Hatcher Pass Avalanche Center

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, February 26th, 2022 - 7:00AM
Expires
Sun, February 27th, 2022 - 7:00AM
Forecaster
Allie Barker
Avalanche risk The Bottom Line

Early spring conditions have dominated HP for the past few days but we still have lots of winter left! It’s been over a week since avalanche cycles produced numerous large and very large avalanches covering and burying the road in an est. 15 to 25 feet of debris.

Although it is becoming harder to trigger a large avalanche, the possibility still exists. It will be possible to human trigger a deep persistent slab 3 to 4 feet deep on all aspects at mid and upper elevation on slopes steeper than 30º.

It will be possible to human trigger a persistent slab 2 to 3 feet deep on all aspects at low elevation on slopes steeper than 30º.

It will be possible to human trigger small wind slabs up to 6 inches thick on west to north aspects at upper elevation on slopes steeper than 35°.

Natural avalanches will be unlikely today.

Last weeks new snow and wind have made it challenging to accurately see snow depth. The Marmot snowstake has gotten an extension that reaches beyond 8 feet. Thanks Jeff

 

 

Special Announcements

The HP road remains closed at mile 11. DOT plowed up to Mile 11 on Friday.

AK State Parks issued an executive order on 2/24 to close the Hatcher Pass East Management Area. Page 1, Page 2 and public comment here.

HPAC will continue to provide avalanche information to the best of our abilities using our weather resources and weather stations and limited backcountry access.

We recognize the enormous amount of work required to clear the road and look forward to working with all agencies to get our community back out recreating.

Sat, February 26th, 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 recent avalanches have been observed or reported since the Valentines Cycle 2/14-18 and the Presidents Storm 2/21-22.

For avalanche photos related to these cycles see obs here and forecasts here.

Avalanche Problem 1
  • Deep Persistent Slabs
    Deep Persistent Slabs
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

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

Deep Persistent Slabs up to 4 feet deep will be possible to human trigger on all aspects at mid and upper elevation on slopes steeper than 30°. Avalanches that were touchy last week will be stubborn to trigger this weekend.

Slabs are thicker and weak layers from Dec 26 and Nov are buried deeper at mid and upper elevation where more snow accumulated last week and temps remain colder than low elevation.

Remotely triggering an avalanche above you or on an adjacent slope is still possible. Deep slabs are inherently more stubborn to trigger because of the depth of the weak layer but carry significantly more consequence. Thin spots in the snowpack will be more likely locations to trigger an avalanche.

To identify this avalanche problem use poles/probes to identify the Dec 26th rain crust and weak sugary snow below. Formal stability tests will be challenging and unreliable due to weak layers being buried so deep.

Human triggered and remotely triggered avalanches will be possible days or weeks after a storm.

 

Avalanche Problem 2
  • 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

Persistent slabs 2 to 3 feet thick will be possible to human trigger on all aspects at low elevation, on slopes steeper than 30º. Natural avalanches are unlikely today.

Below 2500′ received less snow during the past two storms. In addition, over the past 48+ hours temps have been 33 to 40ºF and the snowpack has settled 8″ since 2/22.

Frostbite station is reporting slightly cooler temps this morning at 29º at 5am.

To identify this avalanche problem use poles/probes to identify the Dec 26th rain crust and weak sugary snow below. Formal stability tests may be challenging and unreliable due to weak layers being buried so deep.

Human triggered and remotely triggered avalanches will be possible days or weeks after a storm.

When the avalanche problems are complex and we have limited snowpack data, it’s time to focus on safe travel protocol. In avalanche terrain, only expose one person to steep slopes at a time, choose safe zones out of the reach of avalanches for grouping up, always have a spotter in a safe location, everyone carries a beacon, shovel, and probe, and are prepared and practiced for companion rescue.

 

Avalanche Problem 3
  • Wind Slabs
    Wind Slabs
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
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.

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 wind slabs up to 6″ thick will be possible to human trigger on west to north aspects at upper elevation on slopes above 35º. Natural avalanches are unlikely.

The Marmot weather station anemometer came back online Friday afternoon. There is some uncertainty as to how long winds blew and the intensity since the station has been rimed for 10 days. A significant amount of terrain appeared wind affected during our flights over the past week.

Marmot winds Friday afternoon

To identify this avalanche problem, look for smooth wind-drifted snow and rounded lensed shape features.  Use hand pits and pole/probe tests to identify stiff hard snow sitting on top of soft low density snow. Whumping and shooting cracks are red flags for this avalanche problem.

Weather
Sat, February 26th, 2022

NWS AVG Forecast here.

NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

Observations
Recent Observations for Hatcher Pass