Opens noon on May 15. Provides critical winter/spring habitat to as many as 85 to 90 bighorn sheep from the Thompson Falls herd.Opens noon on May 15. The Roundhorn WMA is 27 acres located on between Thompson Falls and Plains in the lower Clark Fork River Valley. The property consists of rugged, rocky cliffs and flat rangeland, about equally divided in acres. Timber is scattered about in both the cliff areas and pastures. To the North, Lolo National Forest provides the boundary, while private land is found to the East and West and Hwy 200 is along the South side.