####018002006#### AWUS01 KWNH 210026 FFGMPD TXZ000-210504- Mesoscale Precipitation Discussion 0122 NWS Weather Prediction Center College Park MD 825 PM EDT Mon Apr 20 2026 Areas affected...Central TX Concerning...Heavy rainfall...Flash flooding possible Valid 210024Z - 210504Z Summary...Additional thunderstorms are developing over portions of South-Central TX this evening. These cells will maintain the threat of flash flooding as they could train and overlap with areas of heavy rainfall earlier today. Discussion...Radar across South-Central TX depicts a rapid expansion in thunderstorm coverage and intensity along the leading edge of a shortwave near the Big-Bend of TX. At the same time, an axis of persistent shallow convection northeast of San Antonio was finally showing signs of weakening after producing 2-4" of rainfall this afternoon. This activity was quite impactful earlier today, and 1-2"/hr rainfall rates led to at least one report of a swift water rescue near Live Oak TX where CREST Unit Streamflows eclipsed 900 cfs/smi at times. With that in mind, the concern is for additional thunderstorms containing 1-1.5"/hr rainfall rates to expand southwest of San Antonio, in turn leading to periods of training/repeating near areas impacted earlier today. This scenario is supported by recent runs of the HRRR (which is an slow but overall has the best handle on the situation). Taking into account the timing of the HRRR, this suggests the threat of scattered flash flooding should persist through 4-5Z tonight. Localized rainfall amounts of 1-2" could support additional considerable flash flooding impacts, especially if they fall atop the areas of heaviest rainfall today (highlighted in red). Asherman ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...EWX... ATTN...RFC...FWR...NWC... LAT...LON 30109900 30009752 29279747 28959854 29129944 29649956 ####018000667#### PENA01 KWNH 211200 @UHPISF000CNê MPDSUM@V2.0@0101700060@12210426@@0NMCGPHMPD [@!' `' ` @ ê¾& êBñ7)p&¬PNAM02@@Kùúûüüÿ€‚‚ƒ……†‡‡†„„}‚z€zþ|ý}û}û}ú~û@@K€@@K€@@<5€0122 @@d&€MESOSCALE DISCUSSION SUMMARY GRAPHIC @@d&þ€ OF ALL VALID MESOSCALE DISCUSSIONS AT @@d&ü€ TIME OF PRODUCT CREATION:@@d&ú€ ISSUED 04/21/2026 0026Z @@ d™€NOAA/NWS/NCEP@@d™þ€ WEATHER PREDICTION CENTER @@d™ü€ FOR COLOR VERSION SEE: @@d™ú€ WWW.WPC.NCEP.NOAA.GOV @