It has been roughly 4 days since the Valentine’s Day Storm exited the region and 6 days since the peak of the storm. Essentially, that has given the mountains some time to adjust to the new load (2-3+’ of dense snow) but, since all that storm snow fell on a weak surface, instability remains. Today we will be in a “scary moderate” regime where the probability of triggering a 2-3′ slab is lower, but the consequence can be high. This is the major concern for the day and is a tricky problem considering some slopes show better bonding than others.
The weak layer is a thin layer of buried surface hoar and near surface facets. It is deep enough (2-3′) that in most areas digging a snowpit is the only way to assess it. Furthermore, finding a representative and safe place to dig a pit is also a challenge. Be aware that no red flags may be present (whumphing or cracking in the snow) and the pack could have a general “it seems fine to me” feel before someone finds the trigger point. Trigger points are often where the slab is thinner, near rocks or scoured areas. Also keep in mind, these slabs can break above you, release after several tracks are on a slope and be triggered remotely.
Cornices that grew last week could still be teetering on the balance and could break further back than expected. If one does fall it may trigger a slab avalanche below, potentially creating a very dangerous situation. If the sun comes out, warming may increase the potential for them to break.
Cornice hanging over steep terrain on Wolverine ridge. Note the older slab that was triggered on the looker’s right last week.
There is a new glide crack above the flats along Seattle Ridge, just looker’s left of the up-track and Repeat Offender slide path. Avoid hanging out under this crack and any others you may see – these release without warning and are very destructive.
Although cooler temperatures are moving in, the winds should be very light to calm today. This may allow Southerly slopes to warm enough for sun triggered loose snow avalanches in steep Southerly aspects.
At the bottom of the snowpack are various layers of facets with varying degrees of strength. In the Summit Lake zone and some areas in Girdwood Valley and Johnson Pass depth hoar has been found. Last week’s storm cycle tested these layers and only a few avalanches that we know of broke in them (Girdwood Valley, Portage Valley and Summit Lake). These layers will be tough for people to trigger, but possible in shallow snowpack zones. The more likely case is where an avalanche occurring in the upper layers of the pack has the potential to step down and release the entire snowpack. If this does happen the volume will be large and could run long distances.
Obscured skies with a few patches of broken cloud cover filled the region yesterday. Light snow flurries fell in the afternoon and evening with only a trace in most areas, the exception was Girdwood Valley that picked up 3-4+” of very low density snow. Temperatures were in the mid 20’sF below treeline and in the upper teen’s F in the Alpine. Ridgetop winds were calm and with the light cloud cover created a ‘greenhouse’ effect that increased the temperature slightly during the day. Overnight, winds backed to the Northwest bringing in cooler temperatures with a very light flow, near 10F at the high elevations.
Washington’s Birthday (President’s Day), we can expect the cool Northwest flow to remain over the area with temperatures dropping to the single digits in the Alpine and the teens below treeline. Rigetops winds associated with this will be light, 5-10mph. Skies should be partly cloudy with clearing in some areas. A possible instability shower may add a trace of snow to some locations.
Tuesday looks to be another break in weather with mostly clear skies while Wednesday a frontal system moves in with a chance for snow.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||18||trace||0||69|
|Summit Lake (1400′)||19||trace||0||32|
|Alyeska Mid (1700′)||19||3-4||0.2||67|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||15||Rimed||Rimed||Rimed|
|05/06/20||Turnagain||Avalanche: Pastoral Peak, north face||Andy Duenow|
|04/10/20||Turnagain||Avalanche: Wolverine||Mike Records|
|04/10/20||Turnagain||Observation: Eddies lookers right shoulder||Matt Yoder|
|04/09/20||Turnagain||Observation: Bench Peak||Mike Records|
|04/04/20||Turnagain||Observation: Pete’s North||Anonymous|
|03/26/20||Turnagain||Avalanche: Tincan – Proper (SW facing)||CNFAIC Staff|
|03/26/20||Turnagain||Avalanche: Seattle Ridge||W Wagner Forecaster|
|03/25/20||Turnagain||Avalanche: Sunburst Uptrack @ 2000′||J. Boisvert|
|03/24/20||Turnagain||Observation: Turnagain – Road Observations||W Wagner 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: 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.