Hello Patricia,

Hopefully you have sufficient root mass formed before the top layer of the soil freezes.  There is a difference between sufficient roots to provide anchorage and sufficient root mass to prevent desiccation throughout winter and spring.

https://www.extension.purdue.edu/extmedia/ay/ay-28-w.pdf

Current advice is to not cut the lawn lower for winter than you would normally cut it.  So, you would like to cut to 3.5 - 4 inches going into winter dormancy.

As far as preventive fungicides are concerned, there are products carried at "big box" retailers that are labelled for use against snow mold.  Read and follow all label instructions for any fungicide you apply.

https://www.canr.msu.edu/news/managing-lawn-diseases

Professional applicators for lawn care can apply fungicides that are more powerful than what the homeowner has access to.  You may choose to use a professional service for fungicide application.

Hope this helps.