CLT was reporting freezing rain a few years ago. Everyone stopped going to deice pad/runway. Ground asked us why we weren't going to deice, told them no hold over time exists. New ATIS was cut and it magically went to -FZRA. That being said, if vis is down to 1/4 and the only thing affecting visibility is snow, I don't think LGA could not call it +SN. Ground stops and flights cancel at that point. That's been my experience.
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