People are riding around on snowmobiles.
It is snowing.
It doesn't have to be snowing to use a snowmobile.
exists e1 x1 x2.(r_around(e1) & on(e1,x2) & n_snowmobile(x2) & Actor(e1,x1) & v_ride(e1) & n_people(x1))
exists e1 x1.(n_thing(x1) & Actor(e1,x1) & v_snow(e1))