Seasons Mask FS17

[dentonkarl]

Hi
I am trying to edit the seasons mask on The West Coast (Fs17).
I can see the ssSnowMask in GE but when I paint it, nothing happens.
I was hoping to see the existing layer and be able to add/remove sections.

In the map02 folder there is a seasons_mask.ggm rather than seasons_mask.png

Is it possible to edit it at all?

Many thanks