Turnagain Pass

Storm totals (Jan.13th – Jan.16th) 

• Turnagain Pass = 15” (1.1” H20)
• Girdwood = 30” (2.3” H20)
• Summit Lake = 7” (0.6” H20)

Two snow storms over the weekend brought significant snowfall to our region. Girdwood received about 30” total and Turnagain only 15”.  Moderate Easterly winds occurred during the first storm and blowing snow was observed during the early part of the the second event. Observers over the weekend reported good bonding in the popular areas of Tincan trees and SW shoulder of Sunburst. Due to limited visibility there is not much information from the alpine as to how well this snow has bonded to harder surfaces below. Expect Western (SW – NW aspects) to be more top loaded or cross loaded from the first storm event. Since most of the snowfall arrived yesterday without much wind previous loading patterns may be challenging to indentify. Should winds unexpectedly increase today there is a lot of snow available for transport and fresh wind slabs could be very tender. 

Be on the lookout for obvious clues like recent avalanches, shooting cracks and blowing snow. Evaluate the snow as you travel by jumping/riding over small test slopes and looking for places where the snow feels stiffer and more affected by winds. 

In Girdwood wind slabs may be closer to 3’ thick and could be more tender due to higher snowfall totals and more stress on the snowpack. More caution is advised in this area and it is best to avoid slopes steeper than 35 degrees. 

A photo of the loading patterns on the SW aspect of Tincan Proper from Saturday afternon, Jan.14th, following the first snow storm that left up to 12″ in the upper elevations of Turnagain Pass. Photo by Andy Moderow

Yesterday 7” of new snow fell in Turnagain Pass, 13” fell in Girdwood, all without much wind. Snow totals could be deeper in the alpine and triggering a loose snow avalanche will be likely on steeper slopes. Fast moving “sluff” could entrain snow, run further than expected and easily knock you off your feet. Manage this problem by letting the snow move past you and choose terrain that doesn’t have high consequences if you fall. Although it is unlikely to bury a person, keep in mind that larger terrain will have more volume. Cold temperatures could increase this problem today.

A variety of weak layers exist with in the snowpack and vary across our region. In the heart of our forecast zone,Turnagain Pass, Northern aspects are the most suspect. On the Southern end of Turnagain Pass towards Johnson Pass many aspects have a shallow snowpack, and may harbor more suprises. It will be in these location where triggering a slab on an older layer (facets or buried surface hoar) is possible. In Girdwood where twice as much snow fell and limited snowpack information exists, triggering a deeper more high consequence avalanche is more likely. Should you see recent avalanche activity, experience shooting cracks, or “wumpfing” these are obvious clues that the snowpack is unstable. 

In the lower elevations below 1500’ where a layer of surface hoar was buried by this last storm event, it may be possible to trigger a soft slab on steep unsupported terrain features or along steep gully’s. For today this problem is more of a concern below treeline in places like Portage or Placer Valley. Ice climbers and hikers should be aware of the terrain above, and avoid being in the run-out of large steep slopes. Observers yesterday mentioned that snow drifts near Portage Lake were up to 2’ deep. 

A photo of shooting cracks following a large collapse “wumpf” at about 1800′ an a NE aspect of Raggedtop, Girdwood Valley, following the end of the first storm on Saturday afternoon.