The Plains, South and Midwest are expecting another round of severe weather this week, with forecasters warning of thunderstorms capable of producing large hail, damaging winds and “potentially strong to intense” tornadoes. Flash flooding is also expected for several areas.
Warm, humid air from the Gulf of Mexico is spreading northward into the central United States, while cooler, drier air is moving in from the west. This clash of air masses, combined with strong winds higher up in the atmosphere, is creating a very unstable environment — perfect for severe thunderstorms to form.
“The combination of these today are rather strong,” Bryan Smith, a lead forecaster at the Storm Prediction Center, said on Monday. “So with that, we’re expecting severe thunderstorms that develop later today and will rapidly acquire what we refer to as supercell thunderstorm characteristics.”
Supercells are a type of thunderstorm that can produce the most severe weather, including damaging wind gusts, very large hail and sometimes weak to violent tornadoes, according to the National Weather Service. If the conditions in the atmosphere are right, supercell thunderstorms can last for several hours.
Central and eastern Oklahoma, the far northwest of Arkansas, southwestern Missouri, southeastern Kansas and the far north of Texas are at the highest risk on Monday, a Level 4 out of 5 risk for severe weather, according to the Storm Prediction Center.
Some of the thunderstorms may also merge into larger clusters as they move east, producing an additional hazard of straight-line winds.
“Those tend to be the most prolific wind-producing thunderstorms,” Mr. Smith said. “We’re expecting winds generally in the 60- to 80-mile-an-hour range.”
Hail, in some cases greater than the size of a baseball, is an additional hazard on Monday.
Thunderstorms are expected to start forming just west of Interstate 35 — a major highway running through Oklahoma and Texas, and track eastward through Oklahoma and into the Ozarks by evening. The severe weather threat will extend into parts of Missouri and surrounding areas into Monday night.
Severe weather is also expected in parts of Tennessee and the south Appalachian Mountains on Monday. Thunderstorms in the region could bring strong winds and large hail, especially starting Monday afternoon.
The Weather Prediction Center has also warned that “numerous flash floods are likely,” especially in parts of northern Arkansas and southern Missouri, where the ground is already saturated from recent storms. Forecasters have issued a Level 3 out of 4 risk for excessive rainfall leading to flooding, with some areas expected to receive rainfall rates of over two inches an hour. A broader area from southeastern Oklahoma to central Iowa has been placed under a Level 2 out of 4 risk for flooding.
The outbreak of severe weather comes as a series of storms caused widespread damage and resulted in more than 25 deaths across several states. Kentucky and Missouri were especially affected by several tornadoes that also damaged thousands of buildings.
More storms are expected later this week.
There is a continued risk of severe weather on Tuesday, as the storm moves east to a large area stretching from Missouri and Illinois through Kentucky, Tennessee and into parts of the Ohio Valley. All severe weather hazards are still expected, including large hail, damaging winds and tornadoes.
“There’s the potential for a couple of strong tornadoes, centered on parts of southern Kentucky, western and middle Tennessee and into portions of northern Mississippi and Alabama,” Mr. Smith said.
The Storm Prediction Center has highlighted a Level 3 of 5 risk for severe weather in these areas on Tuesday.
On Wednesday, the threat for severe weather is expected to lessen, as the storm moves toward the Atlantic. Still a swath from southeast Virginia and eastern North Carolina, along the East Coast to the Florida and Georgia border, may still experience damaging wind gusts and possibly a tornado, before the storm system eventually clears.
Beyond the middle of the week, forecasters expect a calmer period of weather.
“A little bit of a more benign weather pattern will ensue across the lower 48,” Mr. Smith said.
Nazaneen Ghaffar is a Times reporter on the Weather team.
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