Snow gives the region the cold shoulder

After 116 inches of snow in the last two winters, the decision was just cold logic.

This year, the Voorhees True Value store would "go heavy on the rock salt," manager Ron Rago said, adding resignedly, "You take your chances."

Neither Rago nor the best minds in meteorology could have guessed that come January, the rock-salt business would be hitting rock bottom.

After all, on this date last year, Philadelphia was experiencing its second foot-plus snowfall of the winter and its fifth of the last two seasons.

We were braced for the winter of 2011-12 to deliver more of the same. But defying just about every preseason forecast, it has been amazingly uneventful so far, with the lack of cold air at least as impressive as the scarcity of snow.

Last week, the region had its traditional January thaw. The only thing missing was something to thaw.

It was "the meteorological equivalent of having dessert without having to eat the broccoli," in the words of Tony Gigi, a meteorologist at the National Weather Service office in Mount Holly.

Philadelphia has yet to have a serious cold spell, and still awaits its first three-day stretch in which the temperature fails to climb above 35.

The season got off to one of the most snowless starts in the period of record, dating to 1885, with a mere 0.5 inches through Jan. 20, putting it in the top 15 for snow futility.

Before snow and ice - an official 2.3 inches - crusted the landscape last weekend, the Pennsylvania Department of Transportation had used only 7,344 tons of salt in the entire southeastern region.

By comparison, it used 57,014 tons by Jan. 20 last year. By then, Philadelphia had measured about 36 inches of snow, and, you might recall, 78.7 inches the year before.

Why the difference this year?

Part of the riddle is in the Arctic, said Mike Halpert, deputy director of the government's Climate Prediction Center, outside Washington, and the chief long-range forecaster.

A major player in winter is the so-called Arctic Oscillation index, a measure of air pressure, or the weight of air, in the far, frozen north. When the pressure is high over the Arctic, the index is said to be negative, and cold air can plunge southward into the United States and Europe.

When pressures are lower, the opposite is true.

In December 2009, at the onset of Philadelphia's snowiest winter on record, the index reached its most negative level in 60 years of tracking, said Halpert. The following December, it hit its second-most-negative level.

The December 2011 level, however, was No. 2 on the positive list, and the impacts have been widespread. "It's been quite warm in Europe and Asia," said Halpert.

The warmth in the upper Midwest literally has been almost unbelievable, he added. Minneapolis finished eight degrees above normal in December. "We were looking at the numbers and going, 'Is that right!?' " he said.

Meanwhile, more than 320 inches of snow has fallen on Valdez, Alaska, about double normal. The Arctic Oscillation, said Halpert, has "bottled up the cold air."

The result has been a winter more reminiscent of some recent ones, he said. The previous two were the outliers.

Dating to 1885, of the 14 winters in which Philadelphia's snow total was 0.5 inches or less as of Jan. 20, 14 have occurred since 1992.

Winter may well make a comeback next month, however, said Henry Margusity, a meteorologist with AccuWeather Inc. He said he had seen subtle signs of a pattern change.

"Everything is kind of gearing up for a little wilder and crazy February," he said.

Halpert said he'll believe it when he sees it, and notes this has not been a banner year for seasonal forecasting.

An AccuWeather news release in October quoted a meteorologist as saying, "People in Chicago are going to want to move after this winter." Chicago's temperatures were 7.5 degrees above normal in December.

Nevertheless, Margusity said meteorologists are making some strides in seasonal forecasting. "It's complicated," he said, "but we're getting better at understanding these signals that are going on."

For his part, Rago said a pattern change wouldn't hurt his Voorhees store. As he pointed out, "We're a bad-weather business."