How to keep wedding dress from getting dirty (winter wedding/snow)?

I will be getting married this winter and am planning to do wedding photos before the wedding ceremony. The photographer suggested we do some outside as we are getting married in the Rockies. However, I am wondering how I can prevent my dress/train from getting dirty or soaked from the snow? We don't have a wedding party, so no one would be able to assist carry the train between photos. I read that some brides carried a bed sheet around or bustled their dress. Are there other options besides these ones?