890
AGUS74 KWCO 161512
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1011 AM CDT SAT AUG 16 2025

.Synopsis...
Locally considerable flooding impacts possible for Puerto Rico and the
USVI... Isolated flooding possible this weekend across the Upper Midwest...
Burn scar flash flooding impacts possible across the Southwest... Isolated
flooding possible across the Pacific Northwest and portions of  Texas
today...

.Puerto Rico and the USVI...
Locally considerable flash and urban flooding is possible across the
islands through day 2 (Sun) and into early next week as Hurricane Erin
passes to their north. Landslides in areas of steep terrain and river
flooding will also be possible in Puerto Rico. Rainfall amounts of 2 - 3"
with local amounts up to 4" are expected across northwestern Puerto Rico,
and amounts of 2 - 4" with local amounts up to 6" are expected across
southern and eastern Puerto Rico and the USVI. While the rainfall over the
weekend will be directly associated with Erin, additional rainfall early
next week in its wake will be related to generic tropical moisture in the
region.

.Upper Midwest...
Isolated flash, urban, and small stream flooding is possible across
portions of southern MN, much of WI, and perhaps extreme northern IA
through day 3 (Mon). Daily rainfall amounts are not expected to exceed 2",
but total amounts in these areas may approach 3 - 5". Soils are not very
wet (30 - 60%, 0 - 100 cm RSM, NASA SPoRT) leading into this weekend and
streamflows are generally near normal, though soils are moisening across
southern MN and WI in response to this mornings rainfall and some flows in
MN and IA are elevated (USGS). Overall, this suggests that the hydrologic
environment is not primed and it will take consecutive days of rain to see
any river flooding impacts. River ensemble guidance (HEFS) indicates very
low potential for new or renewed river flooding over the period, leaving
flash and urban flooding as the most likely modes, with small stream
flooding becoming more likely over time as soils saturate and runoff routes
into area streams.

The National Water Model short range forecast continues to indicate
potential for isolated small stream flooding throughout today across
southern MN into central and southern WI. Probabilities for rapid onset
flooding are starting to increase into the 25 - 50% range between La Crosse
and Eau Claire where rainfall over the past 24 hours has moistened
top-layer soils. While some sharp rises can be expected across the region,
out of bank flows are generally not expected as suggested by the flow
forecasts near the high water threshold and 50% AEP.

.Southwest...
Localized flash flooding and debris flows near recently burned areas are
possible today across AZ and NM due to locally heavy rainfall. This threat
persists through the early part of next week in eastern AZ and NM as
monsoonal activity continues.

.Pacific Northwest...
Localized flooding impacts are possible today across WA, OR, and ID due to
periods of heavy rainfall. Dry soils (20 - 45% 0 - 100 cm RSM, NASA SPoRT)
and below to much below normal streamflows (USGS) should mitigate
widespread small stream and river flooding, but sharp rises on streams and
rivers are expected. Localized flash flooding and debris flows near
recently burned areas also cannot be ruled out if heavier rainfall rates
materialize.

.Texas...
Isolated flash flooding impacts are possible across Texas Hill Country
today as remnant tropical moisture progresses across the region. Any
impacts should be highly localized and river flooding is not anticipated.

//JEC

$$