Hatcher Pass

Thurday’s wind event was more intense and longer lasting than forecasted. The winds were strong and drifted snow which overloaded buried weak layers in the snowpack resulting in widespread avalanche activity. One avalanche crossed the Archangel XC trail.

2/10 – Archangel 2 avalanche path, large natural slab avalanche crossed the XC trail.

2/10 – Archangel 2 close up of crowns and avalanches

2/10 – Firn avalanche path, lookers right of Presidents Ridge. Large natural slab avalanche. Wide propagation. Failed on both DEC29 crust and Nov basal facets.

2/10 – Eldorado Uppers, ENE and NE, 4250′, Crown width 550′, up to 3 feet deep, D2 Large Natural Slab Avalanche failing on Dec26 crust and stepping down to Nov basal facets. This avalanche stands out as one of the deeper slabs we have seen triggered this season. The majority of avalanche activity was not this deep. Our main avalanche problem remains a persistent slab problem, but is on the way to transitioning to a deep slab problem, which is larger and more dangerous.

Another view of Eldo uppers, with a peak of the lowers. This photo clearly shows the mid pack crust bed surface, and a few locations where it augered down to the basal facets.

2/10 – Eldorado Uppers and Lowers. Lowers, East, 3700′, Large natural slab avalanche failing in basal facets, Crown est. mainly 1 foot deep, with the upper portion of the crown approaching est. 3 feet deep. This avalanche may have been sympathetically triggered by the larger natural from above.

2/10 – Lodge Run, Marmot Mountain, WNW, 4250′, Large natural avalanche occurred during wind event.

2/10 – One of the Marmot gully avalanches on the SE side of the mountain above the road. A closer look at bed surfaces.

2/10 – Idaho Peak, WSW, 3500′ Large natural slab avalanche.

Hatcher Pass is plagued with a weak snowpack. Each time it is loaded, avalanches are the result. On 2/10 strong winds overloaded this weak snowpack and resulted in numerous and widespread slab avalanches 1-3+ feet deep. This next round of snow has the potential for overloading the snowpack once again.

4-7″ of  new snow is expected by the end of today. Winds are expected to be light to moderate from the South. More snowfall is expected overnight with a storm total of 12” by Sunday morning.

The avalanche hazard will rise today from moderate to considerable by this evening and into Sunday as snowfall continues to accumulate.

Human triggered avalanches will be more likely on Southerly aspects. Natural avalanches are not expected during day light hours today. Natural avalanches will be possible and human triggered avalanches will be likely by the end of day and into Sunday.

Two layers of concern are buried in the snowpack. These are the Dec29 crust sandwich and the Nov sugary basal facets.

In many cases this season avalanches have released on both of these layers in the same slides. Avalanches may fail initially on crusts and then step down into the deeper basal facets near the ground, releasing the entire depth of the snowpack. The average depth of avalanches is expected to be between 1-3+ feet deep.

The overall snowpack depth varies across aspect. In general, West to North aspects have a deeper snowpack and East to South aspects have a shallower snowpack. There has been consistently more avalanche activity this season on the Southerly aspects where the snowpack is thinner, weaker, and therefore easier to trigger. However, avalanches are possible on all aspects.

This pit is on a wind loaded aspect showing a very thick slab pushing 3 feet deep sitting over the problem weak layers. On other aspects the slab can be as thin as 1 foot deep and easier to trigger. Avalanches have been consistently failing on these weak layers each time they are loaded.