Alert archive / Tennessee / Mesoscale Discussions in 2018
Mesoscale Discussion 813
The Storm Prediction Center issued this mesoscale discussion at Jun 21, 2018, 3:56 PM CDT for 6 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 21, 2018, 3:56 PM CDT (20:56 UTC)
- Expired
- Jun 21, 2018, 6:00 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
All 69 counties
Clay County, AR, Craighead County, AR, Crittenden County, AR, Cross County, AR, Greene County, AR, Lee County, AR, Mississippi County, AR, Poinsett County, AR, St. Francis County, AR, Alexander County, IL, Hardin County, IL, Johnson County, IL, Massac County, IL, Pope County, IL, Pulaski County, IL, Union County, IL, Ballard County, KY, Caldwell County, KY, Calloway County, KY, Carlisle County, KY, Crittenden County, KY, Fulton County, KY, Graves County, KY, Hickman County, KY, Livingston County, KY, Lyon County, KY, Marshall County, KY, McCracken County, KY, Trigg County, KY, Dunklin County, MO, Mississippi County, MO, New Madrid County, MO, Pemiscot County, MO, Scott County, MO, Stoddard County, MO, Alcorn County, MS, Benton County, MS, DeSoto County, MS, Marshall County, MS, Prentiss County, MS, Tate County, MS, Tippah County, MS, Tishomingo County, MS, Tunica County, MS, Union County, MS, 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, Humphreys County, TN, Lake County, TN, Lauderdale County, TN, Madison County, TN, McNairy County, TN, Obion County, TN, Perry County, TN, Shelby County, TN, Stewart County, TN, Tipton County, TN, Weakley County, TN
The radar
The Memphis radar (KNQA), 48 km from the middle of the area, began a volume at 20:58 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 (KBYH), launched 12:00Z, 8.9 hours before the alert went out and 94 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
- 399 J/kg
- Mixed-layer CIN
- -64 J/kg
- Mixed-layer LCL
- 736 m above ground
- 0-6 km bulk shear
- 27 kt
- 0-1 km storm-relative helicity
- 79 m²/s²
- 0-3 km storm-relative helicity
- 64 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 0.8
The text
As transmitted.
451
ACUS11 KWNS 212057
SWOMCD
SPC MCD 212056
ALZ000-KYZ000-TNZ000-ILZ000-MSZ000-MOZ000-ARZ000-212300-
Mesoscale Discussion 0813
NWS Storm Prediction Center Norman OK
0356 PM CDT Thu Jun 21 2018
Areas affected...Extreme southern IL...southeast MO...extreme
western KY...western TN...extreme northern MS...and northeast AR
Concerning...Severe Thunderstorm Watch 196...
Valid 212056Z - 212300Z
The severe weather threat for Severe Thunderstorm Watch 196
continues.
SUMMARY...The threat for damaging winds and hail as the primary
severe weather risks persists across WW 196 late this afternoon into
the early evening.
DISCUSSION...Trends in radar imagery indicated a new supercell was
tracking across far northeast AR, while a broken band of storms
extended through the MO Bootheel into southern IL along the cold
front. The environment in vicinity and downstream of these storms
remains very moist and moderately unstable, supportive for
additional sustained updrafts as forcing for ascent spreads east
with the front and within the exit region of a 50-60 kt 500-mb jet.
These winds are also resulting in strengthening bulk shear to
support storm organization for a continued severe threat.
Meanwhile, counties in the wake of the cold front passage can be
canceled early from the watch as the environment stabilizes with the
arrival of lower dew points.
..Peters.. 06/21/2018
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OHX...HUN...PAH...MEG...LZK...
LAT...LON 34789115 35689110 37718928 37668807 36628765 35038795
34478824 34318902 34459050 34789115SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 21, 12:31 PM CDT | Mesoscale Discussion | SPC | Clay, Craighead, Crittenden, Cross, Greene, Lee and 3 more | 2 hr |
| Jun 21, 1:39 PM CDT | Severe Thunderstorm Watch | SPC | Clay, Craighead, Crittenden, Cross, Greene, Lawrence and 5 more | 7 hr |
| Jun 21, 1:53 PM CDT | Mesoscale Discussion | SPC | Henry, Knox, Marshall, Peoria, Rock Island, Stark and 2 more | 3 hr |
| Jun 21, 5:44 PM CDT | Mesoscale Discussion | SPC | Massac | 2 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.