Alert archive / Texas / Mesoscale Discussions in 2021
Mesoscale Discussion 387
The Storm Prediction Center issued this mesoscale discussion at Apr 15, 2021, 8:17 AM CDT for 19 counties in Texas. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 15, 2021, 8:17 AM CDT (13:17 UTC)
- Expired
- Apr 15, 2021, 10:45 AM CDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
Counties Atascosa County, TX, Bandera County, TX, Bexar County, TX, Blanco County, TX, Comal County, TX, Edwards County, TX, Frio County, TX, Gillespie County, TX, Guadalupe County, TX, Kendall County, TX, Kerr County, TX, Kimble County, TX, Kinney County, TX, Medina County, TX, Real County, TX, Uvalde County, TX, Val Verde County, TX, Wilson County, TX, Zavala County, TX
The radar
The Laughlin AFB radar (KDFX), 62 km from the middle of the area, began a volume at 13:16 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
Del Rio, TX (KDRT), launched 12:00Z, 1.3 hours before the alert went out and 110 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
- 2593 J/kg
- Mixed-layer CIN
- -44 J/kg
- Mixed-layer LCL
- 634 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- 169 m²/s²
- 0-3 km storm-relative helicity
- 338 m²/s²
- Significant tornado parameter
- 4.6
- Supercell composite
- 21.4
The text
As transmitted.
781
ACUS11 KWNS 151318
SWOMCD
SPC MCD 151317
TXZ000-151545-
Mesoscale Discussion 0387
NWS Storm Prediction Center Norman OK
0817 AM CDT Thu Apr 15 2021
Areas affected...Southwest and South-central Texas
Concerning...Severe potential...Watch possible
Valid 151317Z - 151545Z
Probability of Watch Issuance...60 percent
SUMMARY...The potential for large hail will likely increase over the
next few hours as cells develop across southwest Texas. Weather
watch issuance may need to be considered.
DISCUSSION...The latest radar imagery shows a couple of isolated
storms ongoing just to the east of Del Rio. These storms are
developing in a warm advection regime where low-level convergence is
maximized. The storms are located along the northern edge of
moderate instability and will move eastward along the instability
gradient over the next few hours. MLCAPE is estimated to be in the
1500 to 2500 J/kg range across much of southwest Texas. The storms
will remain elevated due to a strong capping inversion that is
present. RAP forecast soundings across southwest Texas this morning
show effective shear near 60 kt with 700-500 mb lapse rates near 7.5
C/km. This environment should be favorable for supercells with large
hail. As the storms become more organized this morning, the
possibility for hailstones of greater than 2 inches in diameter will
exist.
..Broyles/Thompson.. 04/15/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CRP...EWX...SJT...
LAT...LON 29080077 28840040 28639964 28649890 28849825 29269792
29829791 30349827 30629882 30610007 30420099 30110116
29730115 29300089 29080077SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 15, 8:36 AM CDT | Severe Thunderstorm Watch | SPC | Bandera, Blanco, Burnet, Concho, Crockett, Edwards and 19 more | 8 hr |
| Apr 15, 10:56 AM CDT | Mesoscale Discussion | SPC | Bandera, Concho, Edwards, Gillespie, Kerr, Kimble and 9 more | 94 min |
| Apr 15, 12:24 PM CDT | Mesoscale Discussion | SPC | Bastrop, Bell, Blanco, Burnet, Coryell, Falls and 12 more | 2 hr |
| Apr 15, 4:55 PM CDT | Mesoscale Discussion | SPC | Austin, Brazoria, Burleson, Fort Bend, Harris, Lee and 4 more | 3 hr |
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.