White RNG Thundurus a pain ?

Hi I’m trying to RNG Thundurus and it has never been that frustrating to hit the right frame. I tried multiple attempts, many times but the delay always changes because of the snowy weather I guess ? Any tips ? It’s the only 6iv spread I got with my TID/SID

[EDIT: Just got it ! Thanks for the help guys ! In fact, it depends on the advance when you leave the house for the future RNG hunters]