New Orleans holds a big lead over Philly in snow totals this winter. Will that change?

No matter the outcome of this year’s Super Bowl in New Orleans, it’s unlikely to upstage one of the all-time January winter-weather upsets.

The 8 inches of snow that fell upon the Big Easy on Jan. 21 not only tripled the city’s erstwhile all-time daily record, it ended up exceeding the combined monthly snowfalls of New York and Philadelphia, and came within a few flakes of matching Boston’s.

The way things have gone so far, the preseason winter outlooks for the Eastern United States look pretty decent — if you turn them upside down. Maybe the groundhog will have better luck on Sunday.

But the human scientists point out that while the sun is getting ever stronger, the birds are checking their flight plans, and February may start off mild, the equinox will have to wait its turn.

On average, February is Philly’s snowiest month, and in its updated monthly forecast posted Friday, the National Oceanic and Atmospheric Administration’s Climate Prediction Center noted that models were showing “a trend toward colder temperatures in the East” in the latter part of the month.

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What has been a slow-motion La Niña — the widespread cooling of waters over a vast area of the tropical Pacific, and a linchpin of all the preseason outlooks — finally took hold in late December and is likely to persist and affect U.S. weather into the spring, according to NOAA’s Climate Prediction Center.

When those sea-surface temperatures are unusually cold, they stay that way for months, chilling the overlying air and affecting the west-to-east winds that carry weather to the United States. In some cases, they’re predictable.

However, this one not only was a late bloomer, it is also a weakling, said Johnna Infanti, a meteorologist with the Climate Prediction Center.

It has had some effects: Wetness on the West Coast, a La Niña signature, has been evident, said Jon Gottschalck, chief of the center’s Operational Prediction Branch.

Also, nor’easters have been absent, another La Niña effect, which was noted in AccuWeather Inc.’s outlook.

Historically, however, a reliable La Niña impact is warmth and dryness in the South. (Don’t laugh, New Orleans.) The climate center’s preseason outlook saw La Niña keeping “the southern tier of the country warmer and drier.”

AccuWeather predicted La Niña would help “limit the potential for cold air to have a sustained presence” in the South.

What has happened to Philly’s share of the white stuff?

“Florida stole our snow,” said AccuWeather’s veteran long-range forecaster, Paul Pastelok. The white sands of the Panhandle were crowned with snow in that Jan. 21 storm. Pensacola’s 8.9 inches of snow surpassed Boston’s total for the month.

Nothing happens in isolation in the chaotic atmosphere, and with a weak La Niña, “it’s not too surprising to see other drivers play a more dominant role,” said the climate center’s Infanti.

One of those drivers, she said, has been another tropical phenomenon, the Madden-Julian Oscillation.

What Gottschalck describes as a massive “disturbance of clouds, rainfall, winds, and pressure,” the oscillation circles the globe around the tropics in 30- to 60-day cycles. On either side of the rising air that sets off the storminess, descending air has a drying effect.

Its disruptive force ripples through the atmosphere and can affect it all the way to the Arctic. Infanti said the oscillation’s cycle was well-positioned to be a major force behind the generally below-normal temperatures east of the Rockies last month.

Judah Cohen, a polar scientist with Atmospheric and Environmental Research, in Massachusetts, said the January cold had a lot to do with “stretched” polar vortex intrusions.

While the planet continues to warm, it still has a plentiful supply of cold air in the Arctic freezer, which usually is dammed up by the vortex’s strong circular winds. Occasionally, the vortex gets “stretched like taffy,” say NOAA scientists Laura Ciasto and Amy Butler, and the chill spills southward.

This winter, it’s as though the vortex has been taking yoga classes: Cohen said he counted seven such stretchings, most or all affecting the contiguous United States.

NOAA scientists, however, were more circumspect about the role of the vortex in the January cold.

The unusual temperature pattern likely had to do with higher-than-normal atmospheric pressure over the Arctic, Canada, and Greenland, said climate center meteorologist Cory Baggett. “This pattern tends to focus the coldest air relative to normal in areas farther south,” he said.

Whatever the causes, said Pastelok, “This was a pretty rough middle of the winter” for the Eastern United States.

While the snow has all but disappeared and exposed the messiness of the bare ground and backyards, like opening the door of an untidy room, chances are excellent that at some point a snow cover will return.

That’s based on history and common sense (for which the atmosphere has little tolerance) and computer model hints that cold may return. And have they ever changed their minds?

In the 20 winters since 1950 that have coincided with La Niña, snow totals in Philadelphia after Jan. 31 have varied from 0.3 inches in 2023 to 22.9 in 1996. But every one of them has produced some snow in Philadelphia after Jan. 31, on average about 6 inches, although some of the years have produced significant snowmakers.

The 2024-25 seasonal total stands at 4.9 inches, with 4.6 of that in the chilliest January in 11 years, when temperatures averaged 3.5 degrees below normal.

While AccuWeather had called for 15 to 20 inches of snow for the season, “It’s probably going to be less.” Pastelok said.

But forecasters aren’t quite seeing their shadows yet.