Global warming?

Could be.  Accumulated snow fall in Portland Oregon has been declining. One would assume the presence of Gorge winds from the east would preclude the ability of the urban heat island effect from increasing temperatures, by removing humidity and rapidly dissipating heat just prior to the onset of offshore moisture from the west.  Since cold, dry Gorge winds are a necessary part of the snow fall equation in Portland, it seems plausible that this is a case of global warming.

I have never ever seen either the Columbia or Willamette rivers come close to freezing up like these 1930 photos.  Anyone that's lived in Portland would probably be shocked to learn that both rivers would regularly freeze up!