Alert archive / Tennessee / Mesoscale Discussions in 2021
Mesoscale Discussion 140
The Storm Prediction Center issued this mesoscale discussion at Feb 28, 2021, 6:27 PM CST for 18 counties in Arkansas; 13 counties in Mississippi; 35 counties in Tennessee. It was in force for 93 min.
The area
The outline as issued.
The facts
- Issued
- Feb 28, 2021, 6:27 PM CST (00:27 UTC)
- Expired
- Feb 28, 2021, 8:00 PM CST
- In force
- 93 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 13
All 66 counties
Arkansas County, AR, Bradley County, AR, Calhoun County, AR, Clark County, AR, Cleveland County, AR, Crittenden County, AR, Dallas County, AR, Desha County, AR, Drew County, AR, Grant County, AR, Jefferson County, AR, Lee County, AR, Lincoln County, AR, Monroe County, AR, Ouachita County, AR, Phillips County, AR, Prairie County, AR, St. Francis County, AR, Alcorn County, MS, Benton County, MS, Bolivar County, MS, Coahoma County, MS, DeSoto County, MS, Lafayette County, MS, Marshall County, MS, Panola County, MS, Quitman County, MS, Tate County, MS, Tippah County, MS, Tunica County, MS, Union County, MS, 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, Lawrence County, TN, Lewis County, TN, Madison County, TN, Marshall County, TN, Maury County, TN, McNairy County, TN, Montgomery County, TN, Perry County, TN, Robertson County, TN, Rutherford County, TN, Shelby County, TN, Stewart County, TN, Sumner County, TN, Tipton County, TN, Wayne County, TN, Williamson County, TN, Wilson County, TN
The radar
The Memphis radar (KNQA), 41 km from the middle of the area, began a volume at 00:26 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
Little Rock, AR (KLZK), launched 00:00Z, 0.5 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
- 229 J/kg
- Mixed-layer CIN
- -269 J/kg
- Mixed-layer LCL
- 782 m above ground
- 0-6 km bulk shear
- 68 kt
- 0-1 km storm-relative helicity
- -399 m²/s²
- 0-3 km storm-relative helicity
- -284 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -1.4
The text
As transmitted.
153
ACUS11 KWNS 010027
SWOMCD
SPC MCD 010027
KYZ000-TNZ000-ALZ000-MSZ000-ARZ000-010200-
Mesoscale Discussion 0140
NWS Storm Prediction Center Norman OK
0627 PM CST Sun Feb 28 2021
Areas affected...Eastern Arkansas through northern Mississippi and
into Middle Tennessee
Concerning...Tornado Watch 13...
Valid 010027Z - 010200Z
The severe weather threat for Tornado Watch 13 continues.
SUMMARY...A damaging wind threat will continue for a few more hours
within tornado watch 13.
DISCUSSION...Storms have struggled to produce much wind damage up to
this point. As the boundary layer cools, the favorable window for
damaging wind will diminish within a few hours. The most organized
cluster of storms is currently north of Memphis, but a sagging
outflow boundary from earlier convection continues to rush ahead of
this convection and has likely resulted in it remaining somewhat
elevated, limiting the overall threat. Some threat will remain,
especially south of this outflow boundary, where storms will likely
be more surface based and have a better chance of producing damaging
winds.
Another area of favorable conditions exists in north-central
Tennessee. A supercell, west of Nashville has exhibited consistent
low to mid-level rotation for the last 30 minutes or so. This cell
will likely be undercut by the southward moving cold front within
the next 30 minutes, but additional convection to the southwest, and
more discrete cells trying to develop may pose a threat for damaging
wind or a tornado or two in the next 1 to 2 hours. The 00Z BNA RAOB
shows MLCAPE around 700 J/kg with effective SRH around 270 m2/s2
showing the environment is currently supportive for damaging winds
and a tornado or two. However, as the boundary layer cools,
inhibition is expected to increase in the next 1 to 2 hours and
mitigate the overall threat.
..Bentley.. 03/01/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LMK...OHX...HUN...PAH...MEG...JAN...LZK...SHV...
LAT...LON 34009333 35169088 36488810 36678713 36688642 36628624
35678627 35318692 33709086 33409193 33449313 34009333SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Feb 28, 9:01 PM CST | Mesoscale Discussion | SPC | Columbia, Hempstead, Lafayette, Miller, Nevada, Union | 89 min |
| Feb 28, 8:49 PM CST | Mesoscale Discussion | SPC | Alcorn, Benton, Prentiss, Tippah, Tishomingo, Union | 56 min |
| Feb 28, 7:11 PM CST | Severe Thunderstorm Watch | SPC | Bedford, Cannon, Clay, Coffee, Cumberland, DeKalb and 14 more | 3 hr |
| 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
Mesoscale Discussions in Tennessee, 2021Mesoscale Discussions in Arkansas, 2021Mesoscale Discussions in Mississippi, 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.