TRAVERSE CITY — A warmer-than-usual start to October could be a sign of things to come if National Weather Service predictions come true.
The NWS’ Climate Prediction Center figures there’s a 60- to 70-percent chance of above-normal temperatures through October for all of Michigan and Wisconsin, most of Iowa and Minnesota and northern Illinois. There’s a smaller chance of above-normal temperatures sticking around in Michigan through December.
Plus, colder-than-normal Pacific Ocean water temperatures along and south of the equator prompted the NWS to issue a La Niña advisory.
That typically would mean that Michigan is on the cold side of a jet stream that spans North America and serves as a divider of sorts, with cold air to the north and warm air to the south, said Jeff Lutz, a NWS meteorologist in Gaylord. During winter, that’s usually true for Michigan anyway, but La Niña conditions also tend to bring more precipitation to the Great Lakes State.
Climate Prediction Center forecasts appear to show the jet stream a little to the west of Michigan for the next three months, meaning temps through the winter might not be as cold as normal, Lutz said. La Niña conditions never bring the extremes that warmer-than-usual waters in the equatorial Pacific — known as El Niño —conditions are known for.
“When you get warm equatorial waters in the Pacific like that, it’s a much more pronounced effect on Michigan’s overall pattern than there is when La Niña gets up there,” he said. “Even if it’s a strong one, they don’t tend to do as much.”
Other weather phenomena, like the Arctic and North Atlantic oscillations, are harder to predict than El Niño/La Niña but tend to have considerable influence by forcing cold Arctic air further south, Lutz said.
Michigan stayed balmy through the first two weeks of October, with temperatures in Traverse City averaging about 10 degrees above normal, Lutz said — Thursday had a high of 71 at Cherry Capital Airport versus the normal at 60. That’s because high pressure over the East Coast kept that same jet stream parked west of Michigan, keeping cold air over the Rocky Mountains and Pacific Northwest.
Many spots in the northern Lower Peninsula haven’t had their first overnight freeze of the fall, according to the NWS. Traverse City’s first freeze, on average, is Oct. 7, with Nov. 1 as the latest on record and Aug. 29 as the earliest. Some areas could see their latest first freeze on record — Houghton Lake’s was Oct. 23 in 1995.
Areas of low pressure will move over the region fairly regularly over the next few days, bringing temperatures back down to normal or a little above, Lutz said. That’s according to most computer models, with one outlier calling for enough cold to allow for snow on Oct. 21.
Lutz said he doesn’t put much stock into that prediction — not yet, anyway.
“We’re in a warm pattern, so I’m not willing to start biting on all this cold air coming down out of Canada yet until we actually see cold air start coming down from Canada,” he said.