Alert archive / Mississippi / Mesoscale Discussions in 2021
Mesoscale Discussion 330
The Storm Prediction Center issued this mesoscale discussion at Apr 7, 2021, 8:52 PM CDT for 16 parishes in Louisiana; 57 counties in Mississippi. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 7, 2021, 8:52 PM CDT (01:52 UTC)
- Expired
- Apr 7, 2021, 11:15 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 40%
All 73 counties
Acadia Parish, LA, Allen Parish, LA, Avoyelles Parish, LA, Beauregard Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Saint Helena Parish, LA, Saint Landry Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Adams County, MS, Alcorn County, MS, Amite County, MS, Attala County, MS, Benton County, MS, Calhoun County, MS, Carroll County, MS, Chickasaw County, MS, Choctaw County, MS, Claiborne County, MS, Clay County, MS, Copiah County, MS, Covington County, MS, Franklin County, MS, Grenada County, MS, Hinds County, MS, Holmes County, MS, Humphreys County, MS, Issaquena County, MS, Itawamba County, MS, Jefferson County, MS, Jefferson Davis County, MS, Lafayette County, MS, Lawrence County, MS, Leake County, MS, Lee County, MS, Leflore County, MS, Lincoln County, MS, Madison County, MS, Marshall County, MS, Monroe County, MS, Montgomery County, MS, Neshoba County, MS, Newton County, MS, Oktibbeha County, MS, Panola County, MS, Pike County, MS, Pontotoc County, MS, Prentiss County, MS, Quitman County, MS, Rankin County, MS, Scott County, MS, Sharkey County, MS, Simpson County, MS, Smith County, MS, Sunflower County, MS, Tallahatchie County, MS, Tate County, MS, Tippah County, MS, Union County, MS, Walthall County, MS, Warren County, MS, Webster County, MS, Wilkinson County, MS, Winston County, MS, Yalobusha County, MS, Yazoo County, MS
The radar
The Jackson/Brandon,MS radar (KDGX), 100 km from the middle of the area, began a volume at 01:50 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
Jackson, MS (KJAN), launched 00:00Z, 1.9 hours before the alert went out and 91 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
- 652 J/kg
- Mixed-layer CIN
- -42 J/kg
- Mixed-layer LCL
- 1178 m above ground
- 0-6 km bulk shear
- 44 kt
- 0-1 km storm-relative helicity
- 146 m²/s²
- 0-3 km storm-relative helicity
- 256 m²/s²
- Significant tornado parameter
- 0.5
- Supercell composite
- 3.4
The text
As transmitted.
275
ACUS11 KWNS 080153
SWOMCD
SPC MCD 080152
MSZ000-LAZ000-080415-
Mesoscale Discussion 0330
NWS Storm Prediction Center Norman OK
0852 PM CDT Wed Apr 07 2021
Areas affected...Portions of southern/eastern LA and much of MS
Concerning...Severe potential...Watch possible
Valid 080152Z - 080415Z
Probability of Watch Issuance...40 percent
SUMMARY...A threat for isolated damaging winds and perhaps a tornado
should continue this evening into tonight. The need for a watch is
uncertain, but issuance remains possible.
DISCUSSION...A persistent supercell that has produced at least one
tornado in northeastern LA is currently moving into far west-central
MS as of 0150Z. 00Z soundings from both LCH and JAN showed a capping
inversion centered near 700 mb, which may help explain the general
lack of more robust storms over the past several hours. A broad
swath of precipitation is ongoing this evening across the lower MS
Valley region ahead of a cold front. This activity is being aided by
lift associated with a 30-40 kt low-level jet. Given the strength of
this low-level flow, storms embedded within the larger precipitation
shield will remain capable of producing isolated strong/gusty
downdraft winds. VWPs from KDGX and KLCH also show around 150-200
m2/s2 of 0-1 km SRH, which is enough to support low-level updraft
rotation and a brief tornado. The main limiting factors appear to be
a messy ongoing storm mode and relatively weak instability,
especially with northward extent into MS. Storms ahead of the front
in southern/central LA will have access to the greatest low-level
moisture, and they appear to have the best potential to
surface-based through the evening and into tonight. It remains
unclear whether the overall severe threat will increase enough to
warrant watch issuance over the next few hours.
..Gleason/Grams.. 04/08/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MEG...JAN...LIX...LCH...
LAT...LON 30609357 30989343 31279271 31269200 31549146 32369102
33049103 33779064 34609016 34948972 34958838 34248832
33018862 32308906 31038998 30419083 30089189 30279331
30609357SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 7, 7:00 PM CDT | Mesoscale Discussion | SPC | Caldwell, Catahoula, Concordia, Franklin, Grant, Jackson and 12 more | 60 min |
| Apr 7, 11:44 PM CDT | Mesoscale Discussion | SPC | Acadia, Ascension, East Baton Rouge, East Feliciana, Iberville, Jefferson Davis and 12 more | 3 hr |
| Apr 8, 2:08 AM CDT | Mesoscale Discussion | SPC | Livingston, Orleans, Saint Bernard, Saint Charles, Saint John the Baptist, Saint Tammany and 2 more | 2 hr |
Nearby
Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Louisiana, 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.