Hi Sharon,
Photoshop is a very useful tool but I do find that most times using a “grad” filter I can get things even better than if just by Photoshop, may be I’m not that good at photo shop
But you also see the results on your camera before you get home, you can get that “threatening” sky very easily with a grey grad, playing with filters can be very helpful and give those dramatic effects straight out of the camera.
Regards Richard