There are several factors to consider between late pre spawn and actual spawning. Big lakes have zones within the lake body that warm faster. For example the wind protected areas that have traditional spawner's located in the upper third of a lake, that doesn't have a cold flowing river entering the area, would be the first zone to consider. The big IF is the river water temperatures being influenced by cold rain run off. IF that is the situation, than you move down lake to the middle zone. The deepest water is always the dam area and that is the last zone to transition, therefor the most stable zone area during cold weather periods. Lots of little things to thinker with when trying to predict bass locations, even during the spawning period. Most big lakes will have a primary spawn, secondary spawn and late bloomers, so during the middle of a "spawn" you will have pre spawn, spawn and post spawn going on at the same time somewhere on the lake. The key where to fish for the big girls and what to target them with. Hope we can answer all that for you.
Tom
Ps; You can be the best bass fisherman on the planet and fish the wrong place at the right time and get skunked or catch a bag of dinks.