Look at the 7day NOAA weather forecasts at various points along the possible route. For Seattle they are talking about another cold day then warming, with a chance of snow in then transition, followed by a wet, possibly heavy, week. And potentially heavy snow in the mountains.
http://graphical.weather.gov/sectors/conus.php?element=WxNOAA forecast map for the next week. The 'weather' loop is particularly instructive. A lots going on in the west right now, though by next Thursday it looks a lot more settled - the exception of the Idaho/MT/WY border mountains.