Alert archive / Tennessee / Mesoscale Discussions in 2021
Mesoscale Discussion 516
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 1:06 AM CDT for 6 states. It was in force for 114 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 1:06 AM CDT (06:06 UTC)
- Expired
- May 4, 2021, 3:00 AM CDT
- In force
- 114 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 95%
All 86 counties
Clay County, AR, Craighead County, AR, Crittenden County, AR, Cross County, AR, Greene County, AR, Jackson County, AR, Lawrence County, AR, Mississippi County, AR, Poinsett County, AR, St. Francis County, AR, Woodruff County, AR, Alexander County, IL, Franklin County, IL, Gallatin County, IL, Hamilton County, IL, Hardin County, IL, Jackson County, IL, Johnson County, IL, Massac County, IL, Pope County, IL, Pulaski County, IL, Saline County, IL, Union County, IL, White County, IL, Williamson County, IL, Posey County, IN, Vanderburgh County, IN, Warrick County, IN, Ballard County, KY, Caldwell County, KY, Calloway County, KY, Carlisle County, KY, Christian County, KY, Crittenden County, KY, Fulton County, KY, Graves County, KY, Henderson County, KY, Hickman County, KY, Hopkins County, KY, Livingston County, KY, Lyon County, KY, Marshall County, KY, McCracken County, KY, McLean County, KY, Trigg County, KY, Union County, KY, Webster County, KY, Bollinger County, MO, Butler County, MO, Cape Girardeau County, MO, Dunklin County, MO, Madison County, MO, Mississippi County, MO, New Madrid County, MO, Pemiscot County, MO, Perry County, MO, Ripley County, MO, Scott County, MO, Stoddard County, MO, Wayne County, MO, Benton County, TN, Carroll County, TN, Chester County, TN, Crockett County, TN, Decatur County, TN, Dyer County, TN, Fayette County, TN, Gibson County, TN, Hardeman County, TN, Hardin County, TN, Haywood County, TN, Henderson County, TN, Henry County, TN, Houston County, TN, Humphreys County, TN, Lake County, TN, Lauderdale County, TN, Madison County, TN, McNairy County, TN, Montgomery County, TN, Obion County, TN, Perry County, TN, Shelby County, TN, Stewart County, TN, Tipton County, TN, Weakley County, TN
The radar
The Paducah radar (KPAH), 73 km from the middle of the area, began a volume at 06:07 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, 6.1 hours before the alert went out and 204 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
- 3608 J/kg
- Mixed-layer CIN
- -3 J/kg
- Mixed-layer LCL
- 1081 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 36 m²/s²
- 0-3 km storm-relative helicity
- 199 m²/s²
- Significant tornado parameter
- 2.3
- Supercell composite
- 15.3
The text
As transmitted.
263
ACUS11 KWNS 040606
SWOMCD
SPC MCD 040606
KYZ000-INZ000-TNZ000-ILZ000-MSZ000-MOZ000-ARZ000-040800-
Mesoscale Discussion 0516
NWS Storm Prediction Center Norman OK
0106 AM CDT Tue May 04 2021
Areas affected...southeastern Missouri...southern
Illinois...southwestern Indiana...eastern Arkansas...western
Tennessee
Concerning...Severe potential...Watch likely
Valid 040606Z - 040800Z
Probability of Watch Issuance...95 percent
SUMMARY...Severe risk will gradually increase across Mid Mississippi
and lower Ohio Valleys, as convection expands/spreads eastward. A
WW will be required.
DISCUSSION...Latest radar loop shows a large MCS -- comprised of a
well-organized bowing band of storms moving eastward across northern
and central Arkansas, and several smaller clusters of intense
convection to the southwest.
Ahead of the convection, a very unstable airmass -- characterized by
mixed-layer CAPE in excess of 2500 J/kg -- exists, in advance of the
cold front crossing Missouri/Oklahoma/eastern Texas at this time.
As this front -- and the associated upper trough crossing
Kansas/Oklahoma/Texas -- progress, risk for damaging winds and hail
will spread across the Mid Mississippi Valley area, with convective
intensity aided by stronger flow spreading across the region ahead
of the upper system. With the Arkansas bowing segment nearing
northeastern portions of WW 137, a new watch -- across the lower
Ohio Valley area and adjacent portions of the Mid Mississippi Valley
-- will be needed within the next hour.
..Goss/Guyer.. 05/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LMK...OHX...PAH...MEG...LSX...LZK...
LAT...LON 37109069 37639053 38248865 38268724 37498709 35328772
34898898 34949019 34969162 37109069SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 3, 8:38 PM CDT | Mesoscale Discussion | SPC | Arkansas, Baxter, Boone, Calhoun, Carroll, Clark and 60 more | 2 hr |
| May 3, 9:10 PM CDT | Severe Thunderstorm Watch | SPC | Baxter, Benton, Boone, Calhoun, Carroll, Clark and 50 more | 7 hr |
| May 3, 10:22 PM CDT | Mesoscale Discussion | SPC | Boone, Crawford, Franklin, Johnson, Madison, Marion and 2 more | 83 min |
| May 3, 11:34 PM CDT | Mesoscale Discussion | SPC | Baxter, Boone, Carroll, Clark, Cleburne, Conway and 27 more | 86 min |
| May 4, 1:41 AM CDT | Severe Thunderstorm Watch | SPC | Clay, Craighead, Crittenden, Cross, Greene, Mississippi and 2 more | 6 hr |
| May 4, 2:02 AM CDT | Mesoscale Discussion | SPC | Clay, Conway, Craighead, Cross, Faulkner, Garland and 16 more | 88 min |
| May 4, 4:17 AM CDT | Mesoscale Discussion | SPC | Crittenden | 88 min |
| May 4, 6:44 AM CDT | Mesoscale Discussion | SPC | Bradley, Calhoun, Clark, Cleveland, Columbia, Dallas and 8 more | 2 hr |
| May 4, 10:52 AM CDT | Tornado Watch | SPC | Ashley, Bradley, Calhoun, Chicot, Columbia, Desha and 2 more | 7 hr |
| May 4, 11:58 AM CDT | Mesoscale Discussion | SPC | Crittenden, Lee, Phillips | 2 hr |
| May 4, 12:18 PM CDT | Severe Thunderstorm Watch | SPC | Phillips | 5 hr |
| May 4, 1:59 PM CDT | Mesoscale Discussion | SPC | Cleburne, Conway, Craighead, Cross, Faulkner, Greene and 17 more | 2 hr |
| May 3, 7:58 PM CDT | Severe Thunderstorm Watch | SPC | Clark, Clay, Crawford, Cumberland, Effingham, Jasper and 2 more | 3 hr |
| May 4, 1:17 AM CDT | Mesoscale Discussion | SPC | Adair, Allen, Barren, Butler, Christian, Clinton and 19 more | 118 min |
| May 4, 5:13 AM CDT | Severe Thunderstorm Watch | SPC | Adair, Allen, Barren, Butler, Clinton, Cumberland and 11 more | 5 hr |
| May 4, 7:31 AM CDT | Mesoscale Discussion | SPC | Anderson, Bedford, Bledsoe, Bradley, Campbell, Cannon and 33 more | 89 min |
| May 4, 8:37 AM CDT | Severe Thunderstorm Watch | SPC | Anderson, Blount, Bradley, Jefferson, Knox, Loudon and 7 more | 3 hr |
Nearby
Mesoscale Discussions in Tennessee, 2021Mesoscale Discussions in Kentucky, 2021Mesoscale Discussions in Illinois, 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.