The History, Villages, Ruins, and Beasts of the Forgotten Realms High Forest Territory
From the introduction:'
The climate of High Forest is varied. In the North, it receives significantly more precipitation and colder extremes during the winter seasons. Fauna is diverse consisting primarily of massive pines interspersed with groves of birch, spruce, and Larch. The Southern region tends to be warmer and drier with a higher concentration of oak, maple, and elm trees mixed among the pines.
A massive forest stands in the middle of Faerun. Easily accessible from the Swordcoast and yet... where is the official sourcebooks for what lays within?
This book is intended for DM's wanting to run adventures within High Forest. It is the result of quite a bit of research on official WotC supplements so should align pretty closely with other products released for the 5th edition setting.