Avalanche Watch Issued: Sunday, February 22, 2015 at 6:00 AM Expires: Monday, February 23, 2015 at 12:00 PM The avalanche danger will rapidly increase on Sunday and Monday. A strong winter storm will bring high snowfall rates, significant snow amounts, and strong southerly winds to the Central and Southern Mountains of Colorado. Conditions will become very dangerous as snow accumulates and drifts. Natural and human-triggered avalanches will become likely. Avalanches will be large and dangerous. Travel in or below avalanche terrain is not recommended. Carefully avoid routes that cross on or under slopes steeper than about 30 degrees, and give yourself a wide margin of safety. Sun, Feb 22, 2015 at 11:24 AM Issued by: blase reardon Statewide Weather Forecast Yesterday, round one of Old Man Winter's comeback dropped 2-8" of new snow, mostly in convective showers. Round two - which started this morning - is a complex storm that's sweeping in from the south with a good Pacific moisture feed. If the models verify, it should produce widespread snowfall across the southern half of the zone. That includes the upper Crystal River, and the headwaters of the big feeder streams for the Roaring Fork - Capitol, Snowmass, Maroon, and Castle Creeks. Current estimates have 7-10" by sunset, and about the same by sunrise, with half that tomorrow. It may be more. For the upper Frying Pan, it looks like much of the water will be lost in transit. The models aren't showing dramatic winds with this system. Expect mostly light to moderate southerly winds with occasional periods of strong gusts. That means that wind drifting and transport won't be widespread, so the primary problems will be Storm and Persistent Slab avalanches. That is, the potential for triggering slides on the old snow surface or on weak layers buried near the snow surface. Wind-blown snow may leave some slopes with thicker, more cohesive slabs, and these will be the most dangerous. If you venture into the backcountry today, a cautious, watchful mindset will serve you well. Beware of slopes where new, recent and wind-drifted snow forms slabs that are cracking or collapsing as you weight them. Don't let your guard down if you head back up for a second lap on a slope; with snowfall rates over an inch an hour, conditions can quickly become more dangerous between runs on the same slope. Look above and around you to see if the terrain you're on is connected to steeper slopes that are being rapidly loaded. Sun, Feb 22, 2015 at 8:00 AM Issued by: blase reardon Today Above Treeline: Considerable (3) Dangerous avalanche conditions. Cautious route-finding and conservative decision-making essential. Near Treeline: Considerable (3) Dangerous avalanche conditions. Cautious route-finding and conservative decision-making essential. Below Treeline: Moderate (2) Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully. Tomorrow Above Treeline: High (4) Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Near Treeline: High (4) Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Below Treeline: Considerable (3) Dangerous avalanche conditions. Cautious route-finding and conservative decision-making essential. Summary The avalanche danger is rising as a powerful winter storm punches in from the south. With bursts of snow at 1-2" an hour and gusty southerly winds, expect conditions to grow increasingly more dangerous. Shooting cracks, whumpfing collapses and fresh avalanches are clear signs that it's time to return home. Convective snow showers the past two days have left highly variable snow totals (2-12") that have favored the peaks around Aspen. The new snow adds to thin slabs of denser snow leftover from last week. On sunny slopes, the building slabs are not bonding well to underlying crusts; on shady slopes, they are sitting above weak layers that didn't yet seem reactive yesterday - "yet" and "yesterday" being key words. As new and drifted snow accumulates today, Storm and Persistent Slab avalanches will become likely on slopes steeper than about 35 degrees with 12" or more of new and wind-drifted snow. They will be possible on lower-angled slopes, lower-elevation slopes, and slopes with less fresh snow. The most dangerous slopes will be those where southerly winds have drifted snow into denser, thicker slabs. Weather models are predicting storm totals of over two feet by Monday morning, with the southern reaches of the zone favored. If these forecasts verify, expect a cycle of large natural avalanches overnight. Dangerous triggered avalanches will be likely Monday, and travel on and below slopes steeper than 30 degrees will be unwise. Avalanche Problem: Persistent Slab Above Treeline Near Treeline NE-NW Possible Large Small 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: Storm Slab Above Treeline Near Treeline All Aspects Likely Large Small Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.