I know that in Californian accent, /æ/ is sometimes realized as [eɪ] only before /ŋ/. So words like hang, bang, rang, sang, gang, which normally end with /æŋ/, end with [eɪŋ]. The reason why it happens is usually attributed to the effect of the following "nasal" sound [ŋ], but I'm not certain about the reason. Also I have only heard it for words with /ŋ/, not other nasals.
I have two closely related questions (to which I didn't find an answer by searching cursorily):
- Does /æ/ become [eɪ] before other nasals like /m/ and /n/? Or does it only happen before /ŋ/?
- Is there any other American accent where /æ/ is realized as [eɪ] before nasals?