605
AGUS74 KWCO 041952
HMDNWC

National Hydrologic Discussion - EXPERIMENTAL
NWS National Water Center - Tuscaloosa AL
200 PM CST THU DEC 4 2025

Confidence increasing in the likelihood of urban and river flooding across
portions of the Pacific Northwest early to mid-next week...

.Pacific Northwest...
A series of frontal systems will bring periods of moderate to potentially
heavy rainfall through at least the middle of next week across western WA
and OR, with urban and river flooding becoming increasingly likely. The
flooding impacts will be greatest on Monday through Wednesday of next week,
when the heaviest rainfall (daily totals of 2 - 4") are expected. Soils
have gradually become wet following waves of precipitation over the past
several weeks, and while streamflows are currently near normal for this
time of year, daily rainfall through next week will sufficiently prime the
hydrologic environment for stream and river responses. The latest river
forecasts indicate widespread river rises and scattered minor to moderate
river flooding, especially along rivers draining into Puget Sound and
across the Lower Columbia Basin in northwest WA. HEFS guidance at the 30%
exceedance (reasonable worst case scenario) continues to indicate the
potential for more significant river flooding in northwest WA, with
isolated major flooding possible. Much of western WA (along and west of the
Cascade Crest) and northwestern OR remain in a Limited flood impacts area,
and given the current guidance, no changes are expected for the afternoon
issuance. However, potential expansion of this area may be warranted, as
the main event gets closer.

//JDP

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