Thunderstorms formed along a frontal boundary in Central Texas and moved through the northeastern part of South Central Texas. Some of these storms produced large hail.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS EWX wrote it up.
Thunderstorms formed along a frontal boundary in Central Texas and moved through the northeastern part of South Central Texas. Some of these storms produced large hail.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Austin/San Antonio, TX wrote its last area forecast discussion before the first event at Apr 12, 5:24 PM CST, 41 minutes earlier.
Area Forecast Discussion National Weather Service Austin/San Antonio TX 624 PM CDT Mon Apr 12 2021 .UPDATE... Thunderstorms to our west in Mexico have shown signs of weakening as they push slowly eastward. Current thoughts on this activity is that chances for it to cross the Rio Grande are quickly waning, but not yet zero. Storms have also fired just north of our area, currently in Mason and McCulloch as of 23Z. We've just added Gillespie, Llano, and Burnet counties to the active Severe Thunderstorm Watch 93 as storms may cross into these areas this evening. Large hail remains the primary threat with any storms that are able to impact our area. && .AVIATION... Anvil outflow from storms in Mexico is impacting DRT at this hour. Current thoughts based on radar trends are that these storms will not directly impact the terminal, but a brief shower cannot be completely ruled out through about 06Z. Overnight, a slow-moving cold front will eventually shift winds to the N/NE and low clouds will gradually build in and lower, with MVFR beginning by 04-06Z at the I-35 sites and 7-10Z at DRT. IFR cigs are expected at AUS/SAT/SSF for much of Tuesday morning before slowly lifting back to MVFR in the afternoon. There is a very small chance for isolated showers at all sites Tuesday afternoon, but right now the only place where confidence is high enough to include VCSH is DRT. && .PREV DISCUSSION... /ISSUED 202 PM CDT Mon Apr 12 2021/ SHORT TERM (Tonight through Tuesday Night)... Very warm and muggy across South-Central Texas this afternoon with dew points in the low to mid 60s. After the cloudy start, clouds have mixed out to mostly sunny to partly cloudy skies. Towards the late afternoon and into the evening, our attention turns to the potential for isolated to scattered strong to severe thunderstorms. The combination of a frontal boundary approaching from the north, subtle disturbances within the flow aloft and strong diurnal heating helps to erode the capping inversion and initiate the convection. Modeled parameters and sounding data support the development of the possibility for isolated and clusters of supercells with MLCAPE values between 2000 to 3000 J/kg, steep mid-level lapse rates of around 7 to 8 C/km and effective bulk shear values of 45 to 55 knots. Latest CAMs show cell initiation near the Serranias del Burro mountains in Mexico with help from orographic influences and along the front to the north across portions of the San Angelo CWA. This activity should approach the region with the high potential aligning along and west of a line from Eagle Pass to Burnet. This region is where the SPC has highlighted a slight risk. The marginal risk then extends a little further east along along and west of a line from Carrizo Springs to Boerne to Georgetown. The main hazards will be large hail and damaging winds. Couldn't rule out potential for significant hail (2 inches or large in diameter) with the most intense cells. These cells could be capable of producing a quick inch or so of rainfall but the overall rain amounts are to general remain unimpressive across the region. The convection will likely gradually weaken and diminish as activity advances toward the I-35 corridor as instability wanes later through the night and as the front potentially starts to undercut the activity. Once the main threat for storms comes to an end, expect cloudy and muggy conditions through the overnight hours and into the day on Tuesday as the front slowly moves southward. The front eventually stalls somewhere near the coastal plains on Tuesday. Expect for temperatures to be cooler behind the front but the daytime highs could become quite tricky depending on how fast the front does advance across the region and on where exactly it stalls. Highs could stay stuck in the 60s for portions of the Hill Country and Southern Edwards Plateau while temperatures approach the mid to upper 80s in the coastal plains closer to the proximity of the front. With the cooler air in wake of the front under the east- northeast surface flow, sufficient isentropic lift will be in place to yield to a continued opportunity for some low end chances of spotty shower activity through the remainder of the short term period. Additionally, isolated elevated thunderstorm chances are possible as well with instability above the 850 mb level. Local MUCAPE values are to range of around 1500 J/kg from Tuesday into Tuesday night while little to no SBCAPE exists. LONG TERM (Wednesday through Monday)... For Wednesday through Friday, surface high pressure ridging into our area maintains the shallow cool airmass on northeasterly lower level flow. A series of weak mid level impulses in a zonal flow aloft maintains a moist southerly flow just above this shallow cool airmass generating periods of widely scattered to scattered showers. Weak instability aloft will allow for mainly isolated thunderstorms. Temperatures will average slightly below normal. For Friday night through Monday, a stronger cold front moves through our area Friday night into early Saturday. Weak mid level impulses generate more rounds of showers with weak instability allowing for mainly isolated thunderstorms. Models have trended toward less QPF with a faster ending of POPs, as showers and storms become more elevated with time due to drier air filtering into our area in the wake of the frontal passage. Average temperatures will cool even further. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 87 63 76 63 75 / - 20 30 30 30 Austin Bergstrom Intl Airport 88 63 76 63 77 / - 20 30 30 30 New Braunfels Muni Airport 89 66 79 65 80 / - 20 20 20 30 Burnet Muni Airport 87 59 72 59 71 / - 30 30 30 30 Del Rio Intl Airport 93 66 75 66 80 / 20 30 30 20 50 Georgetown Muni Airport 87 60 75 61 74 / - 20 30 40 30 Hondo Muni Airport 92 67 81 65 81 / - 20 20 20 30 San Marcos Muni Airport 88 64 78 63 78 / - 20 20 30 30 La Grange - Fayette Regional 87 67 81 66 79 / 0 20 30 30 30 San Antonio Intl Airport 89 67 79 66 79 / - 20 20 20 30 Stinson Muni Airport 90 69 81 67 81 / - 20 20 20 30 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && Short-Term/Aviation...KCW Long-Term...Brady
Hazardous Weather Outlook National Weather Service Austin/San Antonio TX 419 AM CDT Mon Apr 12 2021 TXZ171>173-183>194-202>209-217>225-228-130930- Llano-Burnet-Williamson-Val Verde-Edwards-Real-Kerr-Bandera- Gillespie-Kendall-Blanco-Hays-Travis-Bastrop-Lee-Kinney-Uvalde- Medina-Bexar-Comal-Guadalupe-Caldwell-Fayette-Maverick-Zavala- Frio-Atascosa-Wilson-Karnes-Gonzales-De Witt-Lavaca-Dimmit- 419 AM CDT Mon Apr 12 2021 This Hazardous Weather Outlook is for South-Central Texas.. .DAY ONE...Today And Tonight. Isolated strong to severe thunderstorms are possible across parts of the Hill Country, Edwards Plateau, and Rio Grande Plains this afternoon into late tonight. Any storms that do form off the Serranias del Burro mountains in Mexico and move into the Rio Grande Plains, or develop along the front across the Edwards Plateau and Hill Country could produce large hail and damaging winds. The risk should generally decrease by early Tuesday morning as the front undercuts the storms. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. No hazardous weather is expected at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation is not anticipated.
The Ft Hood radar (KGRK), 148 km away, was scanning. The volume nearest the first event began at 00:05 UTC.
9 hail. Local standard time, as filed.
A thunderstorm produced golf ball size hail southeast of Pontotoc on CR 405. Hail accumulation reached three inches.
A thunderstorm produced baseball size hail near Llano.
A thunderstorm produced three inch diameter hail west of Llano.
A thunderstorm produced quarter to golf ball size hail west of Llano.
A thunderstorm produced tennis ball size hail in Llano. A broadcast media partner provided a photograph of the hail.
A thunderstorm produced golf ball size hail in Llano.
A thunderstorm produced two inch diameter hail in Llano.
A thunderstorm produced baseball size hail which broke car windows west of Llano.
A thunderstorm produced golf ball size hail near Llano.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Texas in 2021Every state in 2021This day in weather historyWarnings in Texas, April 2021
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 954373, 954374, 954375, 954376, 954377, 954378, 954379, 954380, 954381.