I love the feel of this shot - sunlight under stormclouds is really dramatic if it's done right, and you've bought a real sense of atmosphere to this scene.
You have one extremely glaring problem, though - in that the stormcloud plate(s) you are using are all backlit by the setting sun. It's a storm chaser staple to capture these 'sundowner' storms, since it gives the most impressive photos.
You therefore have two suns in your shot.
I'm not entirely sure how you can solve this issue without losing some of the 'feeling' of the shot, but I just thought it was worth pointing out.
Great atmosphere and composition.The tree really nicely guides us into the shot as the sunlit house is revealed.I love the transition between the left,sunny part(I just love it)and right part which is getting dark and stormy.My overall opinion is that this is a great matte painting.Only drawback is that you didn't post it in higher resolution ;).I would love to see it bigger,with all the details standing out more.