It is the heaviest in as many as five decades.
这是五十年来最严重的一次。
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两个地方需要注意。第一，“五十年”，这里用的词是decade（十年）；第二，“在五十年中”，不要丢了介词in。
原句是：
In many areas, where snow has continued falling for several days, the accumulation has been described as the heaviest in as many as five decades.
在许多地区，大雪已连续下了很多天，积雪被称为五十年来最严重的一次。
海纳百川，有容乃大；壁立千仞，无欲则刚。