Basic way to think about it 30 inches is 10 lbs and add one pound from there for each inch. Early in the run the fish tend to be higher and vice versa toward the end, not including kelts. That is for anadramous fish, Lake Run, I am not sure. Great fish regardless of method though.
I catch triploids of similar length and girth. I've caught two that weighed slightly over 18#s. One was 33inches, one 34, but even fatter. But without something other than the lure to gauge, I'd guess around sixteen.