I'm no weather nor Columbia River expert, but your unusually choppy and confused wave/swell pattern is probably caused the westward current flow of the river running against the eastward wind flowing up the Columbia River Canyon.
When the current flow opposes the wind wave pattern, the waves stand/stack up and are much more treacherous than when they run in the same direction and the current lays down the wind waves into smooth gentle wavelets.
This is a classic problem all over the world where tidal flows oppose wind patterns, and especially amplified by the long fetches afforded by the long reaches of the canyon, becoming confused at bends in the river and its flow, and amplified by any changes in depth and other bottom contours.
Existing wave patterns can also be reflected off steep cliff river walls where they exist. Additionally, whirlpool like river flows at bends can also add a nice "washing machine" effect (!)
Using the above as a predictor along with knowledge of your present wind and the anticipated afternoon build up from interior heating (a sea-land breeze) , one should be able to look at a map of the river at predict where the confused wave build ups will be. The exact amount of trouble will depend upon the river current and wind speed.
With time and experience, you'll be able to anticipate the conditions in advance fairly well, and know when and where to be or not to be, or at least understand what's happening where you are at most any time, and what your options are.
With that experience, you'll be able to "read the waves" and wind, and understand whats happening around you. (I got mine on San Francisco Bay!)
At least, that's my best guess, from a guy in Redding, CA. :lol:
Joe. :teeth :thup