Wednesday, March 4, 2015

Snow-cover streak over in Philly

Ice and snow all but vanished from city and South Jersey; remnants hang on north and west.

Snow-cover streak over in Philly

During the weekend an impressive streak of 18 consecutive days of snow cover – defined as an inch or better on the ground -- ended in Philadelphia.

The streak that began officially the morning of Feb. 4 and ended Saturday was the seventh-longest in the period of the snow-depth record, which dates to 1948, according to the National Weather Service.

Of more-immediate interest is that the fading snow-and-ice cover all but eliminates any threat of rapid snowmelt flooding. Also, a lack of snow cover will have a continuing effect on temperatures.

The water content of those gray-and-white remnants ranges from about 1 to 3 inches in Bucks, Chester and Montgomery Counties.

With temperatures not expected to get much above freezing for several days, expect no quick melting, although the pack will continue to erode under the late-winter sun and through “sublimation” when it’s windy.

An inch or so or snow is possible Wednesday, but even on a cold day that wouldn’t have much a chance to survive a few hours of strong sunlight.

Given that temperatures soared during the weekend – near 60 for consecutive afternoons in Philadelphia – one might wonder why anything at all is left.

Temperatures were cooler in areas with denser snowpack,because of the refrigeration effect, and dew points – that’s the point at which water vapor comes out of hiding and condenses -- remained low after Friday afternoon.

Dew points are critical to melting. When water condenses on a snowpack, it release latent heat that can melt snow in a hurry.

Dew points aren’t going to be an issue for awhile, evidently. The long-range forecasts are calling for cold to persist for several days.

Rather than a lion or lamb, March is more likely to come in like a polar bear.

Tony Wood Inquirer Weather Columnist
About this blog

Everyone talks about the weather, and here we write about it.

When we’re around and conditions warrant, we’ll keep you updated about what’s coming, but we will do our best always to discuss weather and climate developments in context and remind you that nothing in the atmosphere happens in a vacuum.

Tony Wood has been writing about the atmosphere for The Inquirer for 26 years.

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Tony Wood Inquirer Weather Columnist
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