Alert archive / Tennessee / Mesoscale Discussions in 2021

Mesoscale Discussion 522

May 4, 20214 counties in Alabama; Dade County, Georgia; 39 counties in Tennessee

The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 7:31 AM CDT for 4 counties in Alabama; Dade County, Georgia; 39 counties in Tennessee. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued
May 4, 2021, 7:31 AM CDT (12:31 UTC)
Expired
May 4, 2021, 9:00 AM CDT
In force
89 min
Issued by
the Storm Prediction Center
Concerning
Severe thunderstorm watch 141
All 44 counties

Jackson County, AL, Lauderdale County, AL, Limestone County, AL, Madison County, AL, Dade County, GA, Anderson County, TN, Bedford County, TN, Bledsoe County, TN, Bradley County, TN, Campbell County, TN, Cannon County, TN, Clay County, TN, Coffee County, TN, Cumberland County, TN, DeKalb County, TN, Fentress County, TN, Franklin County, TN, Giles County, TN, Grundy County, TN, Hamilton County, TN, Jackson County, TN, Lincoln County, TN, Loudon County, TN, Macon County, TN, Marion County, TN, Marshall County, TN, McMinn County, TN, Meigs County, TN, Monroe County, TN, Moore County, TN, Morgan County, TN, Overton County, TN, Pickett County, TN, Putnam County, TN, Rhea County, TN, Roane County, TN, Rutherford County, TN, Scott County, TN, Sequatchie County, TN, Smith County, TN, Van Buren County, TN, Warren County, TN, White County, TN, Wilson County, TN

The radar

The Nashville radar (KOHX), 70 km from the middle of the area, began a volume at 12:35 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

Peachtre/Fal Fld, GA (KFFC), launched 12:00Z, 0.5 hours before the alert went out and 314 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-pSkew-T log-p diagram, Peachtre/Fal Fld, GA at 12:00Z on 2021-05-04Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 590 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Peachtre/Fal Fld, GA at 12:00Z on 2021-05-04The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 207 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
590 J/kg
Mixed-layer CIN
-114 J/kg
Mixed-layer LCL
753 m above ground
0-6 km bulk shear
39 kt
0-1 km storm-relative helicity
207 m²/s²
0-3 km storm-relative helicity
213 m²/s²
Significant tornado parameter
0.0
Supercell composite
2.3

Open this sounding in Storm Lab

The text

As transmitted.

136 
ACUS11 KWNS 041232
SWOMCD
SPC MCD 041231 
TNZ000-GAZ000-KYZ000-ALZ000-041400-

Mesoscale Discussion 0522
NWS Storm Prediction Center Norman OK
0731 AM CDT Tue May 04 2021

Areas affected...Middle Tennessee and adjacent northern Alabama

Concerning...Severe Thunderstorm Watch 141...

Valid 041231Z - 041400Z

The severe weather threat for Severe Thunderstorm Watch 141
continues.

SUMMARY...Severe risk is focused across northern Middle Tennessee at
this time, with downstream areas being monitored.

DISCUSSION...Latest radar loop shows an organized band of
thunderstorms -- and associated outflow -- moving eastward across
Middle Tennessee, while outflow from storms across southern Kentucky
moves southward.  The most vigorous convection is ongoing near the
intersection of these two outflow boundaries intersect -- i.e. over
northern Middle Tennessee.  An area of rotation within the broader
band of convection continues, and is now over western Jackson
county.  While a brief tornadic spin-up remains possible here, and
elsewhere along the leading edge of the convective band, potential
for locally damaging winds will continue/shift eastward across WW
141 this morning, through a favorably unstable/amply sheared
environment.

..Goss.. 05/04/2021

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

ATTN...WFO...MRX...FFC...LMK...OHX...HUN...

LAT...LON   36638594 36598565 36618506 36558386 35408420 34588588
            34808807 35388714 36058669 36318617 36638594

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 3, 7:13 PM CDTMesoscale DiscussionSPCAutauga, Bullock, Chambers, Coosa, Elmore, Lee and 4 more62 min
May 4, 5:13 AM CDTSevere Thunderstorm WatchSPCJackson, Lauderdale, Limestone, Madison5 hr
May 4, 8:33 AM CDTMesoscale DiscussionSPCChoctaw, Clarke, Dallas, Greene, Hale, Marengo and 4 more117 min
May 4, 9:03 AM CDTMesoscale DiscussionSPCBlount, Calhoun, Cherokee, Clay, Cleburne, Cullman and 20 more117 min
May 4, 9:18 AM CDTTornado WatchSPCAutauga, Bibb, Blount, Calhoun, Cherokee, Chilton and 28 more7 hr
May 4, 2:17 PM CDTMesoscale DiscussionSPCChoctaw, Greene, Marengo, Sumter88 min
May 4, 3:03 PM CDTMesoscale DiscussionSPCBibb, Blount, Calhoun, Cherokee, Chilton, Clay and 19 more117 min
May 4, 3:31 PM CDTTornado WatchSPCAutauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 20 more6 hr
May 4, 4:46 PM CDTMesoscale DiscussionSPCAutauga, Baldwin, Bibb, Butler, Chilton, Choctaw and 20 more89 min
May 4, 5:20 PM CDTMesoscale DiscussionSPCBarbour, Bullock, Chambers, Coffee, Covington, Dale and 7 more85 min
May 4, 6:10 PM CDTMesoscale DiscussionSPCAutauga, Coosa, Elmore, Lowndes, Macon, Montgomery and 1 more65 min
May 4, 6:26 PM CDTSevere Thunderstorm WatchSPCBarbour, Bullock, Chambers, Coffee, Covington, Crenshaw and 8 more6 hr
May 4, 9:48 AM CDTSevere Thunderstorm WatchSPCBanks, Barrow, Bartow, Butts, Carroll, Catoosa and 43 more6 hr
May 4, 12:21 PM CDTMesoscale DiscussionSPCBanks, Barrow, Bartow, Carroll, Cherokee, Clarke and 34 more114 min
May 4, 2:07 PM CDTMesoscale DiscussionSPCBanks, Barrow, Bartow, Butts, Carroll, Cherokee and 35 more113 min
May 4, 3:56 PM CDTSevere Thunderstorm WatchSPCBurke, Columbia, McDuffie, Richmond3 hr
May 4, 1:06 AM CDTMesoscale DiscussionSPCBenton, Carroll, Chester, Crockett, Decatur, Dyer and 20 more114 min
May 4, 1:17 AM CDTMesoscale DiscussionSPCClay, Cumberland, Fentress, Jackson, Macon, Overton and 3 more118 min
May 4, 1:41 AM CDTSevere Thunderstorm WatchSPCBenton, Carroll, Chester, Crockett, Decatur, Dickson and 24 more6 hr
May 4, 4:17 AM CDTMesoscale DiscussionSPCBedford, Benton, Cannon, Carroll, Cheatham, Chester and 45 more88 min
May 4, 8:37 AM CDTSevere Thunderstorm WatchSPCAnderson, Blount, Bradley, Jefferson, Knox, Loudon and 7 more3 hr
May 4, 11:58 AM CDTMesoscale DiscussionSPCFayette, Hardeman, McNairy, Shelby2 hr

Nearby

Mesoscale Discussions in Tennessee, 2021Mesoscale Discussions in Alabama, 2021Mesoscale Discussions in Georgia, 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.