Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 2077
The Storm Prediction Center issued this mesoscale discussion at Dec 29, 2021, 3:41 PM CST for 4 states. It was in force for 64 min.
The area
The outline as issued.
The facts
- Issued
- Dec 29, 2021, 3:41 PM CST (21:41 UTC)
- Expired
- Dec 29, 2021, 4:45 PM CST
- In force
- 64 min
- Issued by
- the Storm Prediction Center
- Concerning
- Tornado watch 569
All 41 counties
Ashley County, AR, Chicot County, AR, Desha County, AR, Drew County, AR, Morehouse Parish, LA, West Carroll Parish, LA, Alcorn County, MS, Benton County, MS, Bolivar County, MS, Calhoun County, MS, Carroll County, MS, Chickasaw County, MS, Clay County, MS, Coahoma County, MS, Grenada County, MS, Holmes County, MS, Humphreys County, MS, Itawamba County, MS, Lafayette County, MS, Lee County, MS, Leflore County, MS, Marshall County, MS, Monroe County, MS, Montgomery County, MS, Panola County, MS, Pontotoc County, MS, Prentiss County, MS, Quitman County, MS, Sharkey County, MS, Sunflower County, MS, Tallahatchie County, MS, Tate County, MS, Tippah County, MS, Tishomingo County, MS, Union County, MS, Washington County, MS, Webster County, MS, Yalobusha County, MS, Hardeman County, TN, Hardin County, TN, McNairy County, TN
The radar
The Memphis radar (KNQA), 172 km from the middle of the area, began a volume at 21:42 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 (KLZK), launched 12:00Z, 9.7 hours before the alert went out and 116 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 1900 m above ground
- 0-6 km bulk shear
- 68 kt
- 0-1 km storm-relative helicity
- 131 m²/s²
- 0-3 km storm-relative helicity
- 106 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
130
ACUS11 KWNS 292141
SWOMCD
SPC MCD 292141
ALZ000-TNZ000-MSZ000-ARZ000-LAZ000-292245-
Mesoscale Discussion 2077
NWS Storm Prediction Center Norman OK
0341 PM CST Wed Dec 29 2021
Areas affected...Parts of southeastern AR...northeastern
LA...northern MS...and southwestern TN
Concerning...Tornado Watch 569...
Valid 292141Z - 292245Z
The severe weather threat for Tornado Watch 569 continues.
SUMMARY...The severe risk continues across Tornado Watch 569. A few
tornadoes, damaging wind gusts, and large hail all remain possible
this afternoon and evening.
DISCUSSION...A southwest-northeast oriented line of broken
convection with embedded supercell structures will continue
advancing east-northeastward ahead of a frontal wave draped across
parts of the Mid-South. Ahead of the frontal wave across the open
warm sector, rich boundary-layer moisture (middle/upper 60s
dewpoints) combined with pockets of diurnal heating are supporting
500-1500 J/kg MLCAPE, where the latest mesoanalysis depicts 55-65
knots effective bulk shear. Additionally, the latest VWP data from
GWX shows 55 knot winds at 2.5 to 3 km, indicative of the
strengthening low-level jet overspreading the warm sector.
Relatively backed surface winds beneath the strengthening low-level
flow are evident across northern MS, which are contributing to
150-250 m2/s2 effective SRH ahead of the ongoing convection. While
deep-layer shear vectors and storm motion vectors are oriented
largely parallel to the frontal wave (yielding modest upscale
growth), shear vectors become oriented off the boundary with
northward extent into parts of MS. This could support more discrete
convective modes, which combined with the favorable and increasing
low-level SRH should favor an increasing risk of a few tornadoes,
damaging wind gusts, and large hail.
..Weinman/Hart.. 12/29/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...HUN...MEG...JAN...LZK...SHV...
LAT...LON 33399220 33819165 34389052 34858972 35388872 35338814
35068819 34038824 33628834 33059024 32739139 32759201
32969237 33229234 33399220SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Dec 29, 9:25 AM CST | Mesoscale Discussion | SPC | Ashley, Bradley, Calhoun, Clark, Cleveland, Columbia and 14 more | 2 hr |
| Dec 29, 10:44 AM CST | Mesoscale Discussion | SPC | Arkansas, Ashley, Chicot, Crittenden, Desha, Drew and 5 more | 2 hr |
| Dec 29, 12:05 PM CST | Tornado Watch | SPC | Arkansas, Ashley, Bradley, Calhoun, Chicot, Cleveland and 12 more | 7 hr |
| Dec 29, 1:18 PM CST | Mesoscale Discussion | SPC | Desha, Phillips | 87 min |
| Dec 29, 4:44 PM CST | Mesoscale Discussion | SPC | Clark, Columbia, Hempstead, Lafayette, Miller, Nevada and 1 more | 2 hr |
| Dec 29, 2:49 PM CST | Mesoscale Discussion | SPC | Washington | 86 min |
| Dec 29, 2:03 PM CST | Mesoscale Discussion | SPC | Adams, Claiborne, Copiah, Covington, Franklin, Hinds and 18 more | 87 min |
| Dec 29, 4:38 PM CST | Mesoscale Discussion | SPC | Calhoun, Chickasaw, Clay, Itawamba, Lee, Lowndes and 6 more | 2 hr |
| Dec 29, 2:36 PM CST | Mesoscale Discussion | SPC | Franklin, Giles, Lawrence, Lincoln, Marion, Marshall and 2 more | 2 hr |
| Dec 29, 3:53 PM CST | Tornado Watch | SPC | Franklin, Giles, Lawrence, Lincoln, Marion, Moore and 1 more | 6 hr |
Nearby
Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Arkansas, 2021Mesoscale Discussions in Tennessee, 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.