What Makes a Winter storm?

Cold Air:

Below freezing temperatures in the clouds and near the ground are necessary to make snow or ice.

This image highlights a preponderance of Cold Air 

Moisture:

To form clouds and precipitation, air blowing across body of water, such as a lake or the ocean, is and excellent source of moisture.

Here is a good example of a storm drawing in extra moisture

Lift:

Something to raise the moist air to form the clouds and cause precipitation, for example of lift is warm air colliding with cold air and being forced to rise over the cold dome. The boundary between the warm and cold air masses is called front. Another example of lift is air flowing up a mountainside.

Lift