Across the Midwest and Mississippi Valley, tens of millions of people are bracing for a potentially volatile afternoon and evening.

Fast-moving storms are expected to produce strong, potentially long-track tornadoes capable of tearing through neighborhoods, flipping cars and leveling homes. Power outages are also possible as damaging winds and large hail take down trees, power lines and roofs.

We’re tracking where the risk is highest here and bringing you updates on damage, safety concerns and how communities are responding below:

(05:13 p.m. EDT) Hail In Chesterfield, Missouri

From Content Writer Ada Wood:

In this footage shared on Twitter, a resident of Chesterfield, Missouri, which is west of St. Louis, shows hail raining down near a home.

The National Weather Service (NWS) warned of tennis-ball-sized hail, “several” likely tornadoes. and widespread gusts up to 75 mph as severe storms are anticipated through Monday afternoon. A tornado watch is in effect for St. Louis County until 9 p.m., per the NWS.

(MORE: 5 Things You Should Know About Hail)

(04:37 p.m. EDT) Flood Threat For Mid-Mississippi, Ohio Valleys

From Meteorologist Sara Tonks:

In addition to the threat of severe storms, there is a potential for flash flooding across the mid-Mississippi and Ohio Valleys today as strong storms dump a large amount of rainfall in a short period of time, with rainfall rates reaching 1 to 2 inches per hour.

Rivers across the Central Plains are in moderate flood stage as of Monday afternoon, and monitoring stations across the Ohio Valley are likely to peak in a minor flood stage later this week as water continues to flow downstream.

The threat shifts Tuesday to stretch across the Southern Plains and Deep South into the Tennessee Valley as rainfall totals climb towards 5 or 6 inches.

(04:12 p.m. EDT) Chicago Tops The Misery Map

Travel disruptions are piling up in Chicago as storms intensify there.

According to flight tracker FlightAware, Chicago-area airports are now leading the nation in delays and cancellations.

This likely means a long night ahead of waits, missed connections and changing schedules as severe weather continues to impact one of the country’s busiest air travel hubs.

(03:58 p.m. EDT) Power Outages On The Board

We’re seeing some storm-related power outages tick up in Missouri, where severe weather is making its way across the state.

Randolph, Howard and St. Louis counties have been the hardest hit so far, according to PowerOutage.us.

(03:26 p.m. EDT) What To Expect From Today’s Threat

From meteorologist Sara Tonks:

The same active pattern that caused a violent EF-4 tornado last week in Oklahoma is continuing today as a storm system encounters significant instability in the central U.S., focusing on the mid-Mississippi Valley.

Storms have already started to pop up now, but the threat doesn’t peak until later this evening for cities like St. Louis, Memphis and Chicago.

The region is facing the threat of potential violent, long-lived tornadoes, meaning EF-3 or higher ratings that are capable of staying on the ground for extended periods of time, especially in the mid-Missisippi Valley bullseye, where there is a level 2 of 3 intensity threat.

Widespread damaging winds are also possible in the region along with large to very large hail.

(03:13 p.m. EDT) Tornado Warning Issued For Metro St. Louis

A tornado warning has been issued for St. Louis, Missouri and the surrounding area.

This is an immediate safety situation. Conditions suggest a tornado could be on the ground or develop at any moment. Quarter-sized hail is also possible.

(03:02 p.m. EDT) Ongoing Tornado Warning

A tornado warning is now in effect for parts of southern Illinois, including Greenville, Pocahontas, and Alhambra, where a radar-indicated tornado has been detected.

Pea-sized hail and strong winds are also possible over the next 45 minutes.

(02:53 p.m. EDT) TORCON Upped To 7 In Some Areas For Tonight

Eastern Missouri and Southern Illinois are in the area of highest threat for today.

(02:30 p.m. EDT) If You’re Stuck Outside When A Tornado Strikes

For those facing the risk of tornadoes today, it’s important to prepare for all scenarios.

If you see a tornado while driving or outdoors, and can’t get to sturdy shelter, here’s what to do:

• Get low in a ditch or depression and protect your head and neck from flying debris
• Never shelter under an overpass. It’s a myth that these provide safety during a storm.
• Don’t rely on tornado sirens alone. Instead, have all of your wireless emergency alerts turned on and stay aware as conditions can change rapidly.

Click here for a deeper breakdown of what to do if you’re caught without shelter during a storm.