J is right that it's all about the change...Change in weather are what fish react to.
If you want to get deep into the barometric pressure discussion, realize this... The number you see in the weather report is not the exact physical value for where you are standing. Pressure changes with elevation, the higher you go - the lower it gets. It's reported/predicted/calculated as if it were 'brought' down to sea level to keep everything normalized.
If you look at a weather report for Denver, you'll see normal value...Something between 990 and 1030mb. However the 'raw' number there is probably somewhere around 800mb since it's a mile above sea level (could be off, just guessed...Haven't worked on this stuff in a while). It's standardized to sea level so that it can be useful in forecasting.
How does it relate to bass fishing? Well, it really doesn't. The biggest short term change you'll EVER see in Baro Pressure (think hurricane-type event) is the equivalent of moving up or down maybe foot or two underwater. Think of how many times a day a fish might move a foot or two in depth and you'll soon realize that the atmospheric pressure is pretty much irrelevant to the fish.
What is IS...is a symptom of the larger weather pattern. The pressure changes with things like fronts/storms/ridges. Those things bring wind, clouds, rain, cold, etc...Those are the things that drive fish mood, the pressure is just a symptom of those (as it relates to Bass Fishing). I wouldn't worry about the pressure, I'd worry about the other things...But most importantly, just go fish!
Having a degree in Meteorology certainly helps with some things in the fishing world, at least I'm using it for something since I never became a weatherman .