This has a lot going for it, it could stand a bit of photoshop abuse. Try pushing the contrast a bit, and maybe cooling the colors slightly to bring out emrald green grass.
I think this would have worked better in the "Light" challenge. For me the focus of the shot is the light rays hitting the grass, rather than the clouds.
Normally, viewers will look at an image in two ways left to right and bottom to top. In this case, it's more of a top to bottom view as the darker part of the image fades to a lighter presentation at the bottom. From a technical standpoint, it could have used a little more post processing to bring out the blues in the sky and darken the clouds to create more dramatic tension and impact. Excellant green control which is difficult with digital cameras. A little more thought in capturing the image or post processing would have made a significant improvement.
i see the dark clouds but the image appears bright and almost cheerful to me especially as we can see the rays of sunlight, the warm glow of the grass, and the white from above