Winter Storm Pax Will Bring Anything But Peace To The Eastern U.S.

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The National Weather Service forecast for Tuesday morning, Feb 11, 2014. Pax is just a ripple on the front. The pink line is 32 degrees.

The National Weather Service forecast for Tuesday morning, Feb 11, 2014: Pax is just a ripple on the front. The pink line is 32 degrees. Image courtesy of the NWS.

What was the Weather Channel thinking when they named a winter storm Pax after the Roman goddess of peace? Pax will produce a wide variety of nasty weather from Texas to the east coast, but after that Mother Nature may call a halt to the endless barrage of storms.

No Low Pressure Center Associated With Pax to Start

Like a number of this winter’s storms, Pax will be a result of relatively minor sloshing of air masses across a front that marks the battleground between cold polar air from Canada and a mild, moisture-laden flow from the Gulf of Mexico.

With the polar vortex holding firm over southern Canada, the cold air has kept temperatures far below normal in the northern plains. The leading edge of the cold air has made forays into the deep south, and the freezing line now extends from Texas to the Carolinas.

Ripples in the Jet Stream Produce Precipitation

The core of the jet stream lies above the zone of maximum temperature gradient between the competing air masses, and ripples in the jet stream produce movements of the cold air beneath the warm, and warm air over the cold. Wherever this occurs, the warm air is lifted, and, since it is saturated with water vapor, precipitation occurs.

Just a couple of tenths of an inch of melted precipitation, barely more than the amount in a summer sprinkle, is enough to produce several inches of traffic-stopping snow, and worse, enough of a coating of ice to bring down tree limbs and power lines.

Pax’s Exact Location Will Determine Who Gets Rain and Who Gets Frozen Precipitation

Snow amount predictions are notoriously difficult; they depend on the exact positions and movements of the ripples in the jet stream and the location of the snow-rain line. Freezing rain is even harder to forecast, as the warm and cold air masses must have exactly the right relationship to produce icing.

Snow is already falling, and predictions range between three and six inches from Oklahoma eastward to the northern Carolinas and Virginia between now and Wednesday. The greatest likelihood of freezing rain is in central parts of Louisiana, Mississippi, and Alabama on Tuesday, and from northern Georgia through the Carolinas on Wednesday.

The invading cold air could affect Atlanta, which recorded temperatures in the 60s on Sunday. Winter storm Leon showed what a relatively minor amount of snow and ice can do to that city. In addition to the threat of traditional freezing rain, caused by raindrops freezing on contact with frozen surfaces, there is the possibility of the type of icing that occurred with Leon.

Even if the precipitation falls as snow, it will melt on contact with the warm ground or road surfaces. If the air is below freezing, the melted snow will freeze. A little salt can keep roads wet rather than icy by lowering the freezing temperature of the salt-water mixture. But during Leon, when everyone tried to get home at the same time, the salt trucks couldn’t get through. Hopefully everybody learned a lesson.

Pax Could Develop Into a Nor’easter

A storm system approaching the Atlantic coast combined with a strong frontal boundary is a recipe for a coastal storm. Computer models disagree on Pax’s future: Some models suggest she will continue eastward out to sea without impacting the big cities of the northeast; other models forecast a major coastal storm which could produce heavy snow — or just a lot of rain — in the Megalopolis.

February Weather: A Look Ahead

The polar vortex may relax its grip in the next couple of weeks, though a steep temperature gradient currently persists. If Pax develops into a powerful nor’easter with deep low pressure, she will cause some mixing of the air masses, lowering the potential energy and the probability of another storm. Hopefully there will be a respite — a pax meteorologicus — before the next winter storm, Quintus.

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© Copyright 2014 Jon Plotkin, All rights Reserved. Written For: Decoded Science
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