####018005620#### AGUS74 KWCO 031513 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 1015 AM CDT FRI MAY 3 2024 .Synopsis... Significant flood impact concerns continue for Texas and the Lower Mississippi Valley... Isolated flooding impacts remain possible across portions of the Central and Southern Plains into the Midwest... Potential for isolated flash and urban flooding impacts continues for Puerto Rico and the USVI... Snowmelt runoff and ice jams are causing isolated river and small stream impacts in Alaska... Ongoing small stream and river flooding across the Great Basin and Intermountain West... Flooding impacts will be possible today in American Samoa... .Discussion... .East Texas and the Lower Mississippi Valley... Considerable river and small stream impacts will continue through next week for portions of east Texas, especially along the Navasota, Trinity, East Fork San Jacinto, and Neches Rivers where major and record flooding are observed or forecasted. Additionally, minor and moderate river flooding are observed or forecasted over portions of east Texas into Louisiana. In general, these rivers should be allowed to recede unimpeded however, 1 - 3" of precipitation through day 3 (Sun) may extend the duration flooding impacts within the region. Moderate to heavy rainfall will be possible days 2 into 3 (Sat into Sun) over portions of central and west Texas, bringing the potential of flash and urban flooding to the region. Soils within the region have available infiltration capacity with soil moisture generally 45 - 60% however, heavy rainfall within hilly terrain should be able to overwhelm infiltration capacity allowing for an increased threat of flash flooding. Precipitation in this area continues to trend up, and will have to be watched for potential locally considerable flooding impacts. Rapid rises may be possible on area streams and rivers as well. .Southern and Central Plains into the Midwest... Minor to isolated major river flooding is ongoing or forecast over southeastern KS, through MO, and into western IL. Many locations have crested or are cresting over the next couple of days with only a few locations experiencing broader crests from routed flows into this weekend. Steady rainfall totalling 1 - 2", with locally higher amounts possible, will continue to threaten the region through today with additional flooding impacts possible. Soils remain wet (0 - 100 cm, NASA SPoRT) and streamflows are generally above normal (USGS), creating favorable conditions for rapid runoff into elevated streams. Additionally, isolated flash and urban flooding impacts can not be ruled out across the entire region, particularly where training occurs. Rainfall will return on day 4 (Mon), which could result in new or renewed flooding impacts. Minor to isolated moderate river flooding continues in portions of IA and MN from previous rainfall. Drier conditions settle across the area for a few days before another wet pattern is forecast to return by day 4 (Mon), but the confidence in exact placement and magnitude of forecast rainfall is low due to the extended timeframe. The NWM MRF continues to signal AEPs are around 50% with some isolated smaller order streams signaling AEPs as low as 20%, lending confidence that most small stream rises will not be significant. Moderate to heavy rainfall (1 - 3") on day 3 (Sun) will result in the potential for flash, urban, and small stream flooding impacts over eastern Oklahoma into Arkansas. This area remains wet, with soil moisture generally above 60% (0-10 cm RSM, NASA SPoRT). The combination of wet soils, complex terrain, and heavy rainfall will likely result in flash flooding and rapid runoff into already elevated streams. .Puerto Rico and the USVI... Persistent rainfall over the next several days will continue to provide a threat of flooding impacts, including mudslides, across PR and the USVI. Soils remain saturated across PR and streamflows remain elevated, especially across the eastern half of the island. The heaviest rainfall is expected through day 2 (Sat). Considering the antecedent conditions, any additional heavy rainfall will likely lead to rises on rivers and isolated flooding impacts. .Alaska... Flooding impacts from spring breakup and snowmelt runoff will continue for the next several days and beyond. Out-of-bank flows on Moose Creek and Trooper Creek near Glennallen could impact Glenn Highway and the surrounding floodplain. An ice jam on the Nushagak River between Dillingham and Portage Creek has caused localized flooding across the floodplain. An ice jam is in place on the Tanana River downstream of Manley, and has caused some minor flooding within the town. Finally, ice jams have been reported on the Yukon and Forty Mile rivers in Canada with the breakup front reaching Eagle Wednesday, flooding will be possible in the area if any jams form near the town. .Great Basin and Intermountain West... Isolated minor to moderate river flooding and elevated flows will continue along area rivers, creeks, and streams across portions of southern ID and northern NV in response to runoff from snowmelt. .American Samoa... Heavy rainfall will result in flash and urban flooding impacts through today. //GKendrick $$