Alert archive / Tennessee / Mesoscale Discussions in 2021
Mesoscale Discussion 263
The Storm Prediction Center issued this mesoscale discussion at Mar 25, 2021, 5:52 PM CDT for 29 counties in Kentucky; 30 counties in Tennessee. It was in force for 83 min.
The area
The outline as issued.
The facts
- Issued
- Mar 25, 2021, 5:52 PM CDT (22:52 UTC)
- Expired
- Mar 25, 2021, 7:15 PM CDT
- In force
- 83 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 51
All 59 counties
Allen County, KY, Barren County, KY, Breckinridge County, KY, Butler County, KY, Caldwell County, KY, Calloway County, KY, Christian County, KY, Crittenden County, KY, Daviess County, KY, Edmonson County, KY, Graves County, KY, Grayson County, KY, Hardin County, KY, Hart County, KY, Hopkins County, KY, Larue County, KY, Livingston County, KY, Logan County, KY, Lyon County, KY, Marshall County, KY, McLean County, KY, Muhlenberg County, KY, Ohio County, KY, Simpson County, KY, Todd County, KY, Trigg County, KY, Union County, KY, Warren County, KY, Webster County, KY, Benton County, TN, Carroll County, TN, Cheatham County, TN, Chester County, TN, Crockett County, TN, Davidson County, TN, Decatur County, TN, Dickson County, TN, Fayette County, TN, Gibson County, TN, Hardeman County, TN, Hardin County, TN, Haywood County, TN, Henderson County, TN, Henry County, TN, Hickman County, TN, Houston County, TN, Humphreys County, TN, Lewis County, TN, Madison County, TN, Maury County, TN, McNairy County, TN, Montgomery County, TN, Perry County, TN, Robertson County, TN, Stewart County, TN, Sumner County, TN, Wayne County, TN, Weakley County, TN, Williamson County, TN
The radar
The Ft Campbell radar (KHPX), 76 km from the middle of the area, began a volume at 22:55 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.
The watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Nashville Metro, TN (KBNA), launched 12:00Z, 10.9 hours before the alert went out and 124 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
- 60 J/kg
- Mixed-layer CIN
- -88 J/kg
- Mixed-layer LCL
- 753 m above ground
- 0-6 km bulk shear
- 57 kt
- 0-1 km storm-relative helicity
- 168 m²/s²
- 0-3 km storm-relative helicity
- 113 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
647
ACUS11 KWNS 252253
SWOMCD
SPC MCD 252252
KYZ000-TNZ000-ALZ000-ILZ000-MSZ000-260015-
Mesoscale Discussion 0263
NWS Storm Prediction Center Norman OK
0552 PM CDT Thu Mar 25 2021
Areas affected...Western/central KY...Western/middle TN...Far
northern MS
Concerning...Tornado Watch 51...
Valid 252252Z - 260015Z
The severe weather threat for Tornado Watch 51 continues.
SUMMARY...An increase in the severe threat is possible this evening,
with all hazards possible.
DISCUSSION...Convection has increased in coverage and intensity over
the last hour from far northern MS into western/middle TN and
western/central KY, in advance of a powerful midlevel shortwave
trough over MO and a deepening surface low moving into southern IL.
MLCAPE across the region ranges from around 500 J/kg in the cooler
airmass across KY to over 1000 J/kg into TN/northern MS. Very strong
effective shear in excess of 60 kt (noted in objective mesoanalyses
and the 21Z OHX sounding) will support the potential for organized
storm structures, including the potential for bowing segments
capable of damaging wind gusts, and supercells capable of hail
(especially with any left-moving cells) and perhaps a couple of
tornadoes.
The coverage of the severe threat remains uncertain across this
region, as the strong shear and very dry midlevel air moving in from
the west may cause convection to struggle in an environment where
buoyancy is relatively limited. However, any sustained convection
within this environment will pose a severe threat through the
evening.
..Dean.. 03/25/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LMK...OHX...HUN...PAH...MEG...
LAT...LON 34978961 36438900 37328843 37668796 37748734 37778665
37828589 37408554 35448682 35008819 34858901 34858942
34978961SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 25, 2:33 PM CDT | Mesoscale Discussion | SPC | Ballard, Caldwell, Calloway, Carlisle, Christian, Crittenden and 17 more | 117 min |
| Mar 25, 3:48 PM CDT | Tornado Watch | SPC | Allen, Ballard, Barren, Breckinridge, Bullitt, Butler and 36 more | 7 hr |
| Mar 25, 9:02 AM CDT | Mesoscale Discussion | SPC | Franklin, Giles, Lawrence, Lincoln, Marion, Moore and 1 more | 118 min |
| Mar 25, 10:12 AM CDT | Mesoscale Discussion | SPC | Franklin, Giles, Lincoln, Marion, Moore | 3 hr |
| Mar 25, 11:26 AM CDT | Tornado Watch | SPC | Franklin, Giles, Lawrence, Lincoln, Moore, Wayne | 9 hr |
| Mar 25, 2:29 PM CDT | Mesoscale Discussion | SPC | Bedford, Benton, Cannon, Cheatham, Chester, Davidson and 16 more | 2 hr |
| Mar 25, 4:31 PM CDT | Mesoscale Discussion | SPC | Bledsoe, Blount, Bradley, Hamilton, Loudon, McMinn and 5 more | 119 min |
Nearby
Mesoscale Discussions in Tennessee, 2021Mesoscale Discussions in Kentucky, 2021Every mesoscale discussion 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.