Yeah it would be interesting to see a plot of number of users and number of posts by location, but it does feel like there are more Puget Sound posters than Oregon posters.
Highly unlikely there will ever be an Arkstorm redux in terms of the scale of the flooding, simply because there are a lot more mitigating factors now with irrigation, canals, dams, etc that did not exist back in 1862. Though no doubt a repeat of that weather pattern would still cause extensive flooding and catastrophic damage.
As far as snowmelt goes, as I understand it about 10 feet of precipitation hit the Sierras over a period of few weeks, some rain and some snow. I don't know if the snow level averaging say 1000' higher now than it did then would make that much of a difference when you're talking about that much water either way.
Perhaps we'll find out!
I do like the 2015-16 comparisons. We could do worse (See last winter). The last part of November 2015 was pretty chilly and dry in the Willamette Valley and December was super active. Once we got past the first week of December things got pretty boring and February and March were fairly torchy.