Archived Avalanche Advisory San Juan Tue, Jan 6, 2015 at 7:11 AM Issued by: Scott Toepfer Backcountry Avalanche Forecast Today, Tomorrow - Above Treeline, Near Treeline, Below Treeline: Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully. Summary Summary Though the Avalanche Danger is Moderate you can still trigger avalanches big enough to bury or kill you. The most dangerous slopes will be where winds drifted stiff Persistent Slabs over weak sugar-like snow. You will find this combination on northwest through northeast through southeast-facing slopes near and above treeline, as well as open slopes below treeline. Expect similar conditions to those in reports of triggered avalanches and cracks that propagate significant distances. The best way to manage the risk from Persistent Slabs is to make conservative terrain choices. Avoid very steep (greater than 35°) terrain facing northwest through northeast through southeast that funnels into terrain traps like gullies, sparse forest or road cuts. Southwest winds built Wind Slabs on lee slopes earlier in the week. More recent winds have been from the north and even northeast. These avalanches are getting harder to trigger, but you could still trigger them on upper elevation slopes facing northwest through northeast to southeast. Avalanche Problem: Persistent Slab Where: NW through SE, all elevations Likelihood: Possible Size: Large What You Need to Know About These Avalanches Persistent slabs can be triggered by light loads and weeks after the last storm. You can trigger them remotely and they often propagate across and beyond terrain features that would otherwise confine wind and storm slabs. Give yourself a wide safety buffer to handle the uncertainty. Avalanche Problem: Wind Slab Where: NW through SE, near and above treeline Likelihood: Possible Size: Small - Large What You Need to Know About These Avalanches Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas. Forecast Discussion On Sunday, observers spotted a recent avalanche in "Rusty's" west of Wolf Creek Pass. The avalanche probably occurred on 1/3, and may have been triggered by a snowmobile. It was on a north facing slope below treeline. It was large relative to the path (R4) and big enough to bury a person (D2). Rocks were visible in the bed surface, so it broke into old snow. Persistent Slab, anyone? It sure has the right look and character. Avalanches like this are a reminder that the problem continues. The danger may slowly ease, but it will remain possible to trigger avalanches for many more days. These low-probability, high-consequence events are challenging problems to navigate. More recent avalanche fatalities in Colorado occur during a MODERATE danger than any other rating. Two thirds of recent avalanche fatalities in Colorado involved a Persistent Slab avalanche. Food for thought, especially as we begin to see less and less direct evidence of avalanching. With the warm temperatures some Loose Wet activity may be found out of steep east to south to west aspects near and below treeline over the next few days. These would be small, but if they are triggered from a terrain trap the results could be bad.