National Weather Service United States Department of Commerce

Event Summary

A shortwave moved into the Ozarks area early in the morning on March 21st and sparked convection along a stationary front to the north of the TN Valley. This MCS that originally developed over MO continued eastward along the eastern periphery of an upper level ridge. By the afternoon hours temperatures warmed into the lower 80s with dewpoints in the upper 50s to lower 60s; resulting in an unstable airmass with SBCAPE values upwards of 2,000-2,500 J/kg over northern AL and southern middle TN. 

As the MCS moved into TN it began to interact with the more unstable airmass and intensified over the WFO Nashville CWA. Storms were initially discrete as they strengthened over TN but eventually formed into a cluster near Giles County, TN. During the semi-discrete stage there were multiple reports of golf ball size hail in the Nashville CWA. As the storms moved into Lincoln, TN a strong rear inflow jet developed and was evident on radar. The peak winds evident on HTX radar with this rear inflow jet were upwards of 90kts at the 4,000-7,000 ft level. As the rear inflow jet intensified and surged southeastward there was a tightening of velocity on the northern side of the inflow jet in Moore county. A Tornado Warning was issued as the velocity couplet moved into Franklin county, TN. There wasn’t any verification with the Tornado Warning but widespread tree damage was reported with the strong rear inflow jet.

The storms continued to surge SE into AL and widespread damage continued. Various reports of dime to quarter size hail were reported with the storms. An outflow boundary appeared to have surged out ahead of the line of storms as they moved through northern AL and additional storm development was noted on the western flank of this line. Brief reports of dime to isolated quarter size hail were noted in the Decatur area. Storms continued to move along/just behind the outflow boundary with very limited reports of hail as they exited the Huntsville CWA.  


Storm Reports
Severe Thunderstorm Watch # 76 was issued at 230 PM CDT. Click to image to view the storm reports.

Upper Air Charts

 

250mb Chart at 6am March 21st

500mb Chart at 6am March 21st

850mb Chart at 6am March 21st

250mb Chart at 6pm March 21st

500mb Chart at 6pm March 21st

850mb Chart at 6pm March 21st

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Surface Charts

 

7pm March 20th

1am March 21st

7am March 21st

1pm March 21st

4pm March 21st

7pm March 21st

Upper Air Soundings

 

KBNA Sounding 6am March 21st

 

KBNA Sounding 1pm March 21st

UAH Sounding 4pm March 21st

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SPC Outlooks

 

Day 1 Outlook 
Issued 8am March 21st

 

Day 2 Outlook 
Issued 11:30am March 20th

Day 3 Outlook
Issued 2:30am March 19th

Day 1 Tornado Probability
Issued 8am March 21st

Day 1 Hail Probability
Issued 8am March 21st

Day 1 Wind Probability
Issued 8am March 21st

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Images

 

Quarter Size Hail in Hazel Green (Courtesy of Shannon Grubbs)

 

Near Quarter Size Hail in Petersburg, TN (Courtesy of Audria Richardson)

Dime Size Hail in Petersburg, TN (Courtesy of Audria Richardson)

Near Quarter Size Hail in Decatur (Courtesy of Busy Bee)

Pea Size Hail in Decatur (Courtesy of LeAnne Aldrich)

Nickel Size Hail in Bridgeport, AL (Courtesy of Amanda Huges)

Close to Nickel Size Hail (Courtesy of Amanda Eldredge)

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