Snow levels may drop to the level of the I-5 Freeway over the Grapevine on Monday night

A storm will bring widespread rain to Southern California from Sunday through Monday evening, according to the National Weather Service, and winter weather advisories are in effect beginning as early as noon on Sunday for the higher elevations.

Snow levels are expected to be in the range of 5,500 to 6,500 feet on Sunday, but then lower to between 5,000 and 6,000 feet on Monday. And snow could potentially dip down to 4,500 feet locally on some interior slopes.

It’s possible that there could be snow down to the level of the Grapevine, which is at about 4,100 feet, on Monday night, said Curt Kaplan, a meteorologist at the National Weather Service in Oxnard. That would be the result of this complicating factor: The moist southwest flow bringing the rain may encounter a cold, dry easterly wind, which would cause evaporative cooling. That cold offshore flow could cause snow levels to dip to the level of the I-5 Freeway through the Tehachapi Mountains.

Isolated thunderstorms are also a possibility with this system, especially in the afternoon and evening hours on Monday, because of instability caused by cool temperatures aloft.

Significant snow accumulations are likely above 7,000 feet, with lighter accumulations down to 5,000 feet.

Another storm is expected on Wednesday and Thursday, but the timing is uncertain. However, with this second system, snow levels may drop to 4,000 feet on Thursday, which would affect Interstate 5 over the Grapevine.