overblown vs portentous

overblown and portentous both are adjectives.

Word	Noun	Adjective	Verb	Adverb
overblown	No	Yes	No	No
portentous	No	Yes	No	No

As adjectives, overblown and portentous are synonyms defined as:

Other synonyms of overblown include grandiloquent, pompous, pontifical.

overblown (adjective)	portentous (adjective)
past the stage of full bloom	puffed up with vanity
puffed up with vanity	ominously prophetic
	of momentous or ominous significance