I have to be brief here (I do have a job at the UW!), so a few comments based on the latest runs.
Very little chance of a major lowland snow.
A very good chance of heavy rain and wind.
There will be snow during the initial hours of the event, but will rapidly turning to rain.
Most probable evolution. As the system approach later tomorrow, some locations will see light snow, possibly a few inches, after rush hour. (This times very well for local DOT departments).
Overnight will turn to rain and temps will warm. Wednesday we will see moderate rain over the lowlands and the development of strong winds. VERY strong winds along the coast and over NW Washington. Very heavy snow in the mountains (a few feet!).
Philosophical question for a future blog: with all the uncertainty at 4-7 days out, is my field doing the population a service telling them what might happen?
PS: There are some light snowshowers scattered around today...nothing significant will fall.