El Nino could mean a mild winter for U.P. region

IRON MOUNTAIN -- A mild winter may be ahead for the Upper Peninsula, though surprises could accompany a strengthening El Nino, forecasters say.

"El Nino is upon us," AccuWeather meteorologist Paul Pastelok said. "It came on strong in late summer, and it will continue to be strong and a dominating factor going into our winter forecast."

El Nino is marked by warmer-than-normal waters in the eastern Pacific Ocean and will likely affect weather patterns well into 2024. It's the flip side to La Nina, which has ruled the past three winters.

"December should be mild overall across the Midwest and Great Lakes, with just a couple of brief, chilly periods," Pastelok said.

This pattern will carry over into the start of 2024, but a shift in the polar vortex could cause the Arctic to unleash frigid air across the central and midwestern U.S. later in the winter, he said. Also, if the Great Lakes remain largely ice-free during the first half of winter, blasts of cold air later could produce lake-effect snows.

Overall, snowfall in the U.P. and northeastern Wisconsin could be more than 50% below normal from now through April, according to AccuWeather. Temperatures from December through February might be higher than average by 3 degrees or more, a winter forecast released Wednesday shows.

The National Weather Service generally agrees, calling for a 55% chance of above-normal temperatures in the region from December through February, and just a 10% chance of below-average. The precipitation outlook for the same period suggests a 45% chance of below-average totals, along with a 20% chance of above-normal.

For the near term, the NWS slightly favors temperatures above the norm through December, while the precipitation outlook is neutral.

The U.S. Drought Monitor shows varying levels of drought in nearly all of Wisconsin. The U.P. is mostly free of drought, except for abnormally dry conditions along the southern tier, and moderate to severe drought to the west in Gogebic and Ontonagon counties.

At Iron Mountain-Kingsford, rainfall in September totaled 2.19 inches, which was 1.4 inches below normal. Temperatures last month averaged 61.2 degrees, which was 2.6 degrees above normal.

The highest temperature was 92 degrees on Labor Day, Sept. 4 -- a record for that date. The lowest was 41 degrees Sept. 17 and 18.

The Iron Mountain-Kingsford Wastewater Treatment Plant observation site has yet to report a reading of 32 degrees or lower this fall. A year ago, the first seasonal frost was reported Sept. 23. The record for the latest first frost at Iron Mountain-Kingsford is Oct. 22, set in 2021.

After a balmy start to October, highs in the upper 40s are predicted this weekend. Highs closer to the seasonal norm in the mid-50s are expected later next week.