Alert archive / Tennessee / Mesoscale Discussions in 2021
Mesoscale Discussion 1866
The Storm Prediction Center issued this mesoscale discussion at Oct 15, 2021, 2:52 PM CDT for 5 states. It was in force for 113 min.
The area
The outline as issued.
The facts
- Issued
- Oct 15, 2021, 2:52 PM CDT (19:52 UTC)
- Expired
- Oct 15, 2021, 4:45 PM CDT
- In force
- 113 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 527
All 64 counties
Arkansas County, AR, Clark County, AR, Craighead County, AR, Crittenden County, AR, Cross County, AR, Dallas County, AR, Faulkner County, AR, Garland County, AR, Grant County, AR, Greene County, AR, Hot Spring County, AR, Independence County, AR, Jackson County, AR, Jefferson County, AR, Lee County, AR, Lonoke County, AR, Mississippi County, AR, Monroe County, AR, Poinsett County, AR, Prairie County, AR, Pulaski County, AR, Saline County, AR, St. Francis County, AR, White County, AR, Woodruff County, AR, Caldwell County, KY, Calloway County, KY, Christian County, KY, Fulton County, KY, Graves County, KY, Hickman County, KY, Lyon County, KY, Marshall County, KY, Trigg County, KY, Dunklin County, MO, Pemiscot County, MO, DeSoto County, MS, Tunica County, MS, Benton County, TN, Carroll County, TN, Chester County, TN, Crockett County, TN, Decatur County, TN, Dickson County, TN, Dyer County, TN, Fayette County, TN, Gibson County, TN, Hardeman County, TN, Haywood County, TN, Henderson County, TN, Henry County, TN, Hickman County, TN, Houston County, TN, Humphreys County, TN, Lake County, TN, Lauderdale County, TN, Madison County, TN, Montgomery 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), 38 km from the middle of the area, began a volume at 19:53 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
Little Rock, AR (KLZK), launched 12:00Z, 7.9 hours before the alert went out and 96 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
- 567 J/kg
- Mixed-layer CIN
- -16 J/kg
- Mixed-layer LCL
- 671 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- 69 m²/s²
- 0-3 km storm-relative helicity
- 55 m²/s²
- Significant tornado parameter
- 0.2
- Supercell composite
- 1.5
The text
As transmitted.
685
ACUS11 KWNS 151953
SWOMCD
SPC MCD 151952
TNZ000-KYZ000-MOZ000-MSZ000-ARZ000-152145-
Mesoscale Discussion 1866
NWS Storm Prediction Center Norman OK
0252 PM CDT Fri Oct 15 2021
Areas affected...Arkansas into western Kentucky and Tennessee
Concerning...Severe Thunderstorm Watch 527...
Valid 151952Z - 152145Z
The severe weather threat for Severe Thunderstorm Watch 527
continues.
SUMMARY...Scattered damaging gusts and brief periods of hail remain
possible. The threat may eventually spread east of WW 527 and
farther into Kentucky/Tennessee.
DISCUSSION...Several strong to occasionally severe storms have
formed along the front in central AR, beneath strong, front-parallel
deep shear. Gradual destabilization has taken place with heating
ahead of the front, with MLCAPE around 1500 J/kg common at 20Z.
Other storms were also evident over western KY and TN where theta-e
continues to increase with southwest surface winds.
Low-level shear remains weak, resulting in long, straight
hodographs. The primary result should be forward-tilted storms with
straight-line wind potential, as well as marginally severe hail.
However, later this evening, 850 mb flow is forecast to increase
ahead of the front into parts of TN and KY, and a brief tornado may
become more likely at that time, dependent on an unstable boundary
layer. As such, additional watches could become necessary downstream
of WW 527 later today.
..Jewell.. 10/15/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...OHX...PAH...MEG...LZK...SHV...
LAT...LON 37108810 37248765 37078733 36728718 36128712 35778727
35368822 33749288 33839327 34139345 34529337 34999282
35929132 37108810SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 15, 4:12 AM CDT | Mesoscale Discussion | SPC | Crawford, Franklin, Johnson, Madison, Newton, Washington | 93 min |
| Oct 15, 11:14 AM CDT | Mesoscale Discussion | SPC | Arkansas, Clay, Craighead, Crittenden, Cross, Faulkner and 16 more | 3 hr |
| Oct 15, 12:28 PM CDT | Severe Thunderstorm Watch | SPC | Arkansas, Clark, Clay, Cleburne, Cleveland, Conway and 33 more | 9 hr |
| Oct 15, 5:06 PM CDT | Mesoscale Discussion | SPC | Alcorn, Benton, DeSoto, Lafayette, Marshall, Panola and 5 more | 114 min |
| Oct 15, 6:05 PM CDT | Severe Thunderstorm Watch | SPC | Alcorn, Benton, Coahoma, Itawamba, Lafayette, Lee and 9 more | 4 hr |
Nearby
Mesoscale Discussions in Tennessee, 2021Mesoscale Discussions in Arkansas, 2021Mesoscale Discussions in Kentucky, 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.