Area Hydrologic Discussion
— Latest
Threat
POTENTIAL IMPACTS: Flash flooding likely, locally significant impacts WHERE: Southwest Texas WHEN: Through early Tuesday morning
Rainfall & Conditions
QPF: 2 - 4", locally higher (HRRR) Rain Rates: 2 - 3"/hr (WPC) Soil Moisture: Variable (0 - 10 cm, NASA SPoRT) Streamflows: Variable (USGS)
Discussion
Isolated flash flooding is likely, with locally significant and potentially life-threatening impacts possible, across the area of concern as slow-moving thunderstorms continue tonight into early Tuesday morning. Locally high rainfall rates, complex terrain, and shallow soils will help promote rapid runoff and sharp rises on normally dry washes, arroyos, and small streams, allowing flash flooding to develop quickly. As a result, roadways, residential areas, and recreational facilities near these waterways may become inundated with little to no warning.
While confidence in the exact placement of the heaviest rainfall remains low, confidence in the overall hydrologic threat has remained consistently high through successive forecast cycles. The National Water Model (NWM) continues to highlight isolated pockets of high-magnitude flows on smaller streams and washes within the Nueces, Guadalupe, and San Antonio River basins. NWM Peak Flow Arrival Time forecasts support continued basin responses through early tomorrow, reinforcing the flash flood threat, though impacts are not expected to be widespread. Although antecedent soil moisture and streamflows remain variable across the region, continued widespread rainfall over the next several days is expected to increase confidence in the placement and magnitude of flooding impacts.
Addressed To
WFO: MAF, SJT, EWX RFC: FWR, WPC
000 AGUS74 KWCO 140138 AHDNWC Area Hydrological Discussion #142 - EXPERIMENTAL NWS National Water Center - Tuscaloosa, AL 829 PM CDT Mon Jul 13 2026 POTENTIAL IMPACTS: Flash flooding likely, locally significant impacts possible WHERE: Southwest Texas WHEN: Through early Tuesday morning FORECAST RAINFALL AND ANTECEDENT CONDITIONS... QPF: 2 - 4", locally higher (HRRR) Rain Rates: 2 - 3"/hr (WPC) Soil Moisture: Variable (0 - 10 cm, NASA SPoRT) Streamflows: Variable (USGS) DISCUSSION... Isolated flash flooding is likely, with locally significant and potentially life-threatening impacts possible, across the area of concern as slow-moving thunderstorms continue tonight into early Tuesday morning. Locally high rainfall rates, complex terrain, and shallow soils will help promote rapid runoff and sharp rises on normally dry washes, arroyos, and small streams, allowing flash flooding to develop quickly. As a result, roadways, residential areas, and recreational facilities near these waterways may become inundated with little to no warning. While confidence in the exact placement of the heaviest rainfall remains low, confidence in the overall hydrologic threat has remained consistently high through successive forecast cycles. The National Water Model (NWM) continues to highlight isolated pockets of high-magnitude flows on smaller streams and washes within the Nueces, Guadalupe, and San Antonio River basins. NWM Peak Flow Arrival Time forecasts support continued basin responses through early tomorrow, reinforcing the flash flood threat, though impacts are not expected to be widespread. Although antecedent soil moisture and streamflows remain variable across the region, continued widespread rainfall over the next several days is expected to increase confidence in the placement and magnitude of flooding impacts. GRAPHICAL REPRESENTATION: weather.gov/owp/operations-ahd Additional National Water Center products are available at: weather.gov/owp/operations //Freeman ATTN...WFO...MAF...SJT...EWX ATTN...RFC...FWR...WPC