Below is the surface map mid-morning Monday from the GFS model. Note the  L center is
cutting across Crater Lake.  The position of the low puts our region in the snow zone,
with Portland on the northern edge of accumulation.  If this position holds, I would expect:
1.  Little to no snow north of Portland or Vancouver / heaviest amounts up to 4 or 6” south
toward Salem and Albany and the east side around near Mt. Angel and possibly as far north
as Sandy and east Multnomah county.  
2.  Portland downtown, north to Vancouver and west to Hillsboro may see nothing or 1-2”
at most.  Heaviest snow will fall late tonight, ending before noon Monday.  Daytime highs
around Portland will rise into the mid to upper 30s during the day and possibly 40 degrees
in some areas.  
3.  Keep in mind, some forecast models show 6-8” of snow.  Keep an eye on Salem, Silverton
and other south to east locations for a possible snow bulls-eye.  
This looks to be a classic case of Portland being right on the edge from getting snow to missing out!
Rod Hill