any time now vs momentarily

any time now

adv

  • very soon 

momentarily

adv

  • In a moment or very soon; any minute now, any time now. 

  • In a momentary manner; for a moment or instant. 

  • Progressively; moment by moment. 

How often have the words any time now and momentarily occurred in a corpus of books? (source: Google Ngram Viewer )