LOS ANGELES (AP) — Residents of several Southern California mountain and canyon communities are being urged to voluntarily leave their homes because of possible mud and debris flows from potentially heavy rain starting late Thursday.

The evacuation warnings are posted in parts of Orange and San Bernardino counties where rains are expected to be fed by an atmospheric river.

The National Weather Service has also issued advisories for minor flooding of roadways and low-lying areas in counties around San Francisco Bay, and an avalanche warning has been issued for eastern Sierra Nevada backcountry areas in Mono and Inyo counties.