UPDATED 02/10/12 9:30 p.m.
CHICAGO (CBS) -- A powerful lake-effect snow system began blasting the Chicago area Friday, disrupting travel at O'Hare International Airport and potentially bringing as much as 18 inches of accumulation to some areas in Northwest Indiana.
The snow started to fall in the northern suburbs mid-morning. As the system moved into the Chicago area, the Chicago Department of Streets and Sanitation dispatched 75 snow plow trucks to clear the city's main roads and Lake Shore Drive. More plows were out as the snow picked up.
At O'Hare Airport, conditions canceled more than 300 flights and caused delays of 90 minutes or more, the city's Aviation Department said. Delays were shorter, about 30 minutes, at Midway, where there were only a handful of flights canceled.
The snowfall was expected to pick up as the cool air grows colder.
Things were especially harsh in Northwest Indiana. Commuters headed from the train in Gary, Ind. fought the winds and sharp ice pellets falling from the sky only to have more work cut out for them at their cars.
"I was totally not prepared. I didn't watch the weather report or anything," rail commuter Noel Aponte, who did not have gloves or a heavy coat, told CBS 2's Pamela Jones.
Lake-effect snow usually is not a major concern this late in the winter, given that the lake is usually frozen over and does not send moisture into the atmosphere. But the warm winter this year has given way to different circumstances.
A winter weather advisory is in effect for Cook, Lake and Will counties in Illinois until 9 p.m. Friday. CBS 2 Meteorologist Megan Glaros says snow is likely to total 1 to 3 inches by early evening, but totals could be heavier near the lake and the afternoon commute could be rough.
But for Lake and Porter counties in Northwest Indiana, a lake-effect snow warning is in effect from 3 p.m. Friday to 4 a.m. Saturday. Northwest Indiana will get socked by the system, with 6 to 12 inches falling.
In some areas, particularly along the southern rim of Lake Michigan from Gary to Valparaiso, up to 18 inches of snow may fall.
Close to the lake, some areas could even see more than 12 inches. The National Weather Service says in isolated spots, totals could top out at 18 inches.
Snow will continue during the day Saturday in Northwest Indiana.
And while the weather has been chilly all week, the temperature will stall out at 32 degrees as a cold front swoops down from the north. Overnight, the low drops to 18 degrees, and the high climbs only to 25 on Saturday.
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