CHAT: Palatization before /&/ in English

I've long noticed in the speech of many Americans, not including most
Southerners and Northeasterners, is the tendency to pronounce "now"
something like "nyow". This sounds like palatization of preceding consonants
before short English |a|, almost like what happens in Irish Gaelic with |ea|
and Russian soft consonant + /a/.

What are the details of this feature: demographic, geographic, which
preceding consonants are affected, etc.?

~Danny~