Ethically, it isn't something I would do. First, you have a axe to grind with your current employer? Because the
bridge will be burned. This will leave a bad taste in everyone's mouth.
Is there a reason you can't talk to your boss or HR? Explain that you've been looking, and the situation. Maybe they will agree to just sever you out, pay your Cobra, and you can move on to your new employer guiltfree?
At least that way, they can plan, you can do a normal handover and transition. Better than just coming back from leave and saying, "so long suckers!!! I'm out".
Wow, you'll find that will follow you.