UPDATED | Thursday 5 PM
The heavy rains that fell on the region Wednesday did not produce any new mudslide activity on the southeast flank of Mount Shasta.
A Saturday (Sept. 20) mudslide covered two roads near the mountain; mud, boulders, and debris made Pilgrim Creek Road and Forest Service Road 31 impassable.
The Shasta Trinity National Forest says the Konwakiton Glacier on the southeast side of the mountain is probably the source of the debris flow. Pockets of liquid water trapped in glaciers can be released when the glacier either breaks or melts.
The Forest Service says mudslides are not unprecedented, particularly in the Mud Creek drainage where this one happened. And such events are more common in drought years, when glaciers are exposed to the sun for longer periods.
The warm rains could have caused more slide activity, but Forest Service crews found no evidence of a change Thursday morning.
Crews are working to reopen the roads. Pilgrim Creek Road could be open this weekend. Forest Service Road 31 will take longer, with assessments of how best to clear the debris expected in coming weeks.
The mud flows reached the McCloud River earlier in the week. Muddy water in both the river and McCloud Lake is likely to hang around for weeks.