circumstantially vs unexpectedly

circumstantially and unexpectedly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
circumstantially	No	No	No	Yes
unexpectedly	No	No	No	Yes

As adverbs, circumstantially and unexpectedly are synonyms defined as:

Other synonyms of circumstantially include accidentally, by chance.

circumstantially (adverb)	unexpectedly (adverb)
insofar as the circumstances are concerned	without advance planning
without advance planning	in a way that was not expected
in minute detail
according to circumstances