The San Francisco Bay Area is experiencing its third day of rain and isolated thunderstorms due to a low-pressure system moving inland. Shower activity is expected to decrease by Sunday evening, but residents should watch for flooding and dangerous driving conditions. The Sierra Nevada region has significant snowfall, with ski resorts reporting 10 to 18 inches of new snow, and higher elevations above 7,000 feet seeing 1 to 2 feet. Motorists should be careful when traveling through the Sierra Nevada due to reduced visibility and icy roads, with snow showers expected to diminish by Monday morning.