Hatcher Pass Avalanche Center
Hatcher Pass

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Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, November 25th, 2023 - 7:00AM
Expires
Sun, November 26th, 2023 - 7:00AM
Forecaster
Jed Workman
Avalanche risk The Bottom Line

Avalanche stability at Hatcher has improved slowly with warm temperatures, but we are not out of the woods yet.

A lingering persistent weak layer at the base of the snowpack continues to be problematic. Human triggered persistent slab avalanches up to 3 feet deep will be possible to trigger on all aspects at the mid and upper elevations.

At the upper elevation, remotely triggering a large persistent slab avalanche is still a concern.

Recent avalanches, shooting cracks, and collapsing are red flags for this problem. Stiff snow over weaker snow is also an indicator of this problem and is easy to identify with probing.

At the lower elevations, small but manageable loose wet avalanches may be possible on steep slopes.

Make sure to study up by reading the previous forecast by clicking on the “archives” button in the upper right corner of the web page. This season’s avalanche problem is an ongoing issue worth familiarizing yourself with.

Special Announcements
Wednesday, November 29, 6:00PM
Bearpaw River Brewing Company Taproom (Palmer-Wasilla Hwy)

Join HPAC as we host local guide, avalanche instructor, and author Joe Stock for a presentation marking the release of his newest book, “The Avalanche Factor.” Joe will talk about the book and dive into one of its topics, luck and avalanches.

Sat, November 25th, 2023
Upper Elevation
Above 3,500'
2 - Moderate
Avalanche risk
Mid Elevation
2,500'-3,500'
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

No new avalanches were reported yesterday. Ther last significant avalanche reported was on 11/18.

See previous forecasts and observations for pictures and information on the early season avalanche cycles.

Recent Conditions

A rain/snow mix is in the forecast today with a snow level line around 2000-2400′. The last freeze at 2500′ was on 11/22. Yesterday temperatures ranged from 35-42°F. Light rain persisted for much of the day, saturating the snowpack. The height of snow at 2000′ is 15″. Warm temperatures are forecasted to continue. We do not expect a good freeze until Monday.

We found a surface crust at 1500-2500′ yesterday that was quickly degenerating with rain and warmth.

The last freeze overnight at 3500′ was on 11/23, two days ago.

Overnight temperatures at 4500′ dipped down to 26°F for about 16 hours.

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • 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.
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

Mid and Upper Elevations: Persistent slabs up to 3 feet thick will be possible to human trigger in specific locations, on all aspects, at the mid and upper elevations. Two things are happening with the recent warming which will continue today. One, stability is increasing as snowpack layers and grains bond and round. We are seeing the weak basal facets beginning to round at mid elevation. Two, the slab component is gaining strength and cohesion. Slabs will be more stubborn to trigger, but any avalanche triggered will be larger in size having more propagation potential.

At the upper elevations, the snowpack has remained cooler, preserving the early season of October basal facets. This layer remains our primary concern. Remotely triggered large avalanches may still be possible.

Low Elevation: We do not expect the persistent slab problem at the lower elevations due to a shallow snowpack and recent rain.

The picture below is of an older avalanche, however, this failed on the same weak layer we are concerned about today and is representative of today’s problems.

11.18 Death Gully, remotely triggered by skier on SW face several hundred yards away. SS-ASr-D2.5-O

Avalanche Problem 2
  • Wet Loose
    Wet Loose
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
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

Rain yesterday combined with rain today and a lack of overnight freezing temperatures will make it possible to trigger small wet loose avalanches on all aspects on steep slopes at the lower elevation. With only 15″ of snowpack at 2000′, these will be manageable in size.

The next freeze is expected on Monday.

Weather
Sat, November 25th, 2023

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.

Observations
Recent Observations for Hatcher Pass