Wx symbol LL Prognostiic

[Merf]

I found a symbol I can't find anywhere that defines it. Including Aviation advisory bulletin. It is a black rectangle with what looks like a little "stack" on top. In pairs. They even show it in examples but it's not on the legend. It is shown mostly on top in a "two types of precipitation" format. Under the "slash" is the normal precipitation symbol. What am I missing?

 

[write-stuff]

The triangle means showers and two stacked lines mean fog.

 

[Merf]

The symbol is a solid rectangle with a little stack on the top. In foreflight it is on the 48 hr prog chart. I'm guessing maybe it should be solid circles for rain but some anomaly shows it as described....thx

 

[acrophile]

Screenshot?