Northwest Mountains

Dangerous conditions persist for the mountains surrounding Crested Butte.  Observers reported two large, remotely-triggered avalanches yesterday.  Natural avalanches are not expected, but slopes that face west, north, and easterly are still set up for human-triggered avalanches.  Steep slopes, without signs of previous avalanche activity, should be treated as suspect.  Sunny aspects are less likely to produce avalanches, but a thoughtful snowpack assessment is necessary.  The simplest solution is to travel on lower-angled slopes and avoid being underneath or connected to steep terrain where you find slabs resting over Persistent Weak Layers.  Choose a route plan that accounts for the possibility of remotely-triggering an avalanche. 

Yesterday's Bottom Line stated "Consider the possibility of remotely triggering an avalanche on steep terrain from below or adjacent slopes.  Place a healthy margin between your group and suspect terrain features" and this statement holds true for today.  Yesterday two dangerous avalanches were triggered from an adjacent slope and from a long-running collapse that passed through small terrain features and dense trees.  This type of behavior is to be expected from Persistent Slabs.  Do not let a remotely-triggered avalanche catch you off guard.  Choose conservative up-tracks and regrouping spots that account for this possibility.  Place a large margin between your group and slopes that you are uncertain about.  Even small hillsides near creek-bottoms and gullies pose a threat where debris can pile deeply in terrain traps.

The avalanche danger will begin to trend downward for the snow favored areas in the Northwest Mountains.  Obvious signs of instability are expected to diminish in the coming days.  The trend for tomorrow was set to MODERATE for BTL slopes in the Northwest Mountains anticipating reduced sensitivity.  The avalanche danger is expected to linger at an elevated rating for the Southeast Mountains for longer.  Much of the low and middle elevation terrain around the Southeast Mountains finally developed a thin, but continuous slab; the weak layer below is very pronounced and well-formed.  Anticipate that the snowpack will be more reactive and dangerous in parts of the Southeast Mountains where the weight of a person can easily impact the weak layer.  Even though the snowpack is only 2 -2.5 feet deep at many locations in the Southeast Mountains, that is just enough to produce a dangerous avalanche.

Sunny slopes and terrain that has previously avalanche in the past two weeks offer a significantly reduced likelihood for triggering avalanches.  Steep slopes are never a sure bet.  Recreating on old, bed surfaces requires that you have done your homework and kept close track of previous avalanche activity.  You also need to manage nearby features or slopes that may not have previously avalanched.  You also need to ensure that a new slab has not formed on the old bed surface which creates the "repeat offender" set up.  South and southwesterly slopes have produced relatively few avalanches over the past two weeks.  One big exception to this is on cross-loaded features near and above treeline where the wind can drift slabs behind ridges, ribs, or press slabs into gullies.  If trying to manage the complexities of previous avalanche activity or wind drifting on southerly terrain sounds challenging then take the "lay-up" and enjoy skiing low-angled powder.  Keeping slopes angles below 30 degrees without adjacent or overhead-hazard will be your safest and most logical bet and a great way to start the New Year!.