Great questions on the minds of many gardeners. You are right - we should wait to apply winter mulch to plants after the ground freezes. Spreading a layer of straw or evergreen boughs over the warm soil delays dormancy and can encourage disease. It also provides a great habitat for rabbits and rodents that like to feed on our landscape plants. Snow is the best mulch. We should be grateful every time nature mulches the landscape in snow, even though it means we need to shovel our walks. So keep your mulch handy and once the snow is gone and the ground freezes you can put it in place. Your efforts will not be wasted since much of the damage occurs in late winter. As the soil freezes and thaws over the next few months it can push plants and bulbs right out of the ground. Though bloom may be reduced or a bit of repositioning of plants back into the soil may be needed, most of your hardy plants will survive the changeable weather.