Mon, Feb 13, 2017 at 8:29 AM Issued by: blase reardon Today, Tomorrow, Below, At and Above Treeline Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully. Summary “Gooey,” “spongy,” “sticky,” “slub”…. Not common descriptors for Colorado snow in February. Unusual conditions, and unusual danger. On steep slopes below treeline, you can trigger dangerous Loose Wet avalanches that gouge into wet snow below the recent storm snow, producing cement-like debris that is very difficult to escape. In this elevation band, avoid slopes steeper than about 35 degrees where the snow surface isn’t refrozen and storm snow caps wet snow left by rain and warm temperatures. On slopes with sustained pitches at that angle, these Loose Wet avalanches can entrain more than enough snow to bury you, and they’re moving fast enough that if you hit anything hard, the chances of injury are high. At higher elevations, the primary concern is triggering avalanches that break in the storm snow or at the interface with the old snow. Slopes with more new snow can potentially produce large avalanches. At upper elevations, Saturday’s snow may be covering hard slabs of drifted snow formed by powerful southwesterly winds. Sticking to lower-angled slopes will reduce your exposure to these dangers. Avoid traveling on slopes under large cornices, which can break naturally in these warm temperatures may trigger larger slides. The lingering Persistent Slab avalanche problem is becoming more isolated. You’re unlikely to trigger these except on very steep slopes with multiple trigger points. Avoid this terrain to avoid this low-probability, high-consequences danger. Avalanche Problem Loose Wet Loose Wet avalanches occur when water is running through the snowpack, and release at or below the trigger point. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events. Avalanche Problem Storm Slab Storm Slab avalanches release naturally during snow storms and can be triggered for a few days after a storm. They often release at or below the trigger point. They exist throughout the terrain. Avoid them by waiting for the storm snow to stabilize. Avalanche Problem Persistent Slab Persistent Slab avalanches can be triggered days to weeks after the last storm. They often propagate across and beyond terrain features that would otherwise confine Wind and Storm Slab avalanches. In some cases they can be triggered remotely, from low-angle terrain or adjacent slopes. Give yourself a wide safety buffer to address the uncertainty. Discussion Conditions below treeline don't fit neatly into the danger scale or problem list right now, but there's little question that on specific slopes, you trigger slides that can have serious consequences. Saturday's storm snow is capping wet snow left by rain and warm temperatures, and temperatures have not been cold enough to refreeze this snow. On very steep slopes - those over about 38 degrees - it was easy to trigger slides that produced dangerous amounts of debris Sunday, and people reported similar natural avalanches, mostly triggered by rollerballs from trees and rocks during warmer temperatures Sunday afternoon. The triggered slides were propagating wider than ski length, like slabs, but gouging well below the snow surface, like sluffs. Slubs? Whatever you call them, getting caught in the cement-like debris would be ugly, particularly on slopes with sustained steep pitches and trees or other hard objects to hit. Triggering similar slides is possible today on steep slopes where the snow surface hasn't refrozen and there's little or no crust between the storm snow and older wet snow. Probing with your pole or hand should reveal this structure where it exists. At higher elevations - above about 10500 feet - the primary avalanche concern is a more familiar Storm Slab avalanche problem. That is, triggering slides that break in the new snow or near the interface with the old snow. These can be up to two feet deep in the Crystal River valley. Several natural avalanches on northerly slopes near Marble suggest these may be most likely where the snow is coldest. Slope angle is the key to avoiding this danger. Riding conditions are great on lower-angled slopes, so stick to slopes less than 35 degrees. Southwesterly winds battered upper elevations for much of last week, stripping snow from exposed slopes and forming hard drifts on leeward slopes. Saturday’s snow may have covered these slabs - and added load that can increase the likelihood of triggering them. With that disguise, looking only at the snow surface won’t give you clues to whether they exist. Neither will probing with your pole, since the new snow is sitting on hard surfaces on many slopes. Best to expect them in terrain that collects drifted snow, and stick to lower-angled slopes to reduce your chances of triggering any that do exist. On isolated, very steep slopes, you can still trigger avalanches that break 2 feet or more deep, on failure planes buried in mid-January. These remained reactive to a person’s weight until early last week, particularly on mid-elevation shady slopes. The recent weather is a mixed blessing for these layers. It might have eliminated them altogether on some slopes, or it might have reactivated them by adding a cohesive slab above them. Until it’s clear which situation prevails, I’ll be avoiding steep slopes likely to harbor these layers, as well as likely trigger points. That’s steep, convex rolls on shady, mid-elevation slopes.