I've never forced bulbs, but my initial thought was that you'll need to get that plastic off the top of the bulbs or they may rot. I'm sure you have the same snow today in Boston that we're having in Western Mass. The weight of the snow on the bulbs and the amount of moisture may simply trap the moisture on the ground causing the bulbs to rot.
I hope someone with more experience will chime in because I want to start Caladium bulbs outside early in the Spring. I had planned to pot them up and tent plastic.

What is you goal with this? If you do get them to bloom ahead of time, you will need to keep them covered with plastic and possibly add heat at night so they don't freeze. You won't be able to enjoy looking at them in plastic. Anyway, to force them, you will need provide 12 to 16 weeks of cold (already done), then unfreeze the ground, keep the temperature above 60 and provide light. It may take adding heat, not just covering with plastic to keep the temperature up.

Bulbs are usually forced for indoor bloom. This is done by planting in pots, storing in the fridge for 2 to 3 months then bringing out into the house.

Schenly, caladium are tender, tropical plants and should not be put outside until all danger of frost is past. You can start them early, but must start them inside.

For Caladium info:
http://www.gardenersnet.com/bulbs/caladium.htm

Here is a link that might be useful: forcing bulbs