Interesting. If anyone finds out any more on this I'd like to know, as it may help me improve RAID Weathers. Anyway, I may do some experimenting on this to see if I can figure anything out.
Long shot, sorry to ask (just saying since some other users reported similar things to me about this), but are you sure you have "bUse64bitsHDRRenderTarget=1" enabled in skyrimprefs.ini under [Display].
EDIT: just noticed one of you is the bethini author, so lol, sorry for the above question haha (i dont use bethini tho).