Alert archive / Texas / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 101
The Storm Prediction Center issued this severe thunderstorm watch at Apr 23, 2021, 7:05 PM CDT for 9 counties in Texas. It was in force for 3 hr.
The area
The outline as issued.
The facts
- Issued
- Apr 23, 2021, 7:05 PM CDT (00:05 UTC)
- Expired
- Apr 23, 2021, 9:50 PM CDT
- In force
- 3 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2.5 in
- Strongest gust expected
- 60 kt
Counties Atascosa County, TX, Bexar County, TX, DeWitt County, TX, Fayette County, TX, Gonzales County, TX, Guadalupe County, TX, Karnes County, TX, Lavaca County, TX, Wilson County, TX
The radar
The Austin/San Antonio radar (KEWX), 32 km from the middle of the area, began a volume at 00:07 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.
What SPC expected
The probabilities SPC published with the watch, for the watch area over its life.
- Two or more tornadoes
- 10%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 30%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 40%
- One or more hailstones of 2 inches or more
- 40%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
4 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 23, 7:16 PM CDT | Severe Thunderstorm Warning | EWX | Bexar, Wilson | 29 min |
| Apr 23, 7:39 PM CDT | Severe Thunderstorm Warning | EWX | Atascosa, Karnes | 51 min |
| Apr 23, 7:42 PM CDT | Severe Thunderstorm Warning | EWX | Bexar, Wilson | 48 min |
| Apr 23, 8:14 PM CDT | Severe Thunderstorm Warning | EWX | DeWitt, Gonzales, Karnes, Wilson | 46 min |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Corpus Christi, TX (KCRP), launched 00:00Z, 0.1 hours before the alert went out and 197 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
- 1602 J/kg
- Mixed-layer CIN
- -138 J/kg
- Mixed-layer LCL
- 883 m above ground
- 0-6 km bulk shear
- 58 kt
- 0-1 km storm-relative helicity
- 31 m²/s²
- 0-3 km storm-relative helicity
- 44 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 1.3
The text
As transmitted.
221
WWUS20 KWNS 240001
SEL1
SPC WW 240001
TXZ000-240400-
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 101
NWS Storm Prediction Center Norman OK
705 PM CDT Fri Apr 23 2021
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
South central Texas
* Effective this Friday evening from 705 PM until 1100 PM CDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2.5
inches in diameter possible
Isolated damaging wind gusts to 70 mph possible
SUMMARY...A few storms now forming near and south of San Antonio may
persist for a few more hours while spreading eastward. The storm
environment will support supercells capable of producing isolated
very large hail and damaging gusts.
The severe thunderstorm watch area is approximately along and 35
statute miles north and south of a line from 35 miles south
southwest of San Antonio TX to 75 miles east of New Braunfels TX.
For a complete depiction of the watch see the associated watch
outline update (WOUS64 KWNS WOU1).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 98...WW 99...WW 100...
AVIATION...A few severe thunderstorms with hail surface and aloft to
2.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
27025.
...ThompsonSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Apr 23, 7:42 PM CDT | Severe Thunderstorm Watch | SPC | Bee, Goliad, Live Oak, Victoria | 2 hr |
| Apr 23, 7:43 PM CDT | Mesoscale Discussion | SPC | Clay, Cooke, Grayson, Hardeman, Montague, Wichita and 1 more | 2 hr |
| Apr 23, 8:02 PM CDT | Severe Thunderstorm Watch | SPC | Archer, Clay, Cooke, Denton, Grayson, Jack and 3 more | 4 hr |
| Apr 23, 11:19 PM CDT | Mesoscale Discussion | SPC | Camp, Delta, Fannin, Franklin, Hopkins, Lamar and 2 more | 116 min |
Nearby
Severe Thunderstorm Watches in Texas, 2021Every severe thunderstorm watch 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.