With all due respect Captain. There are too many unknowns. You need the water content of the snow and the concentration of nitrogen in that water. i assume you don't care about the nitrogen in the air spaces in the snow. The water content could vary from a very low percentage in new dry snow, to quite high for wet snow or snow compacted by something like a snowplow. I'll make a couple of guesses and provide a SWAG.
If the water concentration of nitrogen were .5 mg/l, which is not an unreasonable value, and the snow was compacted to be 50 percent water, the amount of nitrogen would be less than 1/2 pound. Even if the snow were heavily compacted to approach 100% water, the amount of nitrogen would be less than one pound. That is if my math and conversion factors are correct.
I am not usually a "joiner" but am now a member of CCA.