Northeastern US to face wintry mix, disruptive snow showers as cold air takes control
By Alex Sosnowski, AccuWeather senior meteorologist
December 06, 2017, 11:43:23 AM EST
A fight with dry air versus snow will unfold across the northeastern United States as progressively colder conditions settle in through this weekend.
Moisture is needed for a big snowfall
Accompanying the cold weather will be dry air. However, the air will first pick up some moisture crossing the Great Lakes, where bands of intense lake-effect snow will unfold. The air will eventually pick up a great deal of moisture but not until it reaches the immediate Atlantic coast.
For much of the Northeast, a dry and cold scenario will unfold, away from the lake-effect snow bands. The coldest air of the season so far will gradually take root.
Temperatures may be no higher than the 30s F with nighttime lows in the 20s F from Philadelphia to Boston on Saturday and Sunday. Temperatures may be just a few degrees higher in Washington, D.C.
Two storms will attempt to organize the moisture that is available as cold air deepens through Sunday.
Since these two storms are likely to remain separated, they will be unlikely to bring a big snowfall to most locations.
First storm likely to graze coastal areas with rain, snow
The first storm is forecast to spread rain across the Deep South through the end of the week. However, on the northern fringe of this storm, the air will be cold enough for sleet, snow or a wintry mix.
As this first storm reaches the coast, it will turn northward.
At this time, it appears the most likely scenario is for much of the interior Northeast to be spared a significant snowfall. In fact, people living in much of the interior may not even see a flake of snow from the first storm.
An exception is most likely along the immediate coastline in the mid-Atlantic and southeastern New England. In these areas, some sort of rain and snow combination is anticipated. Rain may end as snow or a mix of rain and snow may fall for the duration of the storm from late Friday night through Saturday.
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Roads in much of the swath from southeastern Virginia to southeastern New Jersey, Long Island, New York, Rhode Island and southeastern Massachusetts would likely be mainly wet with a few slushy spots. There may be some accumulation on non-paved surfaces with the first storm.
Only if the storm is stronger and tracks farther west would a swath of heavy snow blanket the interior Northeast and parts of the Interstate 95 corridor, including major cities from Washington, D.C., to New York City and Boston. In this scenario, widespread travel problems would occur early this weekend.
Parts of eastern Maine and the Maritime Provinces of Canada stand the best chance of heavy snow, since the storm will have more time to mature Saturday night.
Second, moisture-starved storm to bring snow showers
A second storm is most likely to bring snow showers and the chance of a small accumulation to part of the interior Northeast, aside from lake-effect snowfall from Saturday night to Sunday.
By the time the second storm arrives on the scene, Atlantic Ocean moisture may be out of reach for most areas to receive big snow. However, even a small amount of moisture available for the second storm may be enough to cause some trouble.
The nature of the snow showers may be enough to cover the ground quickly in parts of the southern Appalachians to much of Pennsylvania, northern New Jersey, New York state and New England.
Motorists traveling at high speed on the major highways, such as I-68, I-76, I-78, I-80, I-81, I-84, I-86, I-87, I-88, I-90, I-91 and perhaps I-95, should be on the alert for rapid changes to visibility and road surface conditions from Saturday night to Sunday.
As this second storm pivots across the Northeast, it may have time to grab more moisture from the Atlantic Ocean and deposit that as steadier snow in part of New England on Sunday.
Waves of cold air to trigger more opportunities for snow
Cold air will continue to roll southeastward from northern Canada through the third week of December.
“Riding along with the waves of cold air will be fast-moving clipper storms that can put down some snow over the Ohio Valley and the Northeast,” according to AccuWeather Lead Long-Range Meteorologist Paul Pastelok.
“As these storms reach the Atlantic coast, slow down and turn northward, one or more [of the features] will bring the potential for steady snow in part of the Northeast versus snow showers,” Pastelok said.
There is also the chance of one or two of the clipper storms joining up with storms emerging from the Deep South, which can unleash heavy snow over a larger area.
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