Turnagain Pass

A break in the weather has finally moved in after three days of rain, snow and wind. The rain/snow line rose to 1,500′ in places yesterday, and possibly higher, yet several feet of new snow is now in the mountains above 1,500′. During the past 24 hours between 1-2′ of new snow fell in the region. Favored locations were Portage Valley, Girdwood and the North end of Turnagain Pass. 

STORM TOTALS near 2,000′ above the rain – Thursday morning through 6am Sunday morning:

Turnagain Pass     20-30″  (2.6″ of snow water equivalent)
Girdwood Valley    25-35″  (3.2″ of snow water equivalent)
Summit Lake         10-15″  (1.0″ of snow water equivalent)

Avalanche activity was prevalent in the Tincan Trees yesterday due to heavy snowfall creating a ‘rapid loading’ event. All avalanches were failing under the total storm snow, at the new/old snow surface. The old snow surface is composed of small buried surface hoar (3-7mm) and near surface facets. These are persistent weak layers that don’t bond quickly. Hence, we can expect the storm snow to fail in these layers again today. With the storm past, natural avalanche activity will be decreasing but human triggered avalanches will remain likely. If you are headed out – keep these points in mind:

1-  Slabs triggered will be deep (2-3+ feet) – these are dangerous and unmanageable avalanches
2-  Avalanches could run further than expected
3-  Remote triggering an avalanche from below, or near a slope is possible
4-  Due to the depth of the storm snow, no signs of instability may be present before someone triggers a slab

*Giving the snowpack time to heal from these storms is key. Sticking to low angle terrain with nothing steeper above is recommended. Remember, it’s the first 2 days after a storm where most avalanche fatalities occur. Although there is nice powder at the upper elevations that can lure us, now is not the time to be sampling it.
 

Stom slab avalanches in the Tincan Trees yesterday. The slab on the left was believed to have been natural while the slab on the right was remotely triggered by a group ascending. Recent avalanches, Bulls Eye clues the snowpack is unstable.

Another storm slab avalanche triggered by a skier in the Tincan Trees, note the size of the slab (~2,5′ thick). Big thanks to the folks who sent this photo in to us.

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Rain fell on snow yesterday up to 1,500′ and today, light rain is expected to fall up to 2,200′. With these warm temperatures persisting, wet slab and wet loose avalanches remain possible. There have been some breaks in cloud cover overnight, which has likely helped to start freezing the snow surface at these lower elevations. However, clouds and light rain should move back in today softening any crusts that may have formed. Keep in mind that steep slopes with a wet and saturated snowpack are likely to slide. Even a small slope could have high consequences if heavy wet debris is able to pile up on a person. 

Weak layers within the snowpack have the potential to re-activate with the added load of this week’s new snow (2-3+” of water weight). Additionally, avalanches in the storm snow, discussed above, could step down to these deeper layers and produce a very large avalanche depending on the size of the slope. In short, a layer of buried surface hoar from the New Year’s holiday sits roughly 3-6′ deep at this point and is a concern at elevations above 2,000′. Basal facets, near the ground, remain a concern at elevations above 3,000′.