Winter coming early? Depends on whom you ask

A man walks in the snow in downtown Columbus, Ohio. Accuweather is predicting an early winter and snow before Halloween in parts of the Midwest, including the Ohio Valley.

AccuWeather is predicting early freezes and snow in the Midwest, but not all forecasters agree. Is long-range weather forecasting still more art than science?

If you'd like to keep sweating, visit the sizzling Southwest. For a balmy fall foliage tour, head to New England. But if you're in search of cooler climates, the Midwest might be your best bet.

Weather forecasters agree that the opposite corners of the country will see warmer-than-normal temperatures during the next three months, but AccuWeather is making a bold call for a cold fall and early winter in the Midwest. Their prediction includes early frosts and freezes in the Great Lakes region and the possibility of snow before Halloween in the Ohio Valley and the mid-Atlantic.

The AccuWeather forecast keeps in place the pattern of this summer, when a big dip in the jet stream brought persistent chilly spells to the middle of the country and the mid-South.

The National Weather Service's Climate Prediction Center, on the other hand, says a warm spell from the Great Lakes to the Northeast could linger well into autumn. The International Research Institute for Climate and Society (IRI), which issues global outlooks, has a forecast that closely matches the weather service.

Related: Slow transition to winter in the Northeast; quick in the Midwest

LONG-RANGE FORECASTING: 'CHAOS TAKES OVER'

So why the divergence? Forecasters use various computer models that rely on factors such as ocean temperature patterns to help peg the position of the jet stream, the band of upper-atmosphere winds that steers weather systems across the country. But then each forecasting service adds its own secret sauce and unique expertise when it comes to choosing among models that frequently disagree.

Jeff Masters, co-founder of the Weather Underground, says the newer models give only "a slight improvement" over past efforts at long-term forecasting. Masters says that beyond three to five days in the future, "chaos takes over."

AccuWeather senior meteorologist Paul Pastelok disagrees, saying "the models have gotten a lot better" and are fairly reliable for predictions at least a few months into the future.

Many businesses, especially those in the agriculture industry, want to know what the weather will be like in seasons ahead. That's why farmer's almanacs have been published since the 1700s, relying on moon phases and their own mix of science and folklore to prognosticate. Now computers have taken over from groundhogs and lunar influences.

Lately, the uncertain effects of global warming have added another unknown to the mix of science, experience and art that is long-term forecasting.

AccuWeather's Pastelok admits that the weather of the most recent 45 days plays an important role in his company's forecasts. AccuWeather's prediction of a cooler fall in the Midwest is based on a bet that the jet stream will keep sagging down deep across the middle of the U.S., a "blocking pattern" that many meteorologists have linked to a warming Arctic.

But the government's Climate Prediction Center, generally a bit more cautious in its outlook, sees cooler air relaxing its grip on our mid-section this autumn.

As far as rainfall, the weather service and the IRI both call for a wide swath of wet weather over the next three months from the western Gulf Coast up to the Great Lakes, while AccuWeather puts a risk of flooding farther east on the map: in the mid-Atlantic and parts of the mid-South, where this summer brought record rainfall.

 "It's hard to pinpoint exactly who is going to be hit the worst," hedges Pastelok.

And, for this fall, it seems, hedging is in season. Frost on the pumpkin or Indian Summer? It depends on where you are, and whom you believe.

Related: This summer's wacky weather explained

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