Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX
Issued by NWS Austin/San Antonio, TX
998 FXUS64 KEWX 281808 AFDEWX Area Forecast Discussion National Weather Service Austin/San Antonio TX 108 PM CDT Thu Aug 28 2025 .KEY MESSAGES... - Hot conditions through the late work week into Saturday, then cooler than average conditions Sunday through the start of next week. - Rain chances returning Friday across the northern Hill Country and Austin metro, spreading southward Saturday, and peaking Sunday into Monday. - Main concerns are gusty winds and locally heavy rain that could lead to flooding Friday through Monday. A Level 1 of 4 risk for excessive rainfall that could lead to isolated instances of flash flooding is in place Fri-Mon. && .SHORT TERM (THROUGH FRIDAY NIGHT)... The latest GOES-19 water vapor imagery depicts a weakening 594dm high over west Texas and northern Mexico early this afternoon. Despite the weakening trend, high surface moisture levels and hot afternoon temperatures will lead to elevated heat indices in the 100-106 range again this afternoon as storm development is suppressed. Widespread highs in the mid to upper 90s with triple digits along the Rio Grande and into portions of the I-35 Corridor/Coastal Plains will continue today and again on Friday. However, the primary difference between today and Friday will be the increased threat for showers and thunderstorms along a decaying outflow boundary/pseudo cold frontal boundary entering our northern counties Friday afternoon. While this won`t actually make it all the way into the area until Saturday, we are expected at least 2 more hot days beyond today before relief arrives in the long term period. The hottest day of the week is likely to be Friday, where highs in the upper 90s can be expected for the Hill Country, with highs of 100-105 everywhere else. Factoring in dewpoints in the mid to upper 60s in the afternoon and the compressional warming expected ahead of the approaching frontal boundary will make it feel even hotter. Despite heat indices approaching Heat Advisory criteria, felt as if additional heat messaging would be adequate. Heat indices in the 103-108 range are expected, particularly along I-35 and east tomorrow afternoon. Several Hi-res models, particularly the ARW WRF and the RRFS are rather bullish on convection developing along this southward moving boundary Friday afternoon and early evening. Locally heavy rain that could lead to isolated instances of flash flooding is possible, and a level 1 of 4 ERO is in place for the Austin metro and points north and west on Friday. It is notable that the threat for flash flooding is there despite a rather dry couple of weeks over the region. The 12Z HREF neighborhood probabilities PMM indicates a 10% chance for greater than 3 inches over the northern Hill Country and Austin Metro Friday afternoon and evening. A quick couple of inches of rain is possible from any slow moving storm. && .LONG TERM (SATURDAY THROUGH THURSDAY)... An active pattern is expected to continue into the long term forecast period. A frontal boundary will stall out just north of our CWA or in our northern counties Saturday, with showers and thunderstorms possible as far south as the I-10 corridor Saturday afternoon. WPC highlights much of our area in a Day 3-5 excessive rainfall outlooks (Level 1 of 4) each day through Monday. Notable ingredients for locally heavy rainfall include: - A stalled out frontal boundary for convection to focus on. - PWATs of 2-2.25" will be common Saturday afternoon through Monday afternoon. - Instability will provide fuel for storms. - Slow storm motions and frequent collisions and boundary interactions. These ingredients will be common Saturday afternoon, but particularly common Sunday afternoon and evening, as well as on Monday. The greatest threat for heavy rain will be when the frontal boundary finally shifts south through our region Saturday night. Rainfall rates of 1-2 inches per hour may be possible along with gusty winds in any storms that move through. Cooler than normal temperatures are expected Sunday through Tuesday with highs ranging from the mid 80s to the mid 90s. Continued rain and storm chances linger through mid to late week before another frontal boundary may approach the region for late week. && .AVIATION (17Z THURSDAY THROUGH FRIDAY)... Mostly VFR conditions through the TAF period. Convective allowing models are indicating isolated to widely scattered SHRA and TSRA activity Friday afternoon across portions of the northern Hill Country and into the Austin metro area. A PROB30 TSRA will be included in the 30HR AUS TAF from 29/20Z-29/24Z. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 77 100 77 96 / 0 30 20 40 Austin Bergstrom Intl Airport 77 100 76 97 / 0 20 20 30 New Braunfels Muni Airport 75 100 75 98 / 0 10 10 20 Burnet Muni Airport 76 96 74 92 / 0 30 20 50 Del Rio Intl Airport 78 102 79 101 / 0 0 0 10 Georgetown Muni Airport 76 99 75 94 / 0 40 30 40 Hondo Muni Airport 74 100 75 99 / 0 0 0 20 San Marcos Muni Airport 75 101 74 98 / 0 10 10 30 La Grange - Fayette Regional 76 98 75 96 / 0 20 10 40 San Antonio Intl Airport 77 100 77 98 / 0 10 10 20 Stinson Muni Airport 78 102 78 101 / 0 0 0 20 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term...MMM Long-Term...MMM Aviation...76