Labor Day weekend to bring summer heat for some, disruptive storms for others

Drenching showers and gusty thunderstorms will affect some of the United States for at least part of the Labor Day weekend. See what's expected for your area as you make holiday plans.

As heat builds in the West, drenching showers and locally severe thunderstorms will affect many areas in the central and eastern United States for at least part of the last unofficial weekend of the summer, AccuWeather meteorologists say.

Labor Day weekend travel is estimated to be up nearly 10% from last year, according to AAA, which noted the worst travel times will be Thursday afternoon and evening, Friday afternoon and Saturday morning. Travel home can be busy on Sundays and Monday afternoons and evenings, as well as on Tuesday morning rush, AAA added.

The days leading up to Labor Day weekend will be hot and thundery in the Central and Eastern states, with areas of severe weather. However, the large heat dome that will build from the Midwest to parts of the East will break down late this week and weekend as a strong cold front slices southeastward.

"The big travel day on Friday will feature heavy showers and gusty thunderstorms from the Midwest to the south-central Plains along the front which can lead to delays at airports and roadways from Oklahoma City and Dallas to Detroit and Chicago," AccuWeather Lead Long-Range Meteorologist Paul Pastelok said.

The Plains will be cooler behind the front, especially on Saturday and Sunday of the holiday weekend.

"As the front sags southward in the Central states during the heart of the weekend, showers and thunderstorms will move across the southern Plains, with the potential for much-needed rainfall for parts of western Texas," Pastelok said, "Some storms in Texas and western Oklahoma can be strong to severe."

Farther to the east, a bubble of high pressure will keep much of New England, including Boston, dry and comfortable on Friday as the air remains warm and humid farther to the south and west in the Northeast.

Labor Day weekend forecast

Still, as the front approaches from the Midwest, spotty thunderstorms in the central Appalachians and mid-Atlantic will become more numerous and widespread in the Northeast by Saturday, AccuWeather Lead Long-Range Meteorologist Paul Pastelok said.

While there will be rain-free episodes on Saturday and Sunday that allow some outdoor activities, a small number of the storms that erupt can be severe, with strong gusts of wind and flooding downpours. Enough rain can fall to flood roads in some communities, while gusty winds can break tree limbs, toss canopies and lead to sporadic power outages. The showers and thunderstorms in the East will be most widespread and intense in the afternoon and evening, although there may be some exceptions.

The front's forward speed will determine which parts of the Northeast can dry out on Sunday and which areas might experience more showers and thunderstorms.

On Sunday, drier air is forecast to push across the central Appalachians to the upper mid-Atlantic, with drenching showers and strong thunderstorms extending from the lower Mississippi Valley to the southern Appalachians and the lower part of the mid-Atlantic, including the beaches from southern New Jersey to the Carolinas. Expect travel delays and disruptions to outdoor plans in Atlanta and Charlotte.

While the setup may not pack the tremendous amount of tropical moisture that produced flash flooding in mid-August, the air mass the front will slice into will be warm and humid.

"It is possible there is another big flash flood event somewhere in the East as the front slows its forward speed from Saturday to Sunday," Pastelok warned.

In the wake of the front, cooler and less humid air will progress from the northern Plains to the Midwest and the Northeast as the weekend carries on. Temperatures will dip into the 50s at night around Chicago and Detroit. The less humid air should reach New York City, Philadelphia and Washington, D.C., later on Sunday and continue on Monday.

Much of the zone from the Gulf coast to the southern Atlantic coast, north of the Florida Peninsula, can be quite wet due to showers and locally severe thunderstorms, with some road and air travel delays on Monday. "Labor Day may not be a good beach day for these areas in the South," Pastelok said.

Mainly dry for the West with a few exceptions

Much of the Rockies to the Pacific coast will be rain-free from Friday through Monday. There will be some trouble spots due to afternoon and evening thunderstorms that erupt in portions of Arizona, Colorado, New Mexico and Utah at the start of the weekend that will expand northward by Monday. Downpours produced by the isolated storms can pose a danger due to rapid runoff into canyons, rivers and arroyos (normally dry stream beds). Lightning from the storms is an ever-present danger to hikers.

Smoke from wildfires will be a concern for air quality in some areas of the West, especially the Northwest, where the warmest conditions relative to the historical average are anticipated. It is possible a storm pushes eastward enough to trigger spotty, mainly dry thunderstorms with lightning strikes in parts of the Northwest later in the holiday weekend. Dry thunderstorms increase the risk of new wildfires igniting. The same storm will bring some shower activity to coastal areas of Washington and Oregon by Monday.

Typical late-summer heat will have the biggest impact on tens of millions over the interior West, with temperatures that run up to several degrees above the historical average. The warm pattern follows cool conditions that affected much of the region this past weekend and included some snow for the high country of the Sierra Nevada and Cascades. Meanwhile, temperate conditions are in store for the Interstate 5 corridor and the major cities, with highs ranging from the low 70s in San Francisco to near 80 in Seattle and the low 80s in Downtown Los Angeles.

No tropical threats to US mainland, but Hawaii remains at risk

Meanwhile, in the tropics, Gilma will pass just north of Hawaii over the Labor Day weekend and is forecast to bring locally gusty winds, rough seas and drenching showers and thunderstorms to Hawaii. Gilma was a hurricane at the start of the week, but the storm will lose wind intensity as it nears the islands.

In the Atlantic basin, Pastelok said any system that manages to form over the southern Gulf of Mexico is likely to be carried westward into Mexico.

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