7 feet of snow would weigh around 105 lbs per sq ft.
AT&T stadiums roof is 660,000 SF. 7 feet of snow on it would weigh 69,300,000 lbs.
Fresh snow as measured by constantly clearing your collection (which is how we get snowfall totals) is not very heavy. If you didn't clear it every so often it will pack under its own weight so 4' of snowfall will only be 2' deep.
A general rule of thumb is about 8 lbs per cubic foot for fresh snow. Some wet snow is heavier but it just doesn't pile up much. Buffalo snow is generally pretty fluffy because very cold air coming across the lake is what causes the lake effects.
A site i use to track snowfall in my area has a station in Buffalo. The Christmas snowstorm dropped 52" there. It was only 3.81" of water. Doing a little math (water 62 lbs per CF/12 = 5.16 lbs per 1" deep for water.) 5.16 x 3.81 = 20 lbs or so per square foot for just over 4'.
Data below is from Buffalo. High,low, precip, snowfall.
Now ground snow or compacted snow is more than like 20lbs per SF. But that's not a huge issue in Buffalo because while they get big dumps, it typically warms up and melts off most of the snow within a week.
The engineers in the area know this and have the ground snow load factor (how we determine snow loads for construction to prevent collapse) at 50lbs per SF in Buffalo.
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