Alert archive / Tennessee / Mesoscale Discussions in 2021
Mesoscale Discussion 265
The Storm Prediction Center issued this mesoscale discussion at Mar 25, 2021, 7:36 PM CDT for 17 counties in Tennessee. It was in force for 84 min.
The area
The outline as issued.
The facts
- Issued
- Mar 25, 2021, 7:36 PM CDT (00:36 UTC)
- Expired
- Mar 25, 2021, 9:00 PM CDT
- In force
- 84 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 51
Counties Bedford County, TN, Cannon County, TN, Coffee County, TN, Davidson County, TN, DeKalb County, TN, Grundy County, TN, Lewis County, TN, Marshall County, TN, Maury County, TN, Moore County, TN, Rutherford County, TN, Smith County, TN, Sumner County, TN, Trousdale County, TN, Warren County, TN, Williamson County, TN, Wilson County, TN
The radar
The Nashville radar (KOHX), 60 km from the middle of the area, began a volume at 00:39 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 00:00Z, 0.6 hours before the alert went out and 47 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
- 290 J/kg
- Mixed-layer CIN
- -73 J/kg
- Mixed-layer LCL
- 615 m above ground
- 0-6 km bulk shear
- 85 kt
- 0-1 km storm-relative helicity
- 657 m²/s²
- 0-3 km storm-relative helicity
- 631 m²/s²
- Significant tornado parameter
- 1.0
- Supercell composite
- 7.4
The text
As transmitted.
677
ACUS11 KWNS 260037
SWOMCD
SPC MCD 260036
TNZ000-260200-
Mesoscale Discussion 0265
NWS Storm Prediction Center Norman OK
0736 PM CDT Thu Mar 25 2021
Areas affected...Middle TN
Concerning...Tornado Watch 51...
Valid 260036Z - 260200Z
The severe weather threat for Tornado Watch 51 continues.
SUMMARY...Some increase in the tornado and damaging wind threat is
possible this evening across middle Tennessee.
DISCUSSION...Some increase in storm intensity has been noted with
storms approaching middle TN this evening, with a cell showing
midlevel rotation across Wayne County as of 0030Z, and other
convection increasing near and to the southwest of Nashville. Very
strong midlevel flow/deep-layer shear will continue to support the
potential for organized storms. The tornado threat with the Wayne
County cell, and any other supercell that can evolve over the next
1-2 hours, may increase as it moves into a region where low-level
flow is less veered (compared to areas further west) and effective
helicity values are more favorable, as noted on the 00Z BNA sounding
and recent VWP data from KOHX. Otherwise, the damaging wind threat
may increase with more linear convective elements, as low/midlevel
flow continues to increase across the region through the evening.
..Dean.. 03/26/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OHX...HUN...
LAT...LON 35278788 36478666 36508617 36328575 35768557 35308574
35288676 35248746 35278788SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 25, 7:00 PM CDT | Mesoscale Discussion | SPC | Franklin, Giles, Lawrence, Lincoln, Wayne | 30 min |
| Mar 25, 7:57 PM CDT | Tornado Watch | SPC | Franklin, Giles, Lawrence, Lincoln, Moore, Wayne | 3 hr |
| Mar 25, 9:07 PM CDT | Mesoscale Discussion | SPC | Bedford, Bledsoe, Cannon, Clay, Coffee, Cumberland and 18 more | 83 min |
| Mar 25, 9:26 PM CDT | Tornado Watch | SPC | Anderson, Bledsoe, Bradley, Campbell, Cumberland, Fentress and 14 more | 2 hr |
Nearby
Mesoscale Discussions in Tennessee, 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.