Pacific Northwest Prepares for 5–10 Inches of Rain as Oregon and Washington Face Days of Flood Risk
WASHINGTON & OREGON — A new multi-day atmospheric river event is taking aim at the Pacific Northwest, and forecasters warn that widespread 5–10 inches of rainfall could fall across western Oregon and Washington through early next week. With mountain totals approaching 14 inches, the region is facing another round of potentially serious flooding, landslides, and travel disruptions.
High-resolution model guidance, including the latest GFS run, shows a sustained conveyor belt of Pacific moisture repeatedly targeting the same areas that have already seen heavy rain this month. With soils saturated and rivers running high, officials are cautioning that even moderate additional rainfall could quickly lead to renewed flooding.
Heavy Rainfall Expected Through December 23
Forecast maps show a clear and alarming signal:
- 5–10 inches across the western lowlands of Oregon and Washington
- 8–12 inches in the foothills
- 12–14 inches in the Cascade Range
- Localized pockets above 14 inches possible in southwestern Washington and northwest Oregon
These numbers represent rainfall totals from multiple overlapping storm waves, each carrying substantial moisture due to an active Pacific jet stream.
The WeatherBell GFS projection highlights a persistent atmospheric river concentrating directly over the I-5 corridor and surrounding mountain terrain. This setup is classic for prolonged heavy rain events and contributes significantly to flooding potential.
Flooding Risk Increasing Daily
Because earlier storms have already saturated the ground, the region is more vulnerable than usual.
Key concerns include:
- Rapid river rises, especially along rivers draining the Cascades
- Urban flooding as drainage systems become overwhelmed
- Landslides and debris flows on steep terrain
- Road closures along mountain passes and low-lying highways
Communities that experienced flooding last week may be at higher risk again, as water levels remain elevated in many basins.
Why This Event Is High-Impact
Meteorologists attribute the threat to a combination of:
- A strong Pacific jet extension funneling continuous moisture from the central Pacific
- Successive storm systems impacting the same geographic area
- Warm air involvement, which increases rainfall efficiency
- Limited recovery time between storm waves
This “multi-round” pattern means impacts will build over several days rather than coming from one single storm.
Travel & Safety Considerations
Residents across western Oregon and Washington should prepare for:
- Difficult mountain travel due to flooding or road washouts
- Possible delays along I-5 and coastal highways
- Rising rivers through early next week
- Potential evacuation notices in vulnerable areas
Emergency officials advise monitoring river forecasts and avoiding travel in high-flood-risk zones when heavy rain is occurring.
What Comes Next
Another update cycle will arrive within 12–24 hours as forecasters refine rainfall totals and assess how quickly rivers respond. Given the consistency of recent model runs, confidence is growing that this could be one of the more impactful December flooding events in recent years for the Pacific Northwest.
Chicago Music Guide will continue to monitor the evolution of the storm pattern and provide updated coverage as more information becomes available.
Stay with ChicagoMusicGuide.com for continuing weather updates and community coverage.