Recent Avalanche Activity:
There were several small to medium sized human triggered wind/storm slab avalanches yesterday. There was also evidence of a handful of natural slabs and sluffs occurring mid-storm on 2/7. Several observations were sent in with more detail on yesterday’s activity – check them out!
Tincan – At least 5, but up to 11, small storm/wind slab pockets remotely triggered by skiers. (See photos below)
Sunburst skier triggered soft slab (WSW, 3,650′). Thanks to the party for sending in this photo – check out their additional photos with a write up on triggering the slide HERE.
Tincan small soft slabs on the lower south facing rollovers below the common up track (SW facing, 2,500′). *Note the crack extending from one pocket to the other intersecting the ski track. (Photo: Mark Norquist)
Tincan’s Hippy Bowl larger soft slab (SW, 3,300′). Note the several pockets below the rollover. These are believed to be remotely triggered from above.
Today’s primary concern – Persisting storm/wind slabs:
There is much uncertainly with how the storm snow is bonding with the pre-existing surfaces. There were areas yesterday (i.e. Tincan) where the new snow was quite active and people were able to remotely trigger avalanches from over 100′ away. Yet on Sunburst, only one slide occurred even though many people were skiing/snowboarding. At elevations around 3,000′ and below surface hoar exists between the old hard crust and the storm snow. Additionally, above 3,000′ there is a facet/crust combination that exists below the storm snow (responsible for the Sunburst slide). The trick is the new snow was still unconsolidated enough yesterday that slides were mainly confined to small pockets. With settlement overnight allowing the new snow to become more of a slab over these persistent grain types, we could see remote triggering again today along with wider propagation and subsequent larger avalanche activity.
Quick hand pits and keeping an eye out for cracking and collapsing are good ways to assess the new snow/old snow bonding. These clues are hard to get while on the up track so stepping off it now and then may tell you something. To avoid any avalanche issues today you can steer clear of slopes steeper than 30 degrees.
Once again, we are mentioning the deep slab concern that exists at the upper most elevations (above 3-3,500′). This problem has shown signs of inactivity for the time being and the probability of triggering a deep slab is low yet, the consequences are high. It’s possible another load, or just the right trigger (cornice, a person on a thin spot or a large group of people), could initiate a failure in the weak snow at the base of the pack (basal facets) causing a large full-depth slide.
Below is a cross section of the pack at the site of the Sunburst avalanche mentioned above. You can see the basal facets sitting under the pack that are responsible for the lingering deep slab concern.
Sunny skies prevailed yesterday. Temperatures hovered around 20F above treeline and the mid 20’sF at sea level. Winds were light from the Northwest on the ridgetops. Overnight, VERY cold air has moved in and all elevations are reading in the single digits.
Storm totals from 2/7:
Turnagain Pass above treeline – 16-18″
Turnagain Pass below treeline – 12-16″
Summit Lake above treeline – 6-8″
Summit Lake below treeline – 3-5″
Today should be another blue bird day – but cold. Temperatures may warm up to the teens by mid-day above treeline but likely stay in the single digits at valley bottoms. Ridgetop winds look to slowly switch around to the east but remain light in the 5-10mph range.
Clear and cold weather is forecast to persist into the middle of the week with a chance for snow later in the week.
|04/19/21||Turnagain||Avalanche: Triangle, Seattle creek||Will Morrison|
|04/18/21||Turnagain||Avalanche: Turnagain Pass Road Obs||Andy Moderow|
|04/18/21||Turnagain||Observation: Seattle Ridge, approximately 300 yards south of the up track||Brent Byrne|
|04/17/21||Turnagain||Avalanche: Road obs||Johnston-Bloom / Moderow Forecaster|
|04/16/21||Turnagain||Avalanche: Seattle Ridge||Wendy Wagner Forecaster|
|04/16/21||Turnagain||Avalanche: Turnagain Pass, non-motorized side seen from Seattle Ridge||CNFAIC Staff Forecaster|
|04/16/21||Turnagain||Observation: Sunburst||Lance breeding|
|04/15/21||Turnagain||Observation: Tincan||Schauer/ Rothman Forecaster|
|04/13/21||Turnagain||Observation: Turnagain Pass Road Obs||A Schauer Forecaster|
|04/12/21||Turnagain||Observation: Tincan||Johnston-Bloom / Latosuo Forecaster|
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.