Hatcher Pass Avalanche Center
Hatcher Pass

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, January 1st, 2022 - 7:00AM
Expires
Sun, January 2nd, 2022 - 7:00AM
Forecaster
Allie Barker
Avalanche risk The Bottom Line

Happy New Year!

The avalanche hazard will rise to considerable for wind slabs this afternoon.

The horrendous Christmas crust is now buried under 8 to 12″ of new snow in the last 24hrs!

Unfortunately, winds are forecasted NE 20-44 mph, gusting 49-66 mph today which will build 12 to 24″ thick dangerous wind slabs this afternoon.

Small to large wind slabs will be likely to human trigger on south to west aspects at all elevations on slopes steeper than 35º. Natural avalanches will be possible.

Persistent slabs will be possible to human trigger in isolated locations at all aspects at mid and upper elevation on slopes steeper than 30º.

The best riding will be on lower angle slopes today.

Special Announcements

Join the forecasters on Thursday, January 13 from 4-5pm at the Hatcher Pass Lodge for our first “Forecaster Chat.” Come hear what we have to say about the snowpack and check out our new Swag!

Sat, January 1st, 2022
Upper Elevation
Above 3,500'
3 - Considerable
Avalanche risk
Mid Elevation
2,500'-3,500'
3 - Considerable
Avalanche risk
Low Elevation
Below 2,500'
3 - Considerable
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 new avalanches have been observed since Thursday.

For avalanches earlier in the week click HERE.

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

Approximately 12″ of new snow and 1″ of SWE has fallen in the past 24 hrs at 3450′. Winds are slated to increase significantly today. As of 6am this morning weather stations have calm winds.

Expect wind slabs to build in size throughout the day as winds increase.

Winds are predicted to blow NE 20-44 mph, gusting 49-66 mph!

If winds increase as expected, the avalanche danger will rise this afternoon to considerable.

It will be likely to human trigger a wind slab 12″ to 24″ thick on south to west aspects, at all elevations, on slopes steeper than 35º. Wind slabs will not bond well and will be sitting on firm rain crusts.

Natural avalanches will be possible.

Use probes/poles and hand pits to identify the presence of dense cohesive snow sitting on top of low density soft snow. Cracking and whumping are red flags for this avalanche problem.

 

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

A major weather event on December 26 changed the avalanche paradigm. We had rain on snow up to 5000 ft. A significant amount of moisture entered the snowpack during this event, and natural avalanches occurred. Since then, freezing temperatures have improved stability.

The lingering persistent slab problem will be possible to human trigger on all aspects, at mid and upper elevation in isolated locations on slopes steeper than 30º. Natural avalanches are unlikely.

Wind slabs building throughout the day will have the potential to step down into the persistent slab on south to west aspects at mid and upper elevation.

In most locations the Dec26 Christmas rain crust is supportable above 3800′. The crust is breakable below 3800′.

At low elevation, the snowpack was saturated, is now refrozen, and human triggered persistent slab avalanches are unlikely.

 

 

 

 

Weather
Sat, January 1st, 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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