Downtown Minneapolis and the Mississippi River on 11 April 2019 in Minneapolis, Minnesota. (Photo: Stephen Maturen / Getty Images) 
The system will hammer the Pacific Northwest on Tuesday before raking California and the upper Midwest over the next few days, according to Steve Silver, a senior meteorologist with Maxar Technologies. Winter storm warnings extend to the US-Mexico border, including areas east of Los Angeles and San Diego.
Snow is forecast to fall in the hills around San Francisco Thursday night, with accumulations of 6 to 12 inches (15 to 30 centimetres) on the highest peaks, said Daniel Swain, a climatologist at the University of California, Los Angeles. Even San Francisco itself could see a few “novelty flakes”, he said. The mountains east of Los Angeles, meanwhile, could get two to three feet.
“Just about everybody who lives in California will be able to see snow on nearby hills,” Swain said Tuesday.
As the storm moves east, Minneapolis will likely take the brunt of the impact, with the Twin Cities getting 15 to 25 inches of snow through Thursday from the “historic” storm, according to the National Weather Service. New England may get up to 18 inches by Friday, Maxar said.
The storm will divide masses of warm air, which will head south, and cold air that will go north.
“It should be quite a contrast,” said Silver. “This is definitely a pretty extreme event on both sides.”