773
AGUS74 KWCO 171520
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT SUN AUG 17 2025

.Synopsis...
Locally considerable 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...
Locally considerable flash and urban flooding will remain possible through
day 2 (Mon) due to trailing tropical moisture in the wake of Hurricane
Erin. Landslides and mudslides will also be possible in steep terrain, and
an additional 1 - 2" of expected rainfall (locally higher amounts possible)
will further saturate soils and increase river levels, continuing the flood
threat across the islands.

.Upper Midwest...
Isolated flash, urban, and river flooding remains possible through day 2
(Mon) across much of the region, with the greatest potential focused across
southern MN into northwest IL where the heaviest rainfall is expected.
Top-layer soils (0 - 10cm) across the aforementioned areas, as well as
western IA, are wet but not saturated (65 - 80% 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. While the remainder of the region tends to be dry
to normal, isolated flooding impacts cannot be entirely ruled out,
especially where rain repeats over the same areas or higher rain rates
materialize. The National Water Model (NWM) is signaling generally modest
streamflow responses across the region, with rapid-onset flooding
probabilities below 50% and annual exceedance probabilities (AEPs) mostly
at or below bankfull. However, some higher magnitude AEPs are indicated
across southern MN, suggesting more significant streamflow responses could
occur, likely in smaller, more responsive basins. Additionally, minor to
moderate river flooding is forecast along portions of the Minnesota and
Cottonwood rivers (MN) following several days of rain, with crests expected
by mid-week as flows continue to route downstream.

//Freeman



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