Alert archive / Texas / Mesoscale Discussions in 2021

Mesoscale Discussion 408

April 23, 20214 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 23, 2021, 3:27 PM CDT for 4 counties in Texas. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Apr 23, 2021, 3:27 PM CDT (20:27 UTC)
Expired
Apr 23, 2021, 5:30 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
Concerning
Tornado watch 100

Counties Baylor County, TX, Foard County, TX, Hardeman County, TX, Wilbarger County, TX

The radar

The Altus AFB radar (KFDR), 63 km from the middle of the area, began a volume at 20:27 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

Norman, OK (KOUN), launched 12:00Z, 8.5 hours before the alert went out and 236 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-pSkew-T log-p diagram, Norman, OK at 12:00Z on 2021-04-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Norman, OK at 12:00Z on 2021-04-23The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 284 square meters per square second.1939587897117Sfc1 km3 km6 km9 kmRMLM
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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
751 m above ground
0-6 km bulk shear
53 kt
0-1 km storm-relative helicity
284 m²/s²
0-3 km storm-relative helicity
202 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

323 
ACUS11 KWNS 232028
SWOMCD
SPC MCD 232027 
TXZ000-OKZ000-232230-

Mesoscale Discussion 0408
NWS Storm Prediction Center Norman OK
0327 PM CDT Fri Apr 23 2021

Areas affected...parts of western north-central TX and far
southwestern OK

Concerning...Tornado Watch 100...

Valid 232027Z - 232230Z

The severe weather threat for Tornado Watch 100 continues.

SUMMARY...A mesoscale area most favorable for a tornadic supercell
will be near the adjacent portions of southwest OK/northwest TX
during the 5-7 pm period.  Large to giant hail is possible.

DISCUSSION...Latest subjective surface mesoanalysis places a moist
axis east of the dryline and extending from near Seymour and
protruding north-northwest to near Childress, with lower 60s degree
F dewpoints near and south of the OK border as of 325 pm.  RAP
forecast soundings show continued differential thermal advection
occurring during the next few hours with 500 mb temperatures cooling
from -16 deg C to -18 across this region.  Additional heating and
low-level moistening will contribute to a very unstable airmass
within this confined mesoscale corridor (2500-3000 J/kg MLCAPE). 
Some low-level backing of surface winds is expected which will
contribute to enlarging the hodograph during the 5-7 pm period.  If
an established quasi-discrete supercell manages to develop
(increasingly probable at this point), a tornado risk may accompany
it for an hour or so.  Large to giant hail (1 to 3.5 inches in
diameter) may also occur with the discrete surface-based updrafts. 
Further storm development and consolidation of cold pools into a
cluster by early evening will likely diminish the supercell-tornado
risk towards sunset.

..Smith.. 04/23/2021

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

ATTN...WFO...OUN...LUB...AMA...

LAT...LON   33569969 34179994 34450025 34759999 34459925 34049879
            33699885 33459921 33569969

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 23, 11:29 AM CDTMesoscale DiscussionSPCArcher, Bastrop, Bell, Bexar, Blanco, Bosque and 52 more91 min
Apr 23, 12:37 PM CDTSevere Thunderstorm WatchSPCAnderson, Archer, Bastrop, Bell, Blanco, Bosque and 53 more7 hr
Apr 23, 12:43 PM CDTMesoscale DiscussionSPCBaylor, Childress, Collingsworth, Cottle, Foard, Hall and 2 more3 hr
Apr 23, 12:43 PM CDTMesoscale DiscussionSPCAnderson, Angelina, Brazoria, Chambers, Cherokee, Fort Bend and 25 more2 hr
Apr 23, 2:00 PM CDTTornado WatchSPCAngelina, Austin, Brazos, Burleson, Chambers, Cherokee and 22 more7 hr
Apr 23, 3:14 PM CDTTornado WatchSPCArcher, Baylor, Childress, Clay, Collingsworth, Cottle and 7 more5 hr
Apr 23, 3:28 PM CDTMesoscale DiscussionSPCBosque, Brown, Comanche, Eastland, Erath, Hamilton and 11 more2 hr
Apr 23, 5:26 PM CDTMesoscale DiscussionSPCArcher, Baylor, Clay, Foard, Hardeman, Knox and 2 more2 hr
Apr 23, 5:36 PM CDTMesoscale DiscussionSPCAngelina, Houston, Jasper, Nacogdoches, Newton, Polk and 7 more54 min
Apr 23, 6:46 PM CDTMesoscale DiscussionSPCAtascosa, Bell, Bexar, Blanco, Bosque, Burnet and 19 more89 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.