Hydrometeorological Discussion
Issued by NWS Tuscaloosa, AL
Issued by NWS Tuscaloosa, AL
591 AGUS74 KWCO 061519 HMDNWC National Hydrologic Discussion - EXPERIMENTAL NWS National Water Center - Tuscaloosa AL 915 AM CST WED NOV 6 2024 .Synopsis... Rainfall expected across the Southeast and the Gulf Coast, Central and Southern Plains, and Northwest... Ongoing river flooding will continue in Arkansas and Missouri... Rainfall and flooding impacts will continue for Puerto Rico and USVI... .Discussion... .Southeast and the Gulf Coast... Hurricane Rafael is expected to cross western Cuba and enter the Gulf of Mexico early on day 2 (Thu). There continues to be a lot of uncertainty in its track as it enters the Gulf, the location and magnitude of any rainfall, and associated flooding impacts. With that being said, we will continue to monitor this evolving situation. Heavy rainfall is expected to move into portions of Georgia and South Carolina today and continue into Thursday, with widespread totals of 2 - 4", locally higher (WPC). Soils throughout the column are quite dry (NASA SPoRT) and streamflows are normal to below normal (USGS). Based on these antecedent conditions, flash and urban flooding are the most likely flooding modes, especially with training expected and intense rainfall rates in any convection that may occur. The National Water Model (NWM) HRRR-forced Short Range Forecast (SRF) and the GFS-forced Medium Range Forecast (MRF) is signaling rapid-onset flooding (ROF) probabilities generally less than 50% across GA and southern SC. Corresponding signals from the NWM SRF high flow magnitude forecast service is showing annual exceedance probabilities (AEPs) dipping down in the 4 - 2% range, mainly affecting smaller creeks and streams. Overall, the threat is mostly relegated to being flash or urban in nature due to the antecedent conditions, although some out-of-bank rises on streams and minor river flooding cannot be ruled out. Minor to moderate river flooding will continue for the foreseeable future along the Withlacoochee and St. Johns rivers across central Florida. .Central and Southern Plains... Flash and urban flooding, with localized small stream flooding, is possible across portions of the region on days 2 and 3 (Thu and Fri) due to heavy rainfall (2 - 4"). Portions of northern TX, OK, and central and eastern KS have been wetted from rainfall over the weekend with top layer soils 45 - 65% (0 - 10 cm RSM, NASA SPoRT) and streamflows running much above normal (USGS). These aforementioned areas are somewhat more vulnerable to flooding impacts compared to western KS, where soils are much drier and streamflows are more variable (USGS). Overall, any flooding impacts are most likely to occur in the more vulnerable areas of TX and OK and perhaps central and eastern KS, where streamflows are elevated it should also be mentioned that the precipitation in NM and CO is expected to be frozen rather than liquid, which will mitigate the flooding concerns in those areas. .Northwest... Several rounds of moderate to locally heavy rainfall will start to impact the region over the weekend, continuing into next week, for portions of Oregon and Washington, bringing an isolated risk of flash and urban flooding to the region, including near burn scars. With relative soil moisture of 50 - 65% (0 - 10 cm RSM, NASA SPoRT), streamflows running near normal, and possible lower snow levels, all this will help mitigate any widespread flooding impacts. .Arkansas and Missouri... In the wake of heavy rainfall that impacted the region (6 - 12"+ past 72 hours, MRMS QPE), widespread minor to moderate and isolated major river flooding is forecast or ongoing for numerous rivers across the region. This is slated to continue through the week into the weekend, with minor flooding occurring on other creeks, streams, and rivers across the two states. Another bout of light rainfall will roll through the area of concern on day 4 (Sat), but this is not expected to cause any additional flooding concerns or renewed rises. .Puerto Rico and the USVI... Daily rainfall will continue to bring the risk of flash, urban, and small stream flooding to the islands through day 3 (Fri), especially as top-layer soils remain wet (NASA SPoRT). //Zawislak $$