Winter weather is coming back to the Bay Area — just in time for spring. Starting Monday, the day of the vernal equinox, a week-long system of cool storms will swing through Northern California, bringing several inches of rain to the Bay Area and more snowfall in the snow-stuffed Sierra, according to the National Weather Service. The pattern follows two weeks of mostly sunshine around the region in what now appears to be a limited break from one of the wettest rain seasons in years.