textproduct: Austin/San Antonio

KEY MESSAGES

- A line of storms will continue across the across the Hill Country towards the I-35 corridor early Sunday morning, with heavy downpours and isolated severe weather possible.

- Isolated strong to severe storms with heavy downpours are possible this afternoon and evening across South-Central Texas.

- The potential for strong to severe storms and locally heavy rainfall continues through the weekend into early next week.

UPDATE

Issued at 1037 AM CDT Sun Apr 12 2026

A Flood Watch is now in effect for the I-35 Corridor and Coastal Plains that goes through tomorrow morning. A heavy rain signal continues to increase confidence in potential flooding for areas in the watch this afternoon through tonight.

SHORT TERM

(Today through Monday) Issued at 136 AM CDT Sun Apr 12 2026

As of 1 AM CDT Sunday, a line of strong to marginally severe thunderstorms was moving across the southern Edwards Plateau and Hill Country. It will continue to advance across the Hill Country and portions of the I-35 corridor (mainly near the Austin area) early this morning. The primary concern, given the very moist airmass in place, is locally heavy downpours with the potential for isolated instances of flash flooding. A residual isolated damaging wind threat is also possible and underlies the currently active Severe Thunderstorm Watches. However, that risk that should generally decline during the morning as the storms move farther east and start to lose their definition amid stabilizing air.

The forecast during the day Sunday is more uncertain than usual. The morning storms are expected to consume some of the instability over South-Central Texas and introduce slight capping. However, the storms may leave a surface boundary draped across our area, and the persistence of a warm and moist airmass will allow instability to build throughout the day, especially along and west of the I-35 corridor. Isolated to scattered showers may continue through the morning into the afternoon. If updrafts punch cleanly through the cap, particularly on the leftover outflow boundary, there could be a few isolated thunderstorms with accompanying heavy rain. Not all of the high resolution models depict these stronger storms in the afternoon, but those that do favor the I-35 corridor and Hill Country. Given very high moisture levels for this time of year and favorable atmospheric profiles, even relatively small showers can still be highly efficient rainmakers. Even with the relatively low confidence in storm coverage, the presence of a Level 2 of 4 (Slight) risk of excessive rainfall capable of causing flash flooding underscores the anomalous moisture available to any showers that develop Sunday. Based on this environment, this is our main concern with today's storms.

Towards the evening hours and into Sunday night, sufficient heating over Mexico and a subtle shortwave moving across the Rio Grande may prompt the development thunderstorms. However, it is unclear whether these will also extend into the Rio Grande Plains and southern Edwards Plateau. If they do, the presence of moderately strong wind shear (30-40 kt bulk shear) and high instability (above 2000 J/kg CAPE) could support severe storms, with large hail the primary hazard. This potential is encapsulated in the Level 2 of 5 (Slight) risk for severe weather highlighted by the SPC for areas generally along and west of the I-35 corridor. However, much like the activity earlier on Sunday, the occurrence of this activity is highly sensitive to preceding developments. Most of the hi-res models show very sparse storm coverage Sunday evening, while the coarser synoptic-scale models and machine learning models favor more rain coverage. We'll likely have a better handle on this activity once we're able to assess how the current line of storms impacts the atmospheric environment.

Precipitable water levels ease slightly on Monday, but nonetheless it will remain moist with PW above the 90th percentile. Stronger capping is expected to be in place, and should generally limit shower coverage. Still, a few thunderstorms could develop along the dry line in West Texas, which could produce isolated severe activity in the southern Edwards Plateau Monday evening.

LONG TERM

(Monday night through Saturday) Issued at 136 AM CDT Sun Apr 12 2026

The broad upper-level troughing pattern helping to shape our unsettled weather persists through next week, along with the warm and moist airmass over Texas. Southwesterly flow aloft will provide continued chances for showers and thunderstorms most days, typically in the afternoon and early evening in tandem with daytime heating. Given the anomalous airmass, strong storms with locally heavy rainfall will also be possible throughout the week.

Around midweek, a stronger shortwave associated with the broader pattern swings east into the Central Plains, accompanied by a round of stronger storms over the Central US. While the trajectory of this trough will tend to keep the worst weather farther north, some stronger storms could extend into our area sometime Tuesday or Wednesday. Southwesterly mid- to upper-level flow continues through the remainder of the week, though the lack of well-defined shortwaves during the latter half of the week may limit the potential for stronger storms and keep showers more isolated compared to what we've been seeing the past few days.

Overnight temperatures will be relatively stable through the week, buoyed into the 60s and low 70s by high dew points. Daytime highs will generally be in the 80s, but could warm some into the low 90s late next week during slightly calmer stretches with less rain.

AVIATION

(12Z TAFS) Issued at 607 AM CDT Sun Apr 12 2026

MVFR and IFR conditions are forecast for the local area terminals for a good portion of this forecast cycle. A cluster of storms is moving currently over DRT and could last through 13Z. Showers and storms continue throughout the day with several rounds of moderate to heavy showers and isolated to scattered thunderstorm activity. The most difficult terminals are the ones along the I-35 Corridor as far as the intensity and timing of the storms to move over the terminals. With that said, have added the possible rounds for AUS and the best time frame for the storms to impact the San Antonio sites (mainly in the afternoon). The storm activity could come to an end mid evening, however, IFR cigs are in store for the I-35 sites for the overnight hours through Monday morning. Southeast flow remains through the period with speeds around 10 to 20 knots and gusts up to 25 knots.

PRELIMINARY POINT TEMPS/POPS

Austin Camp Mabry 79 70 85 69 / 80 60 10 0 Austin Bergstrom Intl Airport 79 69 85 68 / 80 60 20 0 New Braunfels Muni Airport 79 69 86 68 / 70 50 20 10 Burnet Muni Airport 77 67 83 67 / 70 50 10 10 Del Rio Intl Airport 85 70 87 70 / 30 10 20 40 Georgetown Muni Airport 79 69 82 67 / 80 60 10 0 Hondo Muni Airport 81 67 85 68 / 60 40 20 20 San Marcos Muni Airport 80 69 85 68 / 70 60 20 10 La Grange - Fayette Regional 80 70 85 69 / 70 50 20 0 San Antonio Intl Airport 80 70 85 70 / 70 50 20 10 Stinson Muni Airport 80 71 86 70 / 60 40 20 10

EWX WATCHES/WARNINGS/ADVISORIES

Flood Watch through Monday morning for TXZ173-191>194-206>209- 223>225.