A large avalanche triggered on or about Valentine’s Day roared down the southern flank of Mt. Shasta, leaving a debris field 30-feet deep and stopping at an elevation just short of the Bunny Flat parking area.

Nick Meyers with the Mt. Shasta Avalanche Center said the slide started at about 12,000 feet on the southeast side of Casaval Ridge and traveled nearly 5,000 feet. At its most destructive point above the tree line, the avalanche was an estimated 1,500 feet wide. The exact location of the slide’s crown, or origin, is still being analyzed.

Heavy snow followed by rapid warming last week created prime conditions for what is being considered a “D4” avalanche, which is one step short of the largest such classification worldwide. For Mt. Shasta, it is one of the largest walls of ice and snow to come crashing down the mountain since an avalanche buried the Old Ski Bowl in 1978. The resort never reopened.

Meyers said the slide snaked down Avalanche Gulch proper, which is a popular route for climbers attempting to summit the 14,169-foot mountain. Everitt Memorial Highway was closed last week due to heavy snow, which meant an area normally filled with backcountry skiers and winter sports enthusiasts was pretty much deserted.

There have been no reports of anyone killed or injured, which is especially fortunate since the avalanche blew through trees and other natural barriers before stopping at an unusually low elevation. The Sierra Club cabin at Horse Camp survived unscathed.

“We think as that thing came down the hill there were probably sympathetic avalanches that were caused and gouged out a large amount of snow on the way down,” Meyers said. “A D4 is a big slide.”

Conditions fostering an unstable and “complicated” snowpack had been building for several days. Strong northern winds were already loading the area around Casaval, and then it snowed several feet followed by mist and rain.

“We call them the red flags of avalanche danger and we had almost all of them nailed right during that time,” Meyers said. “We had avalanche danger high that day and we feel pretty good about that.”

For powder hounds who want to earn their turns Meyers suggested checking the MSAC’s website, which provides the latest information at www.shastaavalanche.org.