Poncho/Bivy in the sierra’s?

im hiking south from la pine OR on the pct next week. its early i know but im fairly experienced in camping on snow. though as you can see from my pic, i was carrying a stupid amount of weight. well i learned my lesson and went ultralight. but im wondering if i can manage with a poncho and bivy combo. i have the sea to summit sil tarp poncho and the rei minimalist bivy.

im going to try this system out in the sisters wilderness first but i wanted to get some feedback from anyone whos hiked through serious mountains or bad conditions, with a similar system.
on a side note, is it worth it bring a ground cloth with a bivy?