The weight of the snow will push the floating ice down into the water. The water being warmer will in turn melt some of the ice that was there. You relieving the pressure of the ice trying to push back up will cause cracking. The slush comes from two things, the ice being pushed down under the water and the holes drilled will let the water up on the surface. It will refreeze, but as snow ice which is weaker than blue/black ice. I stayed off the ice this weekend. Let the colder temps lock things up a little, as with snow on the ice it takes a lot colder temps to freeze from the insulation it gives the ice.