Hatcher Pass Avalanche Center
Hatcher Pass

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, November 18th, 2021 - 7:00AM
Expires
Fri, November 19th, 2021 - 7:00AM
Forecaster
Jake Kayes
Avalanche risk The Bottom Line

Loose Dry is today’s avalanche problem. 

Human triggered Loose Dry avalanches are possible at all elevations in terrain that’s 40° or steeper. While these avalanche’s have decreased in size over the last week, they have increased in speed. Natural avalanches are unlikely.

If you do get caught in an avalanche, rocks, cliffs and other shallowly buried hazards will increase the danger. The snow depth is highly variable and is dependent on elevation and aspect.

Heads up for another cold day in the mountains, especially if the winds pick up.

There is some uncertainty with winds in the forecast this afternoon. Any sustained winds will build wind slabs sensitive to human triggers.

Special Announcements

HPAC is still accepting applications for the Johnny Soderstrom Memorial Scholarship. Click here for more info. Applications are due by Nov 26th. 

Thu, November 18th, 2021
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

There have been numerous human triggered, small, Loose Dry avalanches this past week.

Small human triggered Dry Loose, Upper Eldorado 4600′ NE

Avalanche Problem 1
  • 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

Cold weather and calm winds have allowed the old snow near the surface to remain low density. Small Loose Dry avalanches are possible on slopes 40° or steeper, on all aspects and at mid and upper elevations. At lower elevations, loose dry avalanches will be lower in volume.  Human triggered avalanches are possible, natural avalanches are unlikely. 

While these avalanches have decreased in size, they will gain speed quickly. Don’t let your guard down with these Loose Dry avalanches. Small avalanches can still have high consequences when traveling above rocks, cliffs, and gullies. Know what’s below you and practice good slough management. 

The snowpack depth in Hatcher Pass is highly variable at the moment. Overall snowpack depth is highly dependent on elevation and aspect. There is less than a foot of snow at lower elevations. At the mid elevations the snowpack is averaging two feet in depth.  At upper elevations, the north aspects have as much as 3 feet of snow. On south aspects at the same elevation the snowpack is much shallower, with rocks and tundra just below the surface.

Small human triggered Loose Dry on Marmot NNW 3700′

The snowpack lacks any major structural issues and is right side up.

Additional Concern
  • Wind Slabs
    Wind Slabs
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
More info at Avalanche.org

Wind slabs are not a concern this morning. However, the forecast is calling for the potential for winds increasing to 15-30mph from the NE. With an abundant amount of low density snow available for transport, winds slab may form quickly on South thru West aspects. Any wind slabs formed will be sitting on weak faceted snow and be sensitive to human triggers.

Be on the look out for any signs of recent winds if you head out into the mountains today. Look for blowing snow near ridge tops and smooth drifted snow. Whumping and shooting cracks are red flags for this avalanche problem.

Hopefully any wind event will be short lived and spare the good riding quality.

Weather
Thu, November 18th, 2021

NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

Observations
Recent Observations for Hatcher Pass