An upper level low moved slowly across the southwestern US and generated several rounds of thunderstorms over South Central Texas. Storms during this period produced two tornadoes, damaging winds, large hail, and heavy rain that led to flash flooding. Most of the severe weather occurred in two periods on May 18: the early morning and the late afternoon and evening.

Hail in BURNET, TEXAS
From 17-MAY-21 11:33:00 to 17-MAY-21 11:33:00 (CST-6)
Location: BURNET CRADDOCK ARPT
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

Hail in COMAL, TEXAS
From 18-MAY-21 14:24:00 to 18-MAY-21 14:24:00 (CST-6)
Location: NEW BRAUNFELS
Magnitude: 1.25 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

A thunderstorm produced quarter and larger size hail on the west side of New Braunfels.

Hail in COMAL, TEXAS
From 18-MAY-21 14:34:00 to 18-MAY-21 14:34:00 (CST-6)
Location: GRUENE
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: NWS Employee

Thunderstorm Wind in GUADALUPE, TEXAS
From 18-MAY-21 14:36:00 to 18-MAY-21 14:36:00 (CST-6)
Location: CLEAR SPG
Magnitude: 57.00 EG
Property damage: 0.00K
Crop damage: 0.00K
Reported by: ASOS

A thunderstorm produced wind gusts measured at 66 mph by the ASOS at New Braunfels Regional Airport.

Hail in HAYS, TEXAS
From 18-MAY-21 15:09:00 to 18-MAY-21 15:09:00 (CST-6)
Location: KYLE
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A thunderstorm produced quarter size hail in Kyle.

Thunderstorm Wind in HAYS, TEXAS
From 18-MAY-21 15:20:00 to 18-MAY-21 15:20:00 (CST-6)
Location: BUDA
Magnitude: 61.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Broadcast Media

A thunderstorm produced wind gusts estimated at 70 mph that knocked down a few trees in Buda.

Thunderstorm Wind in LAVACA, TEXAS
From 18-MAY-21 15:50:00 to 18-MAY-21 15:50:00 (CST-6)
Location: SUBLIME
Magnitude: 65.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A thunderstorm produced wind gusts estimated at 75 mph that damaged a barn and some trees near Sublime.

Flash Flood in FAYETTE, TEXAS
From 18-MAY-21 18:28:00 to 18-MAY-21 18:28:00 (CST-6)
Location: FLATONIA MUNI ARPT
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Thunderstorms produced heavy rain that led to flash flooding. FM 609 was flooded under I-10 in Flatonia.

Flash Flood in FAYETTE, TEXAS
From 18-MAY-21 20:58:00 to 18-MAY-21 20:58:00 (CST-6)
Location: LA GRANGE
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorms produced heavy rain that led to flash flooding. The Fayette County Sheriff reported five water rescues and multiple roads closed around the county.

Hail in VAL VERDE, TEXAS
From 19-MAY-21 13:30:00 to 19-MAY-21 13:30:00 (CST-6)
Location: AMISTAD RES EAST
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Public

A thunderstorm produced quarter size hail in Lake View north of Del Rio.

Thunderstorm Wind in BEXAR, TEXAS
From 18-MAY-21 01:20:00 to 18-MAY-21 01:20:00 (CST-6)
Location: SAN ANTONIO
Magnitude: 56.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Public

A thunderstorm produced wind gusts estimated at 65 mph that knocked down some one inch diameter tree limbs in southern San Antonio.

Tornado in LAVACA, TEXAS
From 18-MAY-21 15:54:00 to 18-MAY-21 15:58:00 (CST-6)
Location: SUBLIME
Tornado F-scale: EF1
Property damage: 20.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

Video evidence and an NWS Storm Survey confirmed a tornado touched down roughly one mile northwest of Sublime, south and east of CR 142. The tornado moved northwest and severely damaged a small house as well as snapped large tree branches. Wind speeds at this point were estimated to be 80-100 mph. The tornado crossed CR 142 between CR 159 and CR 143, west of the Navidad River, and continued through open farm land producing sporadic tree damage. The tornado then crossed CR 138 at the Navidad River, completely snapping three foot diameter tree trunks of a few trees near their bases and snapping large limbs of several other trees. Wind speeds at this point were also estimated to be 80-100 mph. The tornado dissipated to the northwest of CR 138. Sporadic straight-line wind damage, in the form of snapped tree limbs, was also observed along CR 159, 211, and 138, west of the tornadic circulation.

Tornado in FAYETTE, TEXAS
From 18-MAY-21 17:42:00 to 18-MAY-21 17:52:00 (CST-6)
Location: SWISS ALP
Tornado F-scale: EF1
Property damage: 100.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The combination of an NWS damage survey and storm chaser video and documentation has concluded that an EF1 tornado occurred during the early evening hours of May 18th near Swiss Alp, TX in Fayette County. The tornado occurred in a large cluster of storms that were generally moving east across Fayette County. There were multiple mid-level circulations evident on radar during this event.  So while a single tornado path has been created, there may have been other smaller satellite tornadoes or vortices that caused minor wind damage in other areas of Fayette County that evening.  Storm Chaser video
showed a multi-vortex tornado on the ground near Swiss Alp and this discussion is the best conclusion we have on the path, width and strength of that tornado. Based on video, storm reports, and tree damage, it appears the tornado first touched down around 6:42 PM CDT just west of Hwy 77near the intersection of Hwy 77 and CR 956.   Some minor tree damage was found in this area as well as power poles snapped on Hwy 77.  As the tornado crossed Hwy 77, it became larger and multi-vortex as it moved northeast across open pasture and farmland. At approximately 6:48 PM CDT it caused significant damage to a cattle farm approximately one mile south of FM 1383.  Metal roofing was removed from multiple cattle shade shelters, there was roof damage to
the business office, and partial structure collapse and roof damage to the main covered building, and cattle working area.  Several trees had significant trunk and branch damage on the property as well. Metal roofing material was found several hundred yards away. The tornado continued to move northeast and eventually crossed Berger
Rd.  Several trees were snapped along Berger Rd. and adjacent properties. It is not totally clear where the tornado dissipated as some sporadic minor tree damage was found farther NE by about a mile.  Due to the weak nature of the damage, we elected to end the track just east of Berger Rd. at 6:52 PM CDT.  Based on the damage seen on the ground, it is estimated that peak winds were near 100 mph (EF1) and the tornado was several hundred yards wide when it was multi-vortex.  It was on the ground for a little over 3 miles.

Thunderstorm Wind in COMAL, TEXAS
From 18-MAY-21 13:14:00 to 18-MAY-21 13:14:00 (CST-6)
Location: BULVERDE
Magnitude: 65.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: NWS Employee

A thunderstorm produced wind gusts estimated at 75 mph that broke large tree limbs that were four to five inches in diameter.