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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, January 31st, 2024 - 7:00AM
Expires
Thu, February 1st, 2024 - 7:00AM
Forecaster
Daniel Krueger
Avalanche risk The Bottom Line

The avalanche danger is MODERATE at all elevations. East winds created fresh wind slabs 1-2′ deep yesterday and new wind slabs will also be forming today as winds pickup throughout the day. It is also possible to trigger an avalanche in the new snow in sheltered areas, especially where more new snow fell over the weekend like in Girdwood and Portage. Additionally, glide avalanches remain a concern and cracks that have not released are much harder to see now due to the new snow. Look out for red flags and be prepared to change travel plans.

Special Announcements

CHUGACH STATE PARK:  A foot of light snow fell in Anchorage’s Front Range last weekend, followed by southerly winds blowing the new snow into wind slabs. Additionally, the new snow may become more cohesive over time increasing the likelihood of a soft slab avalanche. Look for red flags and be prepared to change travel plans if you observe unstable conditions. Check out these two observations to get a sense of the current conditions HERE and HERE.

RESCHEDULED for Feb 3rd!
Anchorage (Glen Alps): The Avalanche Rescue Skills Workshop will be this Saturday. The event is hosted by the Anchorage Nordic Ski Patrol and Friends of Chugach Avy. Come anytime between 10:30am and 3:30pm to practice with your rescue gear. Several stations will be set up and folks available to assist and ask questions. Cross your fingers the weather isn’t too cold this time.

Wed, January 31st, 2024
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Thu, February 1st, 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 1st, 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

Cloudy skies and limited information has made it hard to assess the extent of natural avalanches from this new load of snow. In the Girdwood area two small skier triggered slab avalanches 15-20″ deep at the new/old snow surface were reported yesterday. Storm slab avalanches were also reported in Summit Pass. At the moment no new avalanches have been reported in the Turnagain Pass area.

Soft Slab 15-20″ deep on Orca at 1300′ on a weak layer at the new/old snow surface. Photo by Grant Slesser 1.30.2014

 

Slab avalanche in Summit Pass yesterday, this is out of the forecast area but similar conditions exist across the region. 1.30.2024

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

Moderate winds out of the northwest (10-20 mph) easily transported the light storm snow into touchy winds slabs yesterday (ob here). Although northwest winds were lighter overnight, triggering a wind slab is still possible today. In more wind loaded places these may be large enough to bury a person such as below ridges, rollover convexities, and cross loaded gullies. Red flags such as blowing snow, shooting cracks and stiffer snow over softer snow are great indicators you are traveling on a wind slab. Assess conditions as you travel and change your plan if wind slabs are deeper and more sensitive to triggering, choosing less wind affected areas.

Storm Slab: There was a big difference in the amount of new snow that fell in Girdwood and Portage (15-20″) versus Turnagain Pass (8-10″) over the weekend. In areas that received more new snow it is possible for people to trigger storm slabs in areas sheltered from the wind at the interface with the old snow surface. The layer of new snow has only produced small avalanches so far, possibly due to the fact that the snow is very cold and low density therefore not prone to acting like a cohesive slab. As the new snow settles into a more cohesive layer we could see larger avalanches at the interface with the old snow surface, but we are uncertain how much of a factor that could be in the coming days.

Dry Loose and sluffing snow are likely on steeper slopes. This could become an issue because there is ample snow to slide, entrain, or carry a person off of a cliff.

Rippled texture from wind transporting snow into wind slabs in Summit Pass similar to surface conditions in Turnagain.   1.30.2024

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

Glide cracks are now covered in new snow, making it even more difficult see where they are and avoid traveling under them. When making a travel plan if you are unsure where these now hidden glide cracks are, look back at past observation photos to indicate where some of these are located. As always avoid being under these glide cracks because they can be large and release spontaneously. If you do not have an alternate route limit time under them, expose one person at a time, and move efficiently under them.

Glide avalanche in Summit Pass covered in snow. 1.30.2024

Weather
Wed, January 31st, 2024

Yesterday: Clouds and valley fog lingered throughout the day with sunshine in the afternoon. Ridgetop winds from the northwest decreased from 20-10mph. A trace of snow fell with little accumulation. Otherwise, it was another cold day with temperatures around 0F to -10F.

Today: A few clouds in the morning dissipating to clear skies, Ridgetop winds from the northwest are expected to be 5-15mph increasing throughout the day with 25mph gusts.  Northerly winds averaging 15-30mph and 50mph gusts are forecast along the coastal areas near Portage, Whittier, and Seward. Unfortunately, cold temperatures are expected to continue (-15F to 0F).

Tomorrow: Mostly clear and sunny skies. Sustained ridgetop winds (15-20mph) from the west are forecast to increase throughout the day with gusts 25-35mph.  Temperatures will remain cold with a high of -5F expected and a low of -20F.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 0 1″ .1 80
Summit Lake (1400′) 0 0 0 n/a
Alyeska Mid (1700′) 0 0 0 84
Bear Valley – Portage (132′) 0 0 0

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) -8 W 6 11
Seattle Ridge (2400′) -6 NE 3 5
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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