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Where severe storms could interrupt Memorial Day weekend

Big storms could interfere with Friday travel plans along the East Coast; then severe weather might erupt over the Plains through the long weekend.

A view of a supercell thunderstorm that produced a tornado in Morton, Tex., on Monday. (Matthew Cappucci)
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Memorial Day weekend is right around the corner, and millions of Americans are set to fire up the barbecues. Yet strong to severe thunderstorms could force a change of plans for the unofficial start of summer in some areas.

D.C.-area forecast: Cloudy and mild today before a threat of severe storms on Friday

Any travelers along the East Coast on Friday should stay aware of the potential for severe thunderstorms and even some potential tornado activity. Then Saturday kicks off a multiday stretch of storminess over the northern Plains; the National Weather Service Storm Prediction Center warns that “significant severe weather” is possible.

Elsewhere, wet weather is likely in the Pacific Northwest, while stifling heat will sizzle in the South. Here we break down your Memorial Day weekend forecast.

Trouble spots

Friday on the East Coast

A cold front working east will kick up pockets of warm, humid air that will be present along the Interstate 95 corridor. Frigid air aloft will destabilize the atmosphere even further, with a pocket of high-altitude spin enhancing lift. In that sort of environment, any severe thunderstorms will be able to produce hail the size of half dollars. The most concerning setup exists in the Mid-Atlantic.

Swift upper-level winds associated with a strong dip in the jet stream, moreover, will foster wind shear — or a change of wind speed and/or direction with height. That will set up the possibility of rotating thunderstorms or supercells. A broken squall line with embedded areas of rotation is most likely, but any supercells that form ahead of the main line could become tornadic.

  • Cities affected: The National Weather Service Storm Prediction Center has declared a Level 2 out of 5 risk of severe thunderstorms in Scranton, Pa., Philadelphia, Baltimore, Washington, D.C., Richmond, Raleigh, N.C., and Charleston, S.C. A Level 1 out of 5 marginal risk of severe weather encompasses a strip from northern Maine to the Florida Panhandle and Big Bend, including for cities like Tallahassee, Jacksonville, Fla., Charlotte, New York and Burlington, Vt.
  • Hazards: Damaging winds to 60 mph and hail to half-dollar size. An isolated tornado is possible, primarily in the Mid-Atlantic.
  • Moderate rain is likely too, especially over the Southeast. A half inch to up to an inch is possible in parts of Florida, Georgia and the Carolinas.
  • Saturday will be rather gloomy in New England with a few morning showers, but improving weather is likely during the second half of the day.

Saturday over the northern Plains

The next upper-air disturbance will approach the north central U.S. this weekend, with a modest but still noteworthy jet stream overhead. A subtle dryline, or the boundary between arid air to the west and moisture east, will become established west of Interstate 35 that runs from Kansas to Des Moines to Minneapolis. That will touch off some severe storms with an isolated tornado possible. A “cap” of warm air aloft may inhibit thunderstorm growth much of the day, but thunderstorm cells will probably develop over western South Dakota during the late afternoon. Then they’ll fill in farther south during the evening and overnight.

  • Cities affected: A level 2 out of 5 risk of severe storms covers eastern South Dakota and north central Nebraska, and includes Sioux Falls, Brookings and Watertown, S.D. A level 1 risk extends from Duluth and Minneapolis to the Wyoming Border as well as south along the dryline into north central Kansas; Rapid City, Bismarck and Aberdeen are also in the marginal.
  • Hazards: Damaging winds to 70 mph and hail to half dollar size. An isolated tornado is possible.

Sunday across Northern Plains

The same storm system could trigger more widespread storms on Sunday in roughly the same region. Already, the Storm Prediction Center has highlighted the Northern Plains and Upper Midwest in its Sunday severe weather outlook, writing “[c]onfidence is increasing in significant severe weather for both Sunday and Monday for parts of the central and northern Great Plains into the Upper Midwest.”

  • Cities affected: The Storm Prediction Center has declared an enhanced severe weather risk Sunday from northeast Nebraska along Interstate 25 in southeast South Dakota and southwest Minnesota. Sioux Falls, S.D., Sioux City, Iowa and St. Cloud, Minn. are included. The risk of severe storms, somewhat lesser, extends into Minneapolis and Omaha, Nebraska.
  • Hazards: Damaging winds to 75 mph and large, damaging hail. Tornadoes are possible too, but the exact magnitude of the tornado threat is unclear.

Memorial Day severe weather

On Monday, the storm system — having not moved much — will once again bring severe weather to the Plains and Upper Midwest.

  • Cities affected: An elevated risk of severe storms covers areas from near Duluth to Minneapolis to Omaha to southwestern Kansas.
  • Hazards: Damaging winds, large hail and a few tornadoes.

Rains over the Pacific Northwest and Northern Tier

A coastal low moving onshore will bring clouds, cool temperatures and a few showers to coastal Oregon and Washington beginning early Friday, but the main slug of moisture doesn’t arrive until Saturday when steadier rain arrives. It will pass near the Columbia River Basin on Sunday and saunter toward the Northern Plains on Monday. (This is the same system bringing severe weather to the Plains).

Where nice weather dominates

Some of the nicest weather to kick off the long weekend Saturday will focus across the Southeast, with sunshine and highs in the 80s. It will also be sunny over Texas and the desert Southwest, but scorching hot with highs well into the 90s.

High pressure ahead of a storm system triggering severe storms in the Plains will shift to the East Coast on Sunday and Monday. As long as the high is in control, sinking air and mild temperatures will make for picture-perfect weather. Widespread sunny 80s are likely across the eastern half of the country on Sunday and Monday.