ST. LOUIS — At least 10 people are dead and thousands were left without power Saturday morning after multiple expected tornadoes moved through St. Louis Friday night.

Missouri Governor 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 deployed at around 8:30 a.m. 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.

“NWS St. Louis has 2 damage survey teams in route to begin surveying: one will starting near Villa Ridge/Gray Summit and another near Hillsboro,” the service said Saturday morning. “There is NO way we will be able to survey all the suspected tornado damage today so please be patient. The process takes time.”

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

• A tornado touched down north of Hillsboro near Belews Creek around 9:20 p.m. with a max wind speed of 110 mph. The twister caused trees to uproot and significant roof damage to residential homes.
• A tornado touched down west of Sullivan near Elmont around 8:30 p.m. with max wind speeds of 94 mph. The tornado caused uprooted trees and trunks to snap.

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 This is also important for historical reference.”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.