Following several days of below-normal temperatures and low humidity in the wake of last week's heat, higher temperatures and humidity returned to parts of the interior Northeast and Ohio Valley Tuesday. AccuWeather forecasters say that a cold front slicing into the renewed warmth and humidity could lead to volatile thunderstorms and flooding downpours through Wednesday night.
Temperatures soared into the 80s and 90s F in the eastern Great Lakes and interior Northeast Tuesday, which was record territory for some cities across the region. Cleveland tied a daily record high of 95 degrees, originally set in 1945. Even in the mountains of north-central Pennsylvania, Bradford set a new record of 89 degrees F, topping the old daily record set in 1991 by 1 degree.
The resurgence of heat in addition to higher humidity will be just a few of the ingredients that could aid in the development of thunderstorms into Wednesday night.
"A moist air mass will be in place across much of the interior Northeast at midweek, setting the stage for soaking thunderstorms through the evening," said AccuWeather Meteorologist Matt Benz.
Any thunderstorm that erupts around Cleveland should not be particularly strong as slightly cooler and less humid air will filter into the city and much of northern Ohio. However, people should not let their guard down as thunderstorms can still generate lightning around the area.
A much different story will unfold to the south and east where a later arrival of the cold front will allow more heat to build, supplying more atmospheric fuel for thunderstorms.
Morgantown, West Virginia; State College and Pittsburgh, Pennsylvania; and Cincinnati are just some locations at moderate risk for severe thunderstorms, according to AccuWeather forecasters. Hail and damaging wind gusts will be the main threats, although an isolated tornado is not completely out of the question.
Due to the storms, several major airports issued ground stops in the northeast Wednesday evening, including Logan International Airport in Boston and LaGuardia Airport in New York City. Power outages were also an issue into Wednesday evening, as 248,000 power customers in the eastern United States were cut off as of 8:30 p.m. EDT. This includes over 97,000 customers in Virginia and over 56,000 customers in Pennsylvania, according to PowerOutageUS.
Even where severe weather does not occur, plenty of moisture will be present. This can lead to heavy rain in a broader area. To this end, numerous flood watches have been issued from central New York to central Pennsylvania and northern Virginia. About 1-2 inches of rain can pour down over the course of a couple of hours. Where storms last longer, even more rain may fall and run off. While soil conditions have become dry in many areas in recent weeks, the ground may not be able to absorb all of the rain. Urban areas will be most prone to flooding in this setup.
Besides the front coming in from the west, there is a second cold front that is actually moving from east to west. This is known as a "backdoor front," since they move "backward," or in the direction opposite of normal. Just how far west that front gets will have a direct effect on the eastern extent of severe weather.
"A backdoor front will move inland from the coast, setting up across eastern Pennsylvania south into Maryland and Virginia," said Benz.
He added that the threat of severe weather would be minimal to the east of the backdoor front where cooler marine air will be in place and a lack of energy will be in the atmosphere.
The backdoor front will continue to move southward Thursday, getting as far south as North Carolina. However, the front from the west will still be in play.
"Since this front will not move much, rain will likely continue to fall near either side of the front into Thursday," explained Benz.
With lower temperatures in much of the region, the atmosphere will have less available energy. Therefore, thunder will be limited Thursday, and severe weather is not expected.
The focus of potential severe weather is likely to shift back farther to the west Thursday and Friday. The northern and central Plains will have the threat of severe thunderstorms on both days.
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