Hatcher Pass Avalanche Center

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ARCHIVED - Forecasts expire after 24 hours.
Thu, December 7th, 2023 - 7:00AM
Fri, December 8th, 2023 - 7:00AM
Allie Barker
Avalanche risk The Bottom Line

The persistent slab problem continues to be on our radar and is slowly strengthening over time.

It has been 10 days since the last significant avalanche cycle.

3-5″ of new snow over the past 24hrs will greatly improve riding conditions today.

Another pulse of snow is expected late Thursday.

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Thu, December 7th, 2023
Upper Elevation
Above 3,500'
2 - Moderate
Avalanche risk
Mid Elevation
2 - Moderate
Avalanche risk
Low Elevation
Below 2,500'
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 last reported avalanches were observed or reported on 11/27-28.

See observations from this week HERE. 


Recent Conditions

Conditions have improved over the past 24 hours thanks to 3-5″ of new snow. Expect a variety of bed surfaces under the new snow to consist of old wind slabs, old firm wind crusts, and low density deteriorating wind slabs at low elevation.


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

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 will be possible to human trigger a persistent slab on all aspects, at mid and upper elevation, on slopes steeper than 30º.  Triggering a slab at low elevation is unlikely. Natural avalanches are unlikely.

Yesterday’s 3-5 inches of new snow will not contribute to today’s avalanche problem. The new snow is low density, lacks cohesion, and was deposited without wind.  The possibility of triggering a slab up to 3 feet deep still exists in specific locations, most likely upper elevation where weak sugary facets and facet crust layers still exist but are becoming harder to find.

Snowpack depth varies from 1 foot to over 3 feet deep and is generally thicker on northerly aspects where prevailing winds have deposited snow throughout the season. Southerly aspects, where prevailing winds have scoured snow throughout the season, are generally shallower. Shallower areas will be easier to human trigger, and locations with deeper snowpacks will be harder to trigger, but result in larger and more consequential avalanches.

As small incremental storms continue to bury the deeper weaker layers in the snowpack, performing hand shears, probe pole tests, and instability tests will continue to give us valuable information about the potential for propagation. We are trending towards seeing less propagation in our pits.

The avalanche above is likely from 11/27-28 on a NE aspect at 3300′ on Frostbite. This avalanche is a good example of the complexity of persistent slabs which can be difficult to assess, predict, and manage. In this case, new snow combined with strong wind overloaded the weak layer.  The avalanche stepped down into the persistent weak layer while sympathetically triggering another avalanche.

While this avalanche problem continues to linger, stability also continues to improve.  Since the basal facets were buried in early November we have witnessed numerous avalanche cycles with the basal facets responsible as the culprit weak layer. The Thanksgiving warm up provided moisture, warmth, and rain that assisted weak sugary snow to round and increase the stability, especially below 3500 ft. Without any additional significant loading events, expect the stability to continue to strengthen slowly over time.

Avalanche behavior may be difficult to predict. Use safe travel protocols to increase your margin of safety.

Thu, December 7th, 2023

3″ of new snow with 0.3″ SWE was reported at 2700′ /Frostbite over the past 24 hours.

5″ new snow with 0.5″SWE was reported at 3550’/IM over the past 24 hours.

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