According to the Comparative Tables, the long [ǣ] that had developed from the diphthong [ai] further changed into long [ē] later in the development of Ossiriandic (PE19/25). Since long [ǣ] is attested in The Etymologies in Dan. snæ̂s (Ety/SNAS), it seems likely that this change occurred after the period of the Wars of Beleriand.