Backcountry Avalanche Forecast for Northern San Juan Issued: 02/13/2012 7:33 AM by Matt Steen Avalanche Warning in Effect through 02/14/2012 10:00 AM An Avalanche Warning is in effect until Tuesday morning for the North and South San Juan zones. New snow amounts in the last 24 hours are: Telluride- 8 inches, Red Mountain Pass - 14 inches, Molas and Coal Bank Passes- 16 to 18 inches, Durango Mountain Resort- 13 inches. This translates to an inch or more of water loaded onto a weak snowpack. Combined with westerly winds strong enough to drift the new snow, the avalanche danger is HIGH (Level 4) on leeward slopes. This warning covers the whole zone for the Northern San Juan and the western portion of the zone for the Southern San Juan. Natural avalanches are likely today. Highlights There is an Avalanche Warning in affect for the Northern San Juan zone through Tuesday morning. New snow and wind have increased the avalanche danger to HIGH (Level 4) in most parts of the zone. Natural and human-triggered avalanches are likely. Avoid traveling on or below avalanche terrain. Avalanche Danger The avalanche danger for the North San Juan will be changing through the day. The avalanche danger in the morning is CONSIDERABLE (Level 3) on all aspects and elevations. The danger will rise to HIGH (Level 4) by late afternoon on NW-N-NE-E aspects at all elevations, particularly in areas like Red Mountain Pass where the snowpack is especially weak and fragile. Snow & Avalanche Discussion New snow totals are between 8 and 18 inches in the past 24 hours. The winds were from the southwest in the 10 to 20 mph range until midnight. Early this morning the winds veered to the west and northwest in the 20 to 30 mph range with gusts in the 40's. Molas Pass and Red Mountain Pass received over 14 inches, Coal Bank Pass 18 inches, and areas west of Telluride, 11 to 13 inches. The new snow and wind are overloading our weak snowpack. Today both natural and human triggered avalanches in the new snow layers are likely. Avalanches could also break into one of the many weak layers of old snow. Areas recently loaded by the wind will be the most dangerous. The winds were from the southwest yesterday and shifted to the northwest overnight. Remember that strong winds can cross load gullies and subridges. This storm will exacerbate the avalanche problems that have plagued the Northern San Juan most of the winter. The weak layers in the old snow are still quite sensitive and it is possible to trigger avalanches remotely and from low-angle slopes. On Saturday, south of Telluride a group of skiers remotely triggered an avalanche on a northeast aspect above treeline. The group was traveling on low angle terrain when they collapsed a small slope, which propagated nearly a third of a mile away and released an avalanche 2 to 4 feet deep, 400 feet wide and over 400 vertical feet. Other skier triggered avalanches occurred above and below treeline on nearly every aspect within the past week. Today is a good day to avoid traveling on or below avalanche terrain. Weather Discussion for 11,000ft Issued: 02/13/2012 12:06 PM by Brian Lazar A weak shortwave is moving east across Colorado this afternoon fueling light snowfall across many mountain areas. These on-again/off-again flurries will continue into later this afternoon, with some periods of heavier snowfall for areas favored by zonal (westerly) flow. Total accumulations will generally be in the 2 to 4 inch range by sundown, with some localized areas getting up to 6 inches or so. We have a brief lull this evening before the next system currently digging south along the California coast and gradually sliding east into the Great Basin impacts Colorado late tonight. Recent model runs are taking this system farther south than it looked this morning. This does not bode well for good snowfall for our mountains, so I have trimmed back the snowfall numbers. The heaviest snowfall will fall in the Southern Mountains, but I don't expect much more than 2 to 4 inches overnight, with another 2 to 4 inches on Tuesday. All other mountains areas will see less than that. If the system digs much farther south than its looking now, we could miss out on most of the snowfall and only get a dusting statewide. Unsettled weather and light snowfall will continue into Thursday but I don't expect more than a couple inches falling during each 12-hour forecast period after Tuesday.