A good omen is a sign or indication of positive events to come in the future. There are several synonyms for this phrase that can be used to express the same idea. One of these is a positive augury, which refers to an auspicious or favorable sign that bodes well for the future. Another synonym is a propitious harbinger, which suggests a sense of good fortune or luck that may be on the horizon. A third option is a felicitous portent, which connotes a sense of joy or happiness that may be in store. Overall, these synonyms demonstrate the potential for optimism and positivity that a good omen can bring about.