Storm “bands” cause odd snowfall pattern

Nature dealt meteorologists a generous serving of humility overnight, ambushing the region with its biggest snow in three years, with totals ranging from 4 to almost 10 inches.

In a storm that was full of them, perhaps the biggest surprise occurred at the official measuring station at Philadelphia International, where 8.4 inches was reported, one of the region's highest amounts, and 2.5 times more than the previous total for th entire season.

The forecast was for much less precipitation.

Ordinarily, the low-lying airport, which is next to a swamp, weighs in with snow totals on the low end. Glassboro outdid it, with a hefty 9.5 inches, said Valerie Meola, a meteorologist at the National Weather Service office in Mount Holly.

Underscoring the strangeness of the storm, only 1.5 inches was reported in Wilmington, but 7-plus inches fell upon Clifton Heights and Upper Darby, Delaware County.

The weather people acknowledged they did not see what was coming last night.

Forecasters had called for a nuisance storm, which appeared to be on the money until nightfall yesterday. Even then, they were saying that perhaps an additional inch or two might fall as a storm in the upper atmosphere passed over the region as a coastal storm moved away.

But after a day-long snowfall that left modest accumulations on grass, mailboxes and car roofs and did little more than dampen the roads, the storm took a seriously colder and whiter turn when the sun went down.

During the night, bands of heavy snow formed and stalled across parts of the city and Montgomery, Delaware, Camden and Gloucester Counties.

The computer guidance did suggest that heavy bands would form, said Mike Pigott, a meteorologist with Accu-Weather Inc. "It at least showed the potential," he said. However, they were expected to develop well to the north. Nor was it anticipated, he said, that the bands would keep hammering the same locations.

The computer models that have revolutionized weather weren't able to pick up such small-scale features as the snow bands, the weather service said in a post-mortem this morning.

"Unfortunately," it said, "it thise very mesoscale snow bands that can create havoc."

Contact staff writer Anthon Wood at 610-313-8210 or twood@phillynews.com.