The middle of the nation is experiencing a reprieve from widespread severe weather, but the respite will be brief as thunderstorms are poised to flare up this weekend when a mass of hot air floods into the atmosphere over the Plains and Midwest.Milder air from the Pacific Ocean and western U.S. has surged eastward across the nation in the wake of heavy thunderstorms that swept across the Midwest and continue to drench East Coast late this week. Where sunshine returns, temperatures will climb to near-average levels over the Midwest and record-challenging levels over the Plains. This buildup of warmth is not likely to sit well with the atmosphere as a new wave of chilly air is forecast to sweep southward in stages this weekend and early next week.CLICK HERE FOR THE FREE ACCUWEATHER APPWith the aid of a strong jet stream overhead and the action of the cooler air forcing the warm air to rise, there is the potential for towering thunderstorms to erupt across the central Plains to the middle Mississippi and Ohio valleys during Saturday night and Sunday. The storms could affect cities such as Cincinnati, Ohio, and St. Louis and Kansas City, Missouri, during part of the weekend along the brim of swelling heat over the nation’s heartland.”We often see severe thunderstorms erupt on the northern rim of heat,” AccuWeather Senior Meteorologist Bill Deger said.That northern rim is often the weakest part of a dome of high pressure, so storms tend to form there rather than in the middle of the fair weather system. This is often the location where the air aloft begins to cool, which aids in thunderstorm development.”We had storms erupt on the rim of the heat on Wednesday over the interior Northwest with more in store Thursday, so it’s not surprising to expect more storms farther east where the northern rim ends up being later this weekend,” Deger explained.The main threats with the storms over the central U.S. are expected to be hail, strong wind gusts and flash flooding during Saturday night and Sunday. However, as is sometimes the case with severe thunderstorms during early May, isolated tornadoes cannot be ruled out this far in advance.A second eruption of thunderstorms is anticipated farther to the south over the Plains and the lower Mississippi Valley late Monday to Tuesday night. The storms will ignite as cooler air presses across the Midwest then the Northeast early next week. The storms early next week might roll through Dallas, Oklahoma City and Little Rock, Arkansas. All of the usual threats, including large hail and strong wind gusts to flash flooding and perhaps tornadoes, are possible with these storms once again on Monday and Tuesday.The exact position and timing of the storms are have yet to be determined as the turbulent weather pattern is still days away from developing.It is possible the setup allows large complexes of thunderstorms to form, which can lead not only to a swath of torrential rain and flooding but also the potential for a long-lived high wind event that can move along for several hundred miles. This phenomenon is known as a derecho.Systems such as this are more common from the late spring to the middle of summer, but a destructive derecho unleashed wind damage over portions of the southern Plains and lower Mississippi Valley Tuesday night and early Wednesday morning, and these dangerous storm complexes can occur earlier in the spring when the ingredients align, typically along the boundary of heat to the south and cooler air to the north.Most thunderstorm complexes fall below the criteria for a derecho, which must bring nearly continuous reports of wind gusts of 58 mph or greater over a distance of at least 240 miles.Additional outbursts of severe weather are possible near the boundary between the heat hanging on in the Southwest and the buildup and return of cool air in the Northeast later next week.2020 is off to a wild start with severe weather in what has become the deadliest tornado season since 2011, in which 1,894 twisters touched down. As of April 30, 589 preliminary tornadoes have been reported and more than 3,800 damaging wind reports have been filed this year by the Storm Prediction Center (SPC). Tornadoes have claimed 73 lives in 2020, the SPC reports. AccuWeather will continue to provide updates on the upcoming severe weather as meteorologists analyze new information.Keep checking back on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.
