Alert archive / Tennessee / Severe Thunderstorm Watches in 2021

Severe Thunderstorm Watch 15

February 28, 202120 counties in Tennessee

The Storm Prediction Center issued this severe thunderstorm watch at Feb 28, 2021, 7:11 PM CST for 20 counties in Tennessee. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Feb 28, 2021, 7:11 PM CST (01:11 UTC)
Expired: Feb 28, 2021, 10:00 PM CST
In force: 3 hr
Issued by: the Storm Prediction Center
Largest hail expected: 1 in
Strongest gust expected: 60 kt

Counties Bedford County, TN, Cannon County, TN, Clay County, TN, Coffee County, TN, Cumberland County, TN, DeKalb County, TN, Fentress County, TN, Grundy County, TN, Jackson County, TN, Macon County, TN, Overton County, TN, Pickett County, TN, Putnam County, TN, Rutherford County, TN, Smith County, TN, Trousdale County, TN, Van Buren County, TN, Warren County, TN, White County, TN, Wilson County, TN

The radar

The Nashville radar (KOHX), 66 km from the middle of the area, began a volume at 01:11 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: 10%
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
Feb 28, 7:15 PM CST	Severe Thunderstorm Warning	OHX	Macon, Robertson, Sumner, Trousdale	30 min
Feb 28, 7:26 PM CST	Flash Flood Warning	OHX	Cheatham, Davidson, Macon, Smith, Sumner, Trousdale and 2 more	4 hr
Feb 28, 7:32 PM CST	Severe Thunderstorm Warning	OHX	Cheatham, Davidson, Robertson, Sumner, Williamson, Wilson	43 min
Feb 28, 7:39 PM CST	Severe Thunderstorm Warning	OHX	Clay, Jackson, Macon	36 min
Feb 28, 8:05 PM CST	Severe Thunderstorm Warning	OHX	Smith, Sumner, Trousdale, Wilson	25 min
Feb 28, 8:16 PM CST	Flash Flood Warning	OHX	Clay, Jackson, Overton, Pickett	3 hr
Feb 28, 8:23 PM CST	Flash Flood Warning	OHX	Davidson, Maury, Rutherford, Smith, Williamson, Wilson	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

Nashville Metro, TN (KBNA), launched 00:00Z, 1.2 hours before the alert went out and 68 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 419 J/kg
Mixed-layer CIN: -8 J/kg
Mixed-layer LCL: 979 m above ground
0-6 km bulk shear: 66 kt
0-1 km storm-relative helicity: 220 m²/s²
0-3 km storm-relative helicity: 278 m²/s²
Significant tornado parameter: 0.7
Supercell composite: 4.5

Open this sounding in Storm Lab

The text

As transmitted.

022 
WWUS20 KWNS 010108
SEL5  
SPC WW 010108
KYZ000-TNZ000-010400-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 15
NWS Storm Prediction Center Norman OK
810 PM EST Sun Feb 28 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Far south-central Kentucky
  Middle Tennessee

* Effective this Sunday evening from 810 PM until 1100 PM EST.

* Primary threats include...
  Scattered damaging wind gusts to 70 mph possible
  A tornado or two possible

SUMMARY...Cluster of strong to severe storms may produce damaging
winds and a brief tornado before it weakens later this evening.

The severe thunderstorm watch area is approximately along and 40
statute miles north and south of a line from 80 miles west of
Crossville TN to 20 miles northeast of Crossville TN. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU5).

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 13...WW 14...

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
26045.

...Grams

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 28, 6:27 PM CST	Mesoscale Discussion	SPC	Benton, Carroll, Cheatham, Chester, Crockett, Davidson and 29 more	93 min
Feb 28, 7:16 PM CST	Mesoscale Discussion	SPC	Bedford, Bledsoe, Cannon, Clay, Coffee, Cumberland and 16 more	59 min
Feb 28, 8:45 PM CST	Mesoscale Discussion	SPC	Bedford, Cannon, Clay, Coffee, Cumberland, DeKalb and 14 more	90 min

Nearby

Severe Thunderstorm Watches in Tennessee, 2021 Every 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.