Kate Middleton is making a strong case for swapping jeans for something a little more sophisticated this fall. The Princess of Wales has Us eyeing plaid midi skirts, and it’s easy to see why. Between their rich autumn colors, flattering silhouettes and preppy, rich-mom appeal, they’re the kind of wardrobe staple that makes even a simple sweater feel instantly chic. Middleton stepped out wearing a green plaid midi skirt from Emilia Wickstead, which retails for a whopping $2,058. She paired the statement piece with a white ruffled blouse, tailored black blazer, pointed-toe pumps and an emerald g...