How far north will Helene's rain reach?
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Moisture associated with tropical storms and hurricanes that make landfall in the southern United States often reaches more than 1,000 miles to the north and affects the Northeast and Great Lakes regions.
A large bubble of dry air limiting rainfall from the Upper Midwest to the interior of New England and the mid-Atlantic is still diverting most wet weather away from the regions. There have been some significant rain events in the past several days, but they have been small in scale.
That same dry air is blocking Gulf of Mexico moisture from reaching the Canadian border and forcing storms in Canada to graze the northern tier of the U.S., greatly slowing the northward motion of southern storms.
Case in point with Helene's rain.
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Helene, which is forecast to accelerate northeastward into the Southeast states into Friday, will likely run into a wall over the interior South this weekend. The dividing line between Helene's moisture and mainly dry air will extend across the Ohio Valley, central Appalachians and the lower mid-Atlantic.
Helene will slow down about a day after it moves inland, making it highly unlikely that much rain will reach the northern Great Lakes and New England this weekend.
Some showers will reach Chicago, Detroit, Philadelphia and perhaps New York City, Pittsburgh and Washington, D.C., but not Boston, and probably not Buffalo, New York. A long the mid-Atlantic coast to part of the central Appalachians, the moisture may be more in the form of drizzle and intermittent light rain.
A non-tropical storm will shred some of Helene's moisture and sprinkle it over the western Great Lakes region. The same storm may also play a role in enhancing downpours well to the west of where Helene would typically bring rain. Those downpours may lead to flooding problems in parts of the Ozarks and Tennessee mountains.
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Areas most likely to be dry the entire weekend from much of upstate New York through New England.
"This will truly be a great weekend weatherwise for the leaf peepers in New England and most of New York state," AccuWeather Senior Meteorologist Tom Kines said.
Meanwhile, near the edge of the wet zone, low clouds and spotty drizzle may make for some gloomy conditions from Delaware to much of New Jersey and Pennsylvania, even where rain does not pour down.
Only if the zone of high pressure weakens or the non-tropical storm in the Mississippi Valley shifts its position might Helene's drenching downpours take the highway through the Northeastern states.
With a few exceptions, temperatures in much of the Great Lakes and the Northeast will generally be within 5 degrees Fahrenheit of the historical average. Highs typically range from the mid-60s across the northern tier to within a few degrees of 80 over the lower parts of the Ohio Valley and mid-Atlantic.
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