As spring arrives in Philly, probing the mystery of the missing snowflakes

Yes, it really did use to snow in Philadelphia.

And for a virtual while last week, it appeared that the region’s biggest snowfall in seven years — about a foot and a half — would upstage the first days of the astronomical spring, which arrives officially at 5:24 p.m. Monday.

A quite similar virtual threat had been on tap for March 13.

But at last look, those computer-model forecasts were off by about a foot and a half. The threats that didn’t materialize coincided with the anniversaries of two of the most disruptive March storms in the region’s weather history.

» READ MORE: 10 reasons why spring is special around here

It was that kind of winter around here: A holiday without ice for the snow-fighting highway crews, a lost one for plow contractors, and at times a hallucinatory one for the models.

From here, any virtual blizzards may be especially hallucinatory: On average less than an inch of snow falls on Philly from March 20 on.

The short answer: It landed on the West, the upper Midwest, and some in Buffalo. The seasonal total at Mount Mammoth, in the Sierras, has a decent shot at 600 inches, says Amy Freeze, meteorologist with Fox Weather. (Yes, that is her real name, and, yes, she’s heard all the jokes.)

For those keeping score, that would be about 2,000 times more than the 0.3 inches measured officially at Philadelphia International Airport this season.

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Minneapolis has had more than 80 inches, almost double the normal for the Twin Cities. Buffalo’s total is more than 130 inches, but most of that was lake effect.

Despite the planet’s rising temperatures, and last month’s general warmth across the contiguous United States, February snow cover in the Northern Hemisphere was nearly normal, according to the Rutgers University Snow Lab.

Yet, for a variety of reasons, the I-95 corridor and much of the East has been amazingly snow-resistant, no matter what computers saw coming.

After another week-ahead Northeast threat popped up on Thursday, Judah Cohen, a snow-loving scientist at Atmospheric and Environmental Research, declared his skepticism on Twitter. “I’m done,” he wrote. “I’ve seen this movie before.”

In 1993, computer models performed amazingly in foreseeing the so-called Storm of the Century, which caused $11.5 billion in damage and affected the eastern quarter of the nation.

“They were locked in five, six days in advance,” said Anthony Gigi, who at the time was a meteorologist at the New York National Weather Service office.

This winter, those lock-ins haven’t happened, said Gigi, who later worked in the Mount Holly office and now helps run the philly.wx weather-discussion board.

By his analysis, in terms of accuracy, in forecasting for the level of the atmosphere that is critical for steering weather systems, the U.S. and European models had their worst February in 10 years.

This after both had undergone expensive upgrades.

On at least four occasions, the European, long considered the gold standard in the meteorological community, was forecasting six or more inches of snow in Philly within the next eight days of a model run in the winter of 2022-23.

It’s almost as though the numerical models that were ingesting data and trying to solve the forecast equations couldn’t adjust to what was and wasn’t happening.

» READ MORE: Philly missed winter by about 1,500 miles

Save for a break here and there, “the pattern has been locked in one position,“ Freeze said. The models evidently were basing their calculations on what would be expected in a normal winter, she said. “But there’s been nothing that’s been normal about it.”

The atmosphere is an unapologetically chaotic place, but a major player since the fall had been the vast expanse of below-normal sea-surface temperatures in the equatorial Pacific, a La Niña event. This one, which persisted for three years, finally faded earlier this month.

That cool pool’s interaction with the overlying air had cosmic effects on North American weather. Among the results have been a shunting of frigid air to the north and an all-but-dead East Coast storm track.

Persistent high pressure in the Southeast effectively shut off those nor’easters that form off the Carolina coast and become the classic snow-makers for the I-95 corridor.

This has been a “pitiful nor’easter season indeed,” said Art DeGaetano, director of the Northeast Regional Climate Center. He noted that other underwhelming nor’easter winters have coincided with La Niña and although it’s “nothing that holds much statistical significance, but coastal storm tracks tend to be more likely” when the Pacific waters are above normal — the El Niño state.

Philadelphia’s only two March storms with double-digit snowfalls occurred in 1958 and 1993, winters that did coincide with strong El Niños.

On March 19-21 in 1958, 50 inches of snow fell upon Morgantown, Chester County. Philly had an official 11.4 inches at the airport, the most ever in a March at the time, and Peco’s 400,000 power outages was a record.

The 12 inches of snow and sleet during the March 13-14, 1993, “Storm of the Century” remains the highest total for a March snowfall. Its most impressive legacy was a snow-and-ice cover that defied the March sun and survived six days at the airport’s official observation site. It also was the last verified blizzard in Philadelphia.

Storms never replicate, but a similar storm likely would be juicier today, but not necessarily snowier. In both 1958 and 1993, the temperatures were borderline for rain or snow and never got below freezing while the bulk of the snow accumulated. Average March temperatures are a shade higher than they were then.

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It is true that on April 3-4, 1915, 19.4 inches of snow fell upon Philadelphia. But if computer models see something similar for next week, don’t panic.