For the Washington area, no snow in sight in a winterless winter

(Lynn DeBruin/ AP ) - Frank Arrowchis, left, of the Northern Ute Tribe with Mike Larson at a blessing ceremony for more snow at Park City Mountain Resort in Utah.

(Lynn DeBruin/ AP ) - Frank Arrowchis, left, of the Northern Ute Tribe with Mike Larson at a blessing ceremony for more snow at Park City Mountain Resort in Utah.

The jet stream is, in turn, affected by the North Atlantic Oscillation, which — and yes, there will be a test — is in its “positive phase.” What this means, basically, is that there’s relatively low pressure over Greenland. If, instead, there were high pressure over Greenland — a “blocking high” — the air mass would act like a blast shield, forcing the jet stream to dip south into temperate latitudes in North America. Blocking highs are common — just not this year.

One deeper layer of causality may be climate change, which scientists attribute in part to the burning of fossil fuels, and which has been particularly dramatic in the Arctic. There has been, for example, a steady year-to-year decline in the percentage of the Arctic Ocean permanently covered in ice.

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ARCHIVED VIDEO: A lack of snow in Iowa has cities rejoicing, because they are saving big bucks when it comes to time, equipment and supplies like salt. But winter is not yet over. (Dec. 29)

ARCHIVED VIDEO: A lack of snow in Iowa has cities rejoicing, because they are saving big bucks when it comes to time, equipment and supplies like salt. But winter is not yet over. (Dec. 29)

It could be, Robinson said, that the changes in the Arctic are contributing to what appears to be a more flip-flopping weather pattern. The number of big-snowfall years seems to be about the same as ever, he said, but there are more years with little or no snowfall.

“Snow by its very nature, it’s boom or bust, particularly here in the middle latitudes,” Robinson said. “The climate system is exhibiting more extremes. We see this in annual rainfall. We see this in some annual snowfalls.”

There have been many mild winters before, noted Steve Zubrick, a meteorologist with the National Weather Service. Zubrick has run the numbers on Washington winters going back to 1872. He looked at the first half of meteorological winter, from Dec. 1 to Jan. 15. This year’s average temperature, 43.5 degrees, was the seventh-mildest on record — warm, but not as warm as (starting with the warmest ever) 1889, 2006, 1931, 1949, 1982 or 1971.

As for the lack of snow, that’s not so strange, Zubrick said. There are 16 half-winters on record with no measurable snow in Washington.

There are tentative signs, Robinson said, that the North Atlantic Oscillation’s positive phase could be tipping back toward the negative, which means Greenland would go into jet-stream-
diverting mode again and the February weather in North America would be more traditionally wintry.

If there’s a blizzard yet to come this winter, the experts have a scale with which to assess the severity of it. It’s called the Northeast Snowfall Impact Scale. There are five categories: Extreme, Crippling, Major, Significant, and Notable.

So far this winter, Reagan National Airport has recorded 0.6 inches of snow.

There’s no word for that.

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