California entered 2017 hoping a wet winter could end the state’s six-year drought. Be careful what you wish for. Northern California and the San Joaquin Valley are bracing for potential flooding this weekend, as a massive weather system known as an atmospheric river builds off the coast. Forecasters say that by Monday, rainfall and river flows could reach totals not seen in more than a decade. Already, some regions north of Sacramento are issuing voluntary evacuation orders and several northern counties, including Sacramento, are readying sandbag stations.

An atmospheric river laden with water vapor coming out of the tropics will slam into the Sierra Nevada this weekend and early next week, bringing as much as 10 feet of new, wet snow to the higher elevations, according to the National Weather Service in Sacramento. It is the second of two channels of water-filled clouds that will strike Northern California. By Thursday morning, the first river of water vapor brought nearly seven feet of new snow to Squaw Valley, four feet to Kirkwood and almost as much to Bear Valley.

After many long years of waiting, California’s drought relief may finally be here. Snow has piled up over five feet in some parts of the Sierra Nevada since the Sunday storm. And while the first snow survey of the year actually came in below average in terms of snow accumulation, there are reasons for optimism. “Right now we are on pace to have the wettest water year on record,” said forecaster Mike Kochasic with the National Weather Service in Sacramento, referencing conditions in Northern California.