Weeks after wildfires that killed at least 29 people and destroyed entire neighborhoods, Southern California is facing another extreme-weather threat: Too much rain.

The NWS says excessive rainfall is expected to cause flooding along the Russian River, affecting roadways and agricultural land.

Heavy precipitation is falling mostly in mountain areas. A flood watch in also in effect for the coast of central California, including the San Francisco Bay Area and Sacramento Valley.

A weather system fueled by a "Pineapple Express" originating near Hawaii will unleash torrential rain across Northern California and southern Oregon throughout the week. Up to 20 inches of rain could lead to mudslides and mountain snow could total 6 feet.