Excessive heat to ease in parts of Northeast as storms arrive
Amid the scorching heat, some cities such as Washington, D.C., and Boston will be at risk for potent storms.
Another searing day on Monday -- the third day in a streak of 90-degree plus temperatures -- closed out an official heat wave across much of the Northeast. The excessive heat affected nearly 70 million people up and down the East Coast at the start of the week. However, forecasters say gradual relief is in store for parts of the region.
A weak cool front that began triggering thunderstorms across part of the Northeast on Sunday sagged southeastward and become nearly stationary over the Ohio Valley, central Appalachians and mid-Atlantic coast on Tuesday.
This image, captured on Tuesday afternoon, July 21, 2020, shows a lack of development to the clouds over New England, but thunderstorms were already developing along the old frontal boundary over parts of the central Appalachians. (NOAA/GOES-East)
"Even though this front will be the ongoing focusing point of mainly afternoon and evening drenching and locally gusty thunderstorms into Tuesday night, the overall weather pattern will remain hot over a large part of the Interstate 95 corridor Northeast for at least into the middle of the week," Senior Meteorologist and Lead Long-Range Forecaster Paul Pastelok explained.
Temperatures are forecast to drop in New England, the eastern Great Lakes and in parts of the central Appalachians, but it may take until the middle or end of the week before a more substantial dip in the temperature occurs in the I-95 corridor of the mid-Atlantic. And, even then, when the cool front makes more southward progress, a refreshing dose of air with highs in the 60s and 70s is not in the offing for most of the region.
Temperatures climbed well into the 90s during Monday afternoon with a few spots reaching within a few degrees of 100 along the I-95 corridor from southern New England to the mid-Atlantic.
The high just fell short of reaching the century mark on Monday in D.C., topping out at 99. On Tuesday, the temperature will again climb into the upper 90s, and the AccuWeather RealFeel® Temperature will soar even higher to around 107 F.
Philadelphia's temperature climbed into the mid-90s with an AccuWeather RealFeel Temperature as high as 103 F on Tuesday afternoon. Ninety-degree heat will persist in the City of Brotherly Love through Thursday.
On Sunday, highs of 100 or higher were recorded at Baltimore/Washington International Airport, Maryland; Richmond and Norfolk, Virginia; and Harrisburg International Airport, Pennsylvania. Several eastern U.S. cities broke or tied record high temperatures on Sunday, including in Richmond, Virginia, where the mercury shot up to 101 degrees, tying a record previously set back in 1942.
New York City stopped short of its hottest day of the year so far, which it was expected to challenge on Monday. The highest temperature recorded at Central Park so far this season was 96 on July 6. However, Monday's high temperature of 93 made the current hot streak an official heat wave for the Big Apple, as it was the third consecutive day at or above 90 F. The city extended it streak of 90-degree days on Tuesday.
Even parts of New England ended up enduring an official heat wave in the pattern. Temperatures climbed to 90 F or higher for the third day in a row on Monday in Providence, Rhode Island; Hartford, Connecticut; and Boston to name a few cities.
"The approach of a second front during the middle of the week with its clouds, showers and thunderstorms may keep high temperatures at a level close to or just above average," Pastelok said.
Highs during late July are generally well into the 80s in the mountains and within a few degrees of 90 in the Interstate-95 corridor of the mid-Atlantic.
How much of a temperature and humidity drop in the wake of that system may depend on how far south the jet stream dips and how much of an area is drenched by rain at roughly the same time. If only a slight jet stream dip occurs and rainfall ends up being sporadic, then daytime temperatures may still be quite high, even for July standards.
But, if the jet stream takes a big southward dip and is preceded by widespread showers and thunderstorms, it would allow cooler and less humid air to drain southward from eastern Canada.
"Chances are it will be somewhere in between both scenarios for rainfall, temperature and humidity concerns for the middle and end of the week," Pastelok said.
Motorists should anticipate travel delays from thunderstorms, especially in the swath from southern Ohio and West Virginia to Virginia, Maryland, Delaware and southern New Jersey during the afternoon and evening hours through Tuesday.
More showers and thunderstorms with disruptions to outdoor plans and travel are forecast for Wednesday to Thursday in the Northeast.
Storms that erupt from the central Appalachians to the mid-Atlantic coast could be severe during the afternoon and evening hours on Wednesday.
Rainfall that does not lead to flooding would generally be welcomed by lawn, garden and agricultural interests as rainfall has been less than average during a month when evaporation rates are the highest levels of the entire year. Lawns have turned brown in many communities and some established flower and vegetable plants have been withering in the afternoon heat and sunshine.
Some cities, such as Washington, D.C., may still have a high close to 90 on Friday, Saturday and Sunday, and New York City may experience a few days with highs in the middle 80s. Highs could top out close to 80 in the mountains of Pennsylvania and along the coast of northern New England.
"Some people in the central Appalachians, around the eastern Great Lakes and in central and northern New England may be able to turn off their air conditioners at night later this week and into this weekend," Pastelok said.
Nighttime temperatures may dip well down into the 60s over the interior Northeast late this week.
So while a break from extreme heat is on the way this week, people should not expect a big refreshing change. More heat may also try to surge back in from late this weekend to early next week. Heat will build once again over the Midwest during this weekend.
The National Weather Service's (NWS) Weather Prediction Center (WPC) tweeted that "heat is the leading cause of weather-related deaths in most years,” adding that the central and eastern U.S. are facing dangerously hot conditions. The WPC urged people to seek air conditioning, avoid strenuous activities, wear light clothing, drink plenty of water and avoid leaving children and pets in closed vehicles as well as stressing the importance of recognizing the signs of heat exhaustion and heatstroke.
In the meantime, thunderstorms will be on the prowl in some locations each of the next three or four days, especially during the afternoon and evening hours. People should move indoors at the first rumble of thunder. If you can hear thunder you are at risk for being struck by lightning.
Four men were struck by lightning Sunday evening in the St. Louis area alone as a thunderstorm with frequent lightning approached a park where they had gathered to play a weekly soccer game, according to The Associated Press.
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