Turnagain Pass Avalanche Forecast

Over the past three days there has been a big difference in the amount of new snowfall across our forecast area, with coastal areas like Portage and Placer receiving multiple feet of new snow and more inland areas like Turnagain Pass and Girdwood receiving less than a foot. Natural and human triggered avalanches are very likely in areas that received heavy snowfall, and the potential for remote triggering large avalanches exists because of a layer surface hoar that was buried underneath the new snow. The snowpack needs time to adjust to the large new snow load in these areas and travel in avalanche terrain is not recommended. Widespread avalanche activity was observed in the Spencer Bench area on Thursday and the added snowfall since then will have increased the likelihood of triggering and potential size of avalanches.

In areas that have not been favored by the recent snowfall, like Turnagain Pass and Girdwood, there has still been plenty of east wind to transport the new snow into wind slabs up to 2′ deep that are likely to be triggered by a person. The potential for buried surface hoar underneath the new snow could make triggering avalanches on lower angle slopes possible and produce avalanches with wider than typical propagation. In protected areas the depth of the new snow will determine whether storm slabs are possible to trigger today, with the likelihood increasing in areas with deeper snow totals. Another 2-6″ of new snow is expected today which will increase the potential for storm slab avalanches in protected areas and increase the snow available for wind transport. Using hand pits and test rolls is a great way to check how well the new snow is bonding to the old surface and determine if avalanches are possible in the area you are travelling.

Cornices: The new snow and strong winds over the past 24 hours will have added some fresh load to our existing cornices and could make them more sensitive to human triggers. With poor visibility expected today it is best to avoid spending time underneath areas with cornices because they could release naturally due to added wind loading.

Shooting crack on a wind loaded test roll in the treeline elevation band in the Crow Creek area. Photo 3.4.22

Only a few inches of new snow above a stout melt freeze crust at lower elevations in Crow Creek area yesterday. Photo 3.5.22

In the far northern and southern portions of our forecast area (i.e. Crow Creek, Lynx Creek, Silvertip Creek) the snowpack is thinner and the potential for triggering a large avalanche on a layer of facets from November exists. Yesterday we found the November facets only 6″ down from the surface in a wind scoured area near Crow Creek. This was quite surprising and indicates that human triggered avalanches could be possible on this deeper weak layer if a failure is initiated in a thin spot of the snowpack. Recent avalanche activity on this layer has been associated with significant snowfall events and since these thinner snowpack areas of the forecast region have not received much snow the past three days the likelihood of an avalanche on this layer is relatively low.

Similar thin snowpack conditions exist in the Summit Lake area, which is outside our forecast zone, and triggering avalanches on deeper weak layers is more likely.

Wind scoured area along our skin track with less than 3′ total snowpack depth and weak facets only buried 6″ deep. Photo 3.4.22