Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 342
The Storm Prediction Center issued this mesoscale discussion at Apr 9, 2021, 1:25 PM CDT for 4 states. It was in force for 95 min.
The area
The outline as issued.
The facts
- Issued
- Apr 9, 2021, 1:25 PM CDT (18:25 UTC)
- Expired
- Apr 9, 2021, 3:00 PM CDT
- In force
- 95 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 76
All 50 counties
Arkansas County, AR, Ashley County, AR, Bradley County, AR, Chicot County, AR, Desha County, AR, Drew County, AR, Lee County, AR, Lincoln County, AR, Monroe County, AR, Phillips County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caldwell Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, East Carroll Parish, LA, Jackson Parish, LA, Lincoln Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Red River Parish, LA, Richland Parish, LA, Sabine Parish, LA, Union Parish, LA, Webster Parish, LA, West Carroll Parish, LA, Winn Parish, LA, Bolivar County, MS, Coahoma County, MS, DeSoto County, MS, Grenada County, MS, Humphreys County, MS, Issaquena County, MS, Leflore County, MS, Panola County, MS, Quitman County, MS, Sharkey County, MS, Sunflower County, MS, Tallahatchie County, MS, Tate County, MS, Tunica County, MS, Washington County, MS, Cherokee County, TX, Nacogdoches County, TX, Panola County, TX, Rusk County, TX, San Augustine County, TX, Shelby County, TX
The radar
The Shreveport radar (KSHV), 128 km from the middle of the area, began a volume at 18:24 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
Shreveport, LA (KSHV), launched 12:00Z, 6.4 hours before the alert went out and 118 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
- 928 J/kg
- Mixed-layer CIN
- -310 J/kg
- Mixed-layer LCL
- 1043 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- 6 m²/s²
- 0-3 km storm-relative helicity
- 61 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
098
ACUS11 KWNS 091825
SWOMCD
SPC MCD 091825
MSZ000-ARZ000-LAZ000-TXZ000-092000-
Mesoscale Discussion 0342
NWS Storm Prediction Center Norman OK
0125 PM CDT Fri Apr 09 2021
Areas affected...Parts of northeast Texas...northern
Louisiana...southeastern Arkansas and northwestern Mississippi
Concerning...Severe Thunderstorm Watch 76...
Valid 091825Z - 092000Z
The severe weather threat for Severe Thunderstorm Watch 76
continues.
SUMMARY...Thunderstorms continue to gradually increase and
intensify, with a period of rapid intensification possible by 3-5
PM, as activity spreads into the lower Mississippi Valley. The
potential for large, damaging hail will increase along with the risk
for damaging wind gusts.
DISCUSSION...Aided by forcing for ascent in the left exit region of
the approaching strong high-level jet, mid-level convection
continues to increase in an area now centered across the Ark-La-Tex
region. This has included a number occasionally intensifying
embedded cells, but activity has yet to root within the surrounding
destabilizing boundary layer. To the east of the ongoing activity,
the latest Rapid Refresh continues to indicate that moisture return
and low-level ascent supported by warm advection will contribute to
further deepening of the boundary-layer, beneath steep mid-level
lapse rates associated with the elevated mixed-layer air.
Increasing inflow of this air (with mixed-layer CAPE on the order of
2000-3000 J/kg) seems likely to contribute to rapid intensification
of this convection by 20-22Z, if not before, as it spreads across
northern Louisiana, southeastern Arkansas and the Mississippi Delta
region. In addition to increasing potential for large, damaging
hail, and localized strong surface gusts, further upscale convective
growth and organization is possible as surface cold pools begin to
develop and consolidate.
..Kerr.. 04/09/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MEG...JAN...LZK...SHV...HGX...
LAT...LON 32169536 32349398 33009359 33399229 34069170 34439154
34989121 34898996 33768977 32479101 31759255 31409365
31349514 32169536SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 9, 9:49 AM CDT | Mesoscale Discussion | SPC | Hempstead, Howard, Lafayette, Little River, Miller, Pike and 1 more | 116 min |
| Apr 9, 12:07 PM CDT | Severe Thunderstorm Watch | SPC | Arkansas, Bradley, Calhoun, Clark, Cleveland, Columbia and 20 more | 6 hr |
| Apr 9, 2:50 PM CDT | Mesoscale Discussion | SPC | Baxter, Benton, Boone, Carroll, Clay, Cleburne and 18 more | 85 min |
| Apr 9, 3:10 PM CDT | Mesoscale Discussion | SPC | Arkansas, Ashley, Bradley, Chicot, Cleveland, Desha and 5 more | 95 min |
| Apr 9, 3:13 PM CDT | Severe Thunderstorm Watch | SPC | Baxter, Fulton, Izard, Lawrence, Marion, Randolph and 1 more | 7 hr |
| Apr 9, 3:14 PM CDT | Mesoscale Discussion | SPC | Benton, Crawford, Franklin, Polk, Scott, Sebastian and 2 more | 61 min |
| Apr 9, 3:42 PM CDT | Severe Thunderstorm Watch | SPC | Ashley, Chicot, Clay, Craighead, Crittenden, Cross and 6 more | 7 hr |
| Apr 9, 5:19 PM CDT | Mesoscale Discussion | SPC | Ashley | 116 min |
| Apr 9, 5:32 PM CDT | Severe Thunderstorm Watch | SPC | Columbia, Union | 7 hr |
| Apr 9, 6:34 PM CDT | Mesoscale Discussion | SPC | Benton, Carroll, Crawford, Madison, Washington | 116 min |
| Apr 9, 2:49 AM CDT | Mesoscale Discussion | SPC | Jefferson, Plaquemines, Saint Bernard | 2 hr |
| Apr 9, 6:14 PM CDT | Mesoscale Discussion | SPC | Caldwell, East Carroll, Franklin, Madison, Morehouse, Ouachita and 2 more | 3 hr |
| Apr 9, 11:44 AM CDT | Mesoscale Discussion | SPC | Clay, Kemper, Lauderdale, Lowndes, Monroe, Neshoba and 3 more | 2 hr |
| Apr 9, 5:54 PM CDT | Mesoscale Discussion | SPC | Kemper, Lauderdale, Lowndes, Noxubee | 96 min |
| Apr 8, 9:58 PM CDT | Mesoscale Discussion | SPC | Anderson, Brazos, Cherokee, Freestone, Grimes, Henderson and 7 more | 2 hr |
| Apr 9, 3:59 PM CDT | Mesoscale Discussion | SPC | Bastrop, Bell, Blanco, Bosque, Burnet, Caldwell and 14 more | 2 hr |
| Apr 9, 4:27 PM CDT | Severe Thunderstorm Watch | SPC | Anderson, Bell, Bosque, Collin, Cooke, Coryell and 26 more | 9 hr |
Nearby
Mesoscale Discussions in Louisiana, 2021Mesoscale Discussions in Mississippi, 2021Mesoscale Discussions in Arkansas, 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.