National Weather Service United States Department of Commerce

Event Summary

On Saturday, May 27, the mid level (500 mb) pattern remained near zonal across the TN Valley, with winds generally from the west to east. Meanwhile at the surface and up through 850 mb, strong south-southwesterly flow helped an abundance of moisture filter northward from the Gulf of Mexico. Although showers and thunderstorms were forecast during the day, most of the area saw clearing skies which helped temperatures warm into the lower to mid 80s by the afternoon. The combination of a moist airmass and ample daytime heating allowed instability to rise quite a bit, with MLCAPE values reaching above 2000 j/kg during the early evening hours. In addition to the unstable airmass, the low level jet intensified on Saturday, creating wind shear values in to the 35 to 40 kt range across much of the region. Meanwhile, two areas of thunderstorms developed; one to the northwest of the TN Valley and one to the north. These moved in during the late evening hours on May 27 and continued into the early morning hours on May 28th.

Despite this being an overnight event, conditions remained very unstable across the area while nocturnal effects helped maintain the low level jet. Therefore, these storms continued into an airmass that was prime for organized severe convection. The first line arrived around 9 PM on Saturday, and produced scattered damage mainly across the eastern half of the area, where the line was more organized.  The most notable damage occurred in northern DeKalb County, where multiple trees were downed on Sand and Lookout Mountains. A second line moved rapidly from southern Missouri across west Tennessee.  It knocked out power to around 150,000 customers in the Memphis area, then quickly moved across parts of the HUN CWA untouched by the first line.  Notable tree damage occurred in northwestern Franklin County and a measured 75 MPH wind gust. More damage occurred near Vinemont in Cullman County, where a spotter measured a 78 MPH wind gust.  There were several reports of trees down on residences in Cullman County, but fortunately nobody appears to have been injured.

Storm Reports
Radar loop from 10pm on May 27th through 3 am on May 28th.  Click to image to view the storm reports.

Upper Air Charts


250mb Chart at 7pm May 27th

500mb Chart at 7pm May 27th

850mb Chart at 7pm May 27th

250mb Chart at 7am May 28th

500mb Chart at 7am May 28th

850mb Chart at 7am May 28th

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Surface Charts


4pm May 27th

7pm May 27th

10 pm May 27th

1am May 28th

4am May 28th

7am May 28th

Upper Air Soundings


KBMX Sounding 7pm May 27th

UAH Sounding 8pm May 27th



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SPC Outlooks


Day 1 Outlook 
Issued 8am May 27th


Day 2 Outlook 
Issued 11:30am May 26th

Day 3 Outlook
Issued 2:30am May 25th

Day 1 Tornado Probability
Issued 8am May 27th

Day 1 Wind Probability
Issued 8am May 27th

Day 1 Hail Probability
Issued 8am May 27th

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