As skies cleared yesterday, we were able to see evidence of a widespread natural cycle that occurred during the 1/27-1/28 storm. This included activity in the Girdwood valley (Magpie and Berg Peak), Turnagain Pass (Tincan Proper/Library, Seattle Ridge, Sunburst, Magnum, Pete’s South, and the Johnson Pass area), and in the paths along the Seward Highway south of Girdwood. These avalanches were averaging around 2′ deep, although some were 4′ deep or deeper. Bigger avalanches were occurring on wind-loaded slopes. There are too many photos to include them all here, but it is definitely worth perusing the observations from yesterday to see some of the action.
There were multiple human-triggered avalanches on the back side of Seattle Ridge yesterday. This includes a snowmachine-triggered avalanche in Main Bowl, a large snowmachine-triggered avalanche in Warmup Bowl that ran over 1000′, and a skier-triggered avalanche on Widowmaker in which a skier was caught, carried, and was not buried after deploying an avalanche airbag. The skier that triggered the avalanche was the third set of tracks on the slope. More details in this observation.
|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|
As the skies cleared yesterday we were able to get a sense of a widespread natural avalanche cycle that occurred during the storm on Thursday and Friday. Based on what we saw yesterday in the field, it appears a lot of these avalanches failed at the interface between the storm snow and the old snow surface, which was a layer of stellars (i.e. snowflakes) on top of a very thin, brittle crust from warm temperatures on Wednesday. As clear weather continues today, we expect this layer may still be reactive, which means a person could still trigger a large avalanche 2′ deep or deeper. This will be most likely on upper-elevation slopes that had been wind loaded during the tail end of the storm. We received reports of multiple human-triggered avalanches yesterday in the back bowls of Seattle Ridge (details here).
With good visibility and calm winds today, the urge to get out in the alpine will be strong. It will be important to keep these lingering instabilities in mind, and approach steep terrain with caution. Be on the lookout for warning signs like shooting cracks, collapsing, and more avalanche activity. Seek out more information by using smaller test slopes to test for reactivity. Take the time to hop off your machine or step off the skin track and poke into the snow to see if the storm slab still wants to pop off the layer of older snow. Any of these signs are bulls-eye data that the conditions are dangerous. Keep in mind this note from the Widowmaker avalanche: “No obvious red flags. Ski cut and cornice cut did not effect the slope. The avalanche released on a slightly steeper, more wind loaded aspect. 3rd skier triggered the slope.” This may be a tricky problem to assess, with a high level of uncertainty as to just how reactive these lingering instabilities may be.
As the old saying goes, when the snowpack is the question, terrain is the answer. Stay safe today by avoiding steep, wind loaded slopes. As always, be sure to travel one at a time and keep an eye on your partners. It is looking like today is going to be a fantastic day in the mountains. But a sunny weekend day immediately following a storm means the crowds will be out, and this is the kind of situation where accidents are most likely.
Cornices: The moderate to strong winds during the recent storm have built large cornices. Some of which have already failed naturally. It is very likely these fresh cornices will fail under the weight of a person, so be sure to give them plenty of space while traveling along ridgelines.
Dry Loose Avalanches: With up to 2-3′ of soft snow on the surface, dry loose avalanches (sluffs) will be running fast with a large volume. These are unlikely to be big enough to bury a person, but they can have serious consequences if they carry you down steep, consequential terrain.
Video from the crown of one of the natural avalanches on Sunburst (linked here):
Yesterday: The clouds started breaking up, with some periods of full-on sunshine in the middle of the day. High temperatures were in the mid to upper 20’s F, and lows dropped down to the low teens F. Light westerly winds were blowing 5-10 mph, with no precipitation. Some valley clouds were forming intermittently.
Today: Clouds will continue to dissipate today, with some lingering low-level valley fog possible. Skies should be mostly clear later in the day. Temperatures are currently in the upper teens to low 20’s F, and are expected to drop slowly through the day into the low teens overnight. Winds are expected to remain light around 5 mph, and no precipitation is expected.
Tomorrow: Another day of fair weather is expected tomorrow, with mostly clear skies and light winds around 5 mph. High temperatures are expected in the upper teens to 20 F, and no precipitation is expected.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||26||0||0||95|
|Summit Lake (1400′)||18||0||0||34|
|Alyeska Mid (1700′)||25||0||0||N/A|
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||21||NW2||32||NW2|
1Winds shifted from easterly to westerly around midnight last night.
2Anemometer covered in rime and not reporting until 8 p.m.
|11/26/22||Turnagain||Observation: Eddies||Schauer/ Cullen Forecaster|
|11/26/22||Turnagain||Observation: Eddies||Andy Moderow|
|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|
|11/25/22||Turnagain||Observation: Top of Seattle Ridge uptrack||Nick Crews|
|11/24/22||Turnagain||Avalanche: Sunnyside/Main Bowl||Andy Moderow|
|11/23/22||Turnagain||Avalanche: Seattle Ridge||John Sykes 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.