Sunday, April 30, 2017

Northeastern US: May to start with returning warmth, severe storms

By Alex Sosnowski, AccuWeather senior meteorologist
By Kristina Pydynowski, AccuWeather senior meteorologist
April 30,2017, 3:27:30PM,EDT
 The temperature roller coaster ride in the northeastern United States will continue on Monday, setting the stage for severe thunderstorms over a part of the region.
Cooler air pressed into the Northeast on Sunday, holding temperatures 15 to 25 degrees below Saturday's highs in many communities.
The change was even more dramatic in Boston. After coming close to breaking Saturday's record high of 85 F, temperatures were about 40 degrees lower on Sunday afternoon.
NE Monday temps
An exception to the cooldown on Sunday was the southern mid-Atlantic and locations along and west of the central Appalachians, where the next warm surge has begun.
Along the boundary separating the warmth and cooler air, spotty thunderstorms will erupt from western Pennsylvania to northern Virginia into early Sunday evening. One or two of the thunderstorms can produce strong wind gusts.
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AccuWeather severe weather center
Northeastern US interactive radar

On Monday, temperatures in much of the mid-Atlantic and central New York will climb into the upper 70s and 80s due to strong southerly winds.
Exceptions to the warmth on Monday include the south-facing shoreline areas and eastern New England due to wind blowing off the cool water. Temperatures will be held to the 40s in Portland and Bangor, Maine.
Northeast Severe April 30
Monday's warmth will occur ahead of another cold front, which will trigger more thunderstorms from the Florida Panhandle to Virginia and western New York. Some of the thunderstorms will become severe with hail and damaging winds. The threat will be greatest along the I-79 and I-81 corridors.
An isolated tornado or two may also touch down, mainly north of Interstate 80.
Cities at risk for the violent thunderstorms include Morgantown, West Virginia; Harrisonburg, Virginia; Pittsburgh and Harrisburg, Pennsylvania; and Buffalo and Rochester, New York.
The thunderstorms may weaken below severe criteria upon reaching the I-95 corridor from Washington, D.C., to New York City on Monday night.
The passage of this front will slash highs by 10 to 20 degrees around the eastern Great Lakes for Tuesday. Highs in the lower to middle 70s will be more common from New York City to Washington, D.C., this day.
Long-range outlook
"We expect more significant cooling to take place during the first weekend and second week of May," according to AccuWeather Lead Long-Range Meteorologist Paul Pastelok.
"We have been getting mixed signals as to the magnitude of the cooling trend before the middle of May, but we suspect temperatures may dip below average a bit for much of the second week, followed by near- to above-average temperatures for much of the second half of the month in the Northeast," Pastelok said.
On one hand, there is a scenario that will bring showers and thunderstorms with hail and chilly air during next weekend. Another scenario would bring another brief wave of cool air followed by a big warmup next weekend.
Pastelok remains concerned about the potential for a chance of a brief frost over parts of the interior Northeast prior to the end of May.
Gardeners may be able to plant warm-season vegetables and annual flowers during the upcoming warmth, provided they have a means to protect their investment should a spell of frosty air come calling before the Memorial Day weekend.

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