Please see my post above. Weather files from the NSRDB do not have snow depth data, so they can not be used with SAM's snow model.
If you have hourly snow depth data in centimeters, you could add a column to your weather file with the heading "Snow Depth."
Another option is to model the effect of snow using a fixed DC loss factor, which you can look up for some locations in Alaska in the table in Appendix A of the following publication:
Ryberg, D.; Freeman, J. (2017). Integration, Validation and Application of a PV Snow Coverage Model in SAM. National Renewable Energy Laboratory. 33 pp. TP-6A20-68705. (
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