I have a bunch of 1 gallon nursery containers with upside down 1 gallon ziploc bag "lids". I've just cut a notch in the top of the bags as an air vent. They're working great - several pots are sprouting already. The only potential problem I can foresee is if you get a lot of snow after some of the plants sprout, they might get crushed? We don't get much snow here so I don't know if that's an issue or not. You may find you don't get sprouts until after the snow is all gone in your climate.

Many wintersowers use plastic bags as their containers. You can stick straws or bamboo skewers or some other stiff "frame" into the soil to prevent the plastic from collapsing under the weight of snow or rain onto the sprouts.

Martha