textproduct: Austin/San Antonio

KEY MESSAGES

Updated at 138 PM CDT Mon Sep 28 2026 - Above normal heat persists into mid-week, with some low rain chances along and east of I-35 Tuesday.

- An active pattern is expected mid to late week with widespread rain chances and a potential for flash flooding.

SHORT TERM

(Tonight through Tuesday night) Issued at 138 PM CDT Mon Sep 28 2026

Currently our area remains under the influence of a subtropical ridge with its center located over the Rio Grande Valley over southwest TX. At the same time an upper level low is located over the southwestern U.S. For now our area will continue to be influenced by the subtropical ridge through Tuesday. Today expect another hot and rather humid day for our area with highs well above normal with most in the mid to upper 90s. We could see heat indices within the 100-105 degree range with the increased humidity and party sunny skies. Additionally, rain chances will remain low today due to the aforementioned high near us with just some spotty/isolated showers and storms over the far eastern areas of the Coastal Plains. Tonight expect increasing clouds along with temperatures remaining mild with many remaining in the low to mid 70s overnight.

By Tuesday the upper level low will continue to push eastward towards the desert southwest thus shunting the subtropical ridge currently over our area and pushing it off to the east. As this happens lee side surface troughing east of the rockies will help to bring in stronger southeasterly winds at the surface. This in turn will help pull in more moisture up from the Gulf giving us a better shot at rain and storm chances during the day along with our typical seabreeze. For now have capped rain chances at 30 percent for areas mainly along and east of the I-35 Corridor. By Tuesday night we could start to see rain/storm chances increase as we begin to see the beginning effects of the upper level low over the desert southwest as it slowly deepens and progresses eastward towards the Southern Plains. Additionally, significant amounts of moisture from the remnants of Hurricane Polo and Odalys will be pulled into our area in the upper levels along with lower level moisture being brought in from the Gulf. We could see PWATS approaching and even exceeding 2 inches. As such any storms that do form will be tropical in nature and capable of very heavy rainfall. WPC currently has Val Verde and parts of Edwards counties in a level 1 of 4 risk of excessive rainfall for Tuesday with the risk shifting eastward and increasing further as we get beyond Tuesday night. More about that in the long term portion below. Regarding temperatures, Tuesday will feel very hot and humid with most seeing low to upper 90s for highs. When adding in the increasing humidity it'l feel more like 100-107 degrees. Parts of the Coastal Plains could briefly approach and exceed heat advisory criteria before any afternoon rain/storms occur. Lows Tuesday night once again will remain in the low to mid 70s as the area remains locked under increasing cloud cover overnight.

LONG TERM

(Wednesday through next Monday) Issued at 138 PM CDT Mon Sep 28 2026

The advertised pattern change is on track for mid to late week with increased showers and thunderstorm chances beginning Wednesday and continuing through late week and beyond. An upper low will be located over the Four Corners region Wednesday, eventually moving east across the Central and Southern Plains late week bringing a Pacific cold front across our area. Abundant moisture will be available ahead of this system with some guidance showing PWATs around 200 percent above normal. As to be expected with a strong upper low, models still vary to a certain degree on its progression and speed with the ECMWF continuing its slower trend compared to the GFS. We're starting to get a glimpse into hi-res guidance as this event comes closer giving higher confidence to heavy rain in our area beginning more late Wednesday night in the west and Thursday in the east.

Ahead of an expected line of storms during this timeframe, isolated to scattered thunderstorm activity will be possible across much of the area as moderate onshore flow and hot and humid conditions persist Wednesday. Heat index values exceed 100 degrees for a majority of the area in the afternoon capped under mostly cloudy skies with a breezy southeasterly wind. Any thunderstorm activity will have a heavy rain threat given the environment and cannot rule out some gusty wind or hail as well.

Returning to the Pacific front and the main focus of the extended forecast, expect this feature to slowly move across our area late Wednesday night through Friday. Thunderstorms are likely to develop along the southwest to northeast orientation of the front and could produce heavy rainfall leading to flash flooding. There remains uncertainty in how quickly this front moves, how far it progresses, and where the heaviest rain will fall over the area. An upper low remains to the west Friday into Saturday with continued high moisture residing over the area. This keeps medium to high rain chances over the area Friday into the weekend with high uncertainty on details this far out. Temperatures Friday into the weekend should fall into the mid 70s and 80s given the rain chances and expected cloud cover. While details remain blurred for our late week system, continue to monitor the forecast and be prepared for potential heavy rainfall.

AVIATION

(18Z TAFS) Issued at 1241 PM CDT Mon Sep 28 2026

VFR Cigs expected to begin the forecast period and continue through the majority of the evening before dropping down into MVFR at all I-35 TAF sites around 07/08Z. Moisture being pulled up from the Gulf will help to create a decent cloud deck overnight thus dropping ceilings and leading to rather poor flying conditions. It's possible we would see CIGS deteriorate further into IFR but have held off on mentioning that in this package. CIGs should improve to VFR by late morning/early afternoon (18Z). Winds should remain south-southeasterly throughout the forecast with a chance of isolated showers/storms towards the end of the forecast period for all I-35 sites. Have kept mention out of this package for now but will continue to monitor and amend as needed. For KDRT we are expecting MVFR CIGs slightly later in the overnight (around 10/11Z) and continuing through the majority of the forecast period with VFR returning by 17Z. Additionally, expect south-southeasteryl winds of 10-15 knots throughout the period.

PRELIMINARY POINT TEMPS/POPS

Austin Camp Mabry 75 97 76 96 / 0 20 20 40 Austin Bergstrom Intl Airport 73 96 75 96 / 0 20 20 40 New Braunfels Muni Airport 73 95 74 96 / 10 30 20 40 Burnet Muni Airport 72 92 74 92 / 0 10 20 40 Del Rio Intl Airport 76 98 77 97 / 0 0 40 20 Georgetown Muni Airport 73 95 75 95 / 0 10 20 40 Hondo Muni Airport 74 95 75 96 / 0 10 20 30 San Marcos Muni Airport 73 96 74 96 / 10 30 20 40 La Grange - Fayette Regional 73 97 75 97 / 0 20 20 40 San Antonio Intl Airport 76 94 77 95 / 10 30 20 40 Stinson Muni Airport 76 95 77 96 / 0 20 20 30

EWX WATCHES/WARNINGS/ADVISORIES

None.