SAN FRANCISCO (AP) – The first in a series of storms has touched down in Northern California, bringing high winds and rain to the region.

Roads were slick during the Wednesday morning commute, and there were reports of isolated power outages and flooding. Although rain is expected to continue falling through the day, experts say the worst is yet to come.

A second, more powerful system is expected to arrive on Friday, with rain and wind continuing through the weekend.

Some areas could see as much as 18 inches of rain over a five-day period. Wind gusts could reach as high as 70 mph.

Officials are warning of potential mud slides in the Sacramento Valley, where areas that were burned in recent wildfires are particularly vulnerable.