747
AGUS74 KWCO 111504
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT SAT OCT 11 2025

.Synopsis...
Locally considerable flooding impacts are expected across the
Southwest...Coastal flooding forecast on the East Coast...Urban and small
stream flooding possible in Puerto Rico and the USVI...Considerable to
locally catastrophic coastal flooding in Alaska...

.Southwest...
Multiple days of tropical moisture will bring the potential for flash
flooding across north-central AZ, portions of UT, NM, and CO through
tonight with locally considerable flash and urban flooding continuing
through Monday (day 3), mainly across southeast AZ, southwest NM and
southwest CO. Although most top-soils in the region were initially dry,
recent rainfall over the past several days has helped to moisten soils,
particularly across north-central AZ, north of Phoenix and southwest UT
however, regardless of antecedent conditions, these storms will likely
produce areas of heavy rainfall very quickly, overwhelming available
filtration capacities and leading to subsequent flooding impacts. Given the
widespread and long duration of the rainfall expected over the next several
days, additional significant flooding impacts are becoming increasingly
possible across areas of southeastern AZ and southwestern NM beginning
Sunday (day 2). Furthermore, any heavy rainfall over recent burn scars,
slot canyons, and urban areas could trigger the potential for flash
flooding and debris flows.

While Medium Range Forecast (MRF) signals are limited, the HRRR-Forced
National Water Model (NWM) Short Range Forecast (SRF) signals for
rapid-onset flooding (ROF), generally near 25-50% with localized
probabilities of 51-75% to areas northeast of Phoenix, AZ where soils are
already wet. Given the persistent rainfall, and the known low bias of the
NWM with this region, flooding impacts may be slightly more extensive than
what is shown. Given the NWM signals, out-of-bank rises will be possible.
Initially, the primary impacts are expected to be rapid rises on small
streams, along with urban and arroyo flooding, with isolated river flooding
possible by the end of the weekend.

.East Coast...
A low pressure system will continue to move up the coast bringing
potentially significant coastal flooding through the weekend into early
next week. Heavy rainfall associated with the low pressure system may
result in flash and urban flooding within coastal communities across the
region.

.Puerto Rico and the US Virgin Islands...
Urban and small stream flooding is possible through today in response to
heavy tropical rainfall.

.Western Alaska Coast...
Considerable to locally catastrophic and life-threatening coastal flooding
is expected Sunday into next week (day 2).

//TMK





$$