño or La Niña controls about 38% of your variance, and we are in a La Niña, a decently strong one, and very likely to be in a La Niña through the winter,” he said.

However, don't load up on salt or buy a heavy duty snowblower just yet. Because we're still four months away from the icy season, the center's best models for the Midwest have a hit rate of just about 20%, Rosencrans said.

Jeffrey Frame, professor of atmospheric sciences at the University of Illinois Champaign-Urbana, said two other guideposts for long-range forecasts are climate change and computer models.

The models are based on complicated equations that take into account the atmosphere, the ocean and the earth's surface, Frame said.

“These are solved on supercomputers, and they're similar to but slightly different from the models we use to predict the weather on a daily basis,” he said. “It's not just one or two simulations, but it's actually dozens of them averaged together.”

As for global warming's potential effects on Chicago-area winters, Frame said three progressing outcomes are above average temperatures, heavier rainfall events and a greater tendency for off-season severe weather thunderstorm outbreaks.

Climate change increases the likelihood of these weather events occurring, but does not inherently cause them, Frame said.

“For example, if there's a hurricane two weeks from now, climate change doesn't cause that,” he said. “Can it make certain things more or less likely? Yes. But it doesn't fundamentally cause things to happen.”

There is room for improvement on long-range forecasts, Frame added.

While they can predict general seasonal trends — which vary in accuracy from year to year — they aren't capable of foreseeing individual storms or snowfalls.

“There's a finite predictability limit to it in that basically beyond a certain period of time, maybe a week or two weeks, we really can't predict day-to-day weather anymore,” he said. “We're not going to say we're going to have a white Christmas, or there's going to be a big blizzard on Jan. 26. We do not even have close to the predictive capability for that, and we might never.”

• Jenny Whidden is a Report For America corps member covering climate change and the environment for the Daily Herald. To help support her work, click here to make a tax-deductible donation.