Alert archive / Texas / Mesoscale Discussions in 2021

Mesoscale Discussion 354

April 9, 2021Bryan County, Oklahoma; 23 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 9, 2021, 8:21 PM CDT for Bryan County, Oklahoma; 23 counties in Texas. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Apr 9, 2021, 8:21 PM CDT (01:21 UTC)
Expired: Apr 9, 2021, 11:15 PM CDT
In force: 3 hr
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 82

All 24 counties

Bryan County, OK, Bosque County, TX, Collin County, TX, Coryell County, TX, Dallas County, TX, Delta County, TX, Ellis County, TX, Falls County, TX, Fannin County, TX, Freestone County, TX, Grayson County, TX, Henderson County, TX, Hill County, TX, Hopkins County, TX, Hunt County, TX, Johnson County, TX, Kaufman County, TX, Lamar County, TX, Limestone County, TX, McLennan County, TX, Navarro County, TX, Rains County, TX, Rockwall County, TX, Van Zandt County, TX

The radar

The Dallas/Ft Worth radar (KFWS), 64 km from the middle of the area, began a volume at 01:22 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 00:00Z, 1.4 hours before the alert went out and 68 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: 3129 J/kg
Mixed-layer CIN: -45 J/kg
Mixed-layer LCL: 1600 m above ground
0-6 km bulk shear: 45 kt
0-1 km storm-relative helicity: 101 m²/s²
0-3 km storm-relative helicity: 128 m²/s²
Significant tornado parameter: 0.7
Supercell composite: 11.7

Open this sounding in Storm Lab

The text

As transmitted.

632 
ACUS11 KWNS 100121
SWOMCD
SPC MCD 100121 
TXZ000-OKZ000-100415-

Mesoscale Discussion 0354
NWS Storm Prediction Center Norman OK
0821 PM CDT Fri Apr 09 2021

Areas affected...parts of north Texas

Concerning...Severe Thunderstorm Watch 82...

Valid 100121Z - 100415Z

The severe weather threat for Severe Thunderstorm Watch 82
continues.

SUMMARY...Sporadic cells capable of large hail remain possible
within WW 82. A squall line is expected to back build southwestward
along the front later this evening, with damaging wind potential
into north Texas.

DISCUSSION...The 00Z FWD sounding shows strong instability, with
very steep lapse rates aloft and around 3500 J/kg MLCAPE. The
hodograph is mostly straightline, supporting splitting cells in the
Dallas area.

A strong cold front is currently surging southeast across southern
OK and into northwest TX. A squall line is taking shape over
southern OK, and further back building is expected as the strong
convergence interacts with the more unstable air mass south of the
Red River. Therefore, in addition to a hail threat in the short
term, a damaging wind threat may take shape over the next several
hours. It is difficult to determine how far southwest the squall
line will build, but portions of the I-35 corridor may be at risk
this evening.

..Jewell.. 04/10/2021

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

ATTN...WFO...SHV...TSA...FWD...OUN...

LAT...LON   31449788 32719731 33449692 33959680 34149637 34099567
            33829523 32859547 31869575 31519628 31219703 31129752
            31449788

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 9, 8:44 PM CDT	Severe Thunderstorm Watch	SPC	McCurtain	5 hr
Apr 9, 10:47 PM CDT	Mesoscale Discussion	SPC	Anderson, Angelina, Camp, Cass, Cherokee, Delta and 25 more	118 min
Apr 10, 12:52 AM CDT	Severe Thunderstorm Watch	SPC	Angelina, Cherokee, Gregg, Harrison, Marion, Nacogdoches and 6 more	3 hr

Nearby

Mesoscale Discussions in Texas, 2021 Mesoscale Discussions in Oklahoma, 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.