Hatcher Pass Avalanche Center

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ARCHIVED - Forecasts expire after 24 hours.
Thu, March 2nd, 2023 - 7:00AM
Fri, March 3rd, 2023 - 7:00AM
Jake Kayes
Avalanche risk The Bottom Line

The avalanche danger is MODERATE at all elevations.

Human-triggered persistent slab avalanches 4 to 12 inches thick are possible at all elevations and on all aspects, on slopes 35 degrees and steeper. These avalanches will be small to large in size.

In isolated and extreme terrain at upper elevations on leeward aspects, triggering a persistent slab avalanche even deeper is possible. 

Natural Avalanches are unlikely.

Thu, March 2nd, 2023
Upper Elevation
Above 3,500'
2 - Moderate
Avalanche risk
Mid Elevation
2 - Moderate
Avalanche risk
Low Elevation
Below 2,500'
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

Since the last forecast there have been 2 human-triggered slab avalanches and one human-triggered cornice fall. For more info on human triggered avalanches click here and here.

Human triggered cornice above Rae-Wallace Chutes 4500′ Feb 26th

A picture looking up at the human triggered cornice. The cornice fall was able to entrain a significant amount of low density snow, creating a large pile of debris. Feb 26th

Small human triggered persistent slab avalanche. Microdot, South Aspect. Feb 25th.

Small human triggered persistent slab avalanche. Nosehairs, South aspect Feb 27th. Photo credit Heather Johnson


Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Certain
    Very Likely
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
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.

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

On Feb 28th a storm brought strong SE winds that lasted for 12 hours with gusts up to 28mph at 4500 feet. 6 inches of snow fell and 0.5 inches of SWE. This new snow and wind will increase the thickness of slabs sitting on top of weak sugary snow.

Small to large human-triggered persistent slab avalanches are possible at all elevations and all aspects. These avalanches will be 4 to 12 inches thick.

On slopes 40 degrees and steeper on South thru West aspects, a thin sun crust formed on Feb 19th and has acted as a bed surface for two small human-triggered avalanches on Feb 25 and 27th. This will be the most likely location to trigger an avalanche today.

More unlikely locations to trigger an avalanche are isolated areas and extreme terrain at upper elevations, where the snowpack is thinner and triggering an avalanche even deeper is possible. The snowpack is thinner on Arkose Ridge, slopes that have previously avalanched, and areas that have received significantly more wind.

A trend that forecasters have observed over the last two weeks is that these persistent slab avalanches need a smooth bed surface to slide on. These bed surfaces will either be a sun crust or old smooth wind slabs. All of these bed surfaces have weak sugary facets sitting on top of them.

Identifying this avalanche problem may be difficult due to sun crusts forming on slopes steeper than 40 degrees. On slopes that are less than 40 degrees, it’s important to realize that a sun crust may not have formed everywhere. The persistent slab problem does not exist everywhere. With these current conditions, make sure that your traveling tests and formal tests are representative of what you are going to descend.

A small human triggered avalanche on the south face of Microdot, Feb 25th

Shooting cracks and collapsing will be red flags for this avalanche problem. 

As always use safe travel techniques if you decide to travel in avalanche terrain. This means spreading out when ascending, traveling downhill one at a time, and regrouping out of the runout of avalanches.

Dry Loose: The 6 inches of new snow that fell on Feb 28th has added more low density snow that is capable of producing dry loose avalanches. On leeward features and areas protected from wind, human-triggered dry loose avalanches are possible. These avalanches will be found at all elevations on slopes 40 degrees and steeper. Dry loose avalanches will be small to large in size. 

If you choose to travel in steep terrain good sluff management will be important. 

Additional Concern
  • Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
More info at Avalanche.org

It’s also worth noting that cornices have grown large at upper elevations and near leeward features. A backcountry user unintentionally triggered a cornice above Rae Wallace chutes on 2/26. The cornice that fell was able to entrain a large amount of snow and could have easily injured or buried someone.

This occurred near a common uptrack used to access the Rae Wallace Chutes. Think twice before deciding to ascend steep slopes if cornices are present and other parties are above you.

Give cornice’s a wide berth and realize that they often break further back than anticipated.

Large cornices on Marmot 4500′ above Rae-Wallace Chutes

Thu, March 2nd, 2023

Feb 28th storm snow totals:

Independence Mine 3550′: 6 inches of new snow, 0.5 inches of SWE

Frostbite Bottom 2700′: 3 inches of new sow, 0.4 inches of SWE

NWS AVG Forecast here.

NWS point forecast here.

Marmot Weather Station here.

Independence Mine Snotel here.

Frostbite Bottom Snotel here.

State Parks Snow Report and Motorized Access information here.

XC trail grooming report for Mat-Su, Anchorage, and Kenai here.

Recent Observations for Hatcher Pass