Water Normal flowing in direction of slope (When raining, from stones etc.)

Hello guys.
I am trying to achieve a specific effect that can be seen in some other games - When it’s raining, I would like to have a normal map pan from top to bottom of a mesh / landscape slope.
I have tried a lot of things, including world aligned texture, but world aligned texture is only visible when the slope of landscape is pretty much 90 degrees vertical.
I have also tried through absolute world position and feeding that into the texture, but it’s a no go. If I set it to go in Z axis, it’s flowing, but the texture seems to be rotated and therefore just big waves are visible. When I set it to XY, it doesn’t flow the right direction.
I would really appreciate some help with this.
Thank you.2763cebf0c3096d34f0a056d328a855fb502ed6b.jpeg