|Signal Word||Size (D scale)||Simple Descriptor|
|Small||1||Unlikely to bury a person|
|Large||2||Can bury a person|
|Very Large||3||Can destroy a house|
|Historic||4 & 5||Can destroy part or all of a village|
Triggering a deep slab avalanche, a deep persistent slab avalanche to be correct, is our main concern.
With a couple days of quiet weather behind us and a mostly sunny day on tap, the snowpack is finally getting a chance to adjust to the loading from the past few weeks. Unfortunately for us, we have those buried weak layers to deal with and they don’t heal up in a few days. In fact, it can take weeks or more. These are the same buried weak layers of facets and buried surface hoar that have been responsible for almost all the avalanche activity over the last month, including the several close calls on Dec 2nd and 3rd when two skiers were caught and one snowmachiner was buried. This last storm (12-26″, 6 days ago) also overloaded these layers, producing large natural avalanches.
How reactive are the layers now? There has not been a lot of traffic to test them, but avalanche science says, with time and being buried over 3′ deep, they should be more difficult to trigger. This is the scary MODERATE scenario… slabs are becoming harder to trigger, but can be large and have high consequences.
Here are the main characteristics of a deep persistent slab:
The weak layers are roughly 3-5′ deep in Girdwood and Turnagain Pass, but are much shallower to the south of the pass and in Summit Lake (south of the forecast area). They are most concerning in the 1,500 – 3,000′ elevation band where the Halloween crust sits under them and can exacerbate the issue. Hence, open steep slopes in the trees can be just as dangerous, or more so. It’s a tricky situation and many of us are simply avoiding the issue all together by sticking to slopes 30 degrees or less.
If you are considering stepping into larger/steeper terrain, be mindful of this potential. It’s also good to know slopes that have seen little to no traffic this season are more suspect. Watching your partners closely, only exposing one person at a time, and having an escape route planned are all ways to help hedge your bets. Also, thinking about the consequences if the slope does slide; will the debris pile up deeply in a terrain trap (bad) or spread out (also bad, but better chance for rescue)?
Schematic of a deep persistent slab. (avalanche.org)
Wind Slabs: Lingering wind slabs from Sunday’s winds are likely to be found in exposed terrain and especially in areas on the periphery of the forecast zone – south end Settle Ridge, Summit Lake, etc. Watch for the classic signs of wind loading, cracking in the snow around you and stiff snow over softer snow. Wind slabs could trigger a deeper slab, creating a much more dangerous situation.
Photo from Eddie’s looking toward Kickstep by Andrew Schauer. Andrew’s comment: “Daydreaming of better stability. Getting big ‘You can look but you can’t touch’ vibes right now.” 12.13.2021
Yesterday: Mostly sunny skies were over the region with light north to westerly winds. Temperatures remained in the minus single digits with some areas climbing their way into the positive single digits.
Today: Another sunny day is on tap with what looks like somewhat warmer temperatures by the afternoon. However, an inversion is in place this morning with valley bottoms in the -20 to -5 range and ridgetops around 5-10F. Ridgetop winds will remain from the NW where they are forecast to be 5-10mph with some areas seeing 15mph.
Tomorrow: A weak weather system is headed in for tomorrow with increasing easterly winds late tonight and snowfall beginning Wednesday morning. At this point models are only suggesting 1-3″ of snow with this event. The east winds with the event should be in the 20-30mph range. Temperatures are expected to climb back to a respectable 10-20F range.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||-1||0||0||73|
|Summit Lake (1400′)||-12||0||0||23|
|Alyeska Mid (1700′)||1||0||0||46|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||7||N||3||6|
|11/28/22||Turnagain||Observation: Pastoral||Schauer/ Wadsworth Forecaster|
|11/26/22||Turnagain||Observation: Eddies||Schauer/ Cullen Forecaster|
|11/26/22||Turnagain||Observation: Eddies||Andy Moderow|
|11/26/22||Turnagain||Observation: Lipps||Big Ripper|
|11/25/22||Turnagain||Observation: Sunburst||Hannah Smith|
|11/25/22||Turnagain||Observation: Sunnyside / Seattle Ridge||Matti Silta|
|11/25/22||Turnagain||Observation: Sunburst||John Sykes|
|11/25/22||Turnagain||Observation: Tincan Trees||Andy Moderow|
|11/25/22||Turnagain||Observation: Tincan||Galen Hecht|
Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: email@example.com
|Area||Status||Weather & Riding Conditions|
This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.