Hatcher Pass Avalanche Center
Hatcher Pass

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, March 5th, 2022 - 7:00AM
Expires
Sun, March 6th, 2022 - 7:00AM
Forecaster
Allie Barker
Avalanche risk The Bottom Line

A short and sweet storm will bring 5″ to 7″ of snow today and quickly transition to sunny skies Sunday and Monday.

Strong winds on Friday built small wind slabs that will be possible to human trigger on west to north aspects at mid and upper elevation on slopes steeper than 35°.

Deep persistent slabs will be stubborn to unlikely to human trigger today.

Natural avalanches are unlikely today.

Below 4000′ conditions are variable and include a thin brittle drizzle crust on the surface, a 1″ sun crust on southerlies, wind pressed snow, and soft faceted surfaces with a supportable base in protected locations.

Special Announcements

The road remains closed beyond mile 11. DOT hopes to start mitigation and road clearing within 1-2 weeks. Stay tuned for more information.

Come join HPAC for a screening of the movie, BURIED, at our Beartooth fundraiser Thur March 24th. All new HPAC swag will be available for purchase.

HPAC will continue providing avalanche information till the end of our season April 16.

If you head out into the mountains, please submit an observation!

Sat, March 5th, 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.
Avalanche Problem 1
  • 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

The wind decided to make an appearance Friday at Hatcher Pass with strong SE gusts 31-47 mph for 13 hours. The good news is that minimal snow is available for transport so wind slabs will be small.

Small wind slabs up to 6″ thick will be possible to human trigger at mid and upper elevation on slopes steeper than 35º. Natural avalanches will be unlikely.

This graph shows strong winds gusts at 4500′ on Friday

Expect wind slabs to fail on the thin drizzle crusts and/or near surface facets and to heal within 24-48 hrs.

Plumes off Frostbite ridgeline on Friday

 

Powder Pimple on Friday

Avalanche Problem 2
  • 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 ft deep still exist but will be stubborn to unlikely to human trigger today. Natural avalanches are unlikely.

This problem is a double edged sword. The deeper the weak layers, the harder it will be to trigger an avalanche but if you do trigger an avalanche the consequences will be huge.

The infamous Dec 26 rain crust and Nov facets are now buried 4+ feet deep in many locations. See Pit here. Before the Valentines storm any loading event with 6-8″ of snow or moderate to strong winds for 8-10 hours was enough to cause a large natural avalanche cycle. The tides have turned. Due to the depth of these weak layers, it will take a much more significant loading event to produce large avalanches.

Remember that deep persistent slabs (DPS) are unpredictable and often give infrequent feedback. Human triggering can happen days or weeks after a storm. These avalanches can be remotely triggered in isolated locations from flat terrain and have unusually wide propagation.

A low likelihood exists for triggering a large avalanche this weekend, however,  considering the high consequences we recommend a conservative approach to terrain management.

When the avalanche problems are complex and some uncertainty exists, 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 and expect avalanches to run further than you think, always have a spotter in a safe location, everyone carries a beacon, shovel, and probe, and are prepared and practiced for companion rescue.

Weather
Sat, March 5th, 2022

NWS AVG Forecast here.

NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

Observations
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