Winter solstice will be immediately followed by wet weather in Southern California

Snow in the Verdugo Woodlands area of Glendale on Jan. 11, 1949
A thin blanket of snow covers the Verdugo Woodlands area of Glendale on Jan. 11, 1949, after a rare Los Angeles snowfall.
(Los Angeles Times)

Winter officially arrives with the December solstice Saturday at 8:19 p.m. Pacific time.

Right out of the blocks, the new season is expected to bring moderate rainfall to the Los Angeles region Sunday, according to the National Weather Service, with snow levels about 5,000 feet. At that elevation, the 5 Freeway over the Grapevine is expected to be minimally affected, which will be a relief to holiday travelers.

Those dreaming of a white Christmas will have to head out of the L.A. Basin to find it. There should be accumulations of 3 to 6 inches at higher elevations in Southern California’s mountains by Monday morning.

In Northern California, rain and snow will spread from west to east Saturday morning into the evening, with chain controls possible in the mountains. A winter weather advisory goes into effect from 10 p.m. Saturday to 10 p.m. Sunday for most of the mountains.

Five to 10 inches of snow are expected Sunday above 4,500 feet in the Sierra Nevada, with up to 15 inches south of Highway 50. The Coastal Range and Cascades can expect 5 to 15 inches above 4,000 feet, the National Weather Service said. In Shasta County, 5 to 10 inches could fall above 3,500 feet, with up to 20 inches over the higher peaks.

Historic probability of a white Christmas
(Paul Duginski / Los Angeles Times)

The National Oceanic and Atmospheric Administration has produced a map of the lower 48 states based on data from the National Centers for Environmental Information for 1981 to 2010 showing where dreams of a white Christmas are likely to be fulfilled. The West Coast, Deep South and Gulf Coast are pretty much out of luck. But places such as Minnesota, Maine, upstate New York, Idaho, the Allegheny Mountains of Pennsylvania, and West Virginia are likely to have some of the white stuff. Naturally, the Rockies and Sierra Nevada can count on snow.

What is the winter solstice?

The December solstice in the Northern Hemisphere occurs when the North Pole reaches its maximum tilt away from the sun, causing the shortest period of daylight and the longest night of the year. In about six months, as Earth travels on its yearlong journey around the sun, the Northern Hemisphere will be tilted toward the sun, and the Southern Hemisphere will reach its maximum tilt away from the sun. The seasons are caused by the fact that Earth is tilted on its axis by 23.5 degrees.

What is the winter solstice?
(Paul Duginski / Los Angeles Times)

The winter solstice is regarded as the beginning of winter, but from this point the days begin to lengthen. Still, the coldest part of the winter lags behind the solstice, usually coming in January and February. That’s because Earth is constantly losing heat, and more heat is leaving the reservoir in the Northern Hemisphere’s mid- and high latitudes than is being added to it. In the same way, the warmest days of the year lag behind the summer solstice, much as the hottest part of a summer day occurs several hours after the sun is at its noonday high point.

As Daniel Swain, a climate scientist at UCLA, tweeted, “Indications of a more widespread (& cooler) pattern throughout California. No widespread storms, but looking refreshingly like winter.”

Models don’t agree on the forecast for Monday through Christmas, but they look cool and unsettled with a chance of showers each day.

And there absolutely won’t be snow in L.A. for Christmas. But it sounds like it also won’t be the kind of day Irving Berlin described in his original lyrics for “White Christmas” — the introductory verse that usually is left out in recordings:

The sun is shining,
The grass is green,
The orange and palm trees sway.
There’s never been such a day
In Beverly Hills, L.A.
But it’s December the twenty-fourth,
And I am longing to be up north.