Turnagain Pass

STORM SLABS: A surprise storm that ended yesterday morning dumped 46” (~4’ and 3.4” SWE) of snow in Turnagain Pass to Johnson Pass. This storm arrived with moderate ridgetop winds and very low-density snow. Natural storm slabs and loose snow avalanches were seen across the forecast zone from Girdwood to Portage.  Triggering a storm slab in terrain 35 degrees and steeper today will be an unmanageable hazard. This new snow has been settling, but moderate ridgetop winds may make this new snow more cohesive and slab-like in the alpine. As always it’s important to give all big storms a few days of rest before easing into steeper terrain. In addition we may see 4-8 inches of additional snow today.

LOOSE SNOW AVALANCHES are a very real concern due 4′ of very low-density snow. Triggering a loose snow avalanche could be large and unmanageable. This kind of snow sould easily knock you off your feet and bury you. Avoid all steep terrain features (large and small) over 35 degrees and be extra aware of hidden depressions and creek drainages. Remember that the lower elevations prior to this storm didn’t have much snow coverage. 

Climbing over the second berm into the Center Ridge Parking area. Snow totals in the parking lot were measured at 47″ at 1:30pm yesterday. 

Climbing out of Center Ridge Parking lot yesterday. In the background is Seattle Ridge. Many of the gullys on Seattle were full of fresh debris and numerous storm slab crown could be seen with binos.   

We have been monitoring a facet/crust issue mid-pack between 2000-3000’. Prior to this storm this layer was not showing reactivity and so far there has been no known natural activity on this layer in Turnagain Pass. However, with the addition of 4′ of new snow, uncertainty remains. This is an additional reason to let the snowpack settle out and to give these layers more time to adjust. 

In the Summit Lake zone there is much more potential for triggering a slab on facets near the ground. Several natural avalanches were seen yesterday on the far Northern end of Summit Pass that may have stepped down into older layers of the snow pack. We have a lot of observations over the last week that demonstrate propagation potential within older weak layers (facet/crust mid-pack and near the ground.) New snow in Summit Lake will be adding stress to these layers and human triggered avalanches are a concern. Look out for whumpfing, cracking, and recent avalanches. Please keep in mind that there is no snowpack info from Johnson Pass and Lynx Creek, which often have a similar snowpack structure as Summit Lake.

SE aspect where storm slabs stepped down to an older deep layer in the zone between Summit and Johnson Pass near the Hope Wye. 

If you head to Lost Lake be aware of triggering a slab 2-3′ in an older weak layer of the snowpack. This picture was taken yesterday and the timing of this avalanche is unknown and may be a natural avalanche from a different day. Photo and observation courtesy of Iron (iii) Oxide.

Glide cracks we know about are on Sunburst’s SW face under the weather station, SW face of Tincan Proper, Gold Pan area (behind Cornbiscuit/Magnum) and Moose Mt in Summit Lake and crack that did release in the Johnson Pass area. These cracks can release at any moment. They are not associated with human triggers and the best way to manage the hazard is to avoid being on or beneath slopes with cracks.