Hatcher Pass

Several skiers have reported triggering small wet loose avalanches on steep SE to SW aspects the last few days.  Many small natural wet loose avalanches, some gouging down to ground, have been observed the last few days.  Several cornice triggered avalanches have been observed, including a large, natural cornice-triggered avalanche on a northwest aspect of Rae Wallace Chutes on Marmot that occurred overnight Monday the 25th.

Large cornices have formed above leeward aspects and have released naturally in the last week, triggering large avalanches that have stepped down and failed to ground in places. These large cornices have proven sensitive to human and dog triggers and should be avoided. Give cornices a wide berth as they can break back much further than expected and will be possible to trigger larger avalanches below. We should avoid traveling below cornices. Low visibility can make judging the size and safe route around cornices difficult. Cornices are extremely unpredictable.

Human-triggered small, wet loose avalanches will be possible on steep slopes (>40 degrees) on all aspects at lower elevations and on E to W aspects at mid and upper elevations, in the afternoon.  We are right at the tipping point of seeing more frequent and larger wet avalanches, up to D2 in size. The good news: Wet loose avalanches are predictable and avoidable. Pay attention to aspects and ski and ride southerly aspects early!

Temperatures have remained unseasonably warm this week in Hatcher Pass. The last three days ridgetop temperatures have increased above freezing during the day.  While temperatures have dropped below freezing overnight at ridge tops, temperatures at mid and lower elevations have had superficial freezes.

Pay attention to rollerballs gaining momentum, sinking in up to your shins in the snowpack, and watch for wet loose activity on other aspects and terrain. These are all great clues the wet avalanche hazard is rising and indicators that it’s time to move to shadier and less saturated slopes to travel on. We should avoid traveling over or in terrain traps, as they amplify the consequence of even a small slide.

Human-triggered wet slabs will be possible today on SE to SW aspects, on slopes steeper than 30 degrees, at mid and upper elevations in the afternoon.  Although we have seen few wet slabs in Hatcher Pass, we are right at the tipping point for them to occur with continuous warm temperatures. Wet slabs are becoming more and more likely  with this warming trend, particularly where the snowpack structure is shallower, and has a slab sitting on crusts over weak basal facets and depth hoar.  Wet-slabs could be up to D2 is size, or large enough to bury, injure, or kill a person.

Paying attention to rising temperatures, and lack of overnight freezing for several nights are your best red flags for knowing when wet-slabs will occur. Stepping off your snow machine or out of your skis to see if you are sinking in past your shins is a good clue you should head to lower angle terrain or a different aspect to recreate. Wet-slabs can be remotely triggered and tests can be unreliable.

Wet slabs are unlikely at the lower elevations where the snowpack structure is mostly weak, lacking a slab component. However, wet slabs at mid elevations may run into low elevations so beware of being in run-outs under steep southerly slopes.