ST. LOUIS — At least 13 people are dead and thousands were left without power Saturday morning after multiple expected tornadoes moved through St. Louis Friday night.

Missouri Gov. Mike Kehoe said initial reports indicated as many as 19 tornadoes hit the state Friday night, but the only agency that can verify tornado touchdown claims is the National Weather Service. NWS survey crews have deployed in the days following the storm to assess the damage caused by the storm. The survey crews traveled to areas where damage was reported to confirm whether suspected tornadoes touched down.

The NWS has so far confirmed eight tornado touchdowns in the St. Louis region from the storms, including:

• Tornado damage rated at least EF3 was confirmed around Des Arc, but the survey was not complete as of Sunday night. NWS said the rating may change.

• Tornado damage rated as high as EF2 was observed from Chesterfield through Maryland Heights, Bridgeton, Florissant and other communities, but the survey was not complete as of Sunday night. NWS said the rating may change.

• An EF2 tornado touched down near Rolla around 7:50 p.m. with peak winds of 120 mph. The tornado left one person injured and damaged several homes, schools, and businesses.

• An EF2 tornado touched down southwest of Gray Summit near Villa Ridge around 8:56 p.m. with a max wind speed of 130 mph. The tornado caused significant structure damage and intense, concentrated damage to a heavily wooded area.

• An EF2 tornado touched down north of Hillsboro near Belews Creek around 9:20 p.m. and continued northeast toward Arnold with a max wind speed of 115 mph. The twister caused trees to be uprooted and significant roof damage to residential homes.

• O’Fallon Mayor Herb Roach said Monday that he was informed by the National Weather Service that an EF1 tornado hit the city Friday. Damage surveys are ongoing and the rating is subject to change.

• Tornado damage rated at least EF1 was confirmed around Grady, but the survey was not complete as of Monday morning. NWS said the rating may change.

• An EF1 tornado touched down west of Sullivan near Elmont around 8:30 p.m. with max wind speeds of 105 mph. The tornado primarily damaged several homes, outbuildings, telephone poles, and trees on the southern outskirts of Union.

Outside of the St. Louis region, an EF3 tornado with max wind speeds of 138 mph struck Poplar Bluff, causing severe damage to numerous structures. The storm caused at least one fatality in the city.

Editor’s note: “St. Louis region,” as used in this article, refers to the St. Louis County Warning Area (CWA), the region that the National Weather Service’s St. Louis office covers, rather than the “St. Louis metro area.” Tornadoes rarely touch down in what is considered the St. Louis metro area. For example, of the 1212 confirmed tornadoes in the St. Louis region from 1805 to 2023, only 54 have touched down in St. Louis County.

Radars and electronics can only tell NWS meteorologists so much. To figure out whether a tornado happened, the service has to head out into the field. Less than 24 hours after the storms, the agency sent out multiple survey teams to assess damage and figure out whether a legitimate tornado touchdown occurred.

“The pattern of damage determines if it was a tornado. NOT how much damage was caused,” the NWS said on its website. “We conduct surveys to find out exactly what happened. This helps us to improve our warnings for the future. This is also important for historical reference.”

Tornado damage can often be confused with damage from a microburst, so meteorologists look at the type of damage rather than how much damage occurred.

Damage from a tornado often looks chaotic and leaves large trees uprooted, often crossing each other on the ground, the service said. Smaller snapped branches or trees aren’t usually helpful, since those don’t convey the true severity of winds.

For example, the NWS originally said in a tweet on March 14 that a tornado was confirmed near Maeystown, Illinois. However, about half a dozen surveyors went to the area the next day and couldn’t find any damage indicating a tornado was in the area.