Update: The National Weather Service has revised the storm total for snow measured at Philadelphia International Airport to 6 inches, down from 8.3. This story has been revised to reflect that change. The NWS says the revision was prompted by an earlier calculation error.
The blizzard warnings went up Monday from the Philadelphia region to New York City, with up to two feet of snow expected in what forecasters confidently predicted would be a historic storm that would disrupt lives in one of the nation's densest population corridors.
In the end, however, the would-be Blizzard of '17 could not defy the meteorological odds of March, and the forecasts that prompted a blizzard of closings — a notable exception being a certain Elkins Park bookstore — had at least as much impact as the actual weather.
Not that Tuesday was a day at the beach. This by far was the worst winter storm of the season. Philadelphia's official storm total of 6 inches stands out for a snowfall in March and 4.8 inches on Tuesday set a record for the date by 0.1 of an inch.
The nor'easter produced prodigious amounts of sleet north and west of Philadelphia, where snow and ice totals of six and seven inches were common; freezing rain and high winds knocked out power to more than 25,000 customers in New Jersey; serious coastal flooding at the Shore prompted water rescues; and two feet of snow fell in the Poconos. In the city, SEPTA operated only 34 of its 123 bus routes. Snow creamed central Pennsylvania, and Gov. Wolf urged travelers to stay off the roads if they could.
Light snow late in the day added frosting to the region's caked snow and ice, more impressive for density than depth, and it was about to mutate into concrete as overnight temperatures dove toward 20. Anyone walking on it Wednesday should feel taller.
Locally, the snow amounts were about half of what was anticipated, and the blizzard of 1993 retained its title as the only March storm in the period of record, dating to 1885, to leave a foot of snow on Philadelphia.
"You have to be prepared for the worst," said Gov. Christie. But he labeled the storm a "big underperformer" -- and in his view not the only "underperformer." Of the National Weather Service, he said, "I've had my fill."
Weather service meteorologists did underestimate the extent of snow-melting warm air in the upper atmosphere, said Joe Miketta, the acting chief at the Mount Holly office, but they captured other aspects of the storm, including precipitation totals. And he said the forecasts also were key to preparations, adding, "We thought we were doing what we needed to do."
What went awry?
Meteorologists said the storm tracked closer to the coast than expected, and once it matured, the strong winds it generated from the east carried a stubborn warm layer of air, about 2,500 feet up, all the way to Lancaster.
Sleet is liquified snow that refreezes, and it pelted parts of the region for hours, while raindrops, some of which froze on contact, drenched South Jersey. Snowflakes can take 45 minutes to reach the surface, and they would have spent several melting seconds falling through the half-mile deep warm layer, said Tyler Roys, a meteorologist with AccuWeather.
The water equivalent of all that precipitation would translate to 18 to 24 inches of snow, and the proof is in the shoveling: In some places, what's on the ground weighs as much as 18 to 24 inches of snow.
Sleet bounces off trees and wires, which is one reason that power outages were minimal west of the Delaware River, but it also is slower to melt, since it is ice, and it is a hazard.
"It's like driving on ball bearings," said Greg Carbin, chief of the forecast operations branch at the government's Weather Prediction Center, outside Washington.
Carbin said that he was not surprised by all the mixed precipitation. On Monday, he said, he did not see a classic snowstorm setup, citing a lack of well-entrenched cold air to the north, and the center opted for a more conservative accumulation forecast.
He said that during a Monday briefing with Mount Holly forecasters, he made a case for a more cautious approach. "You have to be very careful about pulling out all the stops because it's harder to back off," he said. "The big challenge is to manage expectations."
The warning decisions, however, are in the hands of local offices, and the ones in Mount Holly and Upton, N.Y., went with the bullish predictions.
"We thought the cold air would be more aggressive," said Miketta. "In the final analysis, more warm air came in. We didn't forecast it accurately."
Carbin said it takes an extraordinary alignment of circumstances to get a mega-snowstorm in East Coast cities in March, and any storm that is a coast-hugger is likely to drag in warmer air off the ocean. Around the time the precipitation started late Monday, the ocean temperature off Atlantic City was just over 41 degrees, according to the National Ocean Data Center.
"It feels like January," said Roys. "We forget that this is March."
Carbin said that the forecasts did have a positive effect, in that they got the attention of emergency managers: "I think that was great."
If anything, the weather did prompt one opening.
Business was as brisk as the weather at the Open Bookstore in Elkins Park, Montgomery County, owned by Lynn Rosen and her husband. Evan Schwartz. They offered shelter from the Doctor Zhivago conditions by serving sugar cookies and hot chocolate, and offering customers a chance to read the likes of The Warmth of Other Suns and The Sun Also Rises.
They might keep the hot chocolate handy.
Once the storm pulls away, the region will be locked into what has been an unusually frigid mid-March week. It might not get above freezing on Wednesday.
(As a public service, we will not mention that the forecast calls for a chance of snow Friday night.)
Staff writers Michael Boren, Jeff Gammage, Maddie Hanna, Justine McDaniel, Maria Panaritis, and Jacqueline L. Urgo, and Karen Langley of the Harrisburg bureau, contributed to this article.