Alert archive / Louisiana / Mesoscale Discussions in 2021
Mesoscale Discussion 574
The Storm Prediction Center issued this mesoscale discussion at May 9, 2021, 5:41 PM CDT for 4 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 9, 2021, 5:41 PM CDT (22:41 UTC)
- Expired
- May 9, 2021, 7:45 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 157
All 67 counties
Arkansas County, AR, Ashley County, AR, Bradley County, AR, Calhoun County, AR, Chicot County, AR, Clark County, AR, Cleveland County, AR, Columbia County, AR, Dallas County, AR, Desha County, AR, Drew County, AR, Grant County, AR, Hempstead County, AR, Hot Spring County, AR, Jefferson County, AR, Lafayette County, AR, Lincoln County, AR, Miller County, AR, Nevada County, AR, Ouachita County, AR, Phillips County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Caldwell Parish, LA, Catahoula Parish, LA, Claiborne Parish, LA, Concordia Parish, LA, De Soto Parish, LA, East Carroll Parish, LA, Franklin Parish, LA, Grant Parish, LA, Jackson Parish, LA, LaSalle Parish, LA, Lincoln Parish, LA, Madison Parish, LA, Morehouse Parish, LA, Natchitoches Parish, LA, Ouachita Parish, LA, Rapides Parish, LA, Red River Parish, LA, Richland Parish, LA, Sabine Parish, LA, Tensas Parish, LA, Union Parish, LA, Vernon Parish, LA, Webster Parish, LA, West Carroll Parish, LA, Winn Parish, LA, Bolivar County, MS, Coahoma County, MS, Humphreys County, MS, Issaquena County, MS, Sharkey County, MS, Sunflower County, MS, Washington County, MS, Angelina County, TX, Cass County, TX, Harrison County, TX, Marion County, TX, Nacogdoches County, TX, Panola County, TX, Rusk County, TX, Sabine County, TX, San Augustine County, TX, Shelby County, TX
The radar
The Shreveport radar (KSHV), 129 km from the middle of the area, began a volume at 22:41 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, 10.7 hours before the alert went out and 119 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
- 853 J/kg
- Mixed-layer CIN
- -220 J/kg
- Mixed-layer LCL
- 639 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 288 m²/s²
- 0-3 km storm-relative helicity
- 490 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.0
The text
As transmitted.
821
ACUS11 KWNS 092241
SWOMCD
SPC MCD 092241
MSZ000-ARZ000-LAZ000-TXZ000-100045-
Mesoscale Discussion 0574
NWS Storm Prediction Center Norman OK
0541 PM CDT Sun May 09 2021
Areas affected...Southern Arkansas...Western
Mississisppi...North-central Louisiana
Concerning...Severe Thunderstorm Watch 157...
Valid 092241Z - 100045Z
The severe weather threat for Severe Thunderstorm Watch 157
continues.
SUMMARY...A severe threat will continue across southern Arkansas,
far northeast Texas and northwest Louisiana over the next few hours.
Large hail, wind damage and an isolated tornado threat will be
possible with the stronger thunderstorms. A new weather watch is
being issued downstream across parts of central and northern
Louisiana.
DISCUSSION...The latest radar imagery shows two clusters of severe
thunderstorms. The first is located in southern Arkansas near a
pocket of strong instability with the RAP estimating MLCAPE in the
2500 to 3500 J/kg range. The cells have remained discrete with
several supercells ongoing. Very large hail (hailstones of greater
than 2 inches in diameter) will be possible with the strongest of
cells. A wind damage and isolated tornado threat will also exist,
especially as low-level flow begins to strengthen over the next 2 to
3 hours.
The second are of severe storms are located further to the southwest
across far east Texas. These storms will move eastward into western
Louisiana over the next hour. Moderate instability is analyzed
across western and central Louisiana with 0-6 km shear in the 35 to
45 kt range. This will support continued supercell development.
Large hail and wind damage will be the primary threats. A weather
watch is being issued for parts of north-central Louisiana at this
time.
..Broyles/Hart.. 05/09/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MEG...JAN...LZK...LCH...SHV...
LAT...LON 34759176 34599254 33849396 32869472 32099488 31559488
31189463 30979388 31129264 31269180 31919123 33039051
33989030 34509080 34689126 34759176SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 9, 3:46 AM CDT | Mesoscale Discussion | SPC | Baxter, Boone, Carroll, Fulton, Izard, Madison and 4 more | 119 min |
| May 9, 12:14 PM CDT | Mesoscale Discussion | SPC | Arkansas, Ashley, Bradley, Calhoun, Chicot, Clark and 46 more | 91 min |
| May 9, 1:14 PM CDT | Severe Thunderstorm Watch | SPC | Arkansas, Ashley, Bradley, Calhoun, Chicot, Clark and 33 more | 8 hr |
| May 9, 2:27 PM CDT | Severe Thunderstorm Watch | SPC | Craighead, Crittenden, Cross, Lee, Mississippi, Phillips and 2 more | 7 hr |
| May 9, 3:42 PM CDT | Mesoscale Discussion | SPC | Arkansas, Ashley, Bradley, Calhoun, Clark, Cleveland and 31 more | 93 min |
| May 9, 5:48 PM CDT | Mesoscale Discussion | SPC | Crittenden, Lee, Phillips, St. Francis | 87 min |
| May 9, 3:53 PM CDT | Mesoscale Discussion | SPC | Madison, Tensas | 2 hr |
| May 9, 5:45 PM CDT | Severe Thunderstorm Watch | SPC | Allen, Avoyelles, Beauregard, Caldwell, Evangeline, Grant and 7 more | 7 hr |
| May 9, 6:40 PM CDT | Mesoscale Discussion | SPC | Calhoun, Chickasaw, Itawamba, Lafayette, Lee, Monroe and 3 more | 65 min |
| May 9, 1:41 PM CDT | Mesoscale Discussion | SPC | Anderson, Bell, Blanco, Brazos, Burleson, Burnet and 27 more | 94 min |
| May 9, 3:01 PM CDT | Severe Thunderstorm Watch | SPC | Anderson, Bell, Blanco, Bosque, Burnet, Comal and 32 more | 7 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.