Yesterday was the first day since the beginning of the Valentine’s Storm Cycle (beginning Monday, Feb 13th) that no natural avalanches were seen. The storm cycle is fading, but we did get another shot of snow last night, adding another 2-6″ to mountains. This last storm cycle has brought a total of 2-3′ of dense new snow to the area and simply put, the new snow is not bonding well with the old snow (seen in video). This is due to a weak layer of buried surface hoar along with near surface facets that is sandwiched between the new snow and old harder snow//crusts. Until proven otherwise, this weak interface is suspect to be on all aspects and elevations.
Things to keep in mind with this ‘persistent slab’ avalanche problem:
What can we do? Terrain management! Sticking to lower angle slopes (under 35 degress with nothing steeper above you) is recommended.
Photo below: A look at the bottom of the slab and the weak layer (buried surface hoar) shining in the sun.
Strong winds have been impacting the mountains for 6 days now. Although we should see a decrease in ridgeop wind today, the Easterly flow should still be strong enough to load leeward slopes. Wind slabs from the past few days have been around 6″ to a foot thick and showing signs of bonding fairly well. However, the problem is this has made for a more solid slab out of the Valentine’s Storm snow that sits over the aforementioned buried surface hoar and facets. Nonetheless, fresh winds slabs should still be something to look for and if triggered, could step-down to the weak layer below. Watch for current wind loading and stiffer, hollow feeling snow over softer snow.
Cornices have grown substantially during the past week and could release naturally with the ongoing wind/snow. If you find yourself along a ridgeline, give them a wide berth as these could be quite touchy and have a good chance of triggering a slab below. Also, keep in mind if there are other groups underneath you in valley bottoms.
Wind plume on the NW ridge of Magnum on Turnagain Pass. This was the theme of yesterday’s weather.
If the sun comes out today, watch for quick changes in the snow surface and an increased change for triggering a slab. Moist to wet loose snow avalanches on Southerly aspects should be expected with the first shot of sunshine.
Weak snow (facets and depth hoar) in the lower layers of the snowpack continues to be a concern in our advisory area. Avalanches occurring in the upper layers of the pack have the potential to step down and release the entire snowpack in some places. If this does happen the volume will be large and could run long distances. A few of the naturals throughout this last storm looked to have run into older faceted snow. The possibility of these large avalanches is another reason for conservative terrain choices.
Several natural slab avalanches on a SE aspect of Fishes Breath in Girdwood Valley, including one that stepped down into an older layer of the snowpack. Photo courtesy of Mike Welch
Mostly cloudy skies were over the area yesterday with light snow flurries in Girdwood and the North side of Turnagain Pass. During the overnight hours another pulse of moisture moved through adding 4-6″ of new snow in the Girdwood Valley, 2-3″ in Turnagain Pass and ~7″ at Summit Lake. Ridgetop winds continue to be strong during the past 24-hours from an Easterly direction with averages from 25-40mph and gusts to 57mph. Temperatures have been warm, low to mid 30’sF at sea level with a rain/snow mix, at 1,000′ in the upper 20’sF and around 20F along the ridgetops.
For today, continued off-and-on instability showers are expected with similar warm temperatures and a rain/snow mix at sea level. Total snowfall expected is 2-4″ (.25 water) today and another 2-5″ (.3 water) tonight. There could also be some clearing skies in between these snow showers. Ridgetop winds should decrease slightly from the East and Southeast with averages in the 15-25mph range (still moderate to strong).
Looking ahead to the weekend, clearing skies and cooler temperatures with a few snow flurries are on tap. Stay tuned.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||30||2||0.2||75|
|Summit Lake (1400′)||30||7||0.5||35|
|Alyeska Mid (1700′)||29||4.6||0.37||70|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||23||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.