Turnagain Pass

The northwest winds are at it again. They are averaging this morning in the 20-25mph range and forecast to peak around midday near 30mph with stronger gusts. Despite the clear skies, these winds are bringing in single digit air and temperatures should stay quite chilly in the upper elevations. Lower, and even some mid elevations out of wind, could see enough daytime warming to melt the surface crusts, we’ll see.

The snow surface is quite variable and could sport a good amount of surface curst today in all but the mid and upper elevation shaded aspects. Yesterday’s warm snowfall event added 7-8″ of new moist snow in upper Girdwood Valley, 1-2″ at Turnagain Pass and 2-3″ in Summit Lake. Very warm afternoon temperatures melted southerly aspects (possibly to ridgetops) and likely some northerly aspects below 1,500′. How much soft dry surface snow is available for today’s winds to transport is the question.

Wind Slabs:  Watching for active wind loading will be key today, and fairly obvious. Wind slabs could form on a variety of aspects, including on top of slick sun crusts or other old hard layers making them even easier to trigger. They are likely to be in the foot thick category and relegated to the higher terrain. These winds can funnel through Turnagain’s non-motorized side from the south, if so, they may not find much snow to transport, limiting wind slab development here, but again something to watch for if headed out. Other than active wind loading, watch for cracks that shoot out from you and hollow feeling snow where stiff snow sits over softer snow.

Loose snow avalanches (sluffs):  If lower elevations warm enough this afternoon/evening, watch for wet sluffs on steep terrain features. Additionally, watch for dry sluffs on any shaded aspect with soft surface snow.

Seattle Ridge’s SE face, the road side, and the common motorized up-track. This slope is called Repeat Offender and the sun shining off the snow surface is a tell-tale sign a surface crust exists on this aspect. 4.3.21. Troy Tempel. 

As anyone who has been reading the forecast for a while now, we are still talking about a few layers of facets and buried surface hoar in the top three feet of the snowpack. It seems that the one or two layers in the top two feet or less are the ones that have been the most reactive, but these are getting harder to trigger. The most recent avalanches in these layers was a week ago in Summit Lake and over a week ago in Girdwood Valley. Shaded aspects, the ones that are most inviting with soft dry snow, are the most suspect place to trigger these now as southerly slopes have various sun crusts.

Knowing these layers are there, listening/feeling for whumpfing and watching for any other signs of instability are good things to keep in mind. As always, use good travel protocol, and consider the consequences if an avalanche does occur. Watch your partners, expose only one person at a time and know your save zones.

Snow pit from Notch Mtn area in upper Girdwood Valley two days ago, Saturday 4/3. Yesterday’s snow added 6-8″ on this surface. Two distinct layers of facets were found in the mid-elevations in the top two feet. These layers showed no signs of propagating, a good sign, but this is not the case everywhere.