Pedestrians cross State Street in the Loop during Friday’s snowfall.
Tyler Pasciak LaRiviere/Sun-Times
A snowstorm along the Wisconsin border on Friday brought the first measurable snowfall to Chicago in a month.
Although the total accumulation measured at O’Hare International Airport was just an inch, up to 9 inches was dumped in the Rockford area and around 6 inches fell in McHenry and Lake counties, the National Weather Service said.
Those are the effects of what are known as “banded” snowstorms – long, thin storms caused by instability in the atmosphere and rapidly changing temperatures over a short distance, said Mark Ratzer, a meteorologist for the weather service.
“It’s able to produce this banded snow where it can be quite intense in a narrow access, but you go 30 or 40 miles on either side of it and you get much lighter amounts or in some cases even nothing,” Ratzer said.
Friday’s snowfall comes after a rather mild winter, including the warmest February on record in Chicago.
It was the first time in March that at least 1 inch of snow was measured in the city. In all, Chicago has seen about 2.15 inches of snow this month. That’s not even halfway to the monthly average for March — 5.5 inches.
Feb. 23 was the last time at least 1 inch of snow fell in Chicago, and the last snow before then fell on Jan. 19, according to the weather service.
No additional accumulation was anticipated Friday night, but lake-effect snow wasn’t being ruled out in the city.
“It’ll wind down early (Saturday morning) and then shift into northwest Indiana and just kind of fall apart,” Ratzer said. “It looks like we’ll probably be dry here for the most part through the weekend.”
But that weather system was still expected to usher in hazardous conditions on Lake Michigan. Winds could cause up to 8-foot waves, prompting the weather service to issue a small craft advisory on the lake, in effect from 4 a.m. to 10 p.m. Saturday.
The high temperature forecast for Saturday is 35 degrees, with temperatures expected to rise to 46 degrees Sunday and 57 degrees Monday, according to the weather service.