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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, January 1st, 2024 - 7:00AM
Expires
Tue, January 2nd, 2024 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

Happy New Year! We’re kicking off 2024 with MODERATE avalanche danger above 1000′. Easterly winds are backing off slightly today, but will still be strong enough to move snow into sensitive wind slabs up to 6-12″ deep that may be easy to trigger. We are also concerned with the alarming rate of glide activity over the past two weeks and expect that glide avalanches remain an issue today. Avoid traveling on or below open glide cracks since they may produce very large and destructive avalanches without warning. The danger is LOW below 1000′.

Mon, January 1st, 2024
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
Tue, January 2nd, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
Tue, January 2nd, 2024
Alpine
Above 2,500'
3 - Considerable
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

There were no new avalanches reported yesterday. The most recent activity is the ongoing glide cycle that we’ve been witnessing from Girdwood to Summit, including ongoing activity on Seattle Ridge, and new activity on the north end of Fresno Ridge.

New glide activity on Fresno Ridge. Photo: Trevor Clayton, 12.30.2023

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

We’re easing into 2024 with a quick break in the active weather today before things get exciting again in the middle of the week. The main player today will be the easterly winds, which will be slightly calmer than they were yesterday but will likely still be blowing snow around at upper elevations. Weather stations only picked up around 1-4″ snow yesterday, which has been getting blown into reactive wind slabs since it started falling. For today, those fresh wind slabs will remain the primary concern. With the winds backing down a little today, these avalanches should be smaller and slightly less reactive than yesterday, but they will still be something to watch out for and avoid.

Expect to find unstable snow in steep terrain just below ridgelines, convex rolls, and in steep gullies. If you are considering getting on a steeper slope, be  sure to assess the snow at the surface first. These new wind slabs have formed on top of weak surfaces, which could make them a bit more reactive than usual. Any warning signs like shooting cracks or collapsing are key indicators that the snow is capable of producing an avalanche. Travel tests like hand pits, test slopes, and simply stepping off the skin track or hopping off your snowmachine to feel the snow surface can be incredibly useful in assessing this type of problem. You can look for safer conditions and higher quality snow in sheltered terrain that hasn’t been affected by the wind.

Small slopes like this one near Lost Lake can be used to test for surface problems like the wind slabs we are concerned with today. 12.28.2023

Avalanche Problem 2
  • Glide Avalanches
    Glide Avalanches
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
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.
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’ve seen an unusually active period of glide activity over the past two weeks, and glide avalanches remain a concern today. Glide cracks have been opening and releasing at an alarming rate, and many of these are in high-traffic areas. This includes multiple glide cracks that are currently moving above common uptracks on the front and back sides of Seattle Ridge, and multiple glide cracks in busy ski terrain at Turnagain Pass and near Summit Lake. While it is impossible to predict exactly when a single slope will release, we’ve seen enough activity over the past two weeks to know that we need to treat these glide cracks with caution.

If it’s possible, consider using a different route where your common skin track or uptrack would take you under an open glide crack. If you can’t avoid traveling under a crack, be sure to limit the time you spend under it and only expose one person at a time to the hazard. An active glide crack may look like a big brown frown if it has opened enough to expose bare ground below, or it may only look like a cracked and wrinkled surface if it is just starting to open up. Keep in mind glide behavior is impossible to predict, and a glide crack may just barely form before releasing as a large and destructive avalanche.

Widespread glide activity along the ridge of Wilson South, viewed from Manitoba. Photo: Trevor Clayton, 12.30.2023

Two new glide cracks opening on Cornbiscuit right next to the one that released last Wednesday. Photo: Sean Fadeley, 12.30.2023

Weather
Mon, January 1st, 2024

Yesterday: Active weather moved in yesterday, complete with warming temperatures, strong winds, and a few inches of snow under cloudy skies. Most stations picked up 2-4” snow equaling only 0.1-0.3” SWE. Winds were out of the east at 15-35 mph with gusts of 45-60 mph. Temperatures climbed from the mid teens to low 20’s in the morning to the mid 20’s to low 30’s this morning. With those rising temperatures the rain line made it up to around 500 feet.

Today: It is looking like we will see a break in the weather today with partly to mostly cloudy skies and lingering valley clouds likely. We may see a trace of new snow with spotty showers, and winds should remain out of the east but back down to 10-20 mph with gusts of 20-30 mph. High temperatures will be in the mid to upper 20’s F today and drop back down to the high teens to low 20’s tonight.

Tomorrow: Stormy weather will pick up again tomorrow and continue to ramp up through Wednesday night. We should see easterly winds increase to 20-35 mph with gusts of 30-55 mph, getting stronger through the day. For now it is looking like we will only see 2-3” snow before the storm intensifies after sunset, possibly bringing a foot of snow through Wednesday. High temperatures will be in the mid 20’s to 30 F, with lows in the low 20’s F. The rain line will creep back up for this storm, making it up to around 1000-1500 feet.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 25 1 0.1 76
Summit Lake (1400′) 24 1 0.1 N/A
Alyeska Mid (1700′) 25 3 0.1 71
Bear Valley – Portage (132′) 32 mix 0.46 –
Grouse Ck – Seward (700′) 28 0 0.3 48

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19 ENE 20 54
Seattle Ridge (2400′) 23 ESE 9 22
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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