Hydrologic Outlook
ORZ101>128-WAZ201>211-060000-

Hydrologic Outlook
National Weather Service Portland OR
357 AM PST Fri Dec 5 2025

...AN ATMOSPHERIC RIVER WILL BRING PERIODS OF HEAVY RAIN FROM
DECEMBER 8-10, RESULTING IN AN INCREASED RISK FOR RIVER AND URBAN
FLOODING...

A series of frontal systems will keep conditions wet through the
weekend and much of next week. The most notable period will be late
Monday through late Wednesday, where a prolonged atmospheric river
may bring significant rainfall and rising rivers across southwest
Washington and northwest Oregon. Rivers draining the Coast Range and
Willapa Hills have a 10-25% chance of reaching moderate flood stage
and a 8-15% chance of reaching major flood stage. There is also the
potential for flooding along small creeks and streams, as well as
urban flooding. Flooding of the Willamette mainstem rivers is
unlikely to occur (less than 10%). Probabilities for specific river
points can be found at the National Water Prediction Service
website. Periods of heavy rain will also increase the risk for
landslides in areas of steep terrain, and debris flows over recently
burned areas.
$$

12

Hydrologic Outlook
WAC009-027-029-031-033-035-041-045-053-055-057-061-067-073-060000-

Hydrologic Outlook
National Weather Service Seattle WA
337 AM PST Fri Dec 5 2025

...THREAT OF RIVER FLOODING ACROSS WESTERN WASHINGTON NEXT WEEK...

A series of atmospheric rivers will provide rounds of increasingly
impactful rainfall starting today and continuing through next week.
Snow levels will fluctuate around 4500 to 6500 feet. Expect rising
rivers with potential for flooding especially for rivers flowing off
the Olympics and Cascades. Urban flooding and landslides are also
possible throughout this period as the soil conditions remain wet.

$$

JD

Hydrologic Outlook
WAZ027-522-523-070015-

Hydrologic Outlook
National Weather Service Pendleton OR
303 PM PST Thu Dec 4 2025

...RIVERS RISING IN THE WASHINGTON CASCADES EARLY NEXT WEEK...

A series of weather systems will bring rain and rising river levels
to the area, especially the Washington Cascades, through this
weekend. Another system fed by a strong atmospheric river early next
week will bring heavier rain amounts. Currently a few locations on
the Naches and Yakima Rivers are forecast to reach action stage
starting Tuesday and Wednesday but the chances of reaching minor
flood stage are very low.


$$

GP

Hydrologic Outlook
ILC007-031-037-043-053-063-075-089-091-093-097-099-103-105-111-141-
197-201-INC007-073-089-111-127-051800-

Hydrologic Outlook
National Weather Service Chicago IL
209 PM CST Thu Dec 4 2025

...Risks for River Ice Formation and Isolated Ice Jams will continue
the next Few Days...

Very cold temperatures tonight will be favorable for additional ice
on rivers and tributaries. Reports from river ice spotters and river
gauges indicate that isolated areas of heavy river ice coverage have
already developed. While not likely, ice jams will be possible in
isolated areas along the Rock, Fox, Des Plaines, and Kankakee
rivers. Ice jams may cause rises on area rivers with little warning.

Despite warmer temperatures expected by this weekend, widespread
melting of river ice is not expected. As a result, most river ice
that develops this week will likely remain in place through early
next week.

This outlook means that elevated water levels and potential impacts
are possible, but not yet certain. Persons with interests along area
rivers should closely monitor the latest forecasts.

This product may be updated by tomorrow afternoon.
$$

WSL/Borchardt