Turnagain Pass

As Southcentral Alaska sits under a cold, clear and very windy weather pattern, there are areas that have been partially spared by the brunt of the Northwest winds. The ridges along the East side of the road along Turnagain Pass are one of these areas. Folks have been able to find some soft snow and venture further into the mountains without incident. That said, there are areas that have not escaped the major winds. An example would be the Crow Pass region of the Girdwood Valley and the mountains on the Southern end of the forecast zone toward Silvertip. In the Summit Lake area (Summit Snowpack Summary here) two avalanches were seen yesterday on Summit Peak. The key, of course, is to find these sheltered areas, both for better riding conditions but clearly for decreased avalanche danger.

Wind slab avalanches:

It will be another day to watch for slopes with recent or current wind loading. Ridgetop winds should again be moderate to strong – in the 15-25mph range from the Northwest. However, there is not nearly as much snow to blow into slabs as there was at the beginning of this wind event 4-5 days ago. Most of the loose surface snow has blown away or been blown into hard slabs, crusts and sastrugi at the higher elevations. Things to keep in mind with wind slabs:

1. Wind slabs are expected to be very hard and stiff (supportable to boots and snowmachines)
2. They are likely to be stubborn and tough to trigger
3. Steep rocky terrain is the most likely place to trigger a slab

Cornbiscuit Ridge on the East Side of Turnagain Pass – one of the ‘less windy’ areas.

It is good to keep in mind that there are areas in the periphery of Turnagain Pass that have a poor snowpack structure. These layers are buried surface hoar 1-3′ deep and facets in the mid and base of the snowpack. The ‘wind event’ has loaded and reactivated some of these older layers. The most recent avalanche activity was seen yesterday in the Summit Lake area. Besides Summit Lake, other areas of concern include the Johnson Pass zone and some areas in the Girdwood Valley. Continual winds with this relentless wind event may be loading these old weak layers to the point of failure.

Recent natural wind slabs in the Summit Lake area, this is just to the South of the forecast zone, seen and documented yesterday. (A bit complicated, but the point is two of the 4 avalanches in the photo occurred yesterday).