Hatcher Pass Avalanche Center

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, April 1st, 2021 - 7:00AM
Expires
Fri, April 2nd, 2021 - 7:00AM
Forecaster
Jake Kayes
Conditions Summary

Today’s Avalanche Problems will be Persistent Slab and Dry Loose. Large human triggered Persistent Slabs will be likely on East thru West aspects at all elevations. Small to Large  Dry Loose avalanches will be possible on all aspects and all elevations on slopes 40° and steeper. 

Remote triggering avalanches will be possible today. 

Careful snowpack evaluation, cautious route finding, and conservative decision making will be essential if you chose to venture up to Hatcher Pass today.

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Thu, April 1st, 2021
Recent Avalanches

On 3/31 there was a remote triggered avalanche on Lower Eldorado. There were several natural avalanches observed this week.

3/31: Lower Eldorado: ESE 3500’:

Avalanche on Lower Eldorado, the circle marks where skier triggered avalanche while ascending.

Remote triggered avalanche Lower Eldorado

Marmot Lodge Run 4200’ W:

A natural wind slab that stepped down into persistent slab on Marmot, this avalanche likely occurred on 3/29

3/29: Marmot 4000′ S natural persistent slab:

This avalanche likely occurred on 3/29

3/29 Idaho Peak S natural storm slab

A natural storm slab likely occurred on 3/29

3/29 Government Peak Seldom Seen 4200′ E: no photo

Avalanche Problem 1
  • 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

Persistent weak layers have continued to be reactive during and after the 3/29 storm that brought 6-10” of new snow with moderate winds. Large human triggered avalanches will be likely today on East thru West aspects, at all elevations on slopes 35° or steeper. REMOTE TRIGGERING from a distance will be possible today.

Many red flags were observed on Wednesday including significant cracking, collapsing, and remote triggering avalanches

The snowpack has extremely poor structure with multiple weak sugary layers and lots of crusts. The layer that is most concerning is a crust facet sandwich that is approximately 1.5 – 2 feet from the surface. This layer was responsible for two large natural avalanches during the last storm. If you do trigger an avalanche on this crust facet sandwich there is the possibility of it stepping down into weak sugary snow near the ground, increasing the size and consequence of any avalanche.

This avalanche problem can be difficult to predict. Previous tracks on the slope will NOT be an indicator of stability with this avalanche problem. 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.

Remote triggered avalanche on Lower Eldorado 3500′ ESE

3/31: Large shooting cracks propagated up to 50′ on SW ridge of Marmot

Near the bottom of the snowpack sits large Depth Hoar.

 

Avalanche Problem 2
  • 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

6-10” of new snow fell during the last storm. This new snow will be capable of producing small to large Dry Loose avalanches at all elevations, and on all aspects, on slopes 40° or steeper. Human triggered avalanches are possible, natural avalanches are unlikely.

We recommend using good sluff management if you decide to step out into steeper terrain. These avalanches will be capable of  catching, carrying and sweeping you through hazards, if not managed properly. Terrain traps can increase the consequences of any avalanche. Know what’s below you and avoid riding above any cliffs or gullies.

 

Weather
Thu, April 1st, 2021

3/28-4/1 new snow totals:

Independence Mine: 10″

Frostbite bottom: 6″


Hatcher started out the week with cold temps in the single digits at both ridge tops and valleys. On the evening of 3/28 a large storm system moved into Hatcher Pass. As this storm progressed temperatures increased, along with speeds. On the evening of 3/29 wind were strong from the S with peak gust upto 36mphs. One the storm left temps began to drop again before spiking on 3/31 with a high of 28°F at Marmot Station.


NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.


Independence Mine 3/28-4/1:


Marmot 3/28-4/1: Marmot station did not report wind speeds for 14 hours on 3/31

Observations
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