Hatcher Pass Avalanche Center
Hatcher Pass

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

Small wind slabs will be possible to human trigger on steep slopes, at upper elevations, on West to North aspects.

Large slab avalanches 1-3′ deep will be possible to human trigger on all aspects and at all elevations on slopes 30° and steeper. In isolated locations it may be possible to remotely trigger a large slab avalanche.

Natural avalanches are unlikely.

The slab avalanche problem remains difficult to predict. Continue to use safe travel protocol to increase your margin of safety when traveling in avalanche terrain.

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Sat, February 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'
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

We are 6-7 days out from large avalanche occurrences.

Several avalanches were remotely triggered by snow machines earlier in the week, click here and here for more info. On 1/29 a natural avalanche cycle occurred.

1/30 Remote trigger, Lane Valley. 10 people had skied the slope before a snow machine triggered this avalanche.

 

1/29 Natural , Microdot S 4400

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

It will be possible to human trigger small winds slabs, at upper elevations on West to North aspects. Natural avalanches are unlikely.

Small dry loose avalanches may be possible to trigger in the new snow on all aspects at upper elevations on slopes 40° and steeper. This is of lesser concern than wind slabs and persistent slabs today.

Triggering any wind slab avalanche may have the potential to step down to the deeper and more dangerous persistent slab avalanche problem. The most likely location for this is on cross-loaded features on southerly aspects.

Overnight winds at 4500′ gusted S/SE 20-25mph for 6 hours.

Storm snow has slowly been adding up since early Thursday morning.  At 3000′, 2-3″ of new snow accumulated early Thursday morning through the daytime Friday.  We picked up another 4″ of new snow overnight.

Winds were substantially calmer at mid to lower elevations. Snow totals were trace to 2″ at 2700′ near Skeetawk overnight, with temps right around freezing. Some rain/snow mix occurred yesterday below 2500′.

Today, NWS is calling for 1-5″ of news snow with light to moderate SE winds.

 

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

Human triggered slab avalanches 1-3′ deep remain possible on all aspects and at all elevations on slopes 30° and steeper.

It will be easier to trigger this avalanche problem where the slab is thinner, on SE, S, and SW aspects, or on cross-loaded southerly terrain features. Identifying exact locations will be difficult. Along with this uncertainty lies the continued potential for remotely triggering slab avalanches.

We are 6-7 days out from the last loading cycle which tipped the balance and resulted in both natural and human triggered large avalanches. The good news is stability slowly increased earlier in the week. The bad news is new snow and wind are reloading the same poor, untrustworthy snowpack structure which has been problematic all season.

While recent avalanche activity has waned, widespread poor structure in the snowpack will continue to be problematic and make human triggering slab avalanches possible. The problem weak layers are the December 26 crust/sugar facet combo and the November basal, sugary facets. In many cases this season, avalanches have failed on top of the crust, and then stepped down deeper into the weak basal facets.

Below is a pit from Friday which is a good visual example of what we are dealing with:

If this looks complex to you, GOOD, because it is. And that brings us around to focusing on travel advice.

When the avalanche problems are complex and our certainty is low, it’s time to simplify the whole enchilada with 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.

On another good note, there’s some nice powder out there to recreate in. If you get out and about, send us your avalanche, snow and weather observations HERE. We love your pictures. You can also share by DM’ing us on Facebook @hpavalanche and Instagram @h_p_a_c

Weather
Sat, February 5th, 2022

New snow this week:

Earlier in the week: 1-2″

Thursday through daytime on Friday: 2-3″

Overnight: 4″

Today NWS is calling for 1-5″ of new snow with light to moderate SE winds and a high of 28F at 3000′.

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