textproduct: Austin/San Antonio

KEY MESSAGES

- Storms with potential for locally heavy rain and severe weather late tonight with the highest risks near the Rio Grande.

- Active weather pattern continues through the upcoming Memorial Holiday weekend. Multiple rounds of storms with heavy rain could lead to localized flooding.

- Wet pattern likely to continue into next week.

SHORT TERM

(Today through Thursday) Issued at 147 AM CDT Wed May 20 2026

Last night's storms exhausted a substantial portion of available instability in the atmosphere. This has muted activity for most of South-Central Texas today aside from some isolated storm activity along the Rio Grande, but the surface boundary layer is expected to recover further with additional low-level moisture returning from the Corpus Christi area towards the Rio Grande and up into West Texas, running up against the dry line there and over Mexico. An impulse of mid- level energy should overlap with the moisture and dry line tonight, leading to the development of storms near the Rio Grande and West Texas in the evening which may organize into an eastward-advancing broken line of storms during the overnight hours into early Thursday morning given the distinctly meridional mid-level flow.

Some initial isolated storms could develop closer to the Rio Grande and Edwards Plateau closer to sunset, but the bulk of the activity and the potential line-to-be are generally favored after midnight and this is reflected in hi-res models. Scattered storms should push across the southern Edwards Plateau, Rio Grande Plains and Hill Country late this evening into the wee hours of the morning, potentially reaching the I-35 corridor in the pre-dawn hours and then the Coastal Plains Thursday morning. Instability and shear are not expected to be as high as last night, so it's somewhat unclear how far east these storms will get... there's a decent chance they could be running out of steam and producing mostly stratiform light/moderate rains as they move over I-35 and the Coastal Plains.

The initial environment along the Rio Grande is supportive of slower storm motions and would be in a >95th percentile precipitable water environment, so a few slow-moving heavy downpours capable of localized flash flooding are possible this evening and tonight especially if storms develop early. The main line of storms should be moving at a decent clip eastward, but will overlap with the areas saturated by last night's storms. This could lead to isolated flooding concerns, particularly in urban areas, despite generally lower rain totals overall farther east. A Level 2 of 4 (Slight) risk of excessive rain capable of flash flooding is indicated by the WPC for all of South-Central Texas through Thursday morning. Broad rain amounts of 0.5-1.5 inches with isolated totals in the 3-5 inch range are possible over the Rio Grande Plains and Edwards Plateau. Amounts generally lessen farther east, with areal amounts in the 0.1-0.75 inch range and isolated pockets of 1-3 inches possible as rains move to the I- 35 corridor and points east. The severe risk will be higher with the initial developments along the Rio Grande and Edwards Plateau where shear and instability are higher, with isolated instances of large hail possible with a transition to isolated damaging wind as the line of storms materializes. Given the lower energy available farther east, the severe threat tapers off towards I-35, though frequent lightning and intermittent gusty winds remain possible. A Level 2 of 5 (Slight) risk for severe weather is depicted for the Del Rio, Rocksprings, Brackettville, and Eagle Pass areas, with a Level 1 of 5 (Marginal) risk extending to just west of a Fredericksburg to San Antonio to Pleasanton line.

With tonight's line of storms, we'll once again repeat the cycle of overnight action keeping daytime activity on the quieter side on Thursday. Conditions are not expected to be as humid during the day, though cooler mid-level temperatures around the core of the aforementioned impulse of mid-level energy and continued southerly flow off the Gulf could support some isolated to scattered thunderstorms Thursday afternoon and evening, with this arrangement tending to produce the greatest chances in the Austin area, Hill County, and Coastal Plains. While the hi-res models disagree on the prospects for another round of an organized storm cluster developing near the Rio Grande later Thursday, the presence of yet another mid- level disturbance moving over the region around that time indicates that there is a window of opportunity for some convective complex moving east across our zone late Thursday into Friday morning. The potential there would probably become clearer once we can diagnose how tonight's line of storms interacts with the environment.

LONG TERM

(Friday through next Wednesday) Issued at 123 PM CDT Wed May 20 2026

The wet pattern is likely to continue through at least the middle of next week, and potentially through the entirety of next week as troughing near our area continues to provide a favorable pathway for moisture and disturbances to repeatedly stream over Texas.

There is a favorable window this weekend for potentially widespread rains with locally heavier amounts. A pronounced trough is expected to swing out of the Baja California Saturday and move across our area during the day into Sunday. While the specifics of how the accompanying rain may set up are fuzzy at the moment, among the various disturbances in the forecast range this one is the most well- defined in the upper-levels of the troposphere. Currently, the medium range ensemble guidance is weighted towards the I-35 corridor and Coastal Plains late Saturday to early Sunday, but expect that timing to be refined in later forecasts.

Ridging builds over the Central and Northern Plains early next week, with both the GEFS and ENS ensemble suites in agreement on this depiction. This holds the trough in place over Texas and could provide additional rounds of rain between Sunday and Tuesday. While the average placement of the trough in the ensembles tends to cycle in drier mid-level air over our area, if the stalled position is slightly farther west, it could amplify rain amounts over South- Central Texas.

Towards the midweek, broader troughing rebuilds over the western US. This allows the stalled trough to get moving again, only to be replaced by more southwesterly flow aloft, keeping the door open for more rain chances. Thus, the overall forecast picture is definitively wet as we start to close out May. The grand ensemble (GEFS, ENS, and GEPS combined) has impressive mean rainfall amounts above 3 inches across nearly all of South-Central Texas through the middle of next week, which is an impressive amount for lower resolution medium range models to be projecting.

Each round of rainfall will continue to moisten/saturate soils, increasing the potential for runoff which may eventually lead to flash flooding or river flooding. Given the dependence on where each round of storms moves across, pinpointing exact rainfall totals is difficult though we do expect many to receive widespread beneficial rainfall. Those that see multiple storms repeatedly tracking over their area could eventually see flooding and cannot rule out a Flood Watch later in the week or weekend. Continue to monitor the forecast and always have a way to receive warning information.

AVIATION

(18Z TAFS) Issued at 1247 PM CDT Wed May 20 2026

A combination of MVFR and VFR conditions are forecast for the local area terminals through Thursday evening. Can't rule IFR cigs at KSSF for a few hours block around sunrise. Another round of storms is forecast for the Rio Grande Plains and Southern Edwards Plateau this evening into the overnight period. Any strong to severe storms that move over the KDRT terminal could bring visibility down a category or two. East to southerly winds are forecast through the forecast period.

PRELIMINARY POINT TEMPS/POPS

Austin Camp Mabry 70 80 69 86 / 60 60 50 30 Austin Bergstrom Intl Airport 70 80 69 86 / 60 60 50 40 New Braunfels Muni Airport 69 81 68 86 / 60 60 40 40 Burnet Muni Airport 67 77 66 84 / 60 60 40 20 Del Rio Intl Airport 67 84 68 88 / 90 20 10 20 Georgetown Muni Airport 68 78 67 85 / 60 60 50 30 Hondo Muni Airport 68 81 67 85 / 90 40 30 10 San Marcos Muni Airport 70 81 69 86 / 60 60 40 40 La Grange - Fayette Regional 71 80 70 85 / 60 70 50 50 San Antonio Intl Airport 70 82 70 86 / 70 50 40 30 Stinson Muni Airport 70 82 70 87 / 70 50 40 20

EWX WATCHES/WARNINGS/ADVISORIES

None.