The Collaborative International Dictionary of English v.0.48:
Sternly \Stern"ly\, adv. In a stern manner. [1913 Webster]WordNet (r) 3.0 (2006):
sternly adv 1: with sternness; in a severe manner; "`No,' she said sternly"; "peered severely over her glasses" [syn: sternly, severely]