Hatcher Pass Avalanche Center

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, March 4th, 2021 - 7:00AM
Expires
Fri, March 5th, 2021 - 7:00AM
Forecaster
Jake Kayes
Conditions Summary

Today’s avalanche problems are Dry Loose and Persistent slab. It will be possible for humans to trigger small Dry Loose at all elevations on all aspects. Small to large persistent slabs 1-3’ thick will be possible at all elevations on East thru West aspects. Natural avalanches are unlikely.

Small avalanches can still be dangerous, especially if they sweep you into terrain traps.

Last weekend’s drizzle crust has created challenging riding conditions, this crust is more prominent towards the southwest end of the forecast area. In some locations the drizzle crust has been observed as high as 5000’.

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Thu, March 4th, 2021
Recent Avalanches

There have been four human triggered slab avalanches this week. 

3/2: Divide Ridge, W aspect 2700’ click here for more info.

3/2: West Face of Marmot 4000′ click here for more info.

2/27 South and East aspects of Government, 3500’, both remotely triggered from 300 yards away. Click here for more info.

Avalanche Problem 1
  • Dry Loose
    Dry Loose
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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

On 3/1 Hatcher Pass received 3-4” of new low density snow. Beneath this low density snow sits a ¼ inch, supportable to breakable drizzle crust which will continue to act as a smooth bed surface for dry loose sluffs. This low density snow will be capable of producing small Dry Loose avalanches at all elevations, and on all aspects, on slopes 35° or steeper. Human triggered avalanches are possible, natural avalanches are unlikely. The low density snow and crust are not bonding well. 

Although sluffs are moving medium to slow, we recommend using good sluff management if you decide to step out into steeper terrain. These avalanches will be small but can catch, carry and sweep you through hazards, if not managed properly. 

Dry loose in Eldorado Bowl

The drizzle crust is making a nice bed surface for the Dry Loose problem.

 

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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

Human triggered persistent slabs 1-3’ deep will be possible on East thru West aspects  at all elevations.. These avalanches will be small to large in size and have the potential to fail near the ground. Persistent slabs have a habit of being active and dormant for weeks to months. After several storms this week with light precipitation we saw remotely triggered and human triggered avalanches. Remotely triggering a persistent slab will be possible from the flats or from a far distance. 

In the upper portion of the pack 3-4” of new snow and the drizzle crust, sit on a layer of decomposing snow and sugary facets. Below this, In the middle of the pack lies an old weak sugary layer of facets. Near the base of the snowpack sits a layer of facets and depth hoar. 

This poor structure has been observed at all elevations and all aspects in Hatcher Pass. However, we believe that there is a greater chance of human triggered avalanches on East through West aspects where a thinner snowpack and poor structure exists. This past week several remote and Human triggered avalanches have occurred on East thru West aspects.

Recent avalanches, whumping, and shooting cracks will be red flags for this avalanche problem. Use ski pole probes to look for stiff snow sitting over weak sugary facets. Use snowpits and hand hardness tests to better identify areas with poor structure. 

We recommend using low risk travel techniques, this includes spreading out when traveling uphill or near avalanche terrain. Riding slopes one at a time and stopping and regrouping out of harm’s way. Avoid riding slopes that have terrain traps below. Terrain traps can increase your burial depth. An increased burial depth reduces the chance of a successful rescue. 

Looking up at the crown of a human triggered avalanche on Divide Ridge W aspect 2700’. This avalanche was large enough to injure, bury or kill a person.

The maximum height of the crown was 3′. This avalanche failed near the ground.

Weather
Thu, March 4th, 2021

New snow totals 2/28-3/04

Independence Mine: 3-4″

The week started out with stormy weather and poor visibility. On 2/27 Hatcher received 6” of new snow, at the tail end of this storm a stout “drizzle” crust formed. This crust is up to ¼ inch thick in places and has quite an effect on ski quality in some areas. On 3/1 3-4” of new snow fell on top of the drizzle crust. During this storm it appears that light winds were able to cause some wind effect on the snow surfaces. During this storm Marmot weather station did not record any data. Since 3/2 there has been relatively stable weather in Hatcher. With temps in the teens during the days and single digits at night.


NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.


Independence Mine 2/28-3/04:


Marmot 2/28-3/04:

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