Backcountry Avalanche Forecast for Front Range Issued: 04/20/2013 6:05 AM by Spencer Logan Highlights A significant amount of new snow fell over the past week and has pushed the old snowpack towards the breaking point. The result are stubborn and hard to trigger avalanches, but once they break they are very large and destructive. These low probability, high consequence avalanches are challenging to evaluate, and conservative terrain choices are an effective strategy to stay safe. The recent snow has drifted into wind slabs on top of the old snow. The drifting patterns are very localized, and may change from valley to valley or even within a basin. Carefully evaluate and potentially areas of drifted snow on steep slopes. Avalanche Danger The avalanche danger for the Front Range zone is CONSIDERABLE (Level 3) on N-NE-E-SE aspects near and above treeline. On other aspects the danger is MODERATE (Level 2). Cautious route-finding, conservative decision-making, and careful snowpack evaluation are essential for safe travel. Snow & Avalanche Discussion A dusting of snow fell in parts of the zone Friday night. A few more inches of snow will fall today. In little more than a week, the snowpack has increased one to two feet in depth, with an inch and a half to two inches of water equivalent. Combined, that is a significant load on the snowpack. It came in smaller increments, and never completely overwhelmed the old snow. It does push the weak layers near the ground closer to breaking, and deep persistent slab avalanches have once again reared their ugly head. The most recent deep persistent slab avalanches occurred on Thursday in the Vail-Summit Zone, with natural avalanches in Straight Creek (west of the Eisenhower Tunnel) and the fatal avalanche near Vail Pass. In many of the avalanches throughout the winter, the culprit weak layers were small facets above a thin crust, on top of depth hoar. Slopes where these layers remain weakest are north through east aspects near and above treeline. The slab above the weak layer may be very hard (P or K) and strong. The strong slab and stubborn, unlikely triggering, give the slopes a false sense of strength. Likely trigger points are where the slab is thin, like shallow rocky areas or along the margins or bottom of the slab. If you find the wrong spot, the resulting avalanche will be very large, destructive, and dangerous. Conservative and cautious route finding and terrain selection are the best ways to avoid the problem. Over the past week of snowfall, strong winds have blown from the south, north, and west. There may be several crusts mixed in. Snowfall amounts varied from day to day and area to area. This you will need to carefully evaluate the local loading and drifting patterns. Expect to find wind slabs up to 3 or 4-plus feet thick on a variety of aspects. Observers are finding everything from thick, widespread, and easily triggered wind slabs, to areas where the slabs are patchy and easily avoided. Carefully evaluate and potentially avoid fat, pillow-like, or smooth areas of drifted snow that are on steep slopes. Cloudy skies and cooler temperatures should keep most wet-loose avalanches at bay. Expect them to be more likely on Sunday as skies clear. Weather Discussion for 11,000ft Issued: 04/20/2013 12:45 PM by Spencer Logan Light snowfall continues through about midnight tonight. There could be localized, heavier snow showers this evening over the Gore, West Elk, and northern San Juan ranges. Skies begin to clear in the early morning. There will be fewer clouds on Sunday, helping temperatures warm a few degrees above Saturday's. Some isolated snow showers may pop up in the afternoon over the Northern and Central Mountains. Winds turn westerly, and will be weak Sunday night. The next weak storm system arrives Monday morning. Most of the storm will stay north of Colorado, but the northern zones should pick up some snow. Cool northwest flow continues well into next week with another weak system possible around mid-week.