Risk isn't just about the likelihood, it's also the outcome.
Even if your manager loves you to death and there's just a .1% chance you misread the situation and your early notice goes wrong... the result of that .1% occurrence could be disastrous.
On the other hand, if a 2 week notice is likely to screw over your team, that's a sign of a bad employer. If 2 full weeks of notice isn't enough to stabilize things enough for you to leave on good terms, what happens if you're injured tomorrow?
2 weeks notice is good. The most you should do earlier than 2 weeks is start documenting the unwritten parts of your process and start getting others to understand those. A good manager will enable that without you saying you're walking out the door.
