The avalanche danger is CONSIDERABLE above 1000′ as winds continue to drift new snow into sensitive slabs 2′ deep or deeper. Human triggered avalanches will be likely with natural avalanches possible on wind-loaded slopes, becoming larger and more sensitive as snowfall continues and winds increase during the day. Cautious route finding and conservative decision making is recommended.
The danger is MODERATE below 1000′, where it will be possible to trigger an avalanche about a foot deep in the storm snow that has fallen in the past two days.
PORTAGE/PLACER VALLEYS: Theses areas are expected to see at least double the snowfall of the rest of the core advisory area, making very dangerous avalanche conditions with natural avalanches likely and human-triggered avalanches very likely. Travel in avalanche terrain is not recommended in the Portage and Placer valleys.
Fri, January 28th, 2022
Alpine
Above 2,500'
3 - Considerable
Treeline
1,000'-2,500'
3 - Considerable
Below Treeline
Below 1,000'
2 - Moderate
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Travel Advice
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Natural avalanches likely; human-triggered avalanches very likely.
Natural and human-triggered avalanches certain.
Avalanche Size and Distribution
Small avalanches in isolated areas or extreme terrain.
Small avalanches in specific areas; or large avalanches in isolated areas.
Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.
Large avalanches in many areas; or very large avalanches in specific areas.
Very large avalanches in many areas.
Avalanche Problem 1
Wind Slabs
Certain
Very Likely
Likely
Possible
Unlikely
Likelihood
Historic (D4-5)
Very Large (D3)
Large (D2)
Small (D1)
Size
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing
avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and
natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.
Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question.
Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to
hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are
relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure,
or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.
The steady flow of snowfall continues this morning, with another 6-9″ snow expected during the day today. Since the snow started accumulating early Thursday morning, storm totals are currently around 12-16″ in the mountains near Girdwood and 8-10″ at Turnagain Pass, with higher totals in the Portage and Placer valleys. The snow line has stayed below 500′ so far, but is expected to rise up to 1000′ by the end of the day today. Easterly winds have been blowing 10-20 mph near ridgetops with gusts at 30-40 mph, and are expected to bump up to 15-25 mph later today. As the snow continues to fall and winds increase slightly during the day, avalanches will become larger and easier to trigger. Conditions will be the most dangerous on wind loaded slopes, which will most likely be found near ridgelines, on convex rollovers, and in gullies. As snow stacks up during the day, be on the lookout for storm slab avalanches a foot deep or deeper on sheltered slopes as well. These wind slabs and storm slabs will usually give you warning signs of unstable conditions including shooting cracks, collapsing, and fresh avalanche activity, so pay attention as you travel in the mountains today.
In addition to the avalanche concerns related to the new snow, there is an outside chance that a person could trigger a larger avalanche on weak snow near the New Year’s crust, which is buried somewhere around 2-6′ deep. This is a tricky problem (which I attempt to explain in the video below, linked here), with high uncertainty and low likelihood. The only known recent activity on this weak layer was a large human-triggered avalanche on Tincan Proper last Thursday (details here). Continued stormy conditions will make travel in the alpine dangerous enough on their own today, but it will be important to keep this layer in mind as well, as one more reason to back off the bigger objectives. This will become more relevant as the storm breaks up over the weekend, but this issue will linger.
Loose Dry Avalanches (Sluffs): Yesterday we found it easy to trigger loose dry avalanches, which were running fast and picking up volume in the new snow. These will be getting larger and easier to trigger throughout the day, with natural avalanches likely as the snow continues. While it is unlikely a dry loose avalanche would bury a person, they can be big enough to carry an unwary traveler into terrain traps like trees, rocks, cliffs, or gullies.
Cornices: As snow continues to fall and winds continue to blow, cornices will grow and remain sensitive to human triggers. As always, give them plenty of room when you are traveling along ridgelines.
Dry loose debris on a small test slope at treeline on Tincan ridge yesterday. 01.27.2022
Weather
Fri, January 28th, 2022
Yesterday: Light snowfall brought 3-6″ to the mountains near Girdwood and only an inch at Turnagain Pass over the past 24 hours. Skies were mostly cloudy with some periods of sun poking through, with high temperatures in the mid 20’s to low 30’s F and lows in the mid 20’s F. Rain level stayed below 500′, with snow to sea level this morning. Winds were out of the east at 5-20 mph with gusts of 35-45 mph.
Today: Snow is expected to continue today, with another 6-9″ near Girdwood and Turnagain Pass, 14-20″ near Portage and Placer, and only 1-2″ at Summit Lake. Easterly winds are expected to pick up slightly throughout the day, blowing 15-25 mph with gusts of 30-40 mph by this afternoon. Rain level is expected to creep up to around 800-1000′ as temperatures hover in the upper 20’s to low 30’s F.
Tomorrow: Snowfall is expected to taper off by tomorrow morning, with another 2-4″ possible overnight tonight. Temperatures are expected to hang in the mid 20’s F overnight and slowly drop into the upper teens F during the day tomorrow. Winds are expected to back down to 5-10 mph out of the northwest, with clouds starting to break up as the low pressure center that has been bringing the snow exits to the east.
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.
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