Refreshing change of pace in store for the Northeast

By Alex Sosnowski, AccuWeather senior meteorologist

This satellite image shows the northeastern United States at around 11:30 a.m. on Monday, Aug. 5, 2019. (Photo/NOAA GOES East)

Heavy, gusty and locally severe storms will precede a push of cooler and less humid air across the Northeast this week.

The weather in the coming days will change hands one or more times.

Humid air that lingered over the mid-Atlantic coast will surge northward across the Appalachians, eastern Great Lakes and New England into Tuesday.

The most dramatic change to more humid conditions will be across New England. Much of the region experienced low humidity, compared to the balance of the region, from Sunday to Monday.

AccuWeather RealFeel® Temperatures will surge to near 100 F in Washington, D.C., Baltimore, Philadelphia, Pittsburgh and Cleveland for several hours during the midday and afternoon.

However, the temperature does not have to hit 90 or RealFeel Temperatures don't need to reach 100 for dangers inside or outside of enclosed vehicles.

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The moisture surge will reach a peak ahead of a cool front that is poised to slice across the region spanning Tuesday and Wednesday.

While spotty drenching storms are in store from the Ohio Valley to the mid-Atlantic Monday night, more numerous storms are forecast to erupt ahead of the front that moves in from Canada and the Upper Midwest into the middle of the week.

"Some of the storms will be marginally severe," according to AccuWeather Meteorologist Clay Chaney.

"The strongest storms can produce localized flooding downpours, strong wind gusts, small hail and frequent lightning strikes," Chaney said.

On Tuesday, the bulk of the storms are forecast to extend from the eastern Great Lakes and parts of the central Appalachians to the lower Ohio and middle Mississippi Valley.

On Wednesday, the swath of storms is likely to reach from the southern Appalachians to the mid-Atlantic and New England.

It may take until the late afternoon or evening hours on Wednesday for storms to fire from Philadelphia to New York City and Boston. Motorists and airline passengers should anticipate substantial delays for the afternoon and evening commute this day along the Interstate 95 corridor.

For those spending time at the beach this week, storms related to the cool front are most likely from Cape Cod, Massachusetts, to Long Island, New York, New Jersey, Maryland and the Virginia capes from late Wednesday to Thursday.

The delay in the arrival of storms at the beach is usually tied to the protection the sea breeze provides during the day. When the sea breeze breaks down in the evening, any storms brewing over the mainland have a better chance of reaching the beaches and barrier islands.

A second batch of thunderstorms is likely to swing from the Great Lakes region to the Appalachians on Thursday.

Far-reaching cooler, less-humid air coming soon

Since the air coming in is originating from north-central Canada, it will feel much less humid across much of the region spanning Thursday to Sunday.

Even in portions of the Chesapeake and Delaware Bay regions, a gradual reduction in humidity is likely by this weekend.

Since the sun is still strong during the first half of August, it will still feel warm during the midday and afternoon hours with the Canadian air mass.

However, that air will regain its identity at night in the form of a quick cooldown during the evening and cool conditions after dark to the start of the following day.

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"While daytime highs may be close to average, nighttime lows are likely be a few degrees below average," Chaney said.

Highs typically range from the upper 70s to near 80 over the northern tier to near 90 over southeastern Virginia. Lows tend to average in the upper 50s to near 60 over the northern tier to near 70 in southeastern Virginia.

Warmth to rebound later in August

Looking farther ahead, during the second half of August, the jet stream may retreat northward and extend from west to east across the U.S./Canada border.

"In this setup, warmth building up over the West will be able to make the trip across the Great Lakes and Northeast," according to AccuWeather Long-Range Meterorologist Max Vido.

"Much of the second half of August may bring above-average temperatures," Vido said.

Pushes of cool air would be locked up across Canada.

During the second half of the month, normal temperatures begin to trend downward, so it may be easier in such a pattern for above-average temperatures to occur.