'Biggest storm of winter' to unleash flooding rain in California into Friday night

A new train of storms has arrived along the Pacific coast, and a potent one has begun to hit California hard with heavy rain, mountain snow and strong winds to end this week.

The first storm focused on areas from Northern California to Washington during Wednesday and Thursday.

The second storm in the series will focus most of its moisture on Central and Southern California into Saturday.

"The late-week storm has the potential to be the biggest of the winter in terms of rainfall and impact to much of Southern California," according to AccuWeather Meteorologist Jim Andrews.

The storm will bring enough rain and excess runoff to cause flash flooding, which can cause major delays for motorists. Along with the heavy rain will be the potential for mudslides in some neighborhoods, especially in recent burn scar locations.

The storm will raise the risk of oceanfront and hillside erosion.

"We expect 3 to 6 inches of rain to fall in the lowlands along the coast and over the Los Angeles basin," according to AccuWeather Senior Meteorologist Ken Clark. "From 6 to 12 inches of rain is likely below snow levels in the mountains, especially along the south-facing slopes."

In the Los Angeles and Santa Barbara, California areas, much of this rain may fall in less than 24 hours ending Friday night. In San Diego, the heaviest rain will fall during Friday night.

That much rain in such a short period of time could lead to some roads becoming impassable for a while.

"From Los Angeles to Santa Barbara County, this storm will bring a widespread and significant flood threat," Clark said.

The combination of heavy rain, a low cloud ceiling and gusty winds will also lead to airline delays.

As the ground becomes soggy again, gusty winds will raise the risk of fallen trees and sporadic power outages.

In addition to strong winds, there can also be locally severe thunderstorms on Friday. It is possible a couple of the strongest storms produce a brief tornado.

Snow levels will remain well above the passes in Southern California. However, those venturing over Donner Pass are likely to encounter slippery conditions. The ski resorts in the Sierra Nevada will likely receive 1 to 3 feet of snow from the storm that ends the week.

In the wake of the big rain through Friday night, spottier showers will continue to dampen the region on Saturday and Saturday night.

However, locally flooding rain will hit the Desert Southwest and northwestern Mexico this weekend.

No rain is projected to fall on Southern California during the period from Sunday through next week. The break in the rain will allow crews and property owners to clean up after the storm.

Another storm will roll ashore from the Pacific during Sunday. Most effects from the storm, including the potential for significant flooding will be focused over Northern California during the first part of next week.

As a result of the ongoing storms, more challenges are ahead for crews, officials and residents in the Oroville, California, area. Damage to the spillway at the Oroville Dam forced evacuations earlier this week.

Rainfall from the storms have the potential to aggravate the situation around Oroville and other reservoirs filled to capacity in Northern California. Additional rainfall will force officials to release more water downstream. Some of these rivers are already at flood stage.

The rainfall to end this week will take another big chunk out of the drought over Southern California.

Total rainfall since Dec. 1 over much of Southern California has ranged from 1.5 to 2.5 times that of average.

While less than 1 percent of the state remained in extreme drought as of last week, much of the region remained in moderate to severe long-term drought, according to the United States Drought Monitor.

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