Don't go out! It ___ hard at the moment.

The sentence describes an ongoing action happening right now, which requires the present continuous tense. The phrase 'It is snowing' correctly uses the present continuous tense to describe the current weather condition. Therefore, 'is snowing' is the appropriate choice to complete the sentence, forming 'Don't go out! It is snowing hard at the moment.' This conveys that the reason for not going out is the heavy snowfall occurring at this time. The other options, 'snow', 'snows', and 'does snow', are not grammatically correct in this context for describing a current, ongoing event. 'Snow' and 'snows' are simple present tense forms, typically used for habitual actions or general truths, and 'does snow' is an auxiliary verb form used for questions or negations in the simple present, neither of which fits the context of an immediate, ongoing situation. The correct answer is is snowing.