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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, January 29th, 2023 - 7:00AM
Expires
Mon, January 30th, 2023 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is MODERATE above 1,000′ on all aspects. Triggering a large slab 2-3′ deep on a layer of buried surface hoar is becoming less likely, but is still possible. Upper elevation slopes without surface crusts are the most likely places to trigger a large slab. Additionally, blustery ridgetop winds could form some small wind slabs in the higher terrain through the day. The danger is LOW below 1,000′.

SUMMIT LAKE/LOST LAKE/SNUG HARBOR: Similar conditions are expected in these areas as well. Summit Lake in particular has a very shallow and weak snowpack. Triggering a slab avalanche could be more likely in this area of the interior Kenai Mtns.

Sun, January 29th, 2023
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
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. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. 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.
Recent Avalanches

The only avalanche activity yesterday we saw or know of were many small to medium sized wet loose avalanches on steep southerly aspects. Some of these were able to pull out small slabs of snow around a foot deep or so.

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

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.

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
More info at Avalanche.org

It was an impressive springlike day for January. Temperatures were near 32F along the ridgetops. The steep southerly facing slopes heated up enough to dampen the surface snow to the point where natural wet loose avalanches were occurring. These aspects are likely to be sporting a bit of a crust now. However, even with the warm up and some wet loose avalanches, we did not see or hear of any slabs breaking in the buried surface hoar 2-3′ deep. Good news. For today, ridgetop southeast winds could blow just enough in some areas to form shallow wind slabs. Watching for active wind loading will be good if traveling along ridges.

The main concern however is triggering a 2-3′ deep slab on that layer of surface hoar that was buried on Jan 10th. The chances for triggering one of these slabs is much less likely than it was a week ago, when folks were popping these off left and right. As many know, a surface crust exists up to 2,000′ (ish). This can help to stabilize the pack in the lower half of the mountains, but the upper half is still a concern. These slabs can be triggered after tracks are on a slope and we are not likely to see any signs of instability to help warn us. This creates a tricky situation, one that we have had to deal a lot with this season.

As the days go by we are finding variable results in our pit tests, and folks are beginning to push into the steeper terrain without incident. We have transitioned into a lower likelihood, but still high consequence situation. If choosing to get onto the steeper terrain above 2,000′, especially the shady (no surface crusts) terrain, remember this layer is lurking. Having all our safety nets out is key. That means exposing one person at a time, have escape routes planned, make sure your partners are watching and they know how to use their rescue gear if the slope slides. Also, remember these slabs have the potential to propagate quite wide, making them large and unmanageable.

Click here to view the video below if it does not load in your browser.

 

Believe it or not, our friends to the south have been dealing with a very similar snowpack. They just posted this great article describing the difficulty with problematic buried weak layers. Check it out! Deep Persistent Slab Management and Mindset.

 

Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

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.

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
More info at Avalanche.org

At the base of the snowpack are those old facets around the Thanksgiving crust. These are buried between 4-8′ deep across the forecast zone. Although it’s been three weeks since the last known avalanche on these layers (Cornbiscuit on 1/7), we are still keeping them on our radar. It’s unlikely a person will trigger this deep layer, but an outlier avalanche could happen if a person hits just the right (or wrong) thin spot or an avalanche in the layers above steps down and triggers a larger slab. Moving forward this problem is heading to a dormant phase, which means it may not react until it gets a new load of snow. This is a typical pattern for these Deep Persistent Slab avalanche problems.

 

Gotta love Turnagain Pass on these sunny days. However, those southerly slopes were baking yesterday. Clouds today with cooler temps should keep those sun crusts from softening. 1.28.23.

Weather
Sun, January 29th, 2023

Yesterday:  Sunny skies were over the region with very light variable winds along ridgelines. Temperatures were near 32F at all elevations, even those near 4,000′.

Today:  High clouds are forecast to move in today with some breezy SE winds. Ridgetops should see winds around 10-15mph with some stronger gusts. Temperatures have dropped to the mid to upper 20’sF at all elevations. Light snow flurries are expected this evening with only a trace of accumulation (light rain below 1,000′).

Tomorrow:   Partly cloudy skies are slated for tomorrow. Ridgetop winds should stay SE, in the 10-15mph range. No precipitation is expected. The next snowfall doesn’t look to be for several days, expect for maybe an inch or two on Tuesday if we’re lucky.

PRECIPITATION 24-hour data (6am – 6am)

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 30 0 0 63
Summit Lake (1400′) 27 0 0 33
Alyeska Mid (1700′) 29 0 0 65
Bear Valley – Portage (132′) 29 0 0

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 32 var 4 13
Seattle Ridge (2400′) 29 var 3 11
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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.