Momentarily means (1) "at any moment," (2) "from moment to moment," and (3) "for a moment": "The blast will be set off momentarily." "Our chances are improving momentarily." "Let's sit down and rest momentarily." Momently, now rarely used, formerly meant only "at any moment": "He will get here momently."In current speech and writing, momently may occasionally be used in any of the three meanings of momentarily but has largely disappeared from the language.
Dictionary of problem words and expressions. Harry Shaw. 1975.