Only when the President declares a snowstorm or specifically authorizes snow assistance, and only for a continuous 48-hour period each applicant chooses. Emergency declarations never include snow assistance.
Records showing the start and end of your chosen 48-hour period, and labor, equipment and contract costs within it. See PAPPG Appendix K.
Pick the 48 hours with your heaviest costs, not the first 48. You can’t change the choice later.