It's not Alaska-specific. With many airlines, fares go up on many routes on most dates in the last few weeks before the flight date because that's when business flyers tend to book, and airlines know that business flyers are typically wiling to pay more than leisure flyers.

However, this can change on dates on which business flyers rarely fly, such as Christmas travel dates, etc.

And, of course, any flight which is way undersold days out from the flight might lower the rates at that point just to sell more seats.

But, again, Alaska is in step with the other major airlines like AA, DL, and UA on this. The only big airline in the US that's classified as "low-cost" (which means low operating cost, and has nothing to do with fares) is Southwest, and then there are several US airlines like Spirit and Frontier which are classified as "ultra-low-cost" (which against means ultra low operating cost, and has nothing to do with total fares; I have to say "total fares" because many "ultra-low-cost" airlines make money by nickel-and-diming additional fees, while pretending to keep the fare low, until you add those fees and you the total fare is not that low).