Alert archive / Texas / Severe Thunderstorm Watches in 2017

Severe Thunderstorm Watch 253

May 20, 201724 counties in Texas

The Storm Prediction Center issued this severe thunderstorm watch at May 20, 2017, 10:15 AM CDT for 24 counties in Texas. It was in force for 11 hr.

The area

The outline as issued.

The facts

Issued
May 20, 2017, 10:15 AM CDT (15:15 UTC)
Expired
May 20, 2017, 9:00 PM CDT
In force
11 hr
Issued by
the Storm Prediction Center
Largest hail expected
2.5 in
Strongest gust expected
60 kt
All 24 counties

Atascosa County, TX, Bee County, TX, Bexar County, TX, DeWitt County, TX, Dimmit County, TX, Duval County, TX, Frio County, TX, Goliad County, TX, Gonzales County, TX, Guadalupe County, TX, Jim Wells County, TX, Karnes County, TX, Kinney County, TX, La Salle County, TX, Lavaca County, TX, Live Oak County, TX, Maverick County, TX, McMullen County, TX, Medina County, TX, Uvalde County, TX, Victoria County, TX, Webb County, TX, Wilson County, TX, Zavala County, TX

The radar

The Austin/San Antonio radar (KEWX), 114 km from the middle of the area, began a volume at 15:18 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
20%
One or more EF2 to EF5 tornadoes
5%
Ten or more severe wind reports
40%
One or more gusts of 65 knots or more
10%
Ten or more severe hail reports
40%
One or more hailstones of 2 inches or more
30%
Six or more combined severe hail and wind reports
60%

Warnings issued inside it

13 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
May 20, 10:48 AM CDTFlash Flood WarningEWXMedina, Uvalde3 hr
May 20, 11:17 AM CDTSevere Thunderstorm WarningEWXFrio, Medina58 min
May 20, 12:22 PM CDTSevere Thunderstorm WarningEWXFrio68 min
May 20, 12:40 PM CDTFlash Flood WarningEWXFrio3 hr
May 20, 1:24 PM CDTSevere Thunderstorm WarningEWXFrio, Zavala81 min
May 20, 3:12 PM CDTSevere Thunderstorm WarningEWXFrio, Zavala48 min
May 20, 3:25 PM CDTSevere Thunderstorm WarningCRPLa Salle39 min
May 20, 4:22 PM CDTSevere Thunderstorm WarningCRPLa Salle38 min
May 20, 4:58 PM CDTSevere Thunderstorm WarningCRPLa Salle, Webb32 min
May 20, 5:29 PM CDTSevere Thunderstorm WarningCRPDuval, La Salle, McMullen, Webb46 min
May 20, 6:14 PM CDTSevere Thunderstorm WarningCRPDuval, Webb46 min
May 20, 6:40 PM CDTSevere Thunderstorm WarningCRPDuval50 min
May 20, 6:55 PM CDTSevere Thunderstorm WarningCRPDuval39 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

Del Rio, TX (KDLF), launched 12:00Z, 3.3 hours before the alert went out and 180 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, Del Rio, TX at 12:00Z on 2017-05-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1534 joules per kilogram.LCLLFCEL10008507005003002001001 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, Del Rio, TX at 12:00Z on 2017-05-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 92 square meters per square second.19395878Sfc1 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
1534 J/kg
Mixed-layer CIN
-49 J/kg
Mixed-layer LCL
661 m above ground
0-6 km bulk shear
33 kt
0-1 km storm-relative helicity
92 m²/s²
0-3 km storm-relative helicity
118 m²/s²
Significant tornado parameter
0.7
Supercell composite
6.1

Open this sounding in Storm Lab

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 19, 7:15 PM CDTMesoscale DiscussionSPCBrown, Callahan, Coke, Coleman, Concho, Fisher and 11 more60 min
May 19, 7:44 PM CDTTornado WatchSPCBrown, Callahan, Coke, Coleman, Concho, Fisher and 15 more7 hr
May 19, 11:05 PM CDTMesoscale DiscussionSPCBrown, Callahan, Coke, Coleman, Comanche, Concho and 14 more115 min
May 20, 7:41 AM CDTMesoscale DiscussionSPCAransas, Atascosa, Bandera, Bee, Bexar, Caldwell and 21 more94 min
May 20, 12:56 PM CDTMesoscale DiscussionSPCAtascosa, Bee, Bexar, DeWitt, Dimmit, Frio and 13 more94 min
May 20, 3:46 PM CDTMesoscale DiscussionSPCAtascosa, Bee, Bexar, DeWitt, Dimmit, Duval and 19 more59 min

Nearby

Severe Thunderstorm Watches in Texas, 2017Every severe thunderstorm watch in 2017

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.