Alert archive / Texas / Mesoscale Discussions in 2021

Mesoscale Discussion 459

April 28, 202110 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 28, 2021, 7:01 PM CDT for 10 counties in Texas. It was in force for 89 min.

The area

The outline as issued.

The facts

Issued: Apr 28, 2021, 7:01 PM CDT (00:01 UTC)
Expired: Apr 28, 2021, 8:30 PM CDT
In force: 89 min
Issued by: the Storm Prediction Center
Concerning: Tornado watch 120

Counties Bastrop County, TX, Bexar County, TX, Caldwell County, TX, Comal County, TX, Gonzales County, TX, Guadalupe County, TX, Hays County, TX, Kendall County, TX, Medina County, TX, Wilson County, TX

The radar

The Austin/San Antonio radar (KEWX), 17 km from the middle of the area, began a volume at 00:04 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.

Tornado Watch 122Apr 28, 10:20 PM CDT

The nearest sounding before it

Corpus Christi, TX (KCRP), launched 00:00Z, 0.0 hours before the alert went out and 216 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: 2321 J/kg
Mixed-layer CIN: -348 J/kg
Mixed-layer LCL: 1029 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 114 m²/s²
0-3 km storm-relative helicity: 121 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.4

Open this sounding in Storm Lab

The text

As transmitted.

462 
ACUS11 KWNS 290001
SWOMCD
SPC MCD 290001 
TXZ000-290130-

Mesoscale Discussion 0459
NWS Storm Prediction Center Norman OK
0701 PM CDT Wed Apr 28 2021

Areas affected...South-central Texas

Concerning...Tornado Watch 120...

Valid 290001Z - 290130Z

The severe weather threat for Tornado Watch 120 continues.

SUMMARY...A threat for very large hail, wind damage and possibly a
tornado will move eastward into the San Antonio Metro around 8 pm
central.

DISCUSSION...The latest radar shows a cluster of severe storms
located about 60 statute miles to the west of San Antonio. Ahead of
these storms, the RAP is analying a pocket of strong instability
with MLCAPE near 4500 J/kg and 0-6 km shear near 50 kt. This
environment will be very favorable for supercells with large hail.
Hailstones of greater than 3 inches in diameter will be possible
with the stronger updrafts. Wind gusts exceeding 65 knots may also
occur, with the possibility of wind driven hail.

..Broyles/Guyer.. 04/29/2021

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

ATTN...WFO...EWX...

LAT...LON   29229768 29109871 29309934 29849916 30159786 30109717
            29539710 29229768

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 28, 7:31 PM CDT	Mesoscale Discussion	SPC	Callahan, Coleman, Collin, Comanche, Cooke, Dallas and 24 more	119 min
Apr 28, 7:55 PM CDT	Tornado Watch	SPC	Bosque, Collin, Comanche, Dallas, Delta, Denton and 29 more	6 hr
Apr 28, 9:13 PM CDT	Mesoscale Discussion	SPC	Bastrop, Bexar, Caldwell, Colorado, Comal, Fayette and 4 more	92 min
Apr 28, 9:19 PM CDT	Mesoscale Discussion	SPC	Bowie, Camp, Cass, Collin, Dallas, Delta and 18 more	116 min
Apr 28, 10:22 PM CDT	Tornado Watch	SPC	Atascosa, Bandera, Bastrop, Bexar, Blanco, Burnet and 27 more	7 hr
Apr 28, 11:03 PM CDT	Mesoscale Discussion	SPC	Atascosa, Bandera, Bastrop, Bell, Bexar, Blanco and 37 more	117 min
Apr 29, 1:09 AM CDT	Mesoscale Discussion	SPC	Bowie, Camp, Cass, Collin, Dallas, Delta and 22 more	2 hr
Apr 29, 2:01 AM CDT	Tornado Watch	SPC	Bowie, Camp, Cass, Delta, Franklin, Gregg and 15 more	6 hr

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.