Large avalanche that failed deep in the snowpack at Ernie Miller. This is the second photo we've recieved of this bowl sliding this season (last one was on Dec. 15th). Photo: F. Madsen
This slide appeared to be triggered by a falling cornice. It broke near the ground and propagated two hundred feet wide. It snapped trees and left a debris pile up to ten feet deep. This avalanche illustrates that large and dangerous avalanches remain possible in the southern Madison Range and mountains near West Yellowstone. Photo: GNFAC
This small slide was triggered by a snowmobiler in the southern Madison Range. Although small, this slide is bull's eye information that larger slides are possible on similar slopes. Photo: GNFAC
Cornices are growing large after a series of storms in the southern Mountains. These cornices make up the rim of Sunlight Basin in the southern Madison Range. Cornices are good indicators of which slopes are wind loaded. It's often best to avoid riding on or underneath slopes attached to large cornices. Photo: GNFAC
<p>The snowpack remains under a tremendous amount of stress from recent loading events (<u><strong><a href="https://www.youtube.com/watch?v=JoXitoUtXfo&index=2&t=0s&li…;). Over the past four days, <a href="https://wcc.sc.egov.usda.gov/reportGenerator/view/customSingleStationRe… Plateau Snotel</a> site near West Yellowstone has received over 2’ of snow totaling close to 3” of <a href="https://www.nrcs.usda.gov/wps/portal/nrcs/detail/or/snow/?cid=nrcs142p2…;. This load is even heavier on wind loaded slopes.</p>
<p>Today, I would steer clear of all steep terrain including low angle slopes connected to steeper slopes above. Slopes loaded by west-southwest winds will be the most likely to hold thick pockets of wind drifted snow and produce human triggered avalanches. These areas should be avoided at all costs. Avalanches failing on weak interfaces in the storm snow are also likely. These slides will break 1-3’ on all aspects and elevations. With 3” of new SWE, slides breaking on weak facets near the ground are also possible (<strong><a href="https://www.mtavalanche.com/images/19/big-snowmobile-triggered-avalanch…;).</p>
<p>Today, dangerous avalanche conditions exist and the avalanche danger is rated <strong>CONSIDERABLE</strong> on all slopes.</p>
<p>Yesterday, Alex was in Cooke and covered lots of ground north of town – he did not observe widespread avalanche activity. He did see one large avalanche that broke 4-6’ deep and hundreds of feet wide on the east face Henderson Mountain (<strong><a href="https://www.mtavalanche.com/images/19/deep-slab-avalanche-heavily-wind-…;). This slide occurred on a heavily wind loaded slope and likely failed on facets near the ground. Fortunately, this slide was the exception and not the rule. However, it does illustrate that large and dangerous avalanches remain possible on heavily wind loaded slopes.</p>
<p>A more common scenario will be slides breaking in the new and wind-blown snow. Yesterday, Alex and his partner easily triggered small wind slabs that broke 1-2’ deep (<strong><a href="https://www.mtavalanche.com/images/19/small-fresh-wind-slab-near-cooke"…;). Winds were strong and gusty on all aspects and elevations yesterday, which developed wind slabs in some unusual areas. Be especially aware of this problem below ridgelines and around cross loaded terrain features.</p>
<p>Today, human triggered avalanches are likely on wind loaded slopes which have a <strong>CONSIDERABLE</strong> avalanche danger. Non-wind loaded slopes have a <strong>MODERATE</strong> avalanche danger.</p>
<p>Heavy snow yesterday morning created touchy conditions in the mountains around Bozeman and Big Sky. Both Bridger Bowl and Big Sky Ski Patrols easily triggered soft slabs during control work that broke 6-12” deep. Activity was most widespread during the morning hours when wind and snow were the strongest.</p>
<p>Overnight, the mountains received 2-3” of low density snow, but winds backed off significantly. Today, I don’t expect conditions be quite as touchy. With that said, it’s essential to evaluate each slope carefully and avoid those that appear to be heavily wind loaded. Be most attentive on slopes below ridgelines and cross loaded terrain features, especially those in higher consequence terrain (<strong><a href="https://www.mtavalanche.com/images/19/small-natural-avalanche">photo</a…;). Outside of wind loaded slopes, the snowpack is generally strong and stable (<u><strong><a href="https://www.youtube.com/watch?v=xuXLoZvikoM&t=0s&index=3&li…;
<p>Today, human triggered avalanches are possible on wind loaded slopes which have <strong>MODERATE</strong> avalanche danger. Non-wind loaded slopes have a <strong>LOW</strong> avalanche danger.</p>
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Soft slabs 6-12" deep triggered during control work.
