Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 521
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 6:44 AM CDT for 14 counties in Arkansas; 9 parishes in Louisiana; 29 counties in Texas. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 6:44 AM CDT (11:44 UTC)
- Expired
- May 4, 2021, 8:45 AM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 80%
All 52 counties
Bradley County, AR, Calhoun County, AR, Clark County, AR, Cleveland County, AR, Columbia County, AR, Dallas County, AR, Drew County, AR, Hempstead County, AR, Lafayette County, AR, Lincoln County, AR, Miller County, AR, Nevada County, AR, Ouachita County, AR, Union County, AR, Bienville Parish, LA, Bossier Parish, LA, Caddo Parish, LA, Claiborne Parish, LA, De Soto Parish, LA, Lincoln Parish, LA, Red River Parish, LA, Union Parish, LA, Webster Parish, LA, Anderson County, TX, Bell County, TX, Brazos County, TX, Burleson County, TX, Camp County, TX, Cass County, TX, Cherokee County, TX, Falls County, TX, Freestone County, TX, Gregg County, TX, Harrison County, TX, Henderson County, TX, Houston County, TX, Lee County, TX, Leon County, TX, Limestone County, TX, Madison County, TX, Marion County, TX, Milam County, TX, Morris County, TX, Nacogdoches County, TX, Panola County, TX, Robertson County, TX, Rusk County, TX, Shelby County, TX, Smith County, TX, Upshur County, TX, Williamson County, TX, Wood County, TX
The radar
The Shreveport radar (KSHV), 37 km from the middle of the area, began a volume at 11:46 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 00:00Z, 11.7 hours before the alert went out and 39 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
- 2938 J/kg
- Mixed-layer CIN
- -99 J/kg
- Mixed-layer LCL
- 1253 m above ground
- 0-6 km bulk shear
- 23 kt
- 0-1 km storm-relative helicity
- 36 m²/s²
- 0-3 km storm-relative helicity
- 101 m²/s²
- Significant tornado parameter
- 0.3
- Supercell composite
- 3.5
The text
As transmitted.
528
ACUS11 KWNS 041145
SWOMCD
SPC MCD 041144
ARZ000-LAZ000-TXZ000-041345-
Mesoscale Discussion 0521
NWS Storm Prediction Center Norman OK
0644 AM CDT Tue May 04 2021
Areas affected...portions of central and eastern Texas northeastward
across the Arklatex
Concerning...Severe potential...Watch likely
Valid 041144Z - 041345Z
Probability of Watch Issuance...80 percent
SUMMARY...Storms developing this morning across central and eastern
Texas and the Arklatex region will likely pose risk for large hail,
along with gradually increasing thread for damaging winds. A WW
will likely be required.
DISCUSSION...Latest radar loop shows scattered showers/weak
thunderstorms evolving across portions of central and eastern Texas
at this time, largely hindered by stout capping indicated by model
soundings across this region. As a cold front advances
southeastward across this area, ascent -- initially in an anafrontal
sense to the cool side of the boundary -- will likely result in
sufficient weakening of the cap to permit isolated/robust storm
development to occur. The expected/elevated nature of the initial
storms suggests that large hail will be the primary threat
initially.
With time, as storms increase in coverage and congeal to some
degree, and shift eastward into areas of weaker antecedent capping,
risk for damaging winds should gradually increase through the
morning hours.
Timing for initial/vigorous storm development remains uncertain,
given the degree of capping; HRRR forecasts have delayed initial
development as compared to earlier runs. At present, thinking is
that WW issuance may be required between 12Z and 13Z.
..Goss/Guyer.. 05/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAN...LZK...SHV...HGX...FWD...EWX...
LAT...LON 34229175 33749158 32469253 31249485 30139725 30909792
32629563 33719400 34229299 34229175SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 3, 8:38 PM CDT | Mesoscale Discussion | SPC | Arkansas, Baxter, Boone, Calhoun, Carroll, Clark and 60 more | 2 hr |
| May 3, 9:10 PM CDT | Severe Thunderstorm Watch | SPC | Baxter, Benton, Boone, Calhoun, Carroll, Clark and 50 more | 7 hr |
| May 3, 10:22 PM CDT | Mesoscale Discussion | SPC | Boone, Crawford, Franklin, Johnson, Madison, Marion and 2 more | 83 min |
| May 3, 11:34 PM CDT | Mesoscale Discussion | SPC | Baxter, Boone, Carroll, Clark, Cleburne, Conway and 27 more | 86 min |
| May 4, 1:06 AM CDT | Mesoscale Discussion | SPC | Clay, Craighead, Crittenden, Cross, Greene, Jackson and 5 more | 114 min |
| May 4, 1:41 AM CDT | Severe Thunderstorm Watch | SPC | Clay, Craighead, Crittenden, Cross, Greene, Mississippi and 2 more | 6 hr |
| May 4, 2:02 AM CDT | Mesoscale Discussion | SPC | Clay, Conway, Craighead, Cross, Faulkner, Garland and 16 more | 88 min |
| May 4, 4:17 AM CDT | Mesoscale Discussion | SPC | Crittenden | 88 min |
| May 4, 10:52 AM CDT | Tornado Watch | SPC | Ashley, Bradley, Calhoun, Chicot, Columbia, Desha and 2 more | 7 hr |
| May 4, 11:58 AM CDT | Mesoscale Discussion | SPC | Crittenden, Lee, Phillips | 2 hr |
| May 4, 12:18 PM CDT | Severe Thunderstorm Watch | SPC | Phillips | 5 hr |
| May 4, 1:59 PM CDT | Mesoscale Discussion | SPC | Cleburne, Conway, Craighead, Cross, Faulkner, Greene and 17 more | 2 hr |
| May 4, 8:33 AM CDT | Mesoscale Discussion | SPC | Avoyelles, Caldwell, Catahoula, Concordia, East Carroll, East Feliciana and 14 more | 117 min |
| May 4, 12:16 PM CDT | Mesoscale Discussion | SPC | Caldwell, Catahoula, Concordia, East Carroll, Franklin, Grant and 9 more | 89 min |
| May 4, 3:31 PM CDT | Tornado Watch | SPC | East Baton Rouge, Livingston, Saint Tammany, Tangipahoa, Washington, West Baton Rouge | 6 hr |
| May 4, 4:46 PM CDT | Mesoscale Discussion | SPC | Saint Tammany, Tangipahoa, Washington | 89 min |
| May 3, 7:01 PM CDT | Severe Thunderstorm Watch | SPC | Atascosa, Bandera, Bexar, Blanco, Burnet, Comal and 9 more | 4 hr |
| May 3, 7:38 PM CDT | Mesoscale Discussion | SPC | Bosque, Collin, Dallas, Denton, Ellis, Fannin and 6 more | 97 min |
| May 3, 8:30 PM CDT | Mesoscale Discussion | SPC | Bexar, Blanco, Comal, Guadalupe, Hays, Kendall | 60 min |
| May 3, 9:10 PM CDT | Mesoscale Discussion | SPC | Callahan, Eastland, Fisher, Haskell, Jones, Nolan and 6 more | 95 min |
| May 3, 9:52 PM CDT | Mesoscale Discussion | SPC | Anderson, Bell, Coryell, Ellis, Falls, Freestone and 12 more | 53 min |
| May 3, 10:22 PM CDT | Severe Thunderstorm Watch | SPC | Anderson, Bell, Collin, Cooke, Dallas, Delta and 28 more | 5 hr |
| May 4, 8:11 AM CDT | Severe Thunderstorm Watch | SPC | Angelina, Austin, Brazos, Burleson, Chambers, Colorado and 22 more | 8 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.