Avalanche forecast

Hatcher Pass

Hatcher Pass Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

The danger for PERSISTENT SLAB and DEEP PERSISTENT SLAB avalanches is MODERATE.

A long duration storm added a significant amount of weight to our existing snowpack's poor structure. This storm also had several phases of wind shifts and density changes that built hard slabs over weaker layers in the snowpack. 

The intense, long duration storm last weekend had several phases of extreme precipitation. It finished with a significant wind event out of the southeast that built hard slabs over weaker layers in the snowpack. 

Triggering an avalanche is less likely than mid-storm but is still possible and has high consequences. Human triggered avalanches could be 1-3' deep on the shallower side and 3-6' on the deeper side. Natural avalanches are unlikely.

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ROAD UPDATE: 

DOT continues to maintain a closure just above Skeetawk while they stage equipment to begin clearing debris from the roadway. They anticipate opening access to the Goldmint Lot this weekend. Read their full update on 511. 

SPECIAL ANNOUNCEMENTS:

It's time to party. The Cabin Fever Reliever, our annual fundraiser is this Saturday, Feb 1. Come celebrate with us, the Valley winter community and the Roland Roberts Band! Tickets available here. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Winds at the end of the large storm leading up to its conclusion on Tuesday were predominantly strong out of the southeast. You are more likely to encounter persistent slabs in the upper snowpack in areas that are not quite as deep such as windward aspects or at mid-elevations. 

    Expect it to be possible to trigger persistent slab avalanches 1-3' deep in terrain 30 degrees and steeper. 

    These could fail on various persistent weak layers in our mid-upper snowpack: buried graupel, facets and a variety of crusts. Shifting winds and density changes during the storm could also contribute to density breaks where lingering hard slabs could fail. 

    We have some uncertainty about this problem since the road has been closed and observations have been limited. Some of the more recent natural avalanches from Sunday and Monday (after the bulk of the precipitation from the last storm) appear to have failed on some of these layers in the top half of the snowpack. You may be able to find this problem around the compass. While it may be stubborn to trigger, mindful terrain selection and safe travel protocol is prudent as we gather more data about its distribution and reactivity. 

    ECTP 12 and ECTP15 failed on a hardness change between newer wind slabs and old wind slabs (with some tiny .25mm facets) ~30cm/1' down. 

    Photo: Andy Paul

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    This last storm event brought an egregious amount of precipitation to mid and upper elevations with 10" of snow water equivalent and nearly 50" of snow. If you were following along, you probably know what this fell on top of: weak, sugary basal facets. These facets at the bottom of the snowpack have been observed up to two feet in depth above the ground. They are loose and vary in state: some are moist and clumpy, some are dry and more indicative of depth hoar--larger with striations. Regardless of their size or status, we have relatively widespread, poor structure in Hatcher Pass.

    It will be possible to trigger a deep persistent slab 3-6' in depth on terrain with consistently more snow and 30 degrees and steeper at mid and upper elevations where hard slabs are sitting over weak, sugary facets. 

    Some folks have asked about the "crush and flush"--that is the elimination of this weak layer by the pressure and weight of snowfall. However, at this time, we are seeing this layer to be prevalent and intact. The only places you could really be sure of this structure being gone are in starting zones and avalanche pathways that ran to the ground. 

    Remember, you are most likely to trigger a deep persistent slab in a shallower spot where the weight of your body or snowmachine is able to impact the weak layer more easily. This is a low likelihood, high consequence avalanche problem. Cautiously evaluate slope angles, avoid mid-slope rocky terrain and have one person at a time on suspect slopes. 

     

     

    Basal facets at the bottom of the snowpack have been observed up to two feet in depth above the ground. They are loose and vary in their state: some are moist and clumpy, some are dry and more indicative of depth hoar--larger with striations. 

    Photo: Hatcher Pass Avalanche Center

Avalanche Discussion

RECENT AVALANCHES:

The storm had numerous natural avalanches, D2-D3 in size. Notable ones were the D3 on Government Peak, Marmot 1 (that ran over the road) and the D2.5  that ran off of Arkose into the Little Su, just north of Skeetawk at Mile 11 on the road.

The DOT did mitigation work yesterday 1/29 with limited results. See photos below of some of the natural avalanches on Marmot's southerly aspects. 

See our storm avalanche observations on the Obs page here. 

Regions covered