。
It snowed heavily last night.
Literal
Last-night heavy-snow [subject-が] fall-[past-った].
大雪 ('heavy snow') is one of a family of 大- + weather-noun compounds: 大雨 (heavy rain), 大雪 (heavy snow), 大風 (strong wind). The prefix 大- ('big, heavy, major') is productive and commonly used for weather or events of unusual magnitude.