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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, February 7th, 2024 - 7:00AM
Expires
Thu, February 8th, 2024 - 7:00AM
Forecaster
Mik Dalpes
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 2,500′ today. A storm bringing mostly wind has arrived creating fresh wind slabs up to one foot deep. This new load will add stress to a weak layer of snow buried in the snowpack that could produce a larger avalanche two feet deep or more. This deeper weak layer could be found anywhere and is more difficult to identify so the best way to avoid this problem is to stick to slopes less than 30 degrees. Below 2,500′ the danger is MODERATE where the same concerns exist and a large avalanche is possible.

Special Announcements

We are sad to share the news of an avalanche fatality last Friday (February 2) near the Knik Glacier. Initial reports indicate a skier on a heli-ski trip was caught in a dry loose avalanche and sustained fatal injuries after being carried over a band of rocks. We extend our sincere condolences to the skier’s family and friends. These incidents can be traumatic for all involved and our thoughts are with the guides and their community as well. You can find a preliminary report of the incident here.

Chugach State Park:  A skier triggered two avalanches in the Falls Creek area on Sunday, check out the update on the CSP Outlook page.

Peninsula Powersports in Soldotna will be hosting us tomorrow, Thursday, Feb 8, 5-6pm. Come by and meet the new forecasters, talk about the state of the snowpack in Summit and Seward, and hear about our “Avalanche Weekend Outlook,” a new forecasting tool we started publishing this year for Summit and Seward!

SnowBall 2024:  Mark your calendars for Valentine’s Day, Feb 14 (7-11pm @ 49th St Brewing). The evening promises costumes, finger food, a rocking band, silent auction, and of course plenty of great company. Join us in supporting Chugach Avy as well as our friends at the Alaska Avalanche School. Details and tickets HERE.

Wed, February 7th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Thu, February 8th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Thu, February 8th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
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

A handful of new dry loose avalanches were observed yesterday in steep terrain. Otherwise, there have been no new avalanches reported since last weekend when three separate human triggered avalanches occurred. Two of these were in the Turnagain forecast zone (Tincan’s Library and Girdwood’s Raggedtop) and one was slightly west of Girdwood in Falls Creek pictured below. We believe the weak layer in all of these avalanches was weak snow from January. Everyone is ok and we are grateful for the information sharing that helps us all learn and prevent future incidents.

Skier triggered avalanche in Falls Creek (Chugach State Park just outside the Turnagain zone) from Sunday. Photo credit Mike Records, 2.4.2024.

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Aspect/Elevation
  • 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.
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

A storm has arrived that is bringing mostly wind and up to 1″ of new snow to Turnagain Pass today. There is also up to 1′ of snow from the last week of storms available to be blown around. Ridgetop winds on Sunburst are coming from the east in the 10-20’s mph as of this writing gusting in the 30-40s mph. This wind will be forming fresh wind slabs in the upper elevations up to 1′ deep. It will be possible to find this problem in exposed areas of the treeline elevation band as well.

Watch for snow blowing off ridgelines or cross loading gullies (example pictured below). Finding a slab in a cross loaded gully might mean you are several turns into your line or mid-way into a climb on your machine when you encounter stiff snow over softer snow. These wind slabs may stick around longer and be larger than expected due to a weak layer buried in the snowpack explained in problem 2.

Examples of a cross loaded gully on Seattle Ridge where wind has come across the feature rather than from above depositing snow on the looker’s right side of the gully. 2.6.2024

Avalanche Problem 2
  • 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

We believe the human triggered avalanches last weekend failed on a layer of weak snow (near surface facets) that formed during the cold spell in January. The new wind slabs that are forming today are adding stress to that weak layer and introducing the weight of a person or machine could tip the balance. We have some uncertainty as to how widespread this layer is, but with the information we have (recent avalanches and snowpits) we think it exists in places around the compass and in all elevation bands. With up to 1′ of new snow on top of this layer in places and several rounds of wind loading these avalanches could be 1-3′ deep.

Persistent slabs can be more stubborn and difficult to test and a snowpit is the best assessment tool for this problem. Test for strength with a compression test (CT) and energy with an extended column test (ECT) and let us know what you find!  Hand pits and test slopes may give you misleading information, but shooting cracks and whumpfing are clear signs of unstable snow. This problem can heal with time and until that happens the only way to completely avoid this problem is to avoid slopes greater than 30 degrees.

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

We are still concerned about glide avalanches despite the lack of activity in the last week. There are open glide cracks in all of the most popular riding areas and with limited visibility today we recommend looking closely for these cracks and avoiding them when possible.

Weather
Wed, February 7th, 2024

Yesterday:  A beautiful calm day yesterday was a break between the storms with mostly clear skies. A light west wind switched to the east in the afternoon on the ridgetops and temperatures were in the low 20s F.

Today:  A storm will be passing through today that will be mostly wind and a little bit of snow. Clouds moved in last night and ridgetop winds on Sunburst have picked up as of this writing and are expected to blow from the east at 20-30 mph gusting in the 40’s mph. Temperatures should be in the mid to upper 20s F and up to 1″ of new snow is forecast for Turnagain Pass.

Tomorrow:  Tomorrow we should see a short break, the sun may poke through the clouds and winds look to calm before a much bigger storm arrives Thursday evening. At this time the models are showing a warmer storm with 1-2′ of new snow possible above 1,000′, we will keep you posted!

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 23 0 0 78
Summit Lake (1400′) 15 0 0 n/a
Alyeska Mid (1700′) 27 0 0 84
Bear Valley – Portage (132′) 20 trace 0.07 –
Grouse Ck – Seward (700′) 20 0 0 55

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 20 E 6 47
Seattle Ridge (2400′) 22 SE 6 24
Observations
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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.
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