Alert archive / Tennessee / Mesoscale Discussions in 2021

Mesoscale Discussion 555

May 6, 202112 counties in Alabama; 18 counties in Mississippi; 24 counties in Tennessee

The Storm Prediction Center issued this mesoscale discussion at May 6, 2021, 5:11 PM CDT for 12 counties in Alabama; 18 counties in Mississippi; 24 counties in Tennessee. It was in force for 94 min.

The area

The outline as issued.

The facts

Issued: May 6, 2021, 5:11 PM CDT (22:11 UTC)
Expired: May 6, 2021, 6:45 PM CDT
In force: 94 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

All 54 counties

Colbert County, AL, Cullman County, AL, Franklin County, AL, Jackson County, AL, Lamar County, AL, Lauderdale County, AL, Lawrence County, AL, Limestone County, AL, Madison County, AL, Marion County, AL, Morgan County, AL, Winston County, AL, Alcorn County, MS, Benton County, MS, Calhoun County, MS, Chickasaw County, MS, Itawamba County, MS, Lafayette County, MS, Lee County, MS, Monroe County, MS, Panola County, MS, Pontotoc County, MS, Prentiss County, MS, Quitman County, MS, Tate County, MS, Tippah County, MS, Tishomingo County, MS, Tunica County, MS, Union County, MS, Yalobusha County, MS, Bedford County, TN, Cannon County, TN, Cheatham County, TN, Coffee County, TN, Davidson County, TN, Franklin County, TN, Giles County, TN, Hardin County, TN, Hickman County, TN, Lawrence County, TN, Lewis County, TN, Lincoln County, TN, Macon County, TN, Marshall County, TN, Maury County, TN, Moore County, TN, Robertson County, TN, Rutherford County, TN, Smith County, TN, Sumner County, TN, Trousdale County, TN, Wayne County, TN, Williamson County, TN, Wilson County, TN

The radar

The Columbus AFB radar (KGWX), 98 km from the middle of the area, began a volume at 22:12 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 nearest sounding before it

Little Rock, AR (KLZK), launched 12:00Z, 10.2 hours before the alert went out and 157 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1745 m above ground
0-6 km bulk shear: 76 kt
0-1 km storm-relative helicity: 47 m²/s²
0-3 km storm-relative helicity: 88 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

354 
ACUS11 KWNS 062211
SWOMCD
SPC MCD 062211 
TNZ000-ALZ000-MSZ000-062345-

Mesoscale Discussion 0555
NWS Storm Prediction Center Norman OK
0511 PM CDT Thu May 06 2021

Areas affected...Northern MS/AL...Middle TN

Concerning...Severe potential...Watch unlikely 

Valid 062211Z - 062345Z

Probability of Watch Issuance...20 percent

SUMMARY...Sporadic wind damage will be possible this evening with a
weakening line of thunderstorms.

DISCUSSION...At 22Z, an arcing line of low-topped thunderstorms is
approaching portions of northern MS/AL into middle TN, in
conjunction with a compact midlevel vorticity maximum moving
southeastward into portions of the OH/TN valleys. Wind gusts of
40-45 kt have been noted with the line across western TN within the
last hour. While buoyancy is weak across the region (MUCAPE
generally 500 J/kg or less), steep low-level lapse rates within a
dry, well-mixed boundary layer continue to support the potential for
stronger wind gusts capable of producing at least isolated wind
damage. 

The already weak instability will diminish even further this
evening, with the onset of nocturnal cooling/boundary-layer
stabilization. However, given the relative strength of the midlevel
system and surface cold pool, some threat for sporadic damaging wind
gusts will continue for awhile this evening as convection gradually
weakens. At this time, the remaining threat appears too limited in
duration and magnitude for additional watch issuance.

..Dean/Hart.. 05/06/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MRX...OHX...BMX...HUN...MEG...JAN...

LAT...LON   34698986 34918869 35608767 36608686 36588594 35468575
            34758597 34208648 33798755 33708858 33738945 33998997
            34279051 34679039 34698986

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 6, 10:05 AM CDT	Mesoscale Discussion	SPC	Benton, Carroll, Chester, Crockett, Dyer, Fayette and 13 more	85 min
May 6, 12:02 PM CDT	Mesoscale Discussion	SPC	Benton, Carroll, Crockett, Dyer, Gibson, Haywood and 8 more	118 min
May 6, 12:38 PM CDT	Severe Thunderstorm Watch	SPC	Carroll, Crockett, Dyer, Fayette, Gibson, Hardeman and 9 more	5 hr
May 6, 2:45 PM CDT	Mesoscale Discussion	SPC	Crockett, Dyer, Gibson, Haywood, Lake, Lauderdale and 5 more	90 min

Nearby

Mesoscale Discussions in Tennessee, 2021 Mesoscale Discussions in Mississippi, 2021 Mesoscale Discussions in Alabama, 2021 Every 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.