Officials in Los Angeles and surrounding counties warned that the giant holiday storm could trigger "widespread flash flooding."

An atmospheric river storm was expected to bring up to 2 inches of rain to some parts of San Diego County before the weekend, with the heaviest rainfall expected on Christmas Eve, NBC 7 meteorologists said. Wednesday's downpours could fall at rates up to an inch per hour, particularly in North County, and thunderstorms are possible.

Parts of Los Angeles County burned by wildfires earlier this year remained vulnerable to flash flooding, mudslides, and debris flows.

After record flooding in Washington state, then a widespread western windstorm, more Pacific storms are targeting different parts of the West through Christmas. Here's the latest forecast.

When it's all said and done, coastal and valley areas are expected to receive 4 to 6 inches of rain over the course of the storm. As much as 1 foot of rain is forecast for the foothills and mountains. We'll keep track of running rain totals here as the storm progresses.

As the Bay Area braces for an atmospheric river-fueled rainstorm, a potentially stronger system is on the horizon - one that could meet the criteria for a bomb cyclone and bring damaging winds.