There's a need for some trail work at Rocky Mountain National Park, where a torrential thunderstorm spawned a rock-and-mud slide that swept trees and other debris across a section of the Fern Lake Trail.

The storm Thursday generated heavy rain, hail, lightning, and localized flooding. Along the Fern Lake Trail, which is accessed from Moraine Park, a large debris flow covered the trail about one mile west of the trailhead near a feature called Arch Rocks. The debris flow originated on the slope to the north of the trail in an area burned over by the 2012 Fern Lake Fire. The debris, consisting primarily of mud, rocks and trees, covered more than 150 yards of trail and in places is estimated to be four feet deep, the park reported.

Hikers and horseback riders in the area at the time were able to self-evacuate to the trailhead or were re-routed out of the area via the Cub Lake Trail.

The two-mile section of the Lower Fern Lake Trail remains closed from the trailhead to The Pool until a damage assessment is complete. Backcountry users can still access the Fern Lake trail above The Pool via the Cub Lake route. Efforts are underway to contact overnight campers in the area regarding the trail closure.

Meanwhile, the condition of the 65-year-old woman who was struck by lightning Thursday afternoon while hiking the Ute Trail above treeline near Trail Ridge Road remained unknown Friday morning, park officials said. She was transported from the park by ambulance and later transferred from the Estes Park Medical Center to Medical Center of the Rockies in Loveland, Colorado.

The National Weather Service was again forecasting showers and thunderstorms Friday throughout areas of northern Colorado, including Rocky Mountain National Park. A flash flood watch was in effect through Friday evening.

Park visitors are reminded of the hazards that may accompany mountain storms. Heavy rain, hail, strong winds, flooding and severe lighting can be expected. Caution should be taken when traveling in burn areas that have been affected by recent wildfires, including the Fern Lake Fire.