It depends on how compacted the snow is, newly fallen at a shallow depth of 130mm on an aircraft wing, not very – so overall mass is closer to 70 to 100 Kg/cu. m. With compaction and ice formation it can increase to 190Kg.cu m.

I would suggest using a figure of 120kg per cu. metre (which equates to 15.6Kg per sq. metre at a depth of 130mm). That gives a maximum of 245Kg of snow on the wings alone