353
AGUS74 KWCO 081521
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
1015 AM CDT WED OCT 8 2025

.Synopsis...
Ongoing coastal flooding and rain on snow in Alaska... Heavy rainfall
potential across the Southwest late this week... Ongoing flash flood threat
in American Samoa... Coastal flash and urban flooding is expected in the
Southeast and Mid-Atlantic Coast...

.Alaska...
A coastal flood event is ongoing across portions of western Alaska, with
moderate to major coastal flooding expected. This event is expected to last
through day 2 (Thu) having been caused by a low pressure system bringing
high winds, locally heavy rainfall, and storm surge. As the associated
precipitation moves further inland, it is expected to melt snow in the
Brooks Range leading to increased runoff into small streams and rivers.

.Southwest...
Confidence is increasing for a multi-day heavy rainfall event expected to
begin on day 2 (Thu)  and likely peak over the weekend on days 4 - 5 (Sat -
Sun). The heaviest and most persistent rainfall is expected to be focused
along the Mogollon Rim in Arizona and extending into the Four Corners
region. Our hydrologic models are showing a strong and consistent signal
for flooding in response to this rainfall. The Global Forecast System (GFS)
forced National Water Model (NWM) is signalling a strong chance of rapid
onset flooding as well as low annual exceedance probabilities which
correspond with high magnitude stream and river flooding. Initially, the
primary impacts are expected to be rapid rises on small streams, along with
urban and arroyo flooding. However, as the event continues, confidence is
increasing that significant impacts may be possible, including the
potential for mainstem river flooding over the weekend. Furthermore, any
heavy rainfall over recent burn scars in the region could trigger the
potential for flash flooding and debris flows.

.American Samoa...
Isolated flash flooding with associated landslides possible through early
day 2 (Thu).

.Southeast and Mid-Atlantic Coast...
Forecast precipitation leading to flash and urban flooding is likely to
begin affecting coastal communities starting on day 4 (Sat). This
precipitation is expected to exhibit a northward progression through day 6
(Mon). Runoff may be impeded by King Tide" backwater effects. There is
still some uncertainty regarding the speed at which the system bringing the
precipitation will move out of the area with any stalling likely to further
enhance flooding impacts.

//Leisure

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