Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 405
The Storm Prediction Center issued this mesoscale discussion at Apr 23, 2021, 11:29 AM CDT for 4 counties in Oklahoma; 58 counties in Texas. It was in force for 91 min.
The area
The outline as issued.
The facts
- Issued
- Apr 23, 2021, 11:29 AM CDT (16:29 UTC)
- Expired
- Apr 23, 2021, 1:00 PM CDT
- In force
- 91 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 95%
All 62 counties
Carter County, OK, Jefferson County, OK, Love County, OK, Marshall County, OK, Archer County, TX, Bastrop County, TX, Bell County, TX, Bexar County, TX, Blanco County, TX, Bosque County, TX, Brazos County, TX, Brown County, TX, Burleson County, TX, Burnet County, TX, Caldwell County, TX, Clay County, TX, Collin County, TX, Comal County, TX, Comanche County, TX, Cooke County, TX, Coryell County, TX, Dallas County, TX, Denton County, TX, Eastland County, TX, Ellis County, TX, Erath County, TX, Falls County, TX, Fayette County, TX, Gillespie County, TX, Gonzales County, TX, Grayson County, TX, Guadalupe County, TX, Hamilton County, TX, Hays County, TX, Hill County, TX, Hood County, TX, Jack County, TX, Johnson County, TX, Kendall County, TX, Lampasas County, TX, Lee County, TX, Limestone County, TX, Llano County, TX, Mason County, TX, McLennan County, TX, Milam County, TX, Mills County, TX, Montague County, TX, Navarro County, TX, Palo Pinto County, TX, Parker County, TX, Robertson County, TX, Rockwall County, TX, San Saba County, TX, Somervell County, TX, Stephens County, TX, Tarrant County, TX, Travis County, TX, Washington County, TX, Williamson County, TX, Wise County, TX, Young County, TX
The radar
The Ft Hood radar (KGRK), 108 km from the middle of the area, began a volume at 16:31 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
Fort Worth, TX (KFWD), launched 12:00Z, 4.5 hours before the alert went out and 142 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
- 14 J/kg
- Mixed-layer CIN
- -89 J/kg
- Mixed-layer LCL
- 578 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- 397 m²/s²
- 0-3 km storm-relative helicity
- 249 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.3
The text
As transmitted.
614
ACUS11 KWNS 231629
SWOMCD
SPC MCD 231629
TXZ000-OKZ000-231800-
Mesoscale Discussion 0405
NWS Storm Prediction Center Norman OK
1129 AM CDT Fri Apr 23 2021
Areas affected...portions of northern and central Texas
Concerning...Severe potential...Watch likely
Valid 231629Z - 231800Z
Probability of Watch Issuance...95 percent
SUMMARY...Thunderstorm activity is expected to increase over the
next couple of hours. Large hail and locally damaging wind gusts
will be possible with this activity through the afternoon/evening. A
severe thunderstorm watch will likely be needed by 18z.
DISCUSSION...An area of deepening, midlevel convection atop the EML
across west-central TX is evident in radar and visible satellite
imagery as of 16z. This is indicative of increasing large-scale
ascent now spreading into western TX, in conjunction with continued
warm advection/increasing moisture beneath the weakening EML. Over
the next couple of hours, convection is expected to continue to
increase with a slow erosion of the cap. This may result in a mix of
elevated storms, transitioning toward surface-based convection
through the afternoon.
Very steep midlevel lapse rates (7.5-8.5 C/km) and favorable,
elongated hodographs will support large hail. PW values increasing
to around 1.5-1.75 with northward extent, and increasing low level
flow will also promote strong/locally damaging gusts.
..Leitman/Hart.. 04/23/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...HGX...FWD...OUN...EWX...SJT...
LAT...LON 29309832 29519883 29789911 30589935 31169932 31449930
34059863 34319832 34409769 34349711 34259672 33769649
33179633 32929633 30459625 29629661 29319716 29269775
29309832SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 23, 12:37 PM CDT | Severe Thunderstorm Watch | SPC | Bryan, Carter, Cotton, Jefferson, Johnston, Love and 3 more | 7 hr |
| Apr 23, 3:14 PM CDT | Tornado Watch | SPC | Comanche, Cotton, Greer, Harmon, Jackson, Jefferson and 2 more | 5 hr |
| Apr 23, 5:26 PM CDT | Mesoscale Discussion | SPC | Cotton, Jackson, Tillman | 2 hr |
| Apr 23, 12:43 PM CDT | Mesoscale Discussion | SPC | Baylor, Childress, Collingsworth, Cottle, Foard, Hall and 2 more | 3 hr |
| Apr 23, 12:43 PM CDT | Mesoscale Discussion | SPC | Anderson, Angelina, Brazoria, Chambers, Cherokee, Fort Bend and 25 more | 2 hr |
| Apr 23, 2:00 PM CDT | Tornado Watch | SPC | Angelina, Austin, Brazos, Burleson, Chambers, Cherokee and 22 more | 7 hr |
| Apr 23, 3:27 PM CDT | Mesoscale Discussion | SPC | Baylor, Foard, Hardeman, Wilbarger | 2 hr |
| Apr 23, 3:28 PM CDT | Mesoscale Discussion | SPC | Bosque, Brown, Comanche, Eastland, Erath, Hamilton and 11 more | 2 hr |
| Apr 23, 5:36 PM CDT | Mesoscale Discussion | SPC | Angelina, Houston, Jasper, Nacogdoches, Newton, Polk and 7 more | 54 min |
| Apr 23, 6:46 PM CDT | Mesoscale Discussion | SPC | Atascosa, Bell, Bexar, Blanco, Bosque, Burnet and 19 more | 89 min |
Nearby
Mesoscale Discussions in Texas, 2021Mesoscale Discussions in Oklahoma, 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.