Snow scarcity has a long tradition in Philly
Philly once went 619 days without measurable snow.
While the region is entering what on average is its peak snow period, it’s beginning to look a lot like so many other winters around here.
The world is unquestionably getting warmer — 2022 ranked as the fifth-warmest in the government database dating to 1880 — but bare ground in winter and snow scarcity are long-standing Philadelphia traditions, dating to the 19th century.
Actually, that’s true even elsewhere in the Northeast, which is the cradle of the snow-making industry.
Since it is subject to “too much natural variability,” snow hasn’t been a reliable indicator of climate change in recent years, says David Robinson, a Rutgers University professor and New Jersey state climatologist who is one of the nation’s leading snow experts.
Philly once went 619 days between measurable snowfalls at a time that well predated the warming trend of recent decades. We still have better than 290 days to go to match that record, and on occasion it’s been known to snow as late as April around here.
However, don’t be shocked if this season’s total ends up being less than 10 inches. It’s happened 22 times in the period of record, and on three occasions, the seasonal total was under an inch. Normal is 23.1 inches.
After a run of near-normal temperatures for the rest of January, the Climate Prediction Center favors a mild February for the Northeast. And while computer models keep seeing snow threats eight and 10 days out, they have been diligent about erasing them in subsequent runs.
“All the action has been out West,” said Steve Decker, a Rutgers meteorology professor.
Upper-level troughs, areas of lighter air that favors cold and storminess, have dominated the West, he said. In response, ridging, or heavier air that promotes drier and milder conditions, has built across the rest of the United States.
Globally, the mass of the atmosphere remains pretty much constant, and areas of lighter and heavier air alternate around the planet, he said. The pattern this season has repelled Arctic intrusions in January for a large part of the contiguous 48 states.
The persistence might have something to do with the tropical Pacific, where sea-surface temperatures over a continent-size swath of water remain below normal. This La Niña is in its third winter.
Weather moves west to east, and oceans change ponderously. Sea-surface temperature anomalies out that way can disturb the overlying atmosphere and affect North America for months.
Philadelphia’s only snowless winter, 1972-73, coincided with a powerful edition of La Niña’s counterpart, El Niño, an unusual warming of the Pacific waters. La Niña was in place in the winter of 1994-95, when the first measurable snow didn’t occur in Philly until Feb. 9, the latest first snow.
Another clear contributor to the snow drought along the East Coast has been the strength of the polar vortex, a powerful system that generates potent winds circling the North Pole.
When it weakens, it can allow frigid air to ooze southward. It will require a major disruption to unleash a significant Arctic invasion, said Paul Pastelok, the veteran long-range forecaster at AccuWeather Inc.
“It’s going to take more than just one push, one punch to disrupt the polar vortex,” he said.
Pastelok says that for now the Atlantic is simply too warm to argue for a major coastal storm for the East.
Storms track along the contrasts of warm and cold air, and under these conditions those boundaries likely would form inland, rather than over the ocean, which would keep Philly on the warmer side of snow-making systems, he said.
He added, however, that it’s possible that snows this week in north-central Pennsylvania and New York State might “change the environment” and moderate the anticipated February mild spell.
He also said that Philly might have a shot at some snow at the end of this month, before a warm-up. “That might be our best opportunity,” he said.
» READ MORE: Computer models do a great job of snow removal.
But that’s probably on the outskirts of fantasyland, said Decker. “I always teach my students anything past day seven or so take with a huge grain of salt.”
Pastelok said that a disturbance could finally weaken the polar vortex sufficiently to allow a cold-air spillage at some point next month or in March.
“It could happen late enough to ruin the spring,” he said.
As things stand, at least the pothole problem shouldn’t be too bad.