The CTA Holiday Train arrives at the Illinois Medical District CTA Blue Line "L" stop as the sun begins to set on Dec. 16, 2021, in Chicago. (Armando L. Sanchez / Chicago Tribune)

       Unless Friday night’s precipitation leads to lasting snow, Chicago this year might break its record for the latest first measurable snow.

       That record date is Dec. 20, 2012, the latest Chicago held off for measurable snow, said Jake Petr, meteorologist with the National Weather Service in Chicago. The weather service’s minimum amount of measurable snow is a tenth of an inch.

       Here’s when Chicago received its first snow of the fall season, going back 135 years ？

       Petr said a weather system was expected to go through Chicago Friday night. But while there was a chance of snow, as well as sleet and freezing drizzle, it was unclear whether it would stick.

       After Friday night’s system, it becomes unlikely there will be snow again until possibly next Thursday going into Dec. 24.

       Even then, the chance for snow going into Christmas Eve is about 20% or less, Petr said.

       “As far as like a true white Christmas, I certainly can’t say yes or no on that but I lean toward probably not,” Petr said. “But there’s still plenty of time for things to change.”

       Chicago Christmas weather: The warmest and coldest since 1871 ？

       Petr said there has been snow in Chicagoland since late November, in places like Rockford and Romeoville, but it hasn’t fallen measurably at O’Hare International Airport, the National Weather Service in Chicago’s official recording site.

       The wind is also expected to calm down from the past week, with gusts reaching 15 mph to 20 mph, Petr said. Temperatures going into next week are expected to be in the lower to mid-30s.

       Analysis of 40 years of Dec. 25 U.S. snow measurements shows that less of the country now has snow for Christmas than in the 1980s, The Associated Press reported Friday.

       Christmas snow cover was down to 38%, with an average depth of 2.7 inches.

       Will Chicago see a white Christmas this year? Here’s what 150 years of weather data predict for Dec. 25. ？

       The change was particularly pronounced in a swath from about the Mason-Dixon Line to just north of Detroit, Chicago and Nebraska. The Christmas snow cover average there went from nearly 55% in the 1980s to slightly above 41% now, University of Arizona data shows. Average snow depth fell from 3.5 inches to 2.4 inches.

       The numbers are small enough that it’s difficult to tell whether this is a meaningful trend and, if so, whether climate change or natural weather variability is the cause, said University of Arizona atmospheric scientist Xubin Zeng, who ran the data.

       Still, Zeng, who has published studies on decreasing snowpack in the western U.S. being connected to climate change, said the downward slide of white Christmases is consistent with global warming.

       Casanova is a Tribune reporter. Borenstein is a writer for The Associated Press.

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       Dec 16, 2021