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

A powerful storm carrying a strong atmospheric river laid siege to California over the last several days — setting records in parts of the state — with evacuations orders still ongoing Thursday because of the risk of life-threatening flooding and debris flows.

LA could see between a third and a half of the total annual precipitation in one storm alone,” observed UCLA climate scientist Daniel Swain, in reference to how serious the atmospheric river conditions pending in the region surrounding Southern California hang,

Downpours were spawned by the region's latest atmospheric storm, a vast airborne current of dense moisture siphoned from the Pacific.

Water flooded the parking lot of a shopping mall in Glendale, California, as powerful winter storm swept southern California on Christmas Eve.Video filmed by Roger Justin Caffier at Glendale Galleria shows water cascading down a flight of stairs onto a completely inundated parking area.

With another round of rain expected to arrive Thursday afternoon, officials are urging people not to let their guard down.

There were more than two dozen outages as of the morning of Dec. 24. An outage map shows restorations are expected to occur throughout the day.

Officials in Los Angeles and surrounding counties warned that a "very dangerous" holiday storm could trigger "widespread flash flooding."