Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 452
The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2021, 1:14 PM CDT for 20 counties in Texas. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 28, 2021, 1:14 PM CDT (18:14 UTC)
- Expired
- Apr 28, 2021, 3:15 PM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch likely
- Chance of a watch
- 95%
Counties Brown County, TX, Callahan County, TX, Coleman County, TX, Comanche County, TX, Cooke County, TX, Denton County, TX, Eastland County, TX, Erath County, TX, Grayson County, TX, Hood County, TX, Jack County, TX, Johnson County, TX, Palo Pinto County, TX, Parker County, TX, Runnels County, TX, Somervell County, TX, Stephens County, TX, Tarrant County, TX, Taylor County, TX, Wise County, TX
The radar
The Dyess AFB radar (KDYX), 72 km from the middle of the area, began a volume at 18:13 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, 6.2 hours before the alert went out and 120 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
- 678 J/kg
- Mixed-layer CIN
- -63 J/kg
- Mixed-layer LCL
- 635 m above ground
- 0-6 km bulk shear
- 51 kt
- 0-1 km storm-relative helicity
- 290 m²/s²
- 0-3 km storm-relative helicity
- 394 m²/s²
- Significant tornado parameter
- 1.7
- Supercell composite
- 12.5
The text
As transmitted.
989
ACUS11 KWNS 281814
SWOMCD
SPC MCD 281814
TXZ000-282015-
Mesoscale Discussion 0452
NWS Storm Prediction Center Norman OK
0114 PM CDT Wed Apr 28 2021
Areas affected...Portions of central into north-central TX
Concerning...Severe potential...Watch likely
Valid 281814Z - 282015Z
Probability of Watch Issuance...95 percent
SUMMARY...The threat for large to very large hail, damaging wind
gusts, and isolated tornadoes should increase this afternoon. Watch
issuance is likely.
DISCUSSION...A convectively reinforced outflow boundary has stalled
across part of central TX this afternoon per recent surface
observations and visible satellite imagery. The airmass along/south
of this boundary is becoming moderately unstable, as surface
temperatures have warmed well into the 80s amidst mid to upper 60s
dewpoints. Latest mesoanalysis and RAP forecast soundings in the
vicinity of San Angelo TX suggest minimal convective inhibition
remains, with MLCAPE in the 1500-2000 J/kg range. As diurnal heating
of this moist low-level airmass continues, a further increase in
instability appears likely. Current expectations are for multiple
storms to initiate along the surface boundary in central TX within
the next couple of hours as ascent associated with a mid/upper-level
trough approaches from the west. These storms should subsequently
move east-northeastward into north-central TX. It is only weakly
unstable at the moment with northward extent into north-central TX
due to the influence of earlier convection. Still, some airmass
recovery appears likely through the remainder of the afternoon
across this region, as rich low-level moisture remains in place.
The deep-layer shear is very favorable for organized severe storms,
with around 50-60 of effective bulk shear in place across the warm
sector. Supercell structures appear likely with initial development,
and large to very large hail (2+ inches in diameter) will be a
threat. This large hail threat should continue into north-central TX
through the afternoon/early evening, but it probably will be
dependent on how much airmass recovery/destabilization can occur.
Isolated straight-line damaging wind gusts also appear possible as
low-level lapse rates gradually steepen. Finally, there may also be
a threat for a few tornadoes, even though the stronger low-level
flow associated with a southerly low-level jet will be shifting
eastward away from this area. Around 100-150 m2/s2 of effective SRH
should support some low-level rotation with any discrete supercells.
Given the expected increase in the overall severe threat this
afternoon, watch issuance will likely be needed.
..Gleason/Hart.. 04/28/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FWD...OUN...SJT...
LAT...LON 31439948 31460024 31720063 32020046 32429973 33009891
33559802 33679753 33689691 33639641 33089663 32579705
32209752 31849808 31539881 31439948SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 27, 8:01 PM CDT | Mesoscale Discussion | SPC | Archer, Baylor, Clay, Fisher, Haskell, Jones and 10 more | 89 min |
| Apr 27, 8:23 PM CDT | Severe Thunderstorm Watch | SPC | Andrews, Archer, Baylor, Borden, Clay, Coke and 29 more | 7 hr |
| 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, 3:01 AM CDT | Tornado Watch | SPC | Archer, Baylor, Callahan, Clay, Cooke, Eastland and 14 more | 7 hr |
| Apr 28, 6:35 AM CDT | Mesoscale Discussion | SPC | Archer, Callahan, Clay, Cooke, Eastland, Jack and 9 more | 3 hr |
| Apr 28, 9:25 AM CDT | Mesoscale Discussion | SPC | Cooke, Denton, Grayson, Parker, Wise | 65 min |
| 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 |
| Apr 28, 6:01 PM CDT | Mesoscale Discussion | SPC | Lamar | 119 min |
Nearby
Mesoscale 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.