Hatcher Pass Avalanche Center
Hatcher Pass

Hatcher Pass RSS

Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, December 8th, 2022 - 7:00AM
Expires
Fri, December 9th, 2022 - 7:00AM
Forecaster
Jake Kayes
Avalanche risk The Bottom Line

The most recent storm brought 2″ of water and between 18-20” of new snow to the forecast area. This new snow has caused stress on a crust in the middle of the snow pack and on the weak snow near the ground.

Human-triggered persistent slab avalanches 2-4’ deep are possible at all elevations and all aspects on slopes 30º or steeper. 

Human-triggered dry loose avalanches are possible in terrain 40º and steeper. 

Natural avalanches are unlikely. 

An avalanche of any size can have severe consequences near rocks, cliffs, gullies and other hazards.

The current height of snow at the Marmot Snow Stake at 3000’ is just shy of 3 feet. We just doubled our snowpack.

NWS forecasts are calling for strong winds from the north today. If this lasts for more than a few hours avalanche danger will increase rapidly. Pay attention to any signs of active wind loading at upper elevations and near ridge lines.

Special Announcements

Avalanche Education Scholarships: Get your application in today! See details CNFAIC HERE and HPAC HERE. Tell your friends!

Sponsorship Opportunity: We’re looking for two corporate sponsors for our webcams this season. Contact marissa@hpavalanche.org if you’d like your logo on the cam.

Don’t miss out on monthly updates from HPAC!  Sign up for our newsletter HERE!

Thu, December 8th, 2022
Upper Elevation
Above 3,500'
2 - Moderate
Avalanche risk
Mid Elevation
2,500'-3,500'
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

No new slab avalanches have been observed since Nov 16th. Visibility was extremely limited over the last few days, Natural avalanches may have occurred and not been reported or observed.

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

Starting on 12/5 18-20” of new snow has fallen with 2” of SWE. Human-triggered persistent slab avalanches 2-4’ deep will be possible at all aspects and elevations on slopes 30º or steeper. Natural avalanches are unlikely. If an avalanche does occur it will likely fail on a recent rain crust (12/5) in the mid-pack and step down or fail at the ground. It has been 24 hours since the last snowfall and stability is expected to be slowly improving.

The rain crust failed on isolation in this stability test. The rain crust is buried about 1 foot deep.

Collapsing and shooting cracks will be red flags for this avalanche problem. Additional ways to identify this avalanche problem are to use hand pits, pole probes, and other traveling tests. Feel for a crust about one foot below the surface and look for weak sugary faceted snow on the ground. Formal Stability tests will also help you identify this avalanche problem.

The current snowpack has a flawed structure and tests have been failing on isolation. Be thoughtful about the slopes you travel on if you decide to head into avalanche terrain. Start on small low consequence terrain features before exploring large steep slopes. Have a plan and use terrain progression to stack the odds in your favor. 

An avalanche of any size will likely have severe consequences due to the fact it will fail near the ground, increasing the chance of traumatic injury.

Continue to use safe travel protocol in avalanche terrain:

  • SPREAD OUT when ascending.
  • Descend ONE at a time and regroup in identified safe zones.
  • Avoid riding above or near cliffs, rocks, gullies or other hazards.
  • As always, carry a transceiver, probe, and shovel, and know how to use them!
Avalanche Problem 2
  • Dry Loose
    Dry Loose
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
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

With 18-20” of new snow human-triggered dry loose avalanches will be possible on slopes 40º or steeper. If you do choose to venture into steeper terrain use good sluff management, to avoid being swept over cliffs and other hazards. 

 

Weather
Thu, December 8th, 2022

NWS AVG Forecast here.

NWS point forecast here.

Marmot Weather Station here.

Independence Mine Snotel here.

State Parks Snow Report and Motorized Access information here.

Observations
Recent Observations for Hatcher Pass