The National Weather Service has called a flash flood watch for Los Angeles County mountain foothills and areas burned in recent brushfires from 6 a.m. to 1 p.m. Thursday.

A very moist air mass associated with an atmospheric river storm system will bring periods of rain to Southwest California through Thursday night.

The heaviest rainfall is expected to occur Thursday morning into early afternoon.

Peak rainfall rates during this period are expected to range between 0.50 and 1.00 inches per hour, with the highest rates focused across south and southwest facing slopes of the Santa Monicas and San Gabriels.

As a result, shallow mud and debris flows will be likely in these first-year burn areas, with the potential for more significant and damaging debris flows.

In addition, roadway flooding is likely, especially in low-lying areas, along with rock and mudslides on canyon roads and below steep terrain.

Meanwhile, LA County Health officials urge residents at risk of fast-rising and fast-moving floodwater during this rain event to take the following preparedness actions to keep themselves, their families and loved ones safe:

* Create a Plan: Create an evacuation plan and identify a primary exit route and a secondary exit route, ensuring your vehicle has enough gas, and with the front of your vehicle facing towards your primary exit route. If you have animals, elderly family members, or special medical needs, make accommodations beforehand to expedite travel and shelter.

* Pack a Go-Kit: Be ready to evacuate by having an emergency kit ready and loaded in your vehicle, which should include items such as extra medication, important documents and warm clothing.

* Stay Informed: Keep aware of road closures, changing road conditions and evacuation messages by watching local media coverage on television & radio, and following these Twitter handles: @CaltransDist7, @LASDHQ, @LHSLASD, @LACoFDPIO and @LACoPublicWorks.

All residents who live in or near the Woolsey Fire burn areas are urged to remain vigilant.
For additional resources on storm preparation, visit lacounty.gov/LARain and follow #LARain and #WoolseyFire on social media.