ROCKY MOUNTAIN NATIONAL PARK, Colo. (AP) -- A wildfire burning on steep, rugged terrain on the east side of Rocky Mountain National Park has grown to 660 acres.

The tough terrain, which includes trees killed by beetles, has prevented a direct attack on the fire from the ground. However no structures are threatened, and two heavy helicopters were available to drop water on the fire Thursday.

The fire is west of the Fern Lake trailhead. It has prompted park officials to close some roads and trails and the Moraine Park Campground.

A chance of precipitation is forecast for Friday.

Rain and snow also is forecast Friday over the 525-acre Goblin Fire, believed to have been sparked by the Durango & Silverton Narrow Gauge Railroad Train in southwest Colorado. Firefighters have kept it away from the railroad tracks.