Alert archive / Texas / Mesoscale Discussions in 2021

Mesoscale Discussion 455

April 28, 20218 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2021, 3:40 PM CDT for 8 counties in Texas. It was in force for 95 min.

The area

The outline as issued.

The facts

Issued: Apr 28, 2021, 3:40 PM CDT (20:40 UTC)
Expired: Apr 28, 2021, 5:15 PM CDT
In force: 95 min
Issued by: the Storm Prediction Center
Concerning: Tornado watch 119

Counties Brown County, TX, Callahan County, TX, Coleman County, TX, Comanche County, TX, Eastland County, TX, Runnels County, TX, Taylor County, TX, Tom Green County, TX

The radar

The Dyess AFB radar (KDYX), 72 km from the middle of the area, began a volume at 20:42 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 nearest sounding before it

Fort Worth, TX (KFWD), launched 12:00Z, 8.7 hours before the alert went out and 230 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

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

Open this sounding in Storm Lab

The text

As transmitted.

727 
ACUS11 KWNS 282041
SWOMCD
SPC MCD 282040 
TXZ000-282215-

Mesoscale Discussion 0455
NWS Storm Prediction Center Norman OK
0340 PM CDT Wed Apr 28 2021

Areas affected...Portions of central TX

Concerning...Tornado Watch 119...

Valid 282040Z - 282215Z

The severe weather threat for Tornado Watch 119 continues.

SUMMARY...The greatest short-term severe threat will exist with a
supercell capable of producing 2+ inch hail. A tornado also remains
possible. Additional storms may form along a stalled surface
boundary.

DISCUSSION...A severe supercell moving from Runnels/Taylor counties
into Callahan/Coleman counties in central TX will continue to pose a
threat for large to very large (2+ inch) hail in the short term.
Surface observations to the south/southeast of this ongoing storm
indicate surface temperatures have warmed into the mid to upper 80s,
while dewpoints remain in the mid to upper 60s. Accordingly,
instability is maximized near this supercell per latest mesoanalysis
estimates, with MLCAPE around 2000 J/kg. Low-level flow appears
fairly week based on recent VWPs from KDYX, but it does strengthen
some with eastward extent into central TX. A tornado remains
possible in the short term with any supercell that can remain
sustained, but large hail will likely remain the primary severe risk
for the next hour or two. Additional storms may form along a stalled
outflow boundary that is draped across this region, particularly
where this boundary intersects a surface dryline near San Angelo TX.
Any additional convection that develops will likely become severe
quickly and pose at a very large hail threat.

..Gleason.. 04/28/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...FWD...SJT...

LAT...LON   31619919 31619992 31340026 31330047 31560046 32280018
            32549965 32639925 32519846 32239838 31839855 31619919

SPC 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, 1:14 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, 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, 2021 Every 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.