STRONG STORM WITH RAIN, SNOW, WIND DUE TUESDAY

A North Pacific storm that’s drawing warm, unstable air from the subtropics will pound San Diego County on Tuesday with heavy rain, moderate snow, potentially damaging winds, and possibly lightning west of the mountains.

The system, which will edge ashore late tonight, will be the biggest storm of autumn and could quickly wipe out San Diego’s roughly 0.70inch rain deficit, says the National Weather Service.

Forecasters estimate that 1 to 1.5 inches of rain will fall from the coast to Interstate 15, likely causing widespread street flooding and possibly mudslides. The precipitation could reach 2 inches — and maybe 3 — on Mount Laguna, on Palomar Mountain and in Julian.

“This will be a full-fledged storm with winds that could reach 45 mph to 50 mph at the coast,” said Brandt Maxwell, a weather service forecaster.

It appears that the heaviest rain will fall on Tuesday afternoon and evening, and that snow will follow in areas above 5,000 feet when the air turns cooler.

Forecasters say the local mountains will get 1 to 4 inches of snow by early Wednesday. At least twice as much could fall in the San Bernardino Mountains.

The storm is sucking up lots of moisture from an area east of Hawaii, producing a wide column of moisture — known as an atmospheric river — that will flow through most of California.

Forecasters say the river will slam the San Francisco Bay Area today before the system sinks to the south. The weather service estimates that greater San Francisco could get as much as 3.5 inches of rain, with most of it falling over an 18hour period.

San Francisco has been a lot wetter than San Diego International Airport, where 1.12 inches of precipitation has fallen since the rainy season began on Oct. 1.

The seasonal average for that period of time is 1.81 inches.