Turnagain Pass

Don’t put away your hand warmers and cold weather gear yet! It seems as though spring will have to wait as very cold air is currently streaming down from the North. For those out in the mountains yesterday, during the afternoon a dramatic change in weather took place as strong Northwest winds kicked up and temperatures plummeted. Overnight some ridgetops are reporting temperatures in the minus single digits…

Wind Slab Avalanches:
The strong Northwest winds peaked early last night, with hourly averages near 40mph. As of this morning, the winds have decreased, but still remain in the moderate category, averaging 15-20mph. Although there were only a few flurries associated with the wind, there is/was 4-8″ of loose snow already on the ground available to be blown into slabs. These are expected to be in the foot thick category and found in exposed areas out of the trees. Some things to keep in mind today:

1. New wind slabs could be both soft and hard depending on the strength of the winds in specific areas
2. They could be further down the slope than expected due to cross loading
3. All aspects are suspect! This Northwest flow tends to be channeled through Turnagain Pass such that Southerly winds are seen on the East side of the highway – loading Northerly slopes
4. Pay close attention to surface texture and areas of wind scouring and wind loading
5. Watch for hollow feeling snow, strong and stiff snow that sits on softer snow
6. Until proven otherwise, expect wind slabs to be touchy and easy to trigger

Photo: Strong Northwest winds were transporting snow onto an Easterly face along ridgelines yesterday in the Girdwood Valley. 

Cornices:  Winds have, and will be, adding more snow to the already large cornices. Remember these unpredictable hazards can break farther back along ridgelines than expected and have the potential to trigger an avalanche on the slope below. Give them extra space and avoid being under them. 

Loose snow avalanches:  If you find terrain that is protected from the winds and harbors loose soft snow, expect to initiate sluffs on steeper slopes. 

Unlike the avalanche concerns associated with the winds, that are easily seen on the surface, we must remember there are lurking weak layers deeper in the snowpack. A widespread layer of buried surface hoar (buried on Feb 9th) sits anywhere from 2-3′ below the surface. This layer continues to be found in most pits and although it is becoming very tough to trigger, it does continue to show potential to fail and propagate. For a better look at this, check out the video in our report from the Girdwood Valley yesterday.

The bottom line here is, there is still a chance that a 2-3′ slab could be triggered on steep slopes above 2000′. It has been 9 days since an avalanche was triggered on this layer and folks have been able to push further into the mountains without incident. However, with added load by winds and the chance a person could accidentally find the right trigger point, these larger slab avalanches remain a concern. Likely trigger spots are in places where the snowpack is thinner – near rock bands or on more scoured features. These slabs can break above you, and release after several tracks are on a slope. Be aware that no red flags may be present.

Deep Persistent Slab: We continue to find various layers of weak faceted snow and depth hoar near the bottom of the pack in certain areas. This includes Summit Lake zone, and some areas in Girdwood Valley and towards the Southern end of Turnagain near Johnson Pass. Similar to the problem above, these layers will be very tough to trigger, but a possibility remains in places with this structure.

Glide avalanches:  The glide crack looks to be continuing to open above the flats along Seattle Ridge, just looker’s left of the up-track and Repeat Offender slide path. Avoid hanging out under this crack and any others you may see.