I have several present weather symbols from the weather depiction chart that I'm not clear on and AC-0045 doesn't have in it's legend.
I know the mist and fog symbols, and these look very similar, but I'm not sure what the broken lines imply. I've added three variations on the symbol below.
Since the other user posted a link that contained the answer that could in the future go 404, I'll provide the answer I found there.
The first symbol means "Fog in patches"
The second symbol is not present but by extrapolations likely means either "Mist in patches" or "Mist with sky visible". The former seems more likely to me.
The third symbol means "Fog, sky visible."