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Excessive Rainfall and Severe Thunderstorms Threaten the Southern U.S. Again Thursday

A Moderate Risk (Level 3 of 4) Excessive Rainfall Outlook and Flood Watches have been issued for portions of east Texas into Louisiana Thursday where flash, urban, and riverine flooding is possible. A Slight Risk (Level 2 of 5) for scattered severe thunderstorms has been issued from west Texas to the lower Mississippi Valley Thursday afternoon into Thursday night. Read More >

Overview

On the evening of July 9th, intense thunderstorms developed rapidly along a warm front draped from northwest to southeast across the area. There were two rounds of thunderstorms, the first being discrete, rotating storms called supercells. These supercell thunderstorms dropped large hail across portions of western Illinois (Mt. Sterling area) and also across the western St. Louis metro area. Hail in excess of 2 inches was noted in both of these supercells.

Over time, the storms congealed into a large complex of thunderstorms known as a mesoscale convective complex (MCS). This line of storms contained damaging, sometimes destructive winds as they quickly pushed southeast across east-central Missouri into southwest Illinois. The worst damage was noted from Rensselaer, MO southward to Perry, MO, where straight-line winds of 90 mph were found. This same line of storms also affected the St. Louis metro area, bringing widespread 60-70 mph winds across the metro causing many large tree limbs to fall and many to be without power.  

 

This is a three dimensional loop of the storm dropping hail over St. Louis County on July 9th, 2021. Two panel radar image of strong winds passing through Perry, MO. Radar image of a line of storms that caused damage in northeastern Missouri. Two panel radar image of storm that moved through the St. Louis metro area.

3-D radar loop of storm dropping hail over St. Louis County

 

Strong winds passing through Perry, MO

Line of storms that caused damage in northeastern MO

Windstorm that impacted the St. Louis metro area

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