Hatcher Pass Avalanche Center
Hatcher Pass

Hatcher Pass RSS

Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, November 17th, 2022 - 7:00AM
Expires
Fri, November 18th, 2022 - 7:00AM
Forecaster
Jake Kayes
Avalanche risk The Bottom Line

Put on your game face if you’re headed to Hatcher Pass today. Tricky avalanche conditions exist.

Small to large human-triggered persistent slab avalanches are possible at mid and upper elevations on all aspects. Remotely triggered avalanches are possible. Natural avalanches are unlikely.

In the last 24hrs 3 of the 6 red flags for avalanches have been observed: Recent avalanches, shooting cracks, and collapsing(whumping). 

Even a small avalanche could have severe consequences, due to shallow coverage and rocks.

Special Announcements

Thank you to all of our donors who make HPAC forecasting a sustainable reality. We will be thanking supporters individually, and to the many anonymous givers in our community, we send our deepest gratitude. 

To our new community members this season, welcome! Thank you for working with us to foster safer backcountry travel by reading the forecast and submitting your observations. 

Please consider investing in professional avalanche forecasting in Hatcher Pass by clicking the red Donate button at the top of the screen. 

Thu, November 17th, 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'
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

Marmot SW face 3800’ Human triggered avalanche on 11/16

Hatcher Pass Road Willow side 3000’ North aspect. Remote triggered by a snowmachiner on 11/15

Marmot Gully 3, ESE, 3600′ – Natural avalanches on 11/14

Powder Pimple SE aspect 2900’ human triggered avalanche on 11/15

Peak 4600’ NE aspect remote trigger by a skier on 11/15

Near Woman’s Run North aspect 4000’ Natural Avalanche 11/14

Lower Ray Wallace NW aspect 3700’ Natural Avalanche 11/14

Skyscraper North, 4300’- Natural Avalanche on 11/14

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

Small to large human-triggered persistent slab avalanches are possible at upper and mid-elevations, on slopes 30º or steeper. This avalanche problem will be found on all aspects. Remotely triggering an avalanche from a distance is a real concern today. 

The current snowpack structure is horrendously flawed and is still trying to adjust to the load from the storm on Nov 14th. Buried weak faceted snow can be found anywhere you look in the forecast area. What changes as you travel around the forecast area is the thickness of the slab sitting on top of these basal facets. It may be a week or more before we see significant improvement in stability.

In areas that are unaffected by the wind the snowpack is as thin as 10”. In areas with wind loading, the snowpack is up to three feet thick. 

Areas that were previously wind-loaded should be easy to visually identify. To visually identify previously wind-loaded areas look for wind-drifted snow and round lensed shaped features. 

A good example of previous wind loading on SW face of Marmot. Picture taken at 12pm on 11/16.

Same area as photo above. Human triggered avalanche around 3pm 11/16

We are in a tricky set of conditions where we will be tempted to recreate in the areas with better coverage. Unfortunately, this carries the added hazard of potentially triggering larger, deeper avalanches.

If caught in any size avalanche, the danger is compounded by shallow coverage, and the very real possibility of impacting rocks at high speed, potentially injuring or killing a person.

Tracks on slopes are not a sign of stability and should not be trusted to indicate safer locations to recreate. More than one avalanche has been triggered this week, with multiple sets of tracks already on the slope. Unfortunately, this means it’s very difficult to predict where and when triggering an avalanche will occur. 

Recent avalanches, shooting Cracks, and whumping are all red flags for this avalanche problem. Use formal stability tests, pole probes, and hand pits to help you identify areas with a dense slab with weak snow underneath 

Today’s travel advice is:

  • Avoid slopes 30º degrees and steeper.
  • Avoid traveling underneath steep slopes.
  • 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!

 

Weather
Thu, November 17th, 2022

NWS AVG Forecast here.

NWS point forecast here.

Marmot Weather Station here.

State Parks Snow Report and Motorized Access information here.

Observations
Recent Observations for Hatcher Pass