Monument Mountains (The Blackroot Falls Supplement)
From D&D Wiki
A mountain chain composing the eastern border of the Blackroot Falls, the Monument Mountains reach an average height of 18,000 feet, with peaks reaching as high as 28,532 feet. Varying wildly in both height and gradient, sheer precipices can stretch upward, uninterrupted, to over 5,000 feet at a time.
Due to its altitude, the Monument range is nearly constantly experiencing unfavorable weather conditions, from hazardous electrical storms to severe snowstorms and snow drift.