Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 322
The Storm Prediction Center issued this mesoscale discussion at Apr 7, 2021, 11:10 AM CDT for 18 counties in Arkansas; Bossier Parish, Caddo Parish, Webster Parish, Louisiana; 20 counties in Texas. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 7, 2021, 11:10 AM CDT (16:10 UTC)
- Expired
- Apr 7, 2021, 1:15 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 80%
All 41 counties
Clark County, AR, Columbia County, AR, Garland County, AR, Hempstead County, AR, Howard County, AR, Lafayette County, AR, Little River County, AR, Logan County, AR, Miller County, AR, Montgomery County, AR, Nevada County, AR, Perry County, AR, Pike County, AR, Polk County, AR, Pope County, AR, Scott County, AR, Sevier County, AR, Yell County, AR, Bossier Parish, LA, Caddo Parish, LA, Webster Parish, LA, Anderson County, TX, Bowie County, TX, Brazos County, TX, Camp County, TX, Cass County, TX, Cherokee County, TX, Gregg County, TX, Harrison County, TX, Houston County, TX, Leon County, TX, Madison County, TX, Marion County, TX, Morris County, TX, Nacogdoches County, TX, Panola County, TX, Rusk County, TX, Smith County, TX, Titus County, TX, Upshur County, TX, Wood County, TX
The radar
The Shreveport radar (KSHV), 144 km from the middle of the area, began a volume at 16:09 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, 4.2 hours before the alert went out and 144 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
- 532 J/kg
- Mixed-layer CIN
- -229 J/kg
- Mixed-layer LCL
- 506 m above ground
- 0-6 km bulk shear
- 34 kt
- 0-1 km storm-relative helicity
- 267 m²/s²
- 0-3 km storm-relative helicity
- 433 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.6
The text
As transmitted.
366
ACUS11 KWNS 071610
SWOMCD
SPC MCD 071610
ARZ000-LAZ000-TXZ000-OKZ000-071815-
Mesoscale Discussion 0322
NWS Storm Prediction Center Norman OK
1110 AM CDT Wed Apr 07 2021
Areas affected...Parts of eastern/northeastern Texas through western
Arkansas
Concerning...Severe potential...Watch likely
Valid 071610Z - 071815Z
Probability of Watch Issuance...80 percent
SUMMARY...The initiation of strong to severe thunderstorms appears
possible as early 1-2 PM CDT. This may, at least initially, include
discrete supercells, before a squall line tends to evolve, and a
risk for tornadoes, one or two of which could be strong.
DISCUSSION...Cloud cover is slowing moist, warm sector
boundary-layer destabilization, but it appears the air mass is
already potentially moderately unstable as the significant upstream
short wave trough begins to take on a neutral to negative tilt
across the central Great Plains. Downstream of the base of this
troughing, beneath increasingly difluent mid/upper flow,
considerable model output suggests that erosion of inhibition
associated with capping elevated mixed-layer air, coupled with at
least some further boundary-layer warming, will allow for the
initiation of thunderstorm development as early as 18-19Z.
Initially this may be largely discrete, and scattered, but focused
within a zone of enhanced low-level convergence along an eastward
advancing cold front.
With the environment becoming characterized by wind profiles with
strong deep-layer shear and sizable, clockwise-curved low-level
hodographs, in the presence of a deep moist boundary-layer, it
appears conducive to supercells capable of producing tornadoes.
This includes potential for a strong tornado or two, though the
overall tornado potential could be mitigated somewhat by relatively
modest high-level flow and the tendency for upscale convective
growth along the cold front through the afternoon.
..Kerr/Hart.. 04/07/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LZK...SHV...TSA...HGX...FWD...EWX...
LAT...LON 35259406 35569269 32319337 30209670 32799545 34259449
35259406SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 7, 6:40 AM CDT | Mesoscale Discussion | SPC | Benton, Boone, Carroll, Crawford, Franklin, Madison and 2 more | 2 hr |
| Apr 7, 10:18 AM CDT | Mesoscale Discussion | SPC | Benton, Carroll, Madison, Washington | 117 min |
| Apr 7, 12:38 PM CDT | Tornado Watch | SPC | Arkansas, Baxter, Boone, Bradley, Calhoun, Carroll and 55 more | 7 hr |
| Apr 7, 2:22 PM CDT | Mesoscale Discussion | SPC | Arkansas, Ashley, Baxter, Boone, Bradley, Calhoun and 56 more | 53 min |
| Apr 7, 3:40 PM CDT | Mesoscale Discussion | SPC | Arkansas, Ashley, Baxter, Boone, Bradley, Calhoun and 53 more | 65 min |
| Apr 7, 5:12 PM CDT | Mesoscale Discussion | SPC | Chicot, Craighead, Crittenden, Cross, Greene, Lee and 3 more | 2 hr |
Nearby
Mesoscale Discussions in Texas, 2021Mesoscale Discussions in Arkansas, 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.