A two-day winter storm will drop the first measurable snow of the season across much of southern Maine.

Snow started falling in Portland on Sunday night. It will last, off and on, through Tuesday morning, said William Watson, a meteorologist at the National Weather Service station in Gray.

About 1-2 inches are expected overnight in Cumberland County, with higher amounts in southern York County, Watson said. Snow is expected to ease during the day Monday but pick up again overnight.

“We will see another big bump going into Monday night to Tuesday morning,” Watson said. That phase of the storm could leave at least 10 inches on the ground, he said. The storm is coming from the west, where it has already tangled holiday traffic in the South and Midwest.

“It is all part of the same system, but it is coming in two phases,” Watson said.