Turnagain Pass

Last night a cold moist air mass brought a several inch refresh to the Girdwood and Portage Valleys (4-6″), yet only an inch or two for Turnagain Pass. Water weight was only in the .25 – .1″ range, but most of us will take what we can get to cover the crusts at the lower elevations! With that said, until we see more weather, snow, rain, etc, our avalanche problems on the surface remain on the small side (see below) and our main concern still lies with a much larger, but stubborn avalanche problem.

Deep persistent slab avalanches remain our primary concern, which exist in the high elevation terrain above 3,000′. On these upper elevation slopes, there is a dense hard slab sitting on a variety of weak layers in the mid pack (buried surface hoar) and old November facets near the ground. Triggering a deep slab is becoming more and more difficult, but still possible. The most likely trigger spots are thin areas in the snow cover, often near rocks, or where the slope rolls over. High peaks, that see wind, can also be thinner and more likely to find a deep slab.

Again, here are a few points that keep sending home with our current snowpack set up:

–  We have a ‘low probability, high consequence’ situation at the upper elevations for deep slab avalanches
–  Obvious signs of instability are not likely to been seen before a deep slab is triggered (such as whumpfing and cracking)
–  Remote triggering is possible 
–  Last, this issue can simply be avoided by sticking to terrain below 3000’ (which is a good portion of terrain at Turnagain) or choosing low-consequence terrain in the alpine

Photos of old avalanche debris from the Seattle Headwall area. Last week’s warm storm initiated very large avalanches on many slopes, yet many still remain intact and did not avalanche. 

  
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Ridgetop winds bumped up slightly last night into the 10-15mph range from a generally Easterly direction. This isn’t much for wind, but with such loose surface snow existing right now, it could be enough to form shallow wind slabs along ridgelines. Watch for recent wind texturing on the snow surface and feel for stiffer wind packed snow over softer snow or a crust. If you happen to find a fresh wind slab, expect it to be quite touchy.

Again, the loose surface snow is quick to sluff and has been running far on steep slopes. Hence, watch your sluff on the steeper slopes. Any additional new snow from overnight will add to the volume of these and could catch a person by surprise. 

Photo of loose surface snow (near surface facets) over a stout crust in the mid-elevations. Another crop of surface hoar (on the top of the snow in photo below) grew last weekend and now sits under the little bit of new snow from last night. 

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