Archived Avalanche Advisory Vail & Summit County Wed, Dec 31, 2014 at 7:11 AM Issued by: Ethan Davis The incident this is archived for may have been in the Front Range zone. It appears from their comments and tweets that is was Vail and Summit. It was near the boundary and the two zones had similar advisories. 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 The avalanche danger today is MODERATE and while natural avalanche activity is unlikely human-triggered avalanches are possible. We are currently dealing with two slab avalanche problems: Persistent Slab and Wind Slab. Triggering a Wind Slab avalanche is possible above treeline on slopes facing east. Be on the lookout for thick pillows of snow located just below ridgelines, on the lee sides of gullies, and downwind of rock outcrops or clusters of trees. Remember, local topography may have funneled drifting snow onto unexpected slopes. If the snow begins to sound “hollow” under you, or takes on a smooth, pillowed look, back off and choose to travel on more windward terrain or stick to ridgetops. Although it's becoming more difficult to trigger a Persistent Slab, the possibility remains on shady, northwest to north through east-facing slopes at all elevations. Persistent Slab avalanches can be triggered from a distance. This means a "whumpf" or collapse of a buried weak layer of snow may result in an avalanche on a nearby slope. Avoid this problem by staying off of and out from under steep (>35°), shaded slopes. Enjoy your last winter outing of the year and resolve to keep yourself and your travel partners safe. Continue to use wise travel techniques. Only expose one rider to a slope at a time. Keep each other within eyesight and trust those uneasy feelings should they arise. Avalanche Problem: Persistent Slab Where: NW through East, all elevations Likelihood: Possible Size: Very Large to 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: NE through S, above treeline Likelihood: Possible Size: Small 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 The danger is MODERATE today as we continue to deal with two avalanche problems: Wind Slab and Persistent Slab. The recent incremental loading tested the buried persistent weak layers, and by and large, they have held up to the test. This avalanche problem is trending towards a lower likelihood, but high-consequence type of situation. This can be a tricky transition, as we very well may not see obvious signs of instability prior to triggering a large and destructive avalanche. It's common in these periods for confidence levels to rise faster than the snowpack is stabilizing. Highway avalanche mitigation continued to bring down D2 Wind Slab avalanches near Loveland Pass Monday. These slides were all approximately 2 feet deep and ran on north-facing slopes near treeline. These pockets of slab are slowly healing and those that do exist will mostly be small, but don't let your guard down in consequential terrain. And remember, in many places the Wind Slabs are overlapping with the Persistent Slab distribution. In these areas a small Wind Slab could break down into more deeply buried weak layers. The resulting slide would certainly be something you would not want to tangle with.