As a high pressure system over the west coast moves out of the way, massive amounts of precipitation are being funneled into California and Oregon. As orographic lifting squeezes the moisture out of the air mass some areas in the Sierras could receive up to two feet (24 inches!) of precipitation before this event is over. If most of it falls as snow in the mountains, the peaks in the Sierras could see up to 10 feet of snow.
It has already started, as you can see in the graphic below showing the snow received as of Wednesday morning. And the storm has just begun.
It remains to be seen how this will affect California’s five-year drought and the 2017 fire season. In 2016 the northern part of the state saw some relief from the drought, but there was not much change farther south.