By Saturday, deepening upper level troughing will develop over the Gulf of Alaska. This trough is associated with cold air, and the tight packing of the height lines suggest strong jet stream winds.
During the next few days (Tuesday AM), the trough plummets southwards, bring much colder air over the NW (see graphic below)
First, for the 24-h ending 5 PM on Saturday. Up to 8 inches in the north Cascades and mountains of southern British Columbia, with lighter amount spreading down into norther Oregon.
The next 24 hrs (ending Sunday at 5 PM), the same thing.
This is all great impetus for us to get our application Seattle SNOWWATCH ready for this winter, with new capabilities that I will describe in a later blog.