As he watched the distant storm, a deep sense of foreboding filled his heart.

foreboding 是由前缀 fore-（表示"预先、在前"）和动词 bode（预示）加上-ing 后缀构成的名词。fore-表示"提前"，bode 意思是"预示"，合起来 foreboding 指"对即将发生的不祥之事的预感或预兆"。