Advisory – February 16, 2013

Bottom Line:

Moderate Hazard (see the danger scale): primarily for wind slabs around certain terrain features.  Wind slabs created from the 9-10” dump at the beginning of the week formed during a period of strong midweek winds and are now covered, and likely hidden, by several inches of fresh snow from Friday. New, shallower, and relatively soft wind slabs, as well as sluffing, are also possible in our fresh snow from Friday.

Primary Concern:

Deeper wind slabs 3-8” thick formed midweek near peaks, ridges, in upper alpine bowls, and in other deposition and catchment areas (i.e. flanks of cross-loaded gullies). These wind slabs are likely to be covered and hidden by several inches of new snow from Friday.

Secondary Concern:

Relatively soft wind slabs 3-6” thick that have formed, or are forming currently, from Friday’s new snow. These are likely only problematic at the uppermost elevations (near peaks and ridges), as winds have been relatively calm during our most recent deposit of new snow. Loose snow avalanches (sluffing) in steep terrain is also possible in Friday’s new snow.

Mountain Weather:

Expect partly sunny to partly cloudy skies with light winds and mountain temperatures in the teens. Don’t be discouraged by seemingly low visibility in town in the morning. It is likely just low hanging fog and the upper hillsides are probably above it – check the webcams in this regard.

Further Snowpack Discussion:

It is hard to say how hidden and reactive the more deeply buried wind slabs (primary concern) are, due to low visibility and the resulting hindered mobility to poke around in the snowpack on Friday. However, findings from the Canyon Road area suggest relatively low energy and moderate strength in these buried wind slabs. Hand pits on the way up Peak 3 revealed 3-4” thick, 1F hard wind slabs with a faceting base sitting on top of our old melt-freeze/rain crust at mid elevations. These wind slabs were covered by 3” of new snow by Friday afternoon. I’m not too concerned about a problem here.

However, in the upper alpine bowl of Peak 3 and near the summit there is significantly more new snow (~6” by Friday afternoon). The wind slab here, formed by midweek winds from the snow deposited at the beginning of the week, is buried deeper and is a significantly thicker slab (6-8”). I was actually able to find a couple layers of wind slab at the upper elevations, with thin layers of softer snow sandwiched between – the bottom most wind slab sitting atop the melt-freeze/rain crust and with a faceting base. This crust is buried well over a foot deep in the upper elevations. Hand pits approaching the summit revealed easy failures in the new snow as a very soft slab ~6” thick. A decent pull on the column was required to get anything to fail beneath the new snow (the buried wind slabs from midweek).

In general, small wind slabs and sluffing are possible in the steeper sections of the standard-fare Front Range ski runs. While likely not pulling out enough snow to be buried, one could take an unpleasant ride.

I would approach these areas with more caution: steeper north facing runs (such as those accessed from Arctic Valley) and the bowls and gullies accessed from Hiland Road (Lynx, 3 Bowls, Harp, etc. – I have less data on conditions here). I would avoid steep north facing couloirs altogether this weekend as the snowpack is still relatively thin and weak and the likely numerous wind slabs need more time to bond.

Please remember the snowpack is still thin and, as always, the Chugach Front harbors many lightly covered rocks. Watch out for shark attacks!