Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
Issued by NWS Austin/San Antonio, TX
606 FXUS64 KEWX 111801 AFDEWX Area Forecast Discussion National Weather Service Austin/San Antonio TX 101 PM CDT Mon Aug 11 2025 ...New SHORT TERM, LONG TERM, AVIATION... .KEY MESSAGES... - Chances for isolated showers and storms continue this week, mainly in the afternoon to early evening. - Seasonably hot weather continues with similar high temperatures this week and slight warming this weekend into early next week. && .SHORT TERM... (Tonight through Tuesday night) Issued at 1256 PM CDT Mon Aug 11 2025 The most recent mesoanalyses and water vapor imagery place the axis of an inverted trough over the Coastal Plains, extending southwestward to the I-35 corridor. The additional moisture accompanying this feature supports isolated showers and storms continuing this afternoon mainly over the Coastal Plains with the bulk of the moisture, though a few pop-up storms along the Balcones Escarpment are also possible with late afternoon convergence. An approaching polar trough over the Central Plains is beginning to interact with the coastal disturbance, forcing the disturbance to stretch and curve northeast over the next 24 hours. This track away from South-Central Texas should limit the inland extent of coastal shower activity, and remaining showers are expected to fizzle after sunset. The polar trough becomes a more influential driver of weather over our area Tuesday as it slowly swings east, maintaining a weakness in the ridging over our area. Outflow from storms along a frontal zone over the Texas Panhandle this afternoon may push a few outflow boundaries near or into our region beginning Tuesday morning, with a few light morning showers possibly straddling the initial push. Northwesterly flow immediately rearward of the polar trough axis brings an accompanying increase in mid-level moisture, supporting chances for isolated showers and storms across South-Central Texas. Chances for rain are higher over the Edwards Plateau and Hill Country where greater instability is anticipated, but a farther southeastward progression of outflow boundaries would lead to a southeastward shift and expansion in the more favored areas for rain, including the I-35 corridor and Coastal Plains. The aforementioned front broadens to the northwest without pushing into our area, so the resulting storm activity looks more diurnally driven with better rain chances in the late afternoon to early evening Tuesday along preexisting outflow boundaries. Simulated reflectivity from the high-resolution guidance depicts varied outcomes ranging from single cell storms to marginally more structured clusterings of storms. Low bulk wind shear below 20 kts should limit organization, though gusty winds are possible with the stronger cells. Storm motions are expected to be slow (around 5 to 10 kts) and mainly southwards, but weak 850 mb flow should lead to mainly short- lived downpours. Still, warm atmospheric profiles could facilitate isolated pockets of an inch or more of quick-hitting rain along intersecting storm outflows. Rain-cooled air over the Edwards Plateau may help moderate temperatures slightly over the Hill Country, but highs should hold steady for Tuesday with mid to upper 90s for most of South-Central Texas. && .LONG TERM... (Wednesday through Monday) Issued at 1256 PM CDT Mon Aug 11 2025 Although the bulk of the polar trough continues east into the Ohio River Valley Wednesday, a straggling portion gets left behind over North Texas and prevents ridging from reestablishing at the mid- levels, leaving a weakly convergent 500 mb shear axis over South- Central Texas. The highest rain chances are forecast to be north of our area, situated around the strongest baroclinicity and forcing for ascent. However, expanding outflows from this activity amid a weakly capped environment support the continued potential for isolated storms mainly north of I-10 for Wednesday. Without upper-level assistance, the residual trough over Texas weakens Thursday as a ridge strengthens over the northern Gulf and begins a gradual crawl and expansion westward. While the mid-level subsidence brings some initial reduction in rain coverage, strengthened onshore flow along the southwestern periphery of the ridge could bring continued opportunities for isolated coastal showers in the late week before the ridge becomes more firmly entrenched over our area. A tropical wave looks to ride the ridge periphery along the western Gulf Thursday and Friday, with the GFS and ECMWF-IFS bringing the northward end of its low-level vorticity and moisture pouch into the Texas coast, though the GFS is a little faster with a Friday morning arrival compared to the ECMWF-IFS`s Saturday morning arrival. Trends in the strength and orientation of ridging will determine whether the bulk of the vorticity nears our area or stays farther south into Mexico, but in either case the southerly 850-700 mb flow on the western half of the ridge should ensure some of that moisture spreads into our area. This will support an increase in diurnal shower and storm activity Friday and Saturday with the best chances over the Coastal Plains and I-35 corridor. The tropical wave stretches out and diffuses into the southerly flow Sunday as the ridge strengthens further. By Monday, medium-range ensemble guidance places the ridge center over Texas, bringing drier and warmer conditions. Highs for most of South-Central Texas this week are expected to stay mostly in the 90s with troughing persisting over our area, but highs around to just over 100 potentially become more widespread over the I-35 corridor and Rio Grande this weekend with the expanding ridge. Daytime heat indices are forecast to hover mainly in the 100 to 105 degree range outside of higher elevations in the Hill Country, though some areas in the Coastal Plains could push a few degrees higher for heat indices later in the week with the added coastal moisture and warmer air. && .AVIATION... (18Z TAFS) Issued at 1256 PM CDT Mon Aug 11 2025 We expect VFR conditions to prevail at all terminals through this TAF period. There is a less than 20% chance for showers or thunderstorms this afternoon in the Austin and San Antonio areas. With southeasterly flow continuing overnight there may be some MVFR level clouds in the Austin and San Antonio areas and a very low chance for brief ceilings. Winds will be less than 10 kts in Austin and San Antonio and mainly from the southeast. At DRT wind speeds will be a little stronger right at 10 kts. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 77 98 77 98 / 0 30 10 20 Austin Bergstrom Intl Airport 75 98 75 98 / 10 20 10 20 New Braunfels Muni Airport 74 98 74 98 / 10 20 10 20 Burnet Muni Airport 74 94 75 95 / 0 30 10 30 Del Rio Intl Airport 79 100 79 100 / 0 10 10 20 Georgetown Muni Airport 75 97 76 97 / 0 30 10 30 Hondo Muni Airport 74 99 74 98 / 0 10 10 20 San Marcos Muni Airport 74 99 74 99 / 10 20 10 20 La Grange - Fayette Regional 75 96 75 96 / 10 20 10 20 San Antonio Intl Airport 76 98 77 98 / 10 20 10 20 Stinson Muni Airport 76 100 76 100 / 10 10 10 20 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term...Tran Long-Term...Tran Aviation...05