Lead
Who: Western Washington communities and the National Weather Service. When: a second atmospheric river arriving Sunday after a major event earlier this week. Where: river valleys across northwest Washington, including the Nooksack, Skagit, Skykomish and Snohomish systems. What and result: the new plume is forecast to be weaker and shorter-lived than the storm that rolled in Monday, but existing saturated ground and swollen rivers mean renewed rises and elevated landslide risk.
Key Takeaways
- The National Weather Service says a second atmospheric river is expected to arrive Sunday and persist one to two days.
- An earlier system that moved in Monday produced catastrophic flooding along the Nooksack, Skagit, Skykomish and Snohomish rivers, with some locations recording more than 12 inches of rain.
- Warm temperatures during the first event raised snow levels so much that much precipitation fell as rain, accelerating runoff into river channels.
- Forecasters, including Seattle NWS meteorologist Anna Lindeman, describe the upcoming plume as much weaker in moisture content than this week’s event, but still likely to push rivers higher.
- Saturday is forecast to be drier but foggy, with a mostly dry morning and afternoon and showers returning in the evening; temperatures could reach about 55°F at Seattle–Tacoma International Airport.
- Because soils and river systems are already near or above capacity, even modest additional rainfall could worsen localized flooding and increase landslide probability.
Background
Atmospheric rivers are narrow bands of concentrated moisture that frequently affect the U.S. West Coast, producing a range of outcomes from light rain to intense, flood-producing storms. In northwest Washington this week, an atmospheric river that arrived Monday coincided with unseasonably warm temperatures that lifted the snow line; much of the precipitation fell as rain instead of snow, producing rapid runoff into valley rivers. Historically, the combination of high rainfall totals and elevated snow levels has created sharp river rises and widespread inundation in lowland areas.
Local governments, state emergency managers and the National Weather Service monitor these events closely because of their ability to produce both flash flooding and slower-onset river floods. The areas most affected in this cycle—the Nooksack, Skagit, Skykomish and Snohomish basins—contain a mix of rural valleys, small cities and critical infrastructure such as highways and bridges, increasing the potential for community disruption. Flood-control capacity, levees and early-warning systems play a role in outcomes, but extreme input to river systems can exceed designed tolerances.
Main Event
Monday’s atmospheric river brought intense rainfall that hit river valleys hard and led to catastrophic flooding across several communities. Emergency responders reported rapidly rising water in low-lying areas and along mainstem rivers; in multiple locations crews conducted rescues and roads were closed due to inundation and debris. Observations from field teams and local reports indicate that some places recorded rainfall totals exceeding 12 inches during the event, a volume that overwhelmed channels and floodplains.
Seattle NWS meteorologist Anna Lindeman attributed the severity to unusually warm temperatures that raised snow levels, causing precipitation to fall largely as rain and feeding rapid runoff into already vulnerable rivers. The federal and local forecast offices have been issuing warnings and river-stage updates throughout the week as conditions evolved. Communities along the Nooksack, Skagit, Skykomish and Snohomish remain impacted by high water, with ongoing assessments of infrastructure damage.
Looking ahead, the NWS says a second atmospheric river is expected to arrive on Sunday but should be smaller in total moisture and shorter in duration. Forecasters emphasize that while the incoming plume is not predicted to match the recent event’s intensity, it may still cause additional river rises and increase the chance of landslides where soils are saturated and slopes destabilized.
Analysis & Implications
Hydrologically, the key concern is compound risk: river systems and soils are already carrying excess water from the earlier storm, so even a modest additional input can convert minor rises into dangerous overflow events. Rivers that saw major increases this week will have reduced capacity to absorb new inflows, and tributary responses can be rapid where drainage is steep or confined. Emergency managers must therefore treat the next system as a risk multiplier rather than an isolated low-impact event.
The landslide threat is heightened when heavy rains follow closely after a major storm. Saturated ground, combined with undercut streambanks and debris from earlier flows, raises the probability of slope failures in both developed and undeveloped areas. This is particularly relevant for transportation corridors and residential zones built on or below steep hillsides, where a localized slide can sever roads or damage homes.
Economically and socially, repeated storm impacts increase recovery time and costs. Repairing roads, bridges and utilities while keeping communities safe imposes fiscal pressure on local governments already responding to one disaster. Prolonged river high stages can delay damage assessments, insurance processing and repairs, prolonging displacement for affected households and interrupting regional supply chains.
Comparison & Data
| Measure | Recent Event | Upcoming Plume (Forecast) |
|---|---|---|
| Peak reported rainfall | Some areas >12 inches | Not expected to reach same totals |
| Duration | Multi-day impacts following Monday arrival | Forecast 1–2 days |
| Sea‑Tac temperature forecast | — | Up to 55°F Saturday |
The table summarizes the limited quantified observations available: more than 12 inches was recorded in parts of the region during the earlier atmospheric river; forecasters do not expect comparable totals from the system slated for Sunday. Duration differences and temperature behavior matter because warmer conditions favor rain over snow, increasing runoff rates.
Reactions & Quotes
“I know that sounds very scary, but luckily, it’s definitely not going to have as much moisture in terms of what we saw this week,”
Anna Lindeman, Seattle National Weather Service meteorologist
Context: Lindeman conveyed that although the next plume is weaker, the preexisting flood conditions make renewed rises a real concern.
“Expect rivers to respond more quickly given saturated soils and high baseflows,”
National Weather Service river forecast office (summary)
Context: Forecast offices emphasize that hydrologic response depends on antecedent conditions; high baseflow means smaller additional rainfall can produce disproportionate rises.
Unconfirmed
- Detailed, location-by-location rainfall totals for the upcoming plume are not yet available and will depend on the plume’s exact track and thermal profile.
- Precise estimates of additional infrastructure damage from the forecasted river rises are still under assessment by local agencies.
- Longer-term weather patterns beyond the next 7–10 days remain subject to model uncertainty and are not confirmed.
Bottom Line
The immediate takeaway is that the next atmospheric river expected Sunday is forecast to be weaker and shorter than the storm that struck Monday, but it is not risk-free. Because rivers and soils are already saturated and some communities experienced catastrophic flooding and more than 12 inches of rain, even a smaller event can exacerbate river overflows and landslides.
Residents in flood-prone areas should monitor official river-stage updates and obey local evacuation or road-closure orders. Emergency managers must weigh the potential for renewed rises when prioritizing inspections, debris removal and targeted warnings. In short, the forecast reduces the probability of a repeat of this week’s worst-case totals but raises the stakes for compounding impacts.
Sources
- The Seattle Times — regional news report and field observations (media)
- National Weather Service Seattle — official forecasts, river statements and meteorologist briefings (official forecast office)
- NOAA explainer on atmospheric rivers — federal science explainer on atmospheric river dynamics (federal agency)