Turnagain Pass Avalanche Forecast

With decent visibility yesterday it was evident that winds during the storm moved snow around. There were small winds slabs in many of the front side gullies on Seattle Ridge, and lots of cross-loading and scouring. Cornices had grown and there was stiff snow in wind exposed terrain. Today lingering wind slabs are still a concern.  It will be important to pay attention to terrain to with stiff hollow snow, especially steep unsupported slopes and gully features, and look for shooting cracks.

There is a bit of question mark today as well. Are the storm slabs from the Sunday/Monday storm becoming a new persistent slab issue or not? There are signs pointing to a stabilizing snowpack but there is still some uncertainty and with that potential for large human triggered avalanches. As you head out here are few things to keep in mind about this question:

• Much of the snowpack in the forecast area remains untested after this last storm.
• The new snow fell on surface snow that had weakened during our last clear period and below 2500′ this set-up sits on a rain crust.
• During the storm on Monday observers found storm slabs easily sliding on the weak snow on the crust. Tuesday, two parties of skiers, one on Sunburst and one on Magnum, reported turning around due to large whumpfs in the mid elevation band where the old rain crust exists.

On the flip side, the Tuesday observers on Seattle Ridge found the new snow bonding well to the old snow and crust and no signs of instability. This was similar for observers on Sunburst yesterday and skiers and snowmachiners ventured out a bit more with no reported incidents.  This seems promising but is still somewhat of an unknown as folks spread out testing more terrain. As we move into the next couple days of clear skies it is very important to ease into terrain, use good travel protocol, think about consequences and look for signs of instability.

Cornices:  We know cornices have grown. Give them a wide berth as they can now easily break further back than we might expect. As seen last week, they can also trigger an avalanche below, creating a bigger problem if a person is involved.

Wind textured surface snow on Sunburst. 12.9.20. Pay attention to stiff hollow snow and look for shooting cracks. Note the scouring and cross loading on the north side of Magnum as well. 

Will the new storm slab stick to the weak snow on top of 12.1 rain crust? That is still a bit of a question mark. Sunburst snowpack at 2200′, 12.9.20.

In the Alpine, hitting a thin area in the snowpack or traveling in areas with an overall shallower snowpack (around 3-4′deep) is still concerning for triggering a large slab that fails in the old October snow. The southern end of Turnagain Pass through Johnson Pass, Silvertip and Summit Lake all have slopes without as much snow as northern end of Turnagain or Girdwood.

Weak snow at the base of the snowpack on Sunburst at 3200′. 12.9.20.