Backcountry Avalanche Forecast for Northern San Juan Issued 02/11/2010 6:29 AM by Ann Mellick Highlights Northwest flow will keep temperatures cool and bring a chance of flurries to the north side of the range. Lots of human triggered slides have run this week. Human triggered slides remain possible on all aspects and elevations today. Avalanche Danger The avalanche danger for the Northern San Juan is CONSIDERABLE on steep N-NE-E-SE facing slopes near and above treeline and MODERATE elsewhere. Human triggered slides remain possible to probable. Snow & Avalanche Discussion Scattered snow showers left a trace to 3” of new snow over the past 24 hours, bringing totals since the 7th up to ~10”-15” across the zone. Moderate winds have blown from the south, west and now northwest over the past couple days, so expect to find some drifting and fresh slabs on a variety of lee aspects in the alpine zone. Five (or more?) human triggered slides ran in upper Bear Creek near Telluride over the past few days. Thankfully no one was caught in any of them. Some details: On Wednesday, a hard slab ran on a northeast aspect, 3’-4’x750’x 850’. This slide was likely remotely triggered from two skiers on a bench above the slope. On Tuesday, the Temptress, E-Ticket and Deep & Dangerous (2’x40’x500’) ran. Delta Bowl ran on Monday. These slopes are generally east facing and are all above treeline. A skier triggered a slide (1.5’x100’x100’) on a west facing slope below treeline near Red Mountain Pass Wednesday as well. Lots of natural sluffs and several soft slabs ran earlier this week. These slides ran in the new snow, with crowns mostly measuring about a foot deep. A weak and reactive interface exists where the recent storm snow is sitting on low-density stellars that fell last week. These layers are sitting on top of the stout slab left from January’s big storms, about 10”-12” deep on shadier slopes and about half that on sunnier ones. Some skiers near Silverton triggered a slide on this layer on Tuesday. One skier took a short ride, lost a pole and sustained minor injuries on a north facing slope below treeline. This serves a good reminder that even a small slide can take you through trees or over unpleasant rocky terrian. Expect the possibility for shallow human triggered soft slabs and sluffs on this layer, especially on steep shady slopes. While we have seen lots of recent activity in the upper snowpack layers, the threat of deeper slab and/or hard slab avalanches still exists, especially in the alpine zone. If traveling up high, look for big pillows and listen for hollow drummy sounds, which indicate hard slabs sitting on weak snow. You are most likely to trigger these slabs in areas where the slab thins. It is getting harder to trigger this type of avalanche, but the consequences of riding a deep slab remain severe. Human triggered slides remain possible to probable today. Please use caution and sound decision making before committing to consequential terrain. Weather Discussion Moderate northwest flow continues across the state through the weekend. Temperatures remain on the cool side. Moisture within the flow keeps a chance for periods of light mountain snow through the next several days. Areas favored by northwest flow may get an inch or two each day, but significant accumulations are unlikely. Ridgetop winds will be gusty at times along and east of the Continental Divide, but elsewhere wind speeds will not be an issue. Persistent northwest flow continues into next week with little day-to-day weather changes including cool temperatures and periods of light mountain snow favoring northwest aspects.