A new storm headed toward the Southland tonight, promising heavy rain, mountain snow, stormy seas and wind gusts up to 80 miles per hour, according to the National Weather Service.

A flash flood warning is in effect for Long Beach through Saturday.  Rainfall estimates are 1.5 to 3 inches for coastal and valley areas, NWS said.

Officials are warning of challenging travel conditions in the mountains, whiteouts, flooding, debris flows and rockslides in several burn areas.

Rain is expected to start late tonight or early Saturday, NWS forecasters said. Coastal and valley areas are forecast to receive up to 1 inch of rain per hour during peak rainfall, the NWS said, adding that the snow level in the San Gabriels will fall to 5,000 feet amid winds of 40 to 60 miles per hour.

The impacts expected to result from the storm include flooding, downed trees and power outages, increased accidents and travel delays, shallow debris flows, with more significant flows and flash-flooding possible, rockslides on canyon roads, and winter weather driving conditions in the San Gabriel Mountains, the NWS said.

In the San Gabriel Mountains, a winter storm watch is in effect through Saturday afternoon, according to the NWS.

The snow levels are expected to be at 7,000 to 7,500 feet through Saturday morning and drop to around 6,000 feet by Saturday evening, to between 5,000 and 5,500 feet late Saturday night and Sunday, according to an NWS statement. At times, snow may fall as low as 4,500 feet.

Disruptions are also expected at lower elevations, including “significant wind impacts possible for Interstate 5 near the Grapevine, where very strong gusts of 70 to 80 mph will be possible.”

The storm hails from the Gulf of Alaska and will tap into a band of moisture stretching from Hawaii to California as a low pressure system parks itself over California, NWS meteorologist Todd Hall said.