Alert archive / Tennessee / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 143
The Storm Prediction Center issued this severe thunderstorm watch at May 4, 2021, 9:37 AM EDT for 5 counties in North Carolina; 13 counties in Tennessee. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 9:37 AM EDT (13:37 UTC)
- Expired
- May 4, 2021, 1:00 PM EDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 55 kt
Counties Cherokee County, NC, Clay County, NC, Graham County, NC, Macon County, NC, Swain County, NC, Anderson County, TN, Blount County, TN, Bradley County, TN, Jefferson County, TN, Knox County, TN, Loudon County, TN, McMinn County, TN, Meigs County, TN, Monroe County, TN, Morgan County, TN, Polk County, TN, Roane County, TN, Sevier County, TN
The radar
The Knoxville radar (KMRX), 73 km from the middle of the area, began a volume at 13:38 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
- 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
- 50%
Warnings issued inside it
7 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 9:37 AM EDT | Severe Thunderstorm Warning | MRX | Bledsoe, Morgan, Rhea, Roane | 38 min |
| May 4, 10:03 AM EDT | Severe Thunderstorm Warning | MRX | Anderson, Blount, Knox, Loudon, Roane | 13 min |
| May 4, 10:41 AM EDT | Severe Thunderstorm Warning | MRX | Blount, Jefferson, Knox, Sevier | 34 min |
| May 4, 10:45 AM EDT | Severe Thunderstorm Warning | MRX | Blount, Monroe | 30 min |
| May 4, 10:57 AM EDT | Severe Thunderstorm Warning | GSP | Graham, Haywood, Jackson, Macon, Swain | 36 min |
| May 4, 11:10 AM EDT | Severe Thunderstorm Warning | MRX | Cocke, Jefferson, Sevier | 22 min |
| May 4, 12:01 PM EDT | Flash Flood Warning | MRX | Cherokee, Clay | 3 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
Peachtre/Fal Fld, GA (KFFC), launched 12:00Z, 1.6 hours before the alert went out and 266 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
- 590 J/kg
- Mixed-layer CIN
- -114 J/kg
- Mixed-layer LCL
- 753 m above ground
- 0-6 km bulk shear
- 39 kt
- 0-1 km storm-relative helicity
- 207 m²/s²
- 0-3 km storm-relative helicity
- 213 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 2.3
The text
As transmitted.
061 WWUS20 KWNS 041331 SEL3 SPC WW 041331 NCZ000-TNZ000-041700- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 143 NWS Storm Prediction Center Norman OK 930 AM EDT Tue May 4 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Southwest North Carolina Eastern Tennessee * Effective this Tuesday morning and afternoon from 930 AM until 100 PM EDT. * Primary threats include... Scattered damaging wind gusts to 65 mph possible A tornado or two possible SUMMARY...An MCS across Middle Tennessee should spread east into a portion of eastern Tennessee and perhaps southwest North Carolina before weakening. Damaging winds and a brief tornado are the primary hazards. The severe thunderstorm watch area is approximately along and 45 statute miles east and west of a line from 30 miles north of Knoxville TN to 65 miles south southwest of Knoxville TN. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU3). 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 141...WW 142... 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 450. Mean storm motion vector 28040. ...Grams
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 4, 1:04 PM EDT | Mesoscale Discussion | SPC | Caswell, Northampton, Person, Rockingham, Stokes, Surry and 2 more | 56 min |
| May 4, 1:21 PM EDT | Mesoscale Discussion | SPC | Clay, Macon | 114 min |
| May 4, 4:16 PM EDT | Mesoscale Discussion | SPC | Alamance, Anson, Bladen, Cabarrus, Caswell, Chatham and 35 more | 119 min |
| May 4, 4:56 PM EDT | Severe Thunderstorm Watch | SPC | Anson, Bladen, Cumberland, Harnett, Hoke, Lee and 7 more | 3 hr |
| May 4, 2:06 AM EDT | Mesoscale Discussion | SPC | Benton, Carroll, Chester, Crockett, Decatur, Dyer and 20 more | 114 min |
| May 4, 2:17 AM EDT | Mesoscale Discussion | SPC | Clay, Cumberland, Fentress, Jackson, Macon, Overton and 3 more | 118 min |
| May 4, 2:41 AM EDT | Severe Thunderstorm Watch | SPC | Benton, Carroll, Chester, Crockett, Decatur, Dickson and 24 more | 6 hr |
| May 4, 5:17 AM EDT | Mesoscale Discussion | SPC | Bedford, Benton, Cannon, Carroll, Cheatham, Chester and 45 more | 88 min |
| May 4, 6:13 AM EDT | Severe Thunderstorm Watch | SPC | Bedford, Bledsoe, Cannon, Cheatham, Clay, Coffee and 32 more | 5 hr |
| May 4, 8:31 AM EDT | Mesoscale Discussion | SPC | Anderson, Bedford, Bledsoe, Bradley, Campbell, Cannon and 33 more | 89 min |
| May 4, 12:58 PM EDT | Mesoscale Discussion | SPC | Fayette, Hardeman, McNairy, Shelby | 2 hr |
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.