Why oh why does this happen?

This is happening at just about every snow covered ramp in my map when its boardering on the fog of war, if I send units to the spot the problem dissappears but anytime the fog of war and visibilty begin to mix, this happens...

The only way I could think to remove it (and I'm not even really sure) is to create a light source at the ramp's location. Apparently, Wc3 treats ramps as single tiles and doesn't fade per unit like it does else wise.