Forecasters have been tracking a storm that is dropping heavy snow over the Rockies at midweek -- and it is expected to trigger unusually late-season snow across a narrow zone of the Midwest and then the interior northeastern United States prior to week's end.
It's not too late in the season for slippery roads to occur due to a snowfall, including in areas where a snow drought defined the winter season.
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"A lobe of the polar vortex has set up shop near Hudson Bay, Canada, and will try to hold cold air in place in the Northeast as storms approach...a pattern that was lacking for most of the winter," AccuWeather lead long-range meteorologist Paul Pastelok said.
Before the late-week system moved out of the Rockies, a weak disturbance brought a coating to an inch of snow in the Chicago area during Tuesday night and was enough to contribute to a slew of multiple-vehicle crashes early Wednesday morning.
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Even though that leading system is forecast to weaken prior to reaching the coastal Northeast, it can bring a coating of snow, along with icy spots to the eastern Great Lakes and central Appalachians Wednesday evening. Where the snow melts on roads then freezes before the roads dry, there can be dangerous black ice, especially but not limited to bridges, overpasses and areas that do not receive direct sunlight by day.
However, the main threat of a late-season snowfall over the interior Northeast will come late Friday to early Saturday as a storm dumping snow on the Rockies moves eastward into the cold air that recently became established.
"At this time, we expect several inches of snow may fall mainly on non-paved surfaces from the northern tier of Pennsylvania to the southern tier of New York state during Friday night," Brian Wimer, AccuWeather lead snow warning meteorologist, said.
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"Pockets of accumulating snow can also extend over the Catskills in eastern New York state as well as the Berkshires in southwestern New England and perhaps the southern parts of the mountains in Vermont and New Hampshire," he added.
Around Boston, mostly rain with some wet snowflakes is possible, but an accumulation is possible near and west of Interstate 495 in central Massachusetts.
In the Twin Tier area of Pennsylvania and New York state as well as the mountains in southern New England, a general 1 inch to 3 inches of snow is likely with 3 inches to 6 inches over the higher terrain and a whopping AccuWeather Local StormMax of 10 inches over the ridges.
Much less accumulation to a little slush is likely to accumulate on roads, except over the ridges. However, even wet roads could turn icy as the storm pulls away and cold air causes air and road surface temperatures to dip below freezing. Recent rain has washed away most traces of salt and other ice-melting compounds from roadways.
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The Twin Tiers of Pennsylvania and New York state generally receive an average of 2 inches of snow during April, but most of that snow typically falls during the first part of the month and not during the latter half.
Bradford, Pennsylvania, has already received twice its normal snowfall for April with 4.3 inches as of Wednesday. During March, only 0.2 of an inch of snow fell on the area.
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Leaves have not emerged on the trees over much of the zone expected to get accumulating snow, but buds have emerged and blossoming has begun. This can cause more snow to adhere to the trees than usual with a greater surface area to cover, especially since the snow is likely to be wet and clinging in nature. The added weight can cause some tree limbs to sag and break, which can then bring down power lines and cause power outages.
Any shift in the storm track due to a change in storm strength could cause the stripe of accumulating snow to shift northward or southward or to fizzle out or become enhanced. As a result, the chance of steady snow for a time is not zero in places such as New York City, Boston, Philadelphia, Albany, New York, and Providence, Rhode Island.
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Snowfall during the middle of the spring is typically confined to small areas but still can be intense and catch motorists off guard.
For example, a couple of inches of snow fell as late as May 9, 1977, at Wilkes-Barre/Scranton International Airport in Pennsylvania, which sits 948 feet above sea level.
In the wake of the late-week storm, a brief pocket of milder air that originated from the Pacific Ocean will settle in for the weekend.
That mild air and sunshine will cause much of and perhaps all of the snow to melt during the daytime hours, but a reinforcing burst of Arctic air, courtesy of the polar vortex will follow for early next week.
