ominous vs inauspicious

ominous and inauspicious both are adjectives.

Word	Noun	Adjective	Verb	Adverb
ominous	No	Yes	No	No
inauspicious	No	Yes	No	No

As adjectives, ominous and inauspicious are synonyms defined as:

Other synonyms of ominous include ill.

ominous (adjective)	inauspicious (adjective)
threatening or foreshadowing evil or tragic developments	not auspicious; boding ill
presaging ill fortune	contrary to your interests or welfare
	presaging ill fortune