1. Add Northern Eriador biome
Darker grass and occasional snow, similar to Northern Dale. Because now transition between Eriador and Northern Forest is too drastic.
2. Extend Minhiriath farther North.
Minhiriath is what's left of Cardolan. Back in the day Barrow Downs and South Downs were a part of Cardolan. That's why Minhitiath should stretch as far as Bree and South Downs.