A storm system from Canada is dumping wet snow on the city, downing powerlines and causing headaches on Chicago area roadways Friday morning.

The heaviest snow is expected to hit early during the morning rush hour, then taper off by the early afternoon. The system could dump up to three inches of snow on Chicago, with greater ammounts possible north of the city, said National Weather Service Meteorologist Mike Bardou.

“We call them Alberta Clippers, Saskatchewan Screamers, Saskatchewan Scooters,” Bardou said. “Basically they’re fairly fast-moving low-pressure systems that originate in the Canadian prairie region, and then work their way southeast and bring us colder air, as well as snowfall.”

As of Friday morning, the Chicago Department of Aviation reported 150 flight cancellations at O’Hare Airport due to the weather, with minor cancellations at Midway Airport. The city also said it has deployed 183 plows on Chicago streets, though the storm is still snarling Friday morning’s commute.

Meanwhile, several thousand ComEd customers north of the city don’t have power as the heavy, wet snow is downing power lines. ComEd says it has deployed 1,100 work crews.