Alert archive / Tennessee / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 66
The Storm Prediction Center issued this severe thunderstorm watch at Mar 28, 2021, 3:07 AM EDT for 5 counties in North Carolina; 20 counties in Tennessee. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Mar 28, 2021, 3:07 AM EDT (07:07 UTC)
- Expired
- Mar 28, 2021, 9:00 AM EDT
- In force
- 6 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 25 counties
Cherokee County, NC, Clay County, NC, Graham County, NC, Macon County, NC, Swain County, NC, Anderson County, TN, Bledsoe County, TN, Blount County, TN, Bradley County, TN, Cumberland County, TN, Hamilton County, TN, Knox County, TN, Loudon County, TN, Marion County, TN, McMinn County, TN, Meigs County, TN, Monroe County, TN, Morgan County, TN, Polk County, TN, Rhea County, TN, Roane County, TN, Sequatchie County, TN, Van Buren County, TN, Warren County, TN, White County, TN
The radar
The Knoxville radar (KMRX), 129 km from the middle of the area, began a volume at 07:09 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
- 20%
- One or more EF2 to EF5 tornadoes
- 5%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 5%
- Ten or more severe hail reports
- 10%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
11 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 28, 5:07 AM EDT | Flash Flood Warning | MRX | Anderson, Campbell, Claiborne, Morgan, Scott, Union | 5 hr |
| Mar 28, 5:15 AM EDT | Severe Thunderstorm Warning | MRX | Anderson, Campbell, Claiborne, Union | 17 min |
| Mar 28, 5:43 AM EDT | Severe Thunderstorm Warning | MRX | Marion | 47 min |
| Mar 28, 6:36 AM EDT | Flash Flood Warning | MRX | Bledsoe, Marion, Rhea, Sequatchie | 6 hr |
| Mar 28, 6:40 AM EDT | Flash Flood Warning | MRX | Anderson, Knox, Loudon, Morgan, Roane, Union | 5 hr |
| Mar 28, 7:17 AM EDT | Flash Flood Warning | MRX | Bradley, Hamilton, McMinn, Meigs, Rhea, Sequatchie | 6 hr |
| Mar 28, 7:49 AM EDT | Flash Flood Warning | MRX | Grainger, Hamblen, Jefferson, Knox, Sevier | 5 hr |
| Mar 28, 7:52 AM EDT | Flash Flood Warning | MRX | Bradley, Hamilton, Polk | 5 hr |
| Mar 28, 8:03 AM EDT | Flash Flood Warning | MRX | Blount, Knox, Loudon, McMinn, Monroe, Polk and 1 more | 4 hr |
| Mar 28, 8:26 AM EDT | Flash Flood Warning | MRX | Blount, Cocke, Sevier | 5 hr |
| Mar 28, 8:47 AM EDT | Flash Flood Warning | MRX | Cherokee, Clay | 4 hr |
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, 7.1 hours before the alert went out and 216 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
- 200 J/kg
- Mixed-layer CIN
- -290 J/kg
- Mixed-layer LCL
- 839 m above ground
- 0-6 km bulk shear
- 62 kt
- 0-1 km storm-relative helicity
- 341 m²/s²
- 0-3 km storm-relative helicity
- 458 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 3.8
The text
As transmitted.
242 WWUS20 KWNS 280704 SEL6 SPC WW 280704 NCZ000-TNZ000-281300- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 66 NWS Storm Prediction Center Norman OK 305 AM EDT Sun Mar 28 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Western North Carolina Eastern Tennessee * Effective this Sunday morning from 305 AM until 900 AM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible A tornado or two possible SUMMARY...A well-organized band of storms will continue eastward across eastern Tennessee into far western North Carolina through the early morning. Isolated thunderstorm wind damage can be expected, and a brief tornado risk cannot be entirely ruled out. The severe thunderstorm watch area is approximately along and 35 statute miles north and south of a line from 35 miles southeast of Knoxville TN to 40 miles northwest of Chattanooga TN. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU6). 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. && OTHER WATCH INFORMATION...CONTINUE...WW 64...WW 65... AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 26035. ...Guyer
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 28, 2:25 AM EDT | Mesoscale Discussion | SPC | Avery, Buncombe, Cherokee, Clay, Graham, Haywood and 7 more | 2 hr |
| Mar 28, 12:38 PM EDT | Mesoscale Discussion | SPC | Alamance, Anson, Cabarrus, Caswell, Chatham, Cumberland and 19 more | 3 hr |
| Mar 28, 3:24 PM EDT | Severe Thunderstorm Watch | SPC | Beaufort, Bertie, Camden, Chowan, Craven, Cumberland and 26 more | 4 hr |
| Mar 28, 4:53 PM EDT | Mesoscale Discussion | SPC | Beaufort, Bertie, Camden, Chowan, Craven, Currituck and 13 more | 67 min |
| Mar 27, 9:42 PM EDT | Mesoscale Discussion | SPC | Chester, Fayette, Hardeman, Hardin, McNairy, Shelby | 93 min |
| Mar 27, 10:01 PM EDT | Tornado Watch | SPC | Chester, Crockett, Decatur, Fayette, Hardeman, Hardin and 9 more | 7 hr |
| Mar 27, 11:45 PM EDT | Mesoscale Discussion | SPC | Fayette, Giles, Hardeman, Hardin, Lawrence, McNairy and 1 more | 90 min |
| Mar 28, 12:27 AM EDT | Tornado Watch | SPC | Bedford, Coffee, Franklin, Giles, Grundy, Hickman and 6 more | 8 hr |
| Mar 28, 2:57 AM EDT | Mesoscale Discussion | SPC | Franklin, Hamilton, Lincoln, Marion | 93 min |
| Mar 28, 5:56 AM EDT | Mesoscale Discussion | SPC | Bradley | 94 min |
Nearby
Severe Thunderstorm Watches in Tennessee, 2021Severe Thunderstorm Watches in North Carolina, 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.