Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 441
The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2021, 8:01 PM CDT for 5 counties in Oklahoma; 16 counties in Texas. It was in force for 89 min.
The area
The outline as issued.
The facts
- Issued
- Apr 27, 2021, 8:01 PM CDT (01:01 UTC)
- Expired
- Apr 27, 2021, 9:30 PM CDT
- In force
- 89 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe thunderstorm watch 113
All 21 counties
Comanche County, OK, Cotton County, OK, Jefferson County, OK, Stephens County, OK, Tillman County, OK, Archer County, TX, Baylor County, TX, Clay County, TX, Fisher County, TX, Haskell County, TX, Jones County, TX, Knox County, TX, Mitchell County, TX, Nolan County, TX, Shackelford County, TX, Stonewall County, TX, Taylor County, TX, Throckmorton County, TX, Wichita County, TX, Wilbarger County, TX, Young County, TX
The radar
The Dyess AFB radar (KDYX), 97 km from the middle of the area, began a volume at 01:03 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 00:00Z, 1.0 hours before the alert went out and 211 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
- 692 J/kg
- Mixed-layer CIN
- -275 J/kg
- Mixed-layer LCL
- 967 m above ground
- 0-6 km bulk shear
- 61 kt
- 0-1 km storm-relative helicity
- 197 m²/s²
- 0-3 km storm-relative helicity
- 388 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.3
The text
As transmitted.
185
ACUS11 KWNS 280101
SWOMCD
SPC MCD 280101
OKZ000-TXZ000-280230-
Mesoscale Discussion 0441
NWS Storm Prediction Center Norman OK
0801 PM CDT Tue Apr 27 2021
Areas affected...Parts of the Texas South Plains into southwestern
Oklahoma
Concerning...Severe Thunderstorm Watch 113...
Valid 280101Z - 280230Z
The severe weather threat for Severe Thunderstorm Watch 113
continues.
SUMMARY...Thunderstorm activity continues to increase across the
region, with at least some signs of increasing organization. It is
possible that this may continue into late evening, with increasing
potential for strong surface gusts. A new severe thunderstorm watch
will probably be issued prior to 9 PM CDT.
DISCUSSION...A belt of 30-35 kt southerly flow at 850 mb appears to
be contributing to a zone of focused low-level convergence along an
axis from near Snyder, TX into areas west of Wichita Falls, TX, and
enhanced low-level warm advection west/northwest of Wichita Falls
into the Fort Sill, OK vicinity. Associated lift has supported an
intensifying linear band of thunderstorms, with embedded stronger
more discrete/supercellular structures, in the presence of strong
deep-layer shear and instability.
With the onset of boundary-layer cooling, the narrow corridor of
steep low-level lapse to the east of the ongoing activity will begin
to stabilize during the next few hours. However the southerly
low-level jet is forecast to be maintained, with at least some
further strengthening through 03-06Z. Increasing moisture return
above the stabilizing boundary layer, beneath steep mid-level lapse
rates, might be sufficient to support continuing upscale convective
growth across parts of the Texas South Plains and Big Country into
parts of southwestern Oklahoma this evening. If this occurs, a few
downbursts may become increasingly possible along with strengthening
surface cold pools, accompanied be increasing potential for strong
surface gusts.
..Kerr.. 04/28/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FWD...OUN...SJT...LUB...MAF...
LAT...LON 32330121 33140035 33949940 34519915 34809852 34949795
34649735 33549800 32679897 31950042 31980094 32330121SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 27, 8:23 PM CDT | Severe Thunderstorm Watch | SPC | Carter, Cleveland, Comanche, Cotton, Garvin, Jefferson and 10 more | 7 hr |
| Apr 28, 3:01 AM CDT | Tornado Watch | SPC | Adair, Atoka, Carter, Cherokee, Coal, Cotton and 23 more | 7 hr |
| Apr 28, 6:35 AM CDT | Mesoscale Discussion | SPC | Adair, Atoka, Carter, Cherokee, Coal, Garvin and 18 more | 3 hr |
| Apr 28, 9:25 AM CDT | Mesoscale Discussion | SPC | Atoka, Bryan, Coal, Haskell, Johnston, Latimer and 4 more | 65 min |
| Apr 28, 6:01 PM CDT | Mesoscale Discussion | SPC | Atoka, Bryan, Choctaw, Coal, Haskell, Johnston and 7 more | 119 min |
| Apr 27, 10:39 PM CDT | Mesoscale Discussion | SPC | Andrews, Borden, Crane, Dawson, Ector, Howard and 5 more | 2 hr |
| Apr 28, 1:38 AM CDT | Mesoscale Discussion | SPC | Callahan, Coke, Coleman, Eastland, Glasscock, Jones and 10 more | 2 hr |
| Apr 28, 1:14 PM CDT | Mesoscale Discussion | SPC | Brown, Callahan, Coleman, Comanche, Cooke, Denton and 14 more | 2 hr |
| Apr 28, 1:57 PM CDT | Tornado Watch | SPC | Brown, Callahan, Coke, Coleman, Comanche, Concho and 16 more | 9 hr |
| Apr 28, 2:42 PM CDT | Mesoscale Discussion | SPC | Bandera, Blanco, Edwards, Gillespie, Kendall, Kerr and 9 more | 2 hr |
| Apr 28, 3:10 PM CDT | Tornado Watch | SPC | Atascosa, Bandera, Bexar, Blanco, Comal, Dimmit and 23 more | 8 hr |
| Apr 28, 3:40 PM CDT | Mesoscale Discussion | SPC | Brown, Callahan, Coleman, Comanche, Eastland, Runnels and 2 more | 95 min |
| Apr 28, 5:41 PM CDT | Mesoscale Discussion | SPC | Bandera, Bexar, Frio, Kendall, Kinney, Maverick and 4 more | 2 hr |
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.