textproduct: Austin/San Antonio

KEY MESSAGES

Updated at 632 PM CDT Sun Sep 27 2026 - Isolated storms this afternoon and evening over the Hill Country and southern Edwards Plateau.

- A Pacific cold front may bring widespread rain during the second half of the week. Heavy rain is possible.

SHORT TERM

(Tonight through Monday night) Issued at 133 PM CDT Sun Sep 27 2026

Upper level winds this morning and afternoon have shifted to northwesterlies, signaling that the upper level ridge that has dominated our weather for the past week has reoriented itself over Mexico. This afternoon, the lessened influence of the ridge, weak thermally induced convergence, and the presence of a strip of higher instability is forecast to spark a isolated showers and storms over the Hill Country and southern Edwards Plateau. Most of the hi-res models have the first signs of development by about 3-4 PM, with storms continuing through the afternoon and early evening before petering out after sunset. These storms are not expected to be well- organized due to a lack of effective wind shear, but the combination of decently moist PWATs in the 1.6"-1.8" range, lackadaisical storm motion, and DCAPEs above 1000 J/kg indicate the stronger cells may drop a few heavier downpours with strong gusts. The main focus will likely remain in the Hill Country and southern Edwards Plateau, but given the northwesterly flow aloft, a few residual showers and storms could approach the I-35 corridor around 6-9 PM. Those who do see rains today are mostly expected to record amounts ranging from a few hundredths to a few tenths of an inch, with a few localized spots seeing potential for 1-2" under the stronger cells.

Hot weather continues Monday with highs in the 90s for most, to around 100F over the Rio Grande Plains. The nearby ridge over Mexico is forecast to bulge northward and eventually eastward, so rain chances should be lower Monday. Onshore flow will be more pronounced Monday, so there could be a lone shower or two over the Coastal Plains.

LONG TERM

(Tuesday through next Sunday) Issued at 133 PM CDT Sun Sep 27 2026

The strong trough now moving ashore the West Coast will start to shape the weather over our area as we head further into the week. Its approach will impinge on the ridging near our area and eventually shove the ridge eastward. On Tuesday, the trough is forecast to push into the southwestern US. There will still be enough ridging over Texas to keep conditions dry and hot for much of the day, but increasing onshore flow in response to jet divergence caused by the trough raises chances for isolated streamer showers over the Coastal Plains.

Along the leading flanks of the incoming trough, a substantial plume of tropical Pacific moisture will begin flowing across Mexico up into South-Central Texas beginning about late Tuesday, and should continue to do so through at least Thursday with additional contributions from onshore flow off the Gulf. This pattern sets the stage for potential widespread rain during the latter half of the week. There is still some variation in timing with the EPS ensembles generally favoring a slower progression and the GEFS and CMCE ensembles being faster, but the overall depiction of at least the start and midpoint of the rainy period is coming into better agreement. Rain chances start to increase Wednesday areawide as the southerly low-level jet establishes over the region, making for an especially humid and breezy day. However, at this range it does appear that Wednesday's activity will be more in the form of scattered showers embedded in the moist flow off the Gulf. A Pacific cold front acting to concentrate the rain and storm potential will then slowly enter our area from the northwest. The current consensus among the more skillful models suggests heavy frontal rains could commence as early as Wednesday night, slowly advancing east during the night and throughout the day Thursday. Risks of excessive rainfall capable of causing flash flooding applies to all of South-Central Texas during this period. While it's still early to give more specific rain amounts and ranges, models have been consistent in showing a band of heavier amounts on a roughly NNE- to-SSW swath, paralleling the orientation of the slow- moving front. These rains will have access to ample amounts of atmospheric moisture, to the tune of widespread PWATs in excess of 2" as depicted on the latest ensemble means (at or above the 95th percentile). These signals are supportive of a heavy rain event, and we will continue to closely monitor the development of the trough and its front for trends as we enter the workweek.

The greatest overlap in rain chances in the latest models is around Thursday, though that is subject to change depending on how the trough evolves. While there are some deterministic models that clear the front and its rains out of our area at a steady pace, more models have trended towards showing the parent trough slowing down and even stalling over the central and southern Plains. This may keep the front and rain potential in our area into Friday, an outcome best exemplified by the EPS and ML versions of the ECMWF and GFS. We do generally expect that the mid- and upper-level flow will become more zonal over the weekend, breaking up the moisture plume and allowing drier air to finally make its way into the area. The rain forecast for the weekend is uncertain and heavily dependent on how quickly the trough leaves the area, but for now, a gradual decrease in rain chances is depicted.

Temperatures to start the week will be unseasonably warm. The combination of humid air and hot temperatures Wednesday afternoon could may that day especially sultry if clouds from the approaching front are delayed. Higher heat indices near and over 105F are possible over the Rio Grande Plains and portions of the I-35 corridor and Coastal Plains. The Pacific cold front and widespread rain and cloud cover should bring daytime temperatures down Thursday into the weekend, with highs in the 80s becoming more widespread. In the longer term, there have been some indications that a cold front could bring cooler weather next week. I wouldn't count too heavily on that, but it does appear that more opportunities for fall-like temperatures may be on tap through early October.

AVIATION

(00Z TAFS) Issued at 632 PM CDT Sun Sep 27 2026

VFR conditions are forecast for the most part this evening through Monday evening. However, there is a small window from 00Z to 02Z Monday for scattered showers and even a thunderstorm or two to affect KAUS based on radar trends and latest HRRR guidance. Otherwise, southeast winds are forecast to prevail for most of the forecast period and occasional time frames of light and variable winds especially overnight and after sunrise.

PRELIMINARY POINT TEMPS/POPS

Austin Camp Mabry 75 99 74 97 / 10 10 0 10 Austin Bergstrom Intl Airport 74 99 73 97 / 10 0 0 20 New Braunfels Muni Airport 73 97 73 95 / 10 0 0 20 Burnet Muni Airport 72 95 71 92 / 20 10 0 10 Del Rio Intl Airport 77 99 75 97 / 10 0 0 0 Georgetown Muni Airport 74 97 73 96 / 20 10 0 10 Hondo Muni Airport 74 96 73 94 / 10 0 0 20 San Marcos Muni Airport 73 98 72 96 / 10 0 0 20 La Grange - Fayette Regional 73 98 73 97 / 0 0 0 20 San Antonio Intl Airport 75 96 76 94 / 10 0 10 20 Stinson Muni Airport 76 97 75 95 / 10 0 10 20

EWX WATCHES/WARNINGS/ADVISORIES

None.