Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 869
The Storm Prediction Center issued this mesoscale discussion at Jun 7, 2021, 3:08 PM CDT for 5 counties in Arkansas; 20 parishes in Louisiana; Sabine County, San Augustine County, Shelby County, Texas. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Jun 7, 2021, 3:08 PM CDT (20:08 UTC)
- Expired
- Jun 7, 2021, 5:15 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 242
All 28 counties
Ashley County, AR, Bradley County, AR, Columbia County, AR, Lafayette County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle 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, Winn Parish, LA, Sabine County, TX, San Augustine County, TX, Shelby County, TX
The radar
The Shreveport radar (KSHV), 94 km from the middle of the area, began a volume at 20:08 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, 8.1 hours before the alert went out and 86 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
- 2401 J/kg
- Mixed-layer CIN
- -18 J/kg
- Mixed-layer LCL
- 563 m above ground
- 0-6 km bulk shear
- 25 kt
- 0-1 km storm-relative helicity
- 64 m²/s²
- 0-3 km storm-relative helicity
- 123 m²/s²
- Significant tornado parameter
- 0.4
- Supercell composite
- 2.1
The text
As transmitted.
336
ACUS11 KWNS 072008
SWOMCD
SPC MCD 072008
ARZ000-LAZ000-TXZ000-072215-
Mesoscale Discussion 0869
NWS Storm Prediction Center Norman OK
0308 PM CDT Mon Jun 07 2021
Areas affected...Far east Texas and northern Louisiana
Concerning...Severe Thunderstorm Watch 242...
Valid 072008Z - 072215Z
The severe weather threat for Severe Thunderstorm Watch 242
continues.
SUMMARY...Recent intensification has occurred with a line of
thunderstorms in portions of northwest/west-central Louisiana. The
downstream environment will continue to support isolated to
widely-scattered damaging wind gusts. As shear decreases to the
east, some weakening may occur later this afternoon. The need for
additional watches is uncertain. Trends will be monitored.
DISCUSSION...Recent radar trends have shown and increase in 50 dBZ
cores on 7 and 9 km MRMS CAPPI data with the convective line
entering northwestern Louisiana. This is coincident with storm
encountering an increasingly unstable airmass with temperatures in
the mid/upper 80s F and dewpoints in the mid/upper 70s F. Wind gusts
thus far have been sub-severe over the past couple of hours.
Effective shear is only 20-30 kts across the area, with the greatest
values in close proximity to the well-developed MCV in
north-central/northeast Texas. However, KSHV VAD data has recently
observed 40-50 kts of flow in the lowest 2-3 km. Given the large
buoyancy downstream, strong to severe wind gusts will remain
possible with north-south oriented portions of the line.
There is some question how intense the line will remain as it moves
towards the Mississippi River. Given decreasing shear to the east,
it seems probable some weakening will occur as it moves across
northern Louisiana/southern Arkansas. While local areal extensions
of the watch may be needed this afternoon, the need for a new
downstream watch is not clear. Trends will continue to be monitored.
..Wendt.. 06/07/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAN...LZK...LCH...SHV...
LAT...LON 32929404 33359349 33579197 33309144 32809150 31769178
31349198 31279237 31219343 31259393 31439449 32929404SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Jun 7, 12:32 PM CDT | Severe Thunderstorm Watch | SPC | Arkansas, Bradley, Calhoun, Clark, Cleveland, Columbia and 21 more | 6 hr |
| Jun 7, 2:16 PM CDT | Mesoscale Discussion | SPC | Clark, Dallas, Garland, Grant, Hempstead, Hot Spring and 8 more | 119 min |
| Jun 7, 5:09 PM CDT | Severe Thunderstorm Watch | SPC | Ashley, Chicot | 3 hr |
| Jun 7, 5:23 PM CDT | Mesoscale Discussion | SPC | Ashley, Bradley, Calhoun, Chicot, Cleveland, Dallas and 5 more | 67 min |
| Jun 6, 8:49 PM CDT | Mesoscale Discussion | SPC | Armstrong, Briscoe, Carson, Castro, Crosby, Dawson and 14 more | 116 min |
| Jun 6, 9:42 PM CDT | Severe Thunderstorm Watch | SPC | Armstrong, Briscoe, Carson, Castro, Childress, Collingsworth and 22 more | 6 hr |
| Jun 6, 11:47 PM CDT | Mesoscale Discussion | SPC | Briscoe, Cottle, Crosby, Dickens, Floyd, Garza and 8 more | 88 min |
| Jun 7, 1:37 AM CDT | Mesoscale Discussion | SPC | Archer, Baylor, Callahan, Childress, Coleman, Cottle and 20 more | 83 min |
| Jun 7, 2:48 AM CDT | Severe Thunderstorm Watch | SPC | Archer, Baylor, Callahan, Clay, Cooke, Denton and 17 more | 7 hr |
| Jun 7, 4:12 AM CDT | Mesoscale Discussion | SPC | Archer, Baylor, Clay, Foard, Hardeman, Haskell and 12 more | 93 min |
| Jun 7, 7:19 AM CDT | Mesoscale Discussion | SPC | Callahan, Comanche, Eastland, Erath, Hood, Johnson and 3 more | 116 min |
| Jun 7, 9:36 AM CDT | Mesoscale Discussion | SPC | Anderson, Angelina, Bosque, Cherokee, Ellis, Falls and 16 more | 2 hr |
Nearby
Mesoscale Discussions in Louisiana, 2021Mesoscale Discussions in Arkansas, 2021Mesoscale Discussions in Texas, 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.