SEATTLE — A powerful storm system spinning off the Pacific Northwest coast has strengthened sharply, with its central pressure falling into the 960s millibars. That is roughly comparable to the central pressure of a Category 3 hurricane. The storm is expected to steer another atmospheric river into the region, along with strong winds, higher storm surge and dangerous surf.
A Deep Low Spins Off the Coast
Satellite imagery shows a large, well-organized storm swirling over the northeastern Pacific, with cloud bands wrapping tightly around its center. The system stretches from near southeast Alaska and British Columbia south toward the coastlines of Washington, Oregon and Northern California. Its huge size means its effects will reach far beyond the center of the low.
The drop into the 960s millibars puts this storm among the stronger systems to approach the region this fall. While it is not a tropical storm, its central pressure is similar to that of a major hurricane. Deep lows like this can produce long-lasting wind and wave impacts along exposed coastlines.
Another Atmospheric River on the Way
One of the biggest concerns is the storm’s role in steering another atmospheric river toward the Pacific Northwest. The region has already been hit by repeated rounds of heavy rain, leaving soils soaked in many areas. More rain falling on saturated ground could raise the risk of runoff, rising rivers and localized flooding.
Communities around Seattle, Portland and Vancouver should be ready for more periods of steady, heavy rain. The coastal mountains and the Cascades are likely to see the highest totals as moisture is pushed up against the terrain. Landslides may become a concern in steep areas where soils can no longer absorb water.
Strong Winds as the Pressure Gradient Tightens
The deepening low will tighten the pressure gradient across the region, the main driver of strong, gusty winds. Coastal areas of Washington and Oregon are expected to feel the strongest gusts, with wind spreading inland at times. Downed trees, scattered power outages and travel disruptions are possible as the system moves through…