National Hydromet Discussion
— National
Overview
...Potentially life-threatening flash and arroyo flooding possible in portions of Texas... Isolated flash flooding possible across the Central Appalachians and Nevada...
Texas
A Considerable flood threat area was introduced today across portions of the southern Hill Country and middle Rio Grande Valley, where potentially life-threatening flash and arroyo flooding is possible through Thursday. A broader Limited area remains in place across central and southwest Texas.
Forecast confidence has increased regarding a significant rainfall event across the southern Hill Country and middle Rio Grande Valley as multiple rounds of heavy rainfall with intense rainfall rates are expected through Thursday. Current guidance supports the potential for widespread rainfall totals of 4 - 8", with locally higher amounts possible within the axis of heaviest rainfall. From a hydrologic standpoint, the combination of high rainfall rates, complex terrain, and shallow soils across the Edwards Plateau will be highly efficient at producing rapid runoff into normally dry washes and arroyos, allowing flash flooding to develop quickly. As repeated rounds of heavy rainfall continue through the week, infiltration capacity will decrease as soils become increasingly saturated, resulting in greater runoff potential. This rapid runoff response may lead to flash flooding well before significant impacts reach larger river systems. Fast-responding rivers may experience significant rises, with minor to isolated moderate river flooding possible later in the week as high water moves downstream.
Across the broader central and southwest Texas region, isolated flash and urban flooding is expected, with significant impacts possible in some locations. The primary threat will be focused across urban areas, low-lying locations, and areas with poor drainage.
Central Appalachians
Isolated flash flooding remains possible through this evening as slow-moving storms with locally high rainfall rates continue across the region. Widespread flooding is not expected, with the primary threat focused across urban and typical flood-prone locations.
Nevada
Increasing monsoonal moisture will support afternoon and evening thunderstorms on Tuesday and Wednesday, with isolated flash flooding possible. Storms are expected to remain scattered and progressive, limiting the potential for prolonged heavy rainfall and more widespread flooding impacts. However, locally intense rainfall may still produce rapid runoff and flash flooding, particularly across dry washes, arroyos, slot canyons, and recently burned areas.
000 AGUS74 KWCO 132001 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 300 PM CDT MON JUL 13 2026 ...Potentially life-threatening flash and arroyo flooding possible in portions of Texas... Isolated flash flooding possible across the Central Appalachians and Nevada... .Texas... A Considerable flood threat area was introduced today across portions of the southern Hill Country and middle Rio Grande Valley, where potentially life-threatening flash and arroyo flooding is possible through Thursday. A broader Limited area remains in place across central and southwest Texas. Forecast confidence has increased regarding a significant rainfall event across the southern Hill Country and middle Rio Grande Valley as multiple rounds of heavy rainfall with intense rainfall rates are expected through Thursday. Current guidance supports the potential for widespread rainfall totals of 4 - 8", with locally higher amounts possible within the axis of heaviest rainfall. From a hydrologic standpoint, the combination of high rainfall rates, complex terrain, and shallow soils across the Edwards Plateau will be highly efficient at producing rapid runoff into normally dry washes and arroyos, allowing flash flooding to develop quickly. As repeated rounds of heavy rainfall continue through the week, infiltration capacity will decrease as soils become increasingly saturated, resulting in greater runoff potential. This rapid runoff response may lead to flash flooding well before significant impacts reach larger river systems. Fast-responding rivers may experience significant rises, with minor to isolated moderate river flooding possible later in the week as high water moves downstream. Across the broader central and southwest Texas region, isolated flash and urban flooding is expected, with significant impacts possible in some locations. The primary threat will be focused across urban areas, low-lying locations, and areas with poor drainage. .Central Appalachians... Isolated flash flooding remains possible through this evening as slow-moving storms with locally high rainfall rates continue across the region. Widespread flooding is not expected, with the primary threat focused across urban and typical flood-prone locations. .Nevada... Increasing monsoonal moisture will support afternoon and evening thunderstorms on Tuesday and Wednesday, with isolated flash flooding possible. Storms are expected to remain scattered and progressive, limiting the potential for prolonged heavy rainfall and more widespread flooding impacts. However, locally intense rainfall may still produce rapid runoff and flash flooding, particularly across dry washes, arroyos, slot canyons, and recently burned areas. //Freeman Additional National Water Center products are available at www.weather.gov/owp/operations $$