。
We couldn't go for a walk because of the storm.
Literal
Storm [because-of-に-ために] walk [to-に] go-could-not.
のために is the longer form of のため for causal 'because of'; both are interchangeable here. Note that 散歩 is written entirely in kanji while いけなかった is in kana — Japanese writers often convert functional or light verbs like 行く into kana when they carry little semantic load. 散歩に行く ('go for a walk') uses に for the purpose of motion.