Thunderstorms, large hail, destructive wind gusts and strong tornadoes threaten up to 73 million people across the Mississippi, Ohio and Tennessee Valleys on Sunday.

This storm system has impacted parts of the Midwest and South through the weekend, producing more than 50 preliminary damaging wind and hail reports across the Plains on Saturday, including a 3-inch hail report in Amber, Oklahoma.

On Sunday, the National Weather Service’s Storm Prediction Center warned of enhanced risk of severe weather for the valleys leading into the region where Arkansas, Louisiana and Texas meet. Detroit, Indianapolis, Memphis, Nashville, Chicago, Dallas and Cleveland are all included in the risk area.

“Very large hail, significant damaging winds (especially into the evening hours), and tornadoes, a few of which could be strong, can all be expected,” the National Weather Service said in an update Sunday morning. It also warned there could be “heavy downpours” as storms grow into an “organized line into the evening hours” and bring the risk of scattered flash flooding.

Storms are expected to start as early as 1 p.m. across the Midwest, with the risk lingering past midnight for the Ohio and Tennessee valleys.

This line of severe storms will continue to march east Monday, impacting 68 million across the Southeast and mid-Atlantic. The strongest storms will target parts of Alabama, Georgia, the Carolinas and Virginia, where an enhanced risk is in place.

Cities in Monday’s risk area include Charlotte and Raleigh in North Carolina; Atlanta; Philadelphia; Washington, D.C.; and New Orleans. Widespread damaging winds and a few tornadoes may be possible through the afternoon and evening before the severe line moves offshore.

On the north side of this strong storm system, wintry precipitation continues to plague parts of the Upper Midwest, Great Lakes and New England. Winter alerts remain in effect for 9 million people, including in Green Bay, Wisconsin; Marquette, Michigan; Burlington, Vermont; and Portland, Maine.

Snowfall totals as of Sunday morning include 10 inches in Fletcher, Vermont, and Morrisonville, New York.

Heavy snow and ice will continue to impact parts of eastern Minnesota, Wisconsin and Michigan through Sunday night, with gradual clearing by Monday morning. An additional 2 to 5 inches of snow, locally higher, and 0.25 to 0.5 inches of ice will be possible through Sunday. Power outages and additional tree damage are likely in this region.

Freezing rain and snow will continue to impact parts of New England through Sunday afternoon, with a gradual transition to rain anticipated for most areas by Monday morning.

In the West, 5 million people from the coast to the Rocky Mountains are under alerts through Monday, with wind gusts expected to ramp up. Gusts will range anywhere from 25 to 60 mph and continue to fuel fire concerns, especially across Colorado, New Mexico and West Texas.

Two million people are under alerts Sunday, including in El Paso, Texas, with high fire danger lingering into the start of the workweek.