Alert archive / Tennessee / Mesoscale Discussions in 2018

Mesoscale Discussion 1108

July 20, 20186 states

The Storm Prediction Center issued this mesoscale discussion at Jul 20, 2018, 5:54 PM CDT for 6 states. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued
Jul 20, 2018, 5:54 PM CDT (22:54 UTC)
Expired
Jul 20, 2018, 8:30 PM CDT
In force
3 hr
Issued by
the Storm Prediction Center
Chance of a watch
95%
All 125 counties

Colbert County, AL, Cullman County, AL, DeKalb County, AL, Franklin County, AL, Jackson County, AL, Lauderdale County, AL, Lawrence County, AL, Limestone County, AL, Madison County, AL, Marion County, AL, Marshall County, AL, Morgan County, AL, Winston County, AL, Crittenden County, AR, Lee County, AR, Phillips County, AR, St. Francis County, AR, Dade County, GA, Allen County, KY, Barren County, KY, Butler County, KY, Caldwell County, KY, Calloway County, KY, Christian County, KY, Clinton County, KY, Cumberland County, KY, Edmonson County, KY, Graves County, KY, Hickman County, KY, Hopkins County, KY, Logan County, KY, Lyon County, KY, Marshall County, KY, Metcalfe County, KY, Monroe County, KY, Muhlenberg County, KY, Ohio County, KY, Simpson County, KY, Todd County, KY, Trigg County, KY, Warren County, KY, Alcorn County, MS, Benton County, MS, Chickasaw County, MS, Coahoma County, MS, DeSoto County, MS, Itawamba County, MS, Lafayette County, MS, Lee County, MS, Marshall 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, Benton County, TN, Bledsoe County, TN, Cannon County, TN, Carroll County, TN, Cheatham County, TN, Chester County, TN, Clay County, TN, Coffee County, TN, Crockett County, TN, Cumberland County, TN, Davidson County, TN, Decatur County, TN, DeKalb County, TN, Dickson County, TN, Dyer County, TN, Fayette County, TN, Fentress County, TN, Franklin County, TN, Gibson County, TN, Giles County, TN, Grundy 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, Jackson County, TN, Lauderdale County, TN, Lawrence County, TN, Lewis County, TN, Lincoln County, TN, Macon County, TN, Madison County, TN, Marion County, TN, Marshall County, TN, Maury County, TN, McNairy County, TN, Montgomery County, TN, Moore County, TN, Obion County, TN, Overton County, TN, Perry County, TN, Pickett County, TN, Putnam County, TN, Rhea County, TN, Robertson County, TN, Rutherford County, TN, Sequatchie County, TN, Shelby County, TN, Smith County, TN, Stewart County, TN, Sumner County, TN, Tipton County, TN, Trousdale County, TN, Van Buren County, TN, Warren County, TN, Wayne County, TN, Weakley County, TN, White County, TN, Williamson County, TN, Wilson County, TN

The radar

The Ft Campbell radar (KHPX), 131 km from the middle of the area, began a volume at 22:57 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 12:00Z, 10.9 hours before the alert went out and 128 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, Nashville Metro, TN at 12:00Z on 2018-07-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 918 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, Nashville Metro, TN at 12:00Z on 2018-07-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 123 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
918 J/kg
Mixed-layer CIN
-46 J/kg
Mixed-layer LCL
766 m above ground
0-6 km bulk shear
27 kt
0-1 km storm-relative helicity
123 m²/s²
0-3 km storm-relative helicity
206 m²/s²
Significant tornado parameter
0.7
Supercell composite
5.7

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 20, 6:22 PM CDTTornado WatchSPCColbert, DeKalb, Franklin, Jackson, Lauderdale, Lawrence and 4 more8 hr
Jul 19, 7:07 PM CDTSevere Thunderstorm WatchSPCBaxter, Boone, Carroll, Cleburne, Fulton, Independence and 10 more3 hr
Jul 19, 8:02 PM CDTMesoscale DiscussionSPCArkansas, Baxter, Clark, Cleburne, Cleveland, Conway and 40 more118 min
Jul 19, 8:54 PM CDTSevere Thunderstorm WatchSPCArkansas, Bradley, Calhoun, Clark, Clay, Cleveland and 35 more114 min
Jul 19, 11:21 PM CDTMesoscale DiscussionSPCChicot, Desha, Phillips114 min
Jul 20, 9:25 AM CDTMesoscale DiscussionSPCArkansas, Cleburne, Crittenden, Cross, Faulkner, Independence and 13 more2 hr
Jul 20, 12:58 PM CDTMesoscale DiscussionSPCClay62 min
Jul 20, 3:46 PM CDTMesoscale DiscussionSPCBaxter, Boone, Fulton, Izard, Marion, Randolph and 2 more59 min
Jul 20, 3:58 PM CDTSevere Thunderstorm WatchSPCBaxter, Clay, Craighead, Cross, Fulton, Greene and 8 more6 hr
Jul 20, 11:17 AM CDTMesoscale DiscussionSPCButler, Caldwell, Calloway, Christian, Crittenden, Daviess and 11 more58 min
Jul 20, 12:19 PM CDTMesoscale DiscussionSPCAdair, Anderson, Barren, Boone, Boyle, Breckinridge and 33 more56 min
Jul 20, 12:37 PM CDTTornado WatchSPCAdair, Allen, Anderson, Barren, Boone, Bourbon and 54 more7 hr
Jul 20, 2:43 PM CDTMesoscale DiscussionSPCAdair, Anderson, Bath, Boone, Bourbon, Boyle and 60 more62 min
Jul 20, 3:16 PM CDTSevere Thunderstorm WatchSPCBath, Bell, Boyd, Breathitt, Carter, Clay and 31 more6 hr
Jul 20, 5:37 PM CDTMesoscale DiscussionSPCAdair, Allen, Anderson, Barren, Boone, Bourbon and 57 more53 min
Jul 20, 6:24 PM CDTMesoscale DiscussionSPCBath, Bell, Boyd, Breathitt, Carter, Clark and 33 more96 min
Jul 20, 1:23 PM CDTMesoscale DiscussionSPCAttala, Carroll, Choctaw, Clarke, Copiah, Covington and 20 more97 min
Jul 20, 2:11 PM CDTSevere Thunderstorm WatchSPCClarke, Covington, Forrest, Hinds, Jasper, Jefferson Davis and 14 more3 hr

Nearby

Mesoscale Discussions in Tennessee, 2018Mesoscale Discussions in Kentucky, 2018Mesoscale Discussions in Mississippi, 2018Every mesoscale discussion in 2018

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.