Alert archive / Tennessee / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 407
The Storm Prediction Center issued this severe thunderstorm watch at Jul 31, 2021, 11:29 PM CDT for 5 counties in Alabama; 4 counties in Georgia; 25 counties in Tennessee. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Jul 31, 2021, 11:29 PM CDT (04:29 UTC)
- Expired
- Aug 1, 2021, 2:02 AM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 55 kt
All 34 counties
DeKalb County, AL, Jackson County, AL, Lauderdale County, AL, Limestone County, AL, Madison County, AL, Catoosa County, GA, Dade County, GA, Walker County, GA, Whitfield County, GA, Bedford County, TN, Bledsoe County, TN, Bradley County, TN, Cannon County, TN, Coffee County, TN, Franklin County, TN, Giles County, TN, Grundy County, TN, Hamilton County, TN, Hickman County, TN, Lawrence County, TN, Lewis County, TN, Lincoln County, TN, Marion County, TN, Marshall County, TN, Maury County, TN, Meigs County, TN, Moore County, TN, Perry County, TN, Rhea County, TN, Rutherford County, TN, Sequatchie County, TN, Van Buren County, TN, Warren County, TN, Wayne County, TN
The radar
The Northeast Alabama radar (KHTX), 82 km from the middle of the area, began a volume at 04:32 UTC, the scan nearest the moment this went out.
Open the radar archive at this moment
The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 5%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 5%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 40%
Warnings issued inside it
3 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 31, 11:55 PM CDT | Severe Thunderstorm Warning | OHX | Bedford, Cannon, Coffee, Grundy, Rutherford, Van Buren and 1 more | 53 min |
| Aug 1, 12:10 AM CDT | Severe Thunderstorm Warning | MRX | Bledsoe, Marion, Sequatchie | 65 min |
| Aug 1, 12:11 AM CDT | Severe Thunderstorm Warning | HUN | Jackson | 37 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Nashville Metro, TN (KBNA), launched 00:00Z, 4.5 hours before the alert went out and 77 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 1106 J/kg
- Mixed-layer CIN
- -7 J/kg
- Mixed-layer LCL
- 1447 m above ground
- 0-6 km bulk shear
- 44 kt
- 0-1 km storm-relative helicity
- 91 m²/s²
- 0-3 km storm-relative helicity
- 251 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 5.3
The text
As transmitted.
614 WWUS20 KWNS 010426 SEL7 SPC WW 010426 ALZ000-GAZ000-TNZ000-010800- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 407 NWS Storm Prediction Center Norman OK 1130 PM CDT Sat Jul 31 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of northern Alabama northwestern Georgia parts of middle and eastern Tennessee * Effective this Saturday night and Sunday morning from 1130 PM until 300 AM CDT. * Primary threats include... Isolated damaging wind gusts to 65 mph possible SUMMARY...Thunderstorms -- including a couple of stronger bowing clusters -- will continue moving southeastward across the Tennessee Valley area over the next couple of hours. Locally damaging wind gusts in excess of 58 MPH will be possible with stronger storms. The severe thunderstorm watch area is approximately along and 50 statute miles either side of a line from 45 miles north northwest of Muscle Shoals AL to 20 miles northeast of Chattanooga TN. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU7). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 55 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 29040. ...Goss
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 1, 12:09 PM CDT | Mesoscale Discussion | SPC | Autauga, Barbour, Bibb, Bullock, Butler, Chambers and 28 more | 2 hr |
| Jul 31, 10:15 PM CDT | Mesoscale Discussion | SPC | Benton, Cannon, Carroll, Crockett, Decatur, DeKalb and 12 more | 2 hr |
| Jul 31, 11:10 PM CDT | Mesoscale Discussion | SPC | Decatur, Henderson, Lewis, Perry | 2 hr |
Nearby
Severe Thunderstorm Watches in Tennessee, 2021Severe Thunderstorm Watches in Alabama, 2021Severe Thunderstorm Watches in Georgia, 2021Every severe thunderstorm watch in 2021
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.