You’re relying on one analog year?
Since there are several years that match your outlined temperature progression, I’m guessing it’s a +PDO year near/just after solar maximum. Something like 2014, or maybe 1996 if you’re trying to factor in solar minimum.
Bingo, you got it, 1996.
Yeah I'm pretty much relying on this one year. What I did was take a look at all the La Nina years and see if any of them matched the weather it received for April of that year to this years. There was one that really intrigued me and it was 1996. It's not an exact match but close enough. The Oceanic Niño Index for that year also matched this year's progression. Both 1996 and 2018 peaked in the NDJ time with an ONI value of -1.0 and then to -0.9, -0.8 and -0.6 subsequent months.
From 1996 to 2018 there's been about a general increase of +1.0 temperatures here in the PNW based on Mark's blog post where he pointed this out so I factored that in with my final numbers. I also weighed in some seasonal lag to put it all together. I have no idea how my forecast will play out but I really wanted to use analogs and not any of the seasonal forecast that I've seen recently.