Seattle, WA – SNOW! Or rain — or both. As Pacific storms continue to move into the Northwest and Northern California in November, the National Weather Service (NWS) is reminding residents to understand the difference between a Winter Storm Advisory and a Winter Storm Warning before traveling through mountain passes or coastal highways.
According to the NWS, a Winter Storm Warning is issued when heavy snow, sleet, or freezing rain is expected or occurring. In the Pacific Northwest, that often includes snow totals exceeding six inches in 12 hours across the Cascades or Siskiyou Mountains. These warnings signal high confidence that travel will become hazardous or impassable, especially along I-5, I-90, and U.S. 2.
A Winter Weather Advisory, by comparison, indicates that lighter snowfall or freezing rain is likely. While not as severe, these conditions can still cause spin-outs, avalanches, or black ice on mountain roads and foothill routes. Even coastal cities like Portland, Salem, and Redding can see brief snow or freezing rain that shuts down major interstates.
The NWS emphasizes that alert thresholds vary by elevation — meaning a warning in the Cascades may only be an advisory west of the range. Drivers are encouraged to check weather.gov for updated road and avalanche information, carry tire chains, and avoid nonessential travel during active warnings.
