063
AGUS74 KWCO 181519
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT MON AUG 18 2025

.Synopsis...
Isolated flash and urban flooding possible in Puerto Rico and the USVI...
Isolated flash, urban, and river flooding possible in the Upper Midwest...

.Puerto Rico and the USVI...
Rain bands from Hurricane Erin may move over the islands today as the
system continues to the north northwest, bringing the potential for locally
heavy rain. This may result in localized flooding, especially in hilly
areas of the island as bands move over.

.Upper Midwest...
Isolated flash, urban, and river flooding remains possible through day 1
(Mon) across much of the region, with the greatest potential focused across
northeastern IA into southern MN and northwest IL where the heaviest
rainfall is expected. Top-layer soils (0 - 10cm) across the aforementioned
areas, are wet but not saturated (55 - 75% RSM, NASA SPoRT) following
recent rainfall, and combined with above to much above normal streamflows
(USGS), this suggests a hydrologic environment more conducive to flooding
responses in these areas.
The National Water Model (NWM) Short Range Forecast (SRF) does suggest a
low end potential for Rapid Onset Flooding (ROF) over portions of northeast
IA and southeast MN with ROF trend probabilities generally less than 50%
and annual exceedance probabilities (AEPs) around the highwater threshold,
with the exception of isolated small streams near the Mississippi River
that are as low as 4% suggesting the potential for isolated significant
flows. Deterministic ROF signals have started to spread into a significant
part of southern WI however, the significance of these flows will depend
on 1 how far east the current MCS makes it, and 2 the location of
redevelopment. If storms develop farther east than expected, it will result
in impacts mainly being in urban areas.

//GKendrick



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