textproduct: Austin/San Antonio

KEY MESSAGES

Updated at 131 PM CDT Sun Sep 20 2026

- Low chances (15-50%) for showers or storms across the Hill Country and Southern Edwards Plateau from Sunday night into Tuesday.

- Low chances (mainly below 15%) for spotty rain across South Central Texas Tuesday night through next week with most staying dry.

- Oppressive heat continues into next weekend.

SHORT TERM

(Tonight through Monday night) Issued at 131 PM CDT Sun Sep 20 2026

A flattened upper ridge axis sits in an elongated SW-NE axis over the SE half of TX today with weak upper troughing has carved into the NW half of TX. A good sized mid level shortwave is moving into West Central TX and will be a focal point for afternoon and evening convection that will eventually spill south into parts of the southern Edwards Plateau and the Hill Country. Midday skies continue to contain a good amount of cirrostratus which has delayed cumulus growth in the area where storms are expected to initiate. This leaves the projection for rain chances in low confidence as there are not yet any surface boundaries. Looking at the some of the higher res model looks shows some surface outflow winds that could continue to support convective initiation as the shortwave drifts slowly SE. This suggest a possible slow moving cluster of storms and potentially an opportunity for a slightly upscaled system into a small MCS, but not many model solutions favor this. The WPC ERO covers for this area, and a 1-3 inch area of rain could be attainable. Hi-res QPFs a mostly under 2 inches for the higher amounts, but the normally excitable FV3 run did show a maxima over 5 inches around JCT.

There is a more distinct frontal boundary that drops south of the Red River into North Central TX. The timing of this feature is not ideal, so the PoPs to choose from hold mostly close to the more conservative NBM population scheme. It should be noted that there are significant upticks in PoP in both the MAV and MET MOS products in the more populated areas of the I-35 Corridor, and hopefully this comes to fruition and is caught onto by the next runs of the NBM. Should we get more convection in our areas as suggested by GFS/NAM 12Z runs, there could be an increase in downdraft winds approaching severe levels, especially if there's a well defined boundary to trigger convection over the Hill Country as the NAM suggests.

Meanwhile over southern counties, we continue to see the hot, sticky conditions with not much winds and heat indices getting up into the 100-107 degree range. With a slight NW flow pattern starting at 500 mbs and increasing higher up, models show more nocturnal activity to set up where the front washes out which is at our northern CWA border, with southward slow cell motions to offer more chances for locally heavy downpours.

LONG TERM

(Tuesday through next Sunday) Issued at 131 PM CDT Sun Sep 20 2026

Late Tuesday our resident upper ridge gets better established again with the center over E/SE TX. While deep monsoonal flow works over the western periphery, abundant storm activity over Far W TX and NM will only enhance the inflow low level winds and enhance onshore winds. So while the ridge keeps the weather hot, the winds keep the RH values elevated for high heat indices topping 100 each day through mid week. A few showers and storms could get going in the afternoons, but the ridging overhead should keep the coverage closer to around 10 percent after Tuesday. The ridge continues to amplify late in the week which should lead to reduced onshore flow and a drier and more stable regime heading into the weekend. This will hopefully lower morning low temperatures and afternoon heat index values, but offer no relief from the ambient high temperatures.

AVIATION

(18Z TAFS) Issued at 1244 PM CDT Sun Sep 20 2026

VFR CIGs should continue throughout the forecast. There is a very low possibility of MVFR CIGs for KSAT and KSSF but kept mention out of this TAF package for now. Otherwise expect light southerly to southeasterly winds for all I-35 TAF sites. KAUS may briefly have winds switch to the south southwest overnight before returning southerly by daybreak. For KDRT VFR CIGS expected throughout with light southeasterly winds switching to easterly after sunset.

PRELIMINARY POINT TEMPS/POPS

Austin Camp Mabry 76 99 76 99 / 20 10 10 10 Austin Bergstrom Intl Airport 76 99 75 99 / 10 10 10 10 New Braunfels Muni Airport 74 98 74 98 / 10 10 10 10 Burnet Muni Airport 72 95 72 94 / 30 30 30 30 Del Rio Intl Airport 75 99 75 97 / 10 0 30 10 Georgetown Muni Airport 75 98 75 97 / 20 20 20 20 Hondo Muni Airport 73 97 73 96 / 20 10 10 10 San Marcos Muni Airport 74 99 74 98 / 10 10 10 10 La Grange - Fayette Regional 76 99 75 99 / 0 10 10 10 San Antonio Intl Airport 77 97 76 97 / 10 10 10 10 Stinson Muni Airport 76 99 75 99 / 10 10 10 0

EWX WATCHES/WARNINGS/ADVISORIES

None.