Posts

John Homenuk

Significant storm possible this weekend, details uncertain

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Here we are again. Over the last day or so, forecast models have begun to come into agreement on a potentially significant Nor’Easter developing late this weekend into early next week. With a polar upper level low and associated shortwave energy dropping southward from Canada into the Great Lakes, a storm system will develop off the Northeast Coast of the United States on Sunday. But the devil, as always, is in the details. The exact positioning, orientation, and intensity of the mid level energy as it moves toward the coast will have significant impacts on where the coastal storm develops and how strong it is.

Not surprisingly, forecast models have been struggling to pin down the exact track and location of the aforementioned coastal low. Once it develops off the Northeast coast, there is good agreement on one thing: The storm will deepen rapidly. But the location where this occurs depends greatly on the track of the mid and upper level atmospheric energy. Some forecast models take this energy farther north, through New England, and develop the surface low too far north to affect our area. But others track it farther south, allowing the low to develop off the coast of New Jersey and bring snowfall to our area Sunday into Monday.

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Doug Simonian

Arctic cold, multiple chances for snow through next week

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We don’t have it as bad as Boston. Yet, multiple freezing rain and winter weather events have made their way through our region over the past several weeks just the same. Freezing rain, sleet and snow have become mainstay’s in the weekly weather. And the repetitive pattern has many wondering when winter will finally end. Unfortunately, that does not look to be any time soon. While not everything in our current weather pattern screams in support of a major snowstorm, there are widespread indications that arctic cold and multiple chances for Nor’Easters will show their face from late this week into next week.

Both time periods will be evolving remarkably similarly aloft. Over the next few days, a large mid and upper level ridge will begin amplifying on the west coast of the United States, and  powerful shortwaves with potent energy will be diving down from Canada on the eastern periphery of that ridging. The first potential event, this coming Thursday into Friday, looks likely to remain progressive enough for our area to avoid significant snowfall. While the pattern is amplified in the mid levels, it remains slightly progressive — without any high latitude blocking to slow things down. As a result, the developing surface low looks likely to slip just far enough east.

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John Homenuk

Prolonged period of wintry weather to start the week

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A winter storm affecting the Northeast United States will begin as early as Sunday throughout the area, as lift for precipitation develops along a baroclinic zone and thermal gradient near the area. The forecast in terms of precipitation type and amounts, however, is not as cut and dry as it may seem. The thermal gradient both at the surface and aloft will differ in location, creating widespread differences in precipitation type and a very sharp gradient in potential snowfall and winter weather impacts.

In the mid levels, warming will occur between 850-900mb (above our heads, but not very far up in the atmosphere). This warm layer will push northward to a position near New York City on Monday. What this means, is that any snowflake which forms farther up in the atmosphere will fall through a layer of air that is above freezing. Essentially, it will melt. But our problems don’t stop there — the surface layer of the atmosphere (where we are) is very cold. And that means any precipitation which falls as liquid is going to re-freeze on the surface.

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John Homenuk

Monday’s snow threat trends north, still a concern

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The winter weather potential for late this weekend into early next week has been well advertised. A low pressure system is forecast to develop from the Ohio Valley into the Northeast states late this weekend, along a thermal gradient otherwise known as a baroclinic zone, and force the development of precipitation in the Northeast States. Forecast models, however, had been displaying tremendous uncertainty with the positioning of that thermal gradient — uncertainties which were well documented. The past 48 hours have seen forecast models trend farther north with the thermal gradient, changing the complexion of the storm threat completely.

What this means for our area, is that precipitation type and amounts become less certain. The thermal gradient, essentially, is a boundary where there is a large temperature gradient over a short distance. Along and just north of this zone, enhanced lift for precipitation can occur as the development of a low pressure system is promoted near or just south of it. With this gradient trending north, forecast models have introduced warmer temperatures in the mid levels, and have shifted precipitation northward into New England.

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