Snow at sea level? It could happen this weekend WEATHER

From Left, Stephanie Magallon, 10 , and Juan Magallon, 13, of Concord, get help building a snowman from Thanasis Golematis, of Pittsburg at Juniper Camp Ground overlook in Mt. Diablo State Park in Clayton, Calif. on Tuesday, February 22, 2011. Kat Wade / Special to the Chronicle less From Left, Stephanie Magallon, 10 , and Juan Magallon, 13, of Concord, get help building a snowman from Thanasis Golematis, of Pittsburg at Juniper Camp Ground overlook in Mt. Diablo State Park in Clayton, ... more Photo: Kat Wade, Special To The Chronicle Photo: Kat Wade, Special To The Chronicle Image 1 of / 34 Caption Close Snow at sea level? It could happen this weekend 1 / 34 Back to Gallery

(02-22) 12:02 PST SAN FRANCISCO -- Ah, that sneaky, lying sun.

Those blue skies kissing the Bay Area with a chilly semblance of warmth Tuesday were just teasing, it turns out, because the cold - and we do mean cold - hard truth is that snow appears to be on its way to San Francisco.

On Saturday morning, forecasters say, city folks could wake up to find their streets carpeted an inch deep in wet alabaster for the first time in 35 years. And it's expected to be even thicker elsewhere around the Bay Area, especially in the hills.

There have been snowflakes on Twin Peaks as recently as 2009, and flurries peppered even lower spots in San Francisco in 1988, '89 and '98.

But the gold standard of true snowfall is to have it hit sea level - and to stick long enough to make a snowman. That hasn't happened since Feb. 5, 1976.

'A real possibility'

"It's not a lead-pipe cinch, but having snow all the way down to the lowest level in San Francisco is a real possibility," private meteorologist Mike Pechner said Tuesday. "Seeing it on Twin Peaks Boulevard, Portola, Forest Hills? Sure. But in places like the Financial District - we just might see that."

National Weather Service forecasters say the chances for snow are riding with an Alaskan storm now rampaging south. Today should be about the same as Tuesday, when rainless blue skies allowed a tolerable 56 degrees to sneak into San Francisco, but by Thursday things will turn nasty.

How it could happen

If the storm hits California with its expected frosty ferocity by then, daytime highs will drop to the 40s and showers will start. By late Friday night, after a couple of days of frigid sogginess, the stage should be set for a traditional winter wonderland.

If the thermometer in San Francisco dips into the mid- to upper 30s as expected after dark, rain continues to fall and the earth stays chilled so it won't melt everything hitting it, there should be snow everywhere from the Financial District to the Sunset, forecasters say.

As for higher Bay Area spots such as Mount Diablo, Mount Hamilton and Mount Tamalpais, which sported snow blankets last weekend - count on a repeat show of the same, forecasters said. Mount Diablo alone had 8 inches of snow Friday.

"What we're saying is that snow levels will be lower than they were this last weekend, and that was pretty low," said weather service forecaster Bob Benjamin. "We had snow down to 1,500 feet late Friday and Saturday. This next air mass has the properties to be even colder, which will drive the snow levels down to 1,000 feet or lower."

Jinxing it?

Weather predictions and armchair wisdom being what they are, merely mentioning the possibility of a dramatic forecast might well nix the whole prospect. So longtime forecaster Benjamin, far from any armchair as he pored over his charts, and wiser than those without charts, wasn't committing one way or another.

"We're just keeping an eye on it," he said dryly.

Pechner, tongue in cheek, cut even closer to the chase.

"There's no doubt that by even mentioning it, we've jinxed it," he said.

For snow to fall, temperatures have to drop to 36 degrees, Benjamin said. For it to stick on the ground, the temperatures have to dive below 34 degrees.

The forecast now is for temperatures to drop toward the 30s by Friday evening and hit at least 37 degrees in San Francisco early Saturday, matching the record low set for that date in 1962.

By sheer coincidence, 1962 was the last time before 1976 that measurable snow fell in downtown San Francisco.

If rain is falling and Jack Frost decides to give us a lucky kick, the floor-level snow door will be open.

So fingers should legitimately be crossed. Both ways.

Fans and foes

"No, no, no, it can't fall here," Barry Hewett, 53, moaned genially as he manned his usual panhandling spot Tuesday on Fifth Street near Market Street. "Maybe Santa Cruz. They're used to it. But if I have to stay off the street and in my room, I'm going to get pretty hungry that day."

A few doors away, Shirley Tobin, 37, was practically jumping up and down with excitement as she tended the counter at the Latte Express cafe.

"It'll be cold, but I really want to see it," she said. "That would be very special. Here in San Francisco - wow!"

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