Alert archive / Tennessee / Mesoscale Discussions in 2018
Mesoscale Discussion 1113
The Storm Prediction Center issued this mesoscale discussion at Jul 21, 2018, 1:38 AM CDT for 8 states. It was in force for 67 min.
The area
The outline as issued.
The facts
- Issued
- Jul 21, 2018, 1:38 AM CDT (06:38 UTC)
- Expired
- Jul 21, 2018, 2:45 AM CDT
- In force
- 67 min
- Issued by
- the Storm Prediction Center
All 148 counties
Blount County, AL, Colbert County, AL, Cullman County, AL, DeKalb County, AL, Etowah 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, Marshall County, AL, Morgan County, AL, Winston County, AL, Crittenden County, AR, Lee County, AR, Mississippi County, AR, Phillips County, AR, Bartow County, GA, Catoosa County, GA, Chattooga County, GA, Dade County, GA, Fannin County, GA, Floyd County, GA, Gilmer County, GA, Gordon County, GA, Murray County, GA, Pickens County, GA, Walker County, GA, Whitfield County, GA, Allen County, KY, Barren County, KY, Calloway County, KY, Christian County, KY, Clinton County, KY, Cumberland County, KY, Logan County, KY, Monroe County, KY, Simpson County, KY, Todd County, KY, Trigg County, KY, Warren County, KY, Pemiscot County, MO, Alcorn County, MS, Benton County, MS, Calhoun County, MS, Chickasaw County, MS, Coahoma County, MS, DeSoto County, MS, Itawamba County, MS, Lafayette County, MS, Lee County, MS, Marshall County, MS, Monroe County, MS, Panola County, MS, Pontotoc County, MS, Prentiss County, MS, Quitman County, MS, Tallahatchie County, MS, Tate County, MS, Tippah County, MS, Tishomingo County, MS, Tunica County, MS, Union County, MS, Yalobusha County, MS, Cherokee County, NC, Anderson County, TN, Bedford County, TN, Benton County, TN, Bledsoe County, TN, Blount County, TN, Bradley County, TN, Campbell 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, Hamilton 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, Knox County, TN, Lake County, TN, Lauderdale County, TN, Lawrence County, TN, Lewis County, TN, Lincoln County, TN, Loudon County, TN, Macon County, TN, Madison County, TN, Marion County, TN, Marshall County, TN, Maury County, TN, McMinn County, TN, McNairy County, TN, Meigs County, TN, Monroe County, TN, Montgomery County, TN, Moore County, TN, Morgan County, TN, Obion County, TN, Overton County, TN, Perry County, TN, Pickett County, TN, Polk County, TN, Putnam County, TN, Rhea County, TN, Roane County, TN, Robertson County, TN, Rutherford County, TN, Scott 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 Nashville radar (KOHX), 145 km from the middle of the area, began a volume at 06:41 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 00:00Z, 6.6 hours before the alert went out and 133 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
- 3305 J/kg
- Mixed-layer CIN
- -1 J/kg
- Mixed-layer LCL
- 1217 m above ground
- 0-6 km bulk shear
- 53 kt
- 0-1 km storm-relative helicity
- 90 m²/s²
- 0-3 km storm-relative helicity
- 169 m²/s²
- Significant tornado parameter
- 2.2
- Supercell composite
- 11.6
The text
As transmitted.
518
ACUS11 KWNS 210638
SWOMCD
SPC MCD 210638
NCZ000-TNZ000-GAZ000-KYZ000-ALZ000-MSZ000-MOZ000-ARZ000-210745-
Mesoscale Discussion 1113
NWS Storm Prediction Center Norman OK
0138 AM CDT Sat Jul 21 2018
Areas affected...TN...far northeast AR...northern MS...northern
AL...and northern GA
Concerning...Tornado Watch 294...295...
Valid 210638Z - 210745Z
The severe weather threat for Tornado Watch 294, 295 continues.
SUMMARY...New WWs will be coordinated with WFOs across Tennessee,
northeast AR, northern Mississippi, northern Alabama and northern
Georgia to replace Tornado Watches 294 and 295.
DISCUSSION...A reservoir of very strong instability remains in place
across western into middle TN to part of northern MS and northern AL
with MUCAPE exceeding 3500 J/kg. Area VWP data per WSR-88Ds
indicated 30-kt west-southwesterly low-level winds extended from
Memphis to middle TN providing low-level ascent atop an
outflow-reinforced baroclinic zone, which extended from southern KY
to northern GA. Thunderstorms will continue to develop along and
east of this boundary through the overnight with the available
CAPE/shear parameter space favoring a continued severe-weather
threat. Large hail and damaging winds will be the primary threat,
as the exit region of a 60-65-kt northwesterly 500-mb jet spreads
southeast into the Mid-South, Tennessee Valley, and toward the
southern Appalachians overnight. Low-level SRH will remain
sufficient to not rule out a tornado.
..Peters/Edwards.. 07/21/2018
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GSP...MRX...JKL...FFC...LMK...OHX...BMX...HUN...
PAH...MEG...JAN...LZK...
LAT...LON 36288998 37228654 36758517 36408394 35118386 34308441
33968658 33678862 33979082 34239113 35229061 36288998SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jul 20, 10:20 PM CDT | Mesoscale Discussion | SPC | Colbert, Franklin, Lauderdale, Lawrence, Limestone, Madison and 1 more | 115 min |
| Jul 21, 2:00 AM CDT | Severe Thunderstorm Watch | SPC | Blount, Calhoun, Chambers, Cherokee, Clay, Cleburne and 10 more | 7 hr |
| Jul 21, 4:35 AM CDT | Mesoscale Discussion | SPC | Calhoun, Chambers, Cherokee, Clay, Cleburne, DeKalb and 6 more | 115 min |
| Jul 21, 7:10 AM CDT | Mesoscale Discussion | SPC | Calhoun, Chambers, Cherokee, Clay, Cleburne, Etowah and 8 more | 2 hr |
| Jul 21, 10:12 AM CDT | Severe Thunderstorm Watch | SPC | Henry, Houston | 5 hr |
| Jul 21, 2:37 PM CDT | Mesoscale Discussion | SPC | Cherokee, Cleburne, DeKalb, Randolph | 2 hr |
| Jul 21, 4:42 PM CDT | Severe Thunderstorm Watch | SPC | Barbour, Bullock, Calhoun, Chambers, Cherokee, Clay and 9 more | 8 hr |
| Jul 21, 6:24 PM CDT | Mesoscale Discussion | SPC | Bullock, Calhoun, Chambers, Cherokee, Clay, Cleburne and 6 more | 96 min |
| Jul 21, 6:50 PM CDT | Severe Thunderstorm Watch | SPC | Henry, Houston | 5 hr |
| Jul 20, 9:08 PM CDT | Severe Thunderstorm Watch | SPC | Arkansas, Ashley, Baxter, Boone, Bradley, Calhoun and 32 more | 5 hr |
| Jul 20, 9:26 PM CDT | Mesoscale Discussion | SPC | Benton | 94 min |
| Jul 21, 2:33 AM CDT | Severe Thunderstorm Watch | SPC | Arkansas, Ashley, Benton, Bradley, Calhoun, Chicot and 37 more | 4 hr |
| Jul 21, 3:41 AM CDT | Mesoscale Discussion | SPC | Arkansas, Ashley, Benton, Bradley, Calhoun, Chicot and 38 more | 2 hr |
| Jul 20, 7:02 PM CDT | Tornado Watch | SPC | Catoosa, Dade, Murray, Walker, Whitfield | 7 hr |
| Jul 21, 9:30 AM CDT | Mesoscale Discussion | SPC | Atkinson, Baker, Berrien, Brooks, Clinch, Coffee and 14 more | 90 min |
| Jul 20, 9:52 PM CDT | Mesoscale Discussion | SPC | Bell, Clinton, Harlan, Knox, McCreary, Wayne and 1 more | 53 min |
| Jul 21, 6:16 AM CDT | Mesoscale Discussion | SPC | Attala, Carroll, Choctaw, Grenada, Holmes, Humphreys and 9 more | 119 min |
Nearby
Mesoscale Discussions in Tennessee, 2018Mesoscale Discussions in Mississippi, 2018Mesoscale Discussions in Alabama, 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.