textproduct: Austin/San Antonio

KEY MESSAGES

- Low to medium chances for rain this afternoon/evening. Isolated showers and storms may develop with the most favored areas over the southern Edwards Plateau, Rio Grande, and parts of the Hill Country.

- Flood Watch Friday evening through Monday evening for areas along and east of a Kerr to Frio County line.

- Active and unsettled weather pattern continues into next week. Multiple rounds of storms with heavy rain are possible and could lead to localized flooding.

SHORT TERM

(Tonight through Friday night) Issued at 301 PM CDT Thu May 21 2026

A stalled frontal boundary along with previous outflow boundaries will be the main focus for additional thunderstorm development late this afternoon into tonight. Many areas did not receive much in the way of showers and thunderstorms last night which leads to a rather challenging and low confidence forecast for the short term portion. That being said we are starting to see clouds clearing in the western half of the area when looking at visible satellite imagery leading to the possibility of convection to form as the atmosphere begins to destabilize. SPC also has this area in a level 1 of 5 risk for severe weather with the main threats being large hail and damaging wind gusts. We are not anticipating a widespread event initially this evening but rather a more scattered to isolated scenario.

Hi-Res models continue to be all over the place regarding initial placement and timing but the overall consensus is that most would see activity occur after 4 PM and continue through this evening into the overnight. An initial round of activity already located over Llano, Kimble and Mason counties will continue to progress eastward with activity continuing to form back behind it. The recent run of RRFS (18Z) shows this complex of activity slowly drifting southeastward and impacting parts of the Hill Country. The latest 18Z ACAR sounding at SAT shows MUCAPE of 1800 J/kg while the AUS sounding shows around 1600 J/kg and along with SPC meso showing mid-level lapse rates of 6.5 to 7 c/km. Any storms that do form will have the potential to produce damaging winds, large hail and torrential rainfall as moisture remains extremely high over the region. WPC has expanded their level 1 of 4 risk to include the entire area for today due to the recent rainfall and the anomalously high moisture located over our area.

Several short range models show a secondary wave of activity forming over either West TX or Central TX as a another disturbance progresses eastward. This convection would then swing southward through the Rio Grande and Southern Edwards Plateau, possibly clipping portions of Bexar County and perhaps parts of the western Hill Country. However it should be weakening as it does so with most activity ending before daybreak Friday morning with most activity then pushing southward into South TX.

Friday into Friday evening we seem to be in a bit of a lull as we remain trapped between two disturbances with the one moving off to our east and then the next one located over West TX and impacting portions of our western areas beginning as early as Saturday morning.

Additionally due to the area receiving widespread rainfall of 1 to 3 inches over the past 3 days and the potential for additional rounds of heavy rainfall we went ahead and issued a Flood Watch for the entirety of the holiday weekend for areas along and east of a Kerr to Frio county line.

LONG TERM

(Saturday through next Thursday) Issued at 301 PM CDT Thu May 21 2026

As alluded to above, Saturday could shape up to be a very active day as our next disturbance will be approaching the area sparking another round of showers and thunderstorms capable of very heavy rainfall as moisture continues to remain high across the area. There is relative good agreement on the latest model consensus regarding the evolution of a low pushing across our area and stalling over East TX. This low will be the focus for the repeated rounds of thunderstorms and heavy rainfall over the extended weekend. Many areas could see a widespread swath of 2 to 4 inches with some areas seeing isolated totals of up to 6 inches of rainfall especially for those across the Watch area. As such, WPC currently has our area in a level 2 of 4 risk for excessive rainfall for areas along and east of the I-10 to I-35 Corridor including the San Antonio and Austin Metro areas.

Global models continue to indicate this low meandering somewhere across East TX until at least Tuesday as the upper level pattern shows another trough digging down into the Western U.S. This trough will help to finally kick out the meandering low but also puts our area back into southwest flow aloft. This then opens the door for renewed rainfall chances as disturbances continue to push across our area into next week.

As stated previously this is a rather low confidence and challenging forecast as each round of storms moves across parts of our area, more stable conditions will likely follow leading to periods of dry weather as the atmosphere recharges. Even though many chances for precipitation are seen in the extended forecast, periods of dry weather are also expected. Similarly, as each day evolves, the outflow and leftover boundaries from the previous day's convection will be the continued focus for renewed development for the next day. Thus it wont be until 24 to perhaps 48 hrs prior to each day that we will be able to pinpoint the location and eventually trajectory of where storms may fire.

It should be noted that every rain event that occurs will continue to bring soils closer to saturation thus increasing the potential for excessive run off which can lead to flash flooding or river flooding. Please continue to monitor the forecast and always have a way to receive warning information.

AVIATION

(18Z TAFS) Issued at 1235 PM CDT Thu May 21 2026

MVFR cigs are forecast for the next few hours for the San Antonio and Austin area terminals. Then VFR category is projected to remain through the rest of the afternoon into the evening. There is a chance for showers and storms along the Rio Grande Plains late this afternoon and evening. With that said, included a PROB30 group for KDRT late afternoon into the evening for the possibility of thunderstorms. A light east to southeast flow is forecast through the forecast period. MVFR conditions return for the I-35 airports overnight into Friday morning.

PRELIMINARY POINT TEMPS/POPS

Austin Camp Mabry 69 88 72 84 / 30 20 20 90 Austin Bergstrom Intl Airport 68 87 71 83 / 30 20 20 90 New Braunfels Muni Airport 67 86 70 83 / 30 20 20 90 Burnet Muni Airport 66 85 69 81 / 30 20 30 90 Del Rio Intl Airport 67 89 70 85 / 30 0 40 50 Georgetown Muni Airport 67 86 70 82 / 30 10 30 90 Hondo Muni Airport 66 85 69 81 / 30 10 50 90 San Marcos Muni Airport 68 87 71 83 / 30 20 20 90 La Grange - Fayette Regional 69 86 72 83 / 30 30 20 90 San Antonio Intl Airport 69 87 72 83 / 30 20 30 90 Stinson Muni Airport 69 87 72 83 / 30 20 30 90

EWX WATCHES/WARNINGS/ADVISORIES

Flood Watch from Friday evening through Monday evening for TXZ171>173-186>194-204>209-219>225.