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AGUS74 KWCO 171512

HMDNWC



National Hydrologic Discussion - EXPERIMENTAL

NWS National Water Center - Tuscaloosa AL

1013 AM CDT WED APR 17 2024



.Synopsis...

Potential for renewed rises and isolated flooding impacts in East Texas and  

Lower Mississippi Valley... Continued threat of flooding in Puerto Rico and  

USVI... Ongoing flooding in the Ohio Valley...



.Discussion...



.East Texas and Lower Mississippi Valley...

Rounds of rainfall return to the region this weekend and will likely result  

in renewed rises on rivers as well as potentially new flooding impacts.  

Soils have had some time to recover from the last rainfall event, but  

top-layer relative soil moisture remains around 50% (NASA SPoRT), though it  

is higher in the ArkLaTex region. Streams remain above climatological  

normals (USGS) with some rivers still in moderate flood.



The GFS-forced National Water Model (NWM) is beginning to signal scattered  

small stream responses days 4 - 5 in the Trinity, Sabine, Neches, and Lower  

Brazos Basins in east TX, with associated Annual Exceedance Probabilities  

of 10 - 20%, indicating that significant rises are possible on already  

elevated smaller creeks and streams. The NBM-forced NWM isn't signaling  

much throughout this region, decreasing confidence in impacts, especially  

since the NBM is closer to WPCs QPF guidance while the GFS shows higher  

totals. Potential training and higher rain rates will be the main drivers  

of impacts, and antecedent conditions suggest that at least isolated  

flooding impacts are likely.



.Puerto Rico and USVI...

Flooding in urban areas, on roads, along small streams, and along washes  

will remain possible through day 1 (Wed) as periods of heavy rainfall  

continue. Isolated flash flooding and landslides remain possible in  

saturated areas of steep terrain.



.Ohio Valley...

Scattered minor river flooding will continue across the White (IN) and  

Wabash (IN/IL) river basins and along the lower Ohio River through this  

weekend. Additional rainfall day 1 (Wed) may elicit renewed rises and/or  

stalled recessions along already elevated creeks and streams in KY and OH.  

However, convection will rapidly progress east and have minimal resonance  

time in any particular basin, likely mitigating response on larger mainstem  

rivers.



//JEC/Ayala



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