A skier triggered a storm/wind slab avalanche yesterday on one of the lower Eddies rollovers. The avalanche had wide propagation and is suspected to have run on the buried surface hoar/near surface facet layer that was the surface snow from last week. This layer sits just under the new snow from the past few days. No one was caught and the slab broke just under the skier who triggered it. More details on the report linked above.
Section of the crown that was triggered on Eddies yesterday. 1.29.21. Photo: Ryan S.
A wider angle look at the avalanche showing the significant propagation. 1.29.21. Photo: Ryan S.
|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|
It’s going to be a HEAD’S UP sunny day out there. Not only are there tricky avalanche conditions, but we can expect a busy Saturday in the backcountry. We need to be clued into a few simple things. First, for the first time in weeks 8-16″ of new snow fell on a weak layer of buried surface hoar and near surface facets. Second, the new snow is so loose it’s not necessarily forming a slab everywhere, but where it is, avalanches like the one above from Eddies will be possible to trigger. Third, remember our safe travel protocol; exposing one person at a time, watching our partners, having escape routes planned and being patient if others are on the slope ahead of you.
The good news is, these avalanche issues are right at the surface. Additionally, winds during the snowfall were generally moderate from the NE, so wind slabs may not be as prevalent as with other storm events. That said, although the weak layer is there, it’s whether a slab has formed that’s the question. If you are headed out today watch for:
For those folks thinking about getting into the big terrain, soft wind/storm slabs may be found not only along ridgelines but lower on the slope. Even a small slab triggered could entrain a large degree of snow if the slope is steep and sustained.
Estimated storm snow totals at the mid-elevations:
North end of Turnagain Pass: 10-16″
South end of Turnagain Pass: 6-8″
Upper Girdwood Valley: 10-14″
Summit Lake: 1-2″
Portage/Placer Valley: 12-18″
Loose snow avalanches (sluffs): Sluffs are likely to be high volume and fast running. They could entrain not only all the new snow, but a portion of the facets that sit below it.
Cornices: As always, give cornices a wide berth and limit exposure under them. They continue to grow and peel along the ridgelines.
Keep your eyes peeled for any new glide cracks. With the clearing skis we may see more of them opening up. Glide cracks can release into avalanches at anytime. They are completely unpredictable and can be very destructive. There are a few cracks on the SW faces of Eddies, Tincan and Manitoba ridges as well as the roadside of Seattle Ridge. Let us know if you see any new cracks or releases.
Yesterday: Light snowfall and mostly cloudy skies were over the area. Turnagain Pass picked up around 3″ of new snow in the past 24-hours and just a trace in Girdwood and Summit Lake. Ridgetop winds were light to moderate along ridgetops, averaging 5-10mph from the northeast. Temperatures bumped up midday to the mid 20’sF along ridgelines, but have cooled back to the high teens overnight. At sea level, temperatures that were near 30F have also cooled to the low 20’sF.
Today: Mostly clear skies with some valley fog is forecast as yesterday’s system heads out and a high pressure ridge builds in. Ridgetop winds look to shift to the northwest and average in the 5-15mph range. Temperatures are on a slow decline as the northerly flow pushes in cold air. Sea level temperatures look to hover near 20F while valley bottoms and ridgelines drop to the low teens.
Tomorrow: Mostly sunny skies with very cold temperatures are expected for Sunday. Models are suggesting there is potential for a strong NW wind event for Sunday into Monday. Stay tuned and cross your fingers the winds stay quiet.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||25||0.2||3||128|
|Summit Lake (1400′)||20||tr||tr||43|
|Alyeska Mid (1700′)||23||0||0||111|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||21||N/A*||N/A*||N/A*|
*Seattle Ridge anemometer (wind sensor) is rimed and not reporting data.
|03/06/21||Turnagain||Observation: Eddies/Tincan||A Schauer Forecaster|
|03/05/21||Turnagain||Observation: Seattle Ridge – SE face, road side||CNFAIC Staff Forecaster|
|03/05/21||Turnagain||Observation: Tincan, north side||W Wagner Forecaster|
|03/04/21||Turnagain||Observation: Magnum Peak||Carson Jones|
|03/02/21||Turnagain||Observation: Pastoral||Schauer/ Wunnicke Forecaster|
|03/01/21||Turnagain||Observation: Tincan||Schauer/ Rothman Forecaster|
|02/28/21||Turnagain||Observation: Lynx Creek||Graham --AAS Moto Level 1|
|02/28/21||Turnagain||Avalanche: Tincan||Mike Records|
|02/28/21||Turnagain||Observation: Eddies||Andy Moderow|
|02/25/21||Turnagain||Observation: Seattle flats, above power line||Carly AAS Level 1|
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: firstname.lastname@example.org
|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.