When I scooped my back walk yesterday, I found that the ground underneath was not frozen at all. I have seen it where partially and even fully frozen ground has thawed out under a snow cover and grass has actually greened up and started to grow underneath a snow bank, even with pretty bitter air temperatures above it all.

Remember that the water under the ice is never colder than 32 degrees and generally even a little above it; so developing ice can take a real beating under a blanket of snow. That is why so many ice fishers want a good ice layer before the snow falls.

About your 4-wheel drive on ice. You start up much better, BUT you don't stop any better at all; so follow carefully. On icy roads you will need a whole lot more distance to stop safely.