Philly’s only snowless winter was 50 years ago. No flakes are in sight anytime soon.

By the time the weekend is over, the snow total at California’s Mammoth Mountain might reach 400 inches this winter, the product of a relentless procession of “atmospheric river” storms swamping and whitening the West.

“We’re all looking forward to a long break,” said Tyler Salas, with the National Weather Service Office in Reno, Nev., which is responsible for the forecasts for the Sierras.

Maybe they should come to Philly.

That Mammoth Mountain total would be on the order of about 20 winters’ worth at Philadelphia International Airport, which still awaits its first measurable snow of the season, and all indications are that the wait is going to continue indefinitely.

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The government’s Climate Prediction Center has a 70% to 80% likelihood — extraordinarily high probabilities for a long-range outlook — for above-normal temperatures for the next two weeks in the Northeast. AccuWeather sees temperatures 2 to 6 degrees above normal in Philly for the next 30 days, said meteorologist Danielle Kittle.

It isn’t only Philly. The January snow king in the Northeast corridor is Boston, where the monthly total stands at 0.2 inches.

It was 50 years ago that Philadelphia experienced its only winter without measurable snow, but it is way early to assume we are about to experience an encore, or to conclude the start of the new year has been a harbinger.

The first 12 days of January 1973 were far different from the same period of this year: They were significantly colder. Temperatures averaged below normal, and on five days it failed to get above freezing.

By contrast, January readings this year are averaging better than 11 degrees above normal.

» READ MORE: Early outlooks did call for a gentle winter

In 1973, a “trace” of snow at least was detected on Jan. 6; this year, not even a January trace.

The winter of 1972-73 wasn’t especially mild, only about 2 degrees above long-term averages, but the precipitation and the cold air just couldn’t make the connections.

Save for that quite impressive chill around Christmas, the upper-air flow has been more west-to-east, or “zonal,” keeping Arctic air from oozing toward the Northeast, said Kittle.

“Everything is coming out of the Pacific,” she said.

In the tropical Pacific, the La Niña cooling of sea-surface temperatures is due to continue through the winter.

While La Niña’s impacts on snow and cold in the Northeast have been inconsistent through the years, in some winters, early patterns persisted, Kittle said. What happens keeps happening.

The tropical Pacific is the weather’s “engine room,” as one climate researcher has observed. Water temperatures are slow to change, unlike those on land, and thus can have prolonged effects on upper-air currents.

It is also common for weather in the East to be the mirror-opposite to that of the West, all part of an atmospheric seesaw. High pressure systems, or ridges, share space on the planet with areas of low pressure, or troughs.

High pressure, which favors more-benign weather, continues to dominate in the East, and troughiness, associated with storms and cold, in the West.

Those atmospheric rivers, ultra-moist corridors laden with tropical water vapor, have helped deliver prodigious amounts of snow and rain to the West Coast. They are important to the West’s water supply, in some years supplying up to half its annual precipitation, NOAA estimates.

» READ MORE: The magic and mystery of snow endure

However, too much is enough — even for skiers — says the weather service’s Salas. “This is just insane,” he said. The snows have closed roads and ski resorts.

Fortunately, in its two-week outlook, the climate center does see the storms backing off.

The outlook, however, does not see any of that snow coming to Philly or anywhere else in the Northeast, and it appears that the ski operators in the Poconos and elsewhere will have to keep the machines running.

That’s provided it’s cold enough to make snow.

Next week, the climate center says, temperatures in the Northeast could average as much as 20 degrees above normal.