As the meteorological winter ends, Philly has a shot at a snow milestone

Barring something that defies history — and no computer model is suggesting that will happen — Philadelphia’s snow total is going to finish at less than half the long-term average for the fourth consecutive season.

The forecasts are suggesting a near 100% chance that March is going to be annoying, with spring teases alternating with cold shots.

The region may even have one more shot at snow next weekend, but as things stand on this last day of the meteorological winter of 2024-25, this would be the most snow-deprived 10-year period in the 141 seasons of snow recordkeeping in Philadelphia.

Those who were bold enough to venture guesses on the seasonal total predicted it would come up short of the “normal” value of 23.1 inches at Philadelphia International Airport, but would at least beat last season’s 11.2.

So far, not so good.

The total stands at 8.1 inches, just 0.1 more than the seasonal total in New Orleans, and the lowest among National Weather Service stations in the East north of North Carolina.

If fact, the winter generally has been unkind to the long-range forecasters.

The problem: in a word, “January,” said Jon Gottschalck, seasonal forecaster at the government’s Climate Prediction Center.

“It’s amazing what happened in January,” said Gottschalck, who had presented the climate center’s outlook in October, which had the odds favoring above-normal warmth in much of the nation for the Dec. 1-Feb. 28 period.

That is “winter” in the world meteorological community, which acknowledges that weather and astronomy sometimes have a conflicting relationship. In Philadelphia, for example, April temperatures have varied from a wintry 14 to a heat wave-level 95.

As the early outlooks by private weather services, the climate center called for a weak La Niña event — in which sea-surface temperatures would remain 1 to 1.5 degrees below normal over a vast area of the tropical Pacific — to be a major factor in the U.S. winter.

The cooling of the overlying air affects west-to-east upper-air winds that carry weather to the United States. The La Niña was slow to develop, and other forces came into play.

In December, said Gottschalck, potent and persistent high pressure developed off the Pacific coast, reaching all the way into Alaska. Winds circulate clockwise around centers of high pressure, or heavier air, and those winds from the north drove some of the coldest air on the planet into the contiguous United States in January. That more or less blew some La Niña effects out of the water.

What resulted was “incredibly unusual,” Gottschalck said. The invasion, interacting with the warm Gulf waters, set up a storm track on the Gulf Coast that resulted in a record 8-inch snow in New Orleans and a Gulf Coast blizzard. “That’s just unheard-of,” he said.

The cold chilled much of the nation, including Philadelphia, where it also had a drying effect, with less than an inch of precipitation measured in January. As to why Philly ended up with less snow than places to the north, south, east, and west, “I do think there is a good deal of randomness involved,” said Steve Decker, meteorology professor at Rutgers University.

Decker said that in the end, La Niña hasn’t been much of a factor this winter.

Gottschalck added that the pattern driving the cold into the contiguous 48 finally relaxed in February, but “too late for my forecast.”

In Philadelphia, the average temperature for the Dec. 1 through Feb. 28 period will finish near 35 degrees. While only a degree or so below normal, that’s the chilliest it’s been since the winter of 2014-15.

Cold and snow don’t always correlate well, and those who monitor climate trends caution against using snowfall as an indicator.

In Philadelphia, snow has been within 3 inches of the long-term average — 22.1 inches — only about 30% of the winters. Clusters of snow-deprived and snow-abundant seasons are common in the period of record. Snow has averaged about 15 inches a season in the last 10 years. That’s a shade below a similar period ending in the 1930s. In the 10-year period that ended in the 2017-19 season, the average was 33 inches.

Missing this season have been the classic coastal nor’easters that paste the I-95 corridor from Washington to Boston, an absence that is the norm, according to Louis Uccellini, former head of the National Weather Service and expert on winter storms. “They are episodic,” he said, defying a climatology. They require an extraordinary set of circumstances that include warm air off the Gulf Stream and cold air on the mainland.

Repelling those coastal storms this season were strong cross-country upper-air winds that move systems briskly, said Paul Pastelok, the veteran seasonal forecaster for AccuWeather Inc.

Winds were a signature feature around here in both January and February, which combined had more days with 40-mph gusts — nine — than any January-February combination of the last five years.

The winds, said Gottschalck, had to do with the consistent presence of high pressure to the west and lower pressures to the east. Heavier air naturally moves toward lighter air as the atmosphere seeks to maintain a constant pressure across the globe.

Winds blow harder when pressure differences are greatest. “The atmosphere is trying its best to say, ‘This is crazy. I have to recalibrate,’” he said.

March traditionally is one of the year’s windier months as Philly and other areas at temperate latitudes become atmospheric battlegrounds, with winter reluctant to leave and spring getting more ambitious.

This year in particular, “There could be some wild temperature swings,” said Rutgers’ Decker.

Pastelok said that Philly may have just one last shot at snow next weekend as a front crosses the region and the storm approaches form the west. Otherwise, next week has a March-ish look with wintry temperatures Sunday and Monday struggling to get out of the 30s, and then heading back toward 60 Wednesday with showers.

AccuWeather had called for 15 to 20 inches of snow this season, which would have been below normal.

But, Pastelok add, “We weren’t below enough.”