Yes tempo/bcg must be taken into account for planning.
My dispatch is taking in account ceilings ALONG WITH vis to chose wether a second alternate should be used.ie 1500m vis and 200ft ceiling at alternate..a second alternate is added for fuel planning.
However it is up to the pilots to disregard the second alternate fuel uplift since only the visibility is affecting us.
Yes some airports start low vis procedures due to ceiling but thats another debate:-)
Capt std
