Albert Barnes Commentary Jeremiah 48:8

"And the destroyer shall come upon every city, and no city shall escape; the valley also shall perish, and the plain shall be destroyed; as Jehovah hath spoken." — Jeremiah 48:8 (ASV)

The valley - The lowlands on the east bank of the Jordan, and at the top of the Dead Sea.

The plain - An upland pasture; it corresponds closely to downs: as in Jeremiah 48:21.