A strong Pacific storm will begin to uncoil across Oregon, Washington and Northern California through the weekend, promising heavy rain and snow that will replenish water supplies but could also unleash destruction.

Fresh weather model data points to a wet weekend ahead for Northern California and the Bay Area. Forecasts are calling for significantly higher rainfall totals than previously predicted along with several feet of snow piling up in the Sierra by Sunday.

An atmospheric river is poised to hammer Northern California and the Pacific Northwest with heavy rain and snow starting late this week. Flash flooding will be a concern as heavy rain persists from San Francisco to Eureka.