textproduct: Austin/San Antonio

KEY MESSAGES

- Flood Watch in effect for potentially life-threatening flash flooding somewhere in the watch area this afternoon and evening over the I-35 Corridor and Coastal Plains.

- A very humid and unsettled weather pattern continues through the middle of the upcoming week with daily rain and thunderstorm chances.

- Another round of strong to severe storms is possible today, with the greatest threat out west along the Rio Grande.

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

SHORT TERM

(Tonight through Monday night) Issued at 101 PM CDT Sun Apr 12 2026

Broad southwesterly flow at 500mb will continue for the foreseeable future. This will lead to a series of mid-level shortwaves rippling through this broad SW flow aloft. Each shortwave may fire off showers and storms, but both storm intensity and coverage are highly dependent on the timing of these individual shortwave disturbances. One such shortwave will move through the region this afternoon/evening, with the HRRR along with HREF indicating the potential for flash flooding and severe storms with large hail and damaging winds.

Locally heavy rainfall that could lead to flash flooding is possible, especially over the I-35 Corridor and Coastal Plains where a Flood Watch is in effect through Monday morning for potential of 2- 4 inches of rain with some isolated amounts between 5-10 inches. PWATs between 1.25-1.75" are around 150-175% of of normal for mid-April over South Central Texas. Any storms that form will likely contain torrential rainfall, with training of storms being the primary reason for the flooding concerns. Rainfall rates of up to 2-3" per hour are possible given the environment in place and a quick 5-10" is possible within the watch area. Be sure to monitor the weather and have Wireless Emergency Alerts active on your phone in the event of a Flash Flood Warning.

Despite dryline storm initiation yesterday, any convection that forms this afternoon/evening will be tied to the strength of the mid-level shortwave embedded in this southwesterly flow. Model Theta- e forecasts indicate the dryline will sharpen well west of our area, over West Texas, however, 0-6km Bulk Shear of 35-45 kts, in combination with HREF SBCAPE values in the 2000-3000 J/kg range will produce a favorable environment for severe storms to form. Large hail appears to be the primary concern as well given the HRRR spitting out MUCAPE values >3000 J/kg and 700-500mb lapse rates between 7-8 C/km. Any storms that can tap into this environment out west this afternoon may produce golf ball to tennis ball size hail. Damaging wind and a tornado cannot be ruled out either, but hail looks to be the biggest threat. The Storm Prediction Center has most of our area within a Level 2/5 risk today, given the environment noted above.

Monday will feature yet another threat for strong to severe storms. SPC has another level 1 of 5 risk for the Edwards Plateau and Rio Grande Plains. Monday's storm threat will be focused more on dryline development than Sunday's storms. Storms would develop over west of the Rio Grande and move off higher terrain or the dryline over west Texas and into the EWX CWA. Once again, the greatest threat from any storms that form looks to be large hail, but damaging wind is also a possibility. PWATs are not as high on Monday out west, so the flooding threat is low.

LONG TERM

(Tuesday through next Sunday) Issued at 101 PM CDT Sun Apr 12 2026

The long term period will remain active, as that persistent southwesterly 500mb flow continues. An upper level trough that's slowly moving inland over California will finally move into the Four Corners by Tuesday morning. Another round of showers and storms, some strong to severe is possible Tuesday, again over the Southern Edwards Plateau and Rio Grande Plains. Another round of showers and storms, some possibly strong to severe, will occur Wednesday afternoon and evening, primarily west of I-35, but some of these storms could work east into the I-35 Corridor late Wednesday evening.

The upper level trough will eventually eject and open up over the Plains on Wednesday, bringing an end to our more active stretch of weather the past week. Thursday and Friday will feature highs back in the mid to upper 80s with dry conditions. Beyond that, global models are actually in agreement on the passage of a fairly strong cold front for mid-April. While the ECMWF has a passage on Saturday afternoon, the GFS has a frontal passage on Saturday night. Both models feature rain and thunderstorms developing along this front. It is too early to say whether severe weather is possible with this boundary, but keep checking back over the next couple days as the forecast is further refined and confidence increases.

AVIATION

(00Z TAFS) Issued at 550 PM CDT Sun Apr 12 2026

Mainly VFR to MVFR conditions across the area to start the period with MVFR ceilings favored to develop again first over I-35 corridor and Coastal Plains, then spread west across the area into early Monday morning. Showers may continue over the I-35 terminals for the next few hours with low chances for thunderstorm redevelopment tonight that will need to be monitored. Ceilings likely drop to IFR between 03-06Z at I-35 terminals, then around 12Z for KDRT. Ceilings may drop to LIFR and patchy dense fog may develop, but confidence is low and not mentioned in the forecast. Ceilings are slow to lift and scatter with IFR to MVFR conditions into early Monday afternoon.

PRELIMINARY POINT TEMPS/POPS

Austin Camp Mabry 70 85 69 86 / 60 10 0 10 Austin Bergstrom Intl Airport 69 85 68 85 / 60 20 0 10 New Braunfels Muni Airport 69 86 68 86 / 50 20 10 10 Burnet Muni Airport 67 83 67 82 / 50 10 10 20 Del Rio Intl Airport 70 87 70 84 / 10 20 40 40 Georgetown Muni Airport 69 82 67 82 / 60 10 0 10 Hondo Muni Airport 67 85 68 85 / 40 20 20 20 San Marcos Muni Airport 69 85 68 85 / 60 20 10 10 La Grange - Fayette Regional 70 85 69 87 / 50 20 0 0 San Antonio Intl Airport 70 85 70 85 / 50 20 10 10 Stinson Muni Airport 71 86 70 86 / 40 20 10 10

EWX WATCHES/WARNINGS/ADVISORIES

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