Hatcher Pass

The avalanche danger is MODERATE above 3,500' for PERSISTENT SLAB avalanches. The danger is LOW elsewhere. 

Yesterday, a party remote triggered a large persistent slab avalanche on Microdot, no one was caught or injured. 

It remains possible to trigger a large, consequential avalanche up to 3 ft deep in upper elevation terrain where weak snow is preserved near the ground. 

You may also find isolated pockets of shallower wind-drifted instabilities near ridgelines, alpine bowls, or cross-loaded gullies. Skiing and riding steep, upper-elevation terrain continues to be a roll of the dice. Stack the odds in your favor by sticking to terrain less steep than about 30°.  Travel one at a time and select more uniformly covered slopes, with clean runouts and free of wind-loading.

SPECIAL ANNOUNCEMENTS:

Come celebrate with us at the 8th Annual HPAC Cabin Fever Reliever on Saturday, February 7th! More info and tickets in the pinned post and on our website at hpavalanche.org.

Triggering an avalanche deeper in the snowpack, failing on buried weak layers near the ground, remains possible. Yesterday, this was proven by a party on Microdot that remotely triggered a large, consequential avalanche. This was the first human-triggered persistent slab avalanche in almost two weeks. During this time, despite a lack of activity, we've continued to communicate the possibility of this problem for several reasons:

• Overall, the snowpack structure remains poor—especially on shallow or rocky slopes. 
• We continue to receive reports of snowpack collapsing (Observation), likely failing on weak snow near the ground. 
• Following the last storm cycle (01/26-01/27), skies and riders observed several natural persistent slab avalanches in the upper elevation band. With continued poor visibility, it is challenging to date these slides, and we can't rule out the possibility that these occurred naturally during or shortly after the most recent storm (Observation). 

So, how do we manage a persistent slab problem that provides limited or intermittent feedback? The easiest way is to select terrain with a steepness of less than about 30 degrees. If you do choose to get into avalanche terrain (slopes steeper than 30 degrees), you're rolling the dice, and you should do some additional homework to stack luck on your side. Dig down to assess if the aspect you're planning to ride is holding weak snow on the ground. Areas with a deeper snowpack will be more difficult to trigger an avalanche on this layer. You can choose terrain with a seemingly uniformly deep snow pack greater than about 3' deep—although be aware that you could trigger a slide from the edges or the middle of a slope where the snowpack is shallow and variable. This problem is more likely to exist on the northern half of the compass, where the last week of warm temperatures and sunny skies has played little role in improving stability, but as yesterday's avalanche proves, there is a high degree of spacial variability on any given slope, meaning the structure to support this problem could be present on all aspects. Remember to ski and ride steep slopes one at a time, always carry the appropriate rescue gear, and consider the consequences of even a small slide carrying you into gullies or rocks. 

You may find and be able to trigger lingering wind slabs in upper elevation terrain where strong winds over the last few days have built 1-2' thick drifts. This problem most likely exists near ridgelines, alpine bowls, or in cross-loaded gullies. While continuing to trend more stubborn and unlikely, expect the size and likelihood of triggering a slide to increase as you climb in elevation into more wind-affected terrain. 

Be on the lookout for smooth, firm, and hollow-sounding snow surfaces. Shooting cracks are signs that you have found an unstable slab of snow. Pole probing and hand pits are good tests for this problem as you travel. Be increasingly wary where you find a stiff slab of wind-drifted snow resting above a thin crust from warm temperatures and light rain last week. 

RECENT AVALANCHES: 

Yesterday, a party remote triggered a large persistent slab avalanche on Microdot after several people had skied the slope. Earlier in the week, several natural avalanches were observed that occurred in the night or early that morning of the 27th/28th as wind speeds peaked. These include slides in Marmot Gullies, west-facing Marmot, Skyscraper, Eldorado, the north-facing aspect of 4068', and Wimp Bowl. Also on Wednesday, skiers on President's Ridge triggered two small avalanches while traveling. See all recent observations here.