Hatcher Pass Avalanche Center

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, February 16th, 2023 - 7:00AM
Expires
Fri, February 17th, 2023 - 7:00AM
Forecaster
Jake Kayes
Avalanche risk The Bottom Line

The avalanche danger is MODERATE at all elevations.

At upper and mid elevations, human-triggered wind slabs 4 to 16 inches thick are possible on southwest through north aspects and cross-loaded features on slopes 35 degrees or steeper.

At all elevations and aspects, small to large human-triggered dry loose avalanches are possible on slopes 40 degrees and steeper. 

Yesterday there was a near miss that occurred on a southwest aspect of Marmot. A person was caught, carried, and partially buried. The rider was able to self-rescue and thankfully is ok. Numerous natural wind slabs and dry loose avalanches were also observed yesterday.

Thu, February 16th, 2023
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

There have been several recent natural avalanches and two observed human-triggered avalanches. Yesterday on Feb 15th a near miss occurred on a Southwest aspect on Marmot Click HERE and HERE for more info. On Feb 14th a rider triggered an avalanche on Blueberry Knoll click HERE for more info. Yesterday forecasters observed numerous natural wind slabs and dry loose avalanches that likely occurred on Feb 14th see photos below. 

2/14 D1 wind slabs Peak 4068. North Aspect 4000′.

2/14 D1 wind slabs on Bennett’s Ridge. North aspect 3600′

 

2/14 D2 windslab on Punkspines. Northwest aspect 3300′

2/15 D1 Dry Loose avalanches on Eldorado. East face 3600′

2/15 D1-D2 dry loose in Eldorado Bowl. East aspect 4500′

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

On Feb 14th winds from the ESE with gusts, up to 30 mph lasted for 12 hours. These winds were able to transport low-density snow from the Feb 11-13 storm that brought 12 inches to HP, building wind slabs 4 to 16 inches thick.

Human-triggered wind slabs are possible at upper and mid elevations on southwest thru north aspects at ridge lines and cross-loaded gullies on slopes 35 degrees and steeper. These avalanches will be small to large in size, natural avalanches are unlikely. 

The video above shows shooting cracks and a small slab failing on a wind loaded feature at mid elevation and small cornice breaking at ridge line on Marmot at upper elevation.

Yesterday there was a near miss that occurred on a SW aspect of Marmot. A person was caught, carried, and partially buried. The avalanche was triggered mid-slope and carried the rider 800′ feet before the avalanche stopped. Click HERE for more information. 

Small wind slabs and cornices on Marmot. These avalanches had slabs up to 16 inches thick.

Yesterday forecasters observed small natural avalanches at upper elevations at ridgeline and on some cross-loaded features. The slabs that have formed may not present the typical textures that are associated with wind slabs, such as smooth lensed shaped features, hollow-sounding snow and sastrugi. This lack of clues may cause terrain choices to be difficult.

An example of a cross loaded gully

Using hand pits, pole probes and other traveling tests will be critical to identifying any wind slab, look for dense snow on top of weak snow below.

Shooting cracks and collapsing will be red flags for this avalanche problem. 

As always we recommend carrying the appropriate rescue gear and knowing how to use it. Safe travel techniques are important every time you enter avalanche terrain. This means spreading out when ascending slopes, descending one at a time, and regrouping well outside of the runout zone. 

Avalanche Problem 2
  • Dry Loose
    Dry Loose
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    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

Small to large human-triggered dry loose avalanches are possible at all elevations and aspects. These avalanches will be found on slopes 40 degrees and steeper. This avalanche problem is more prevalent due to low density snow sitting on top of old firm bed surfaces.

We’ve seen some impressive natural dry loose avalanches on Idaho peak and in Eldorado Bowl. Some of the dry loose avalanches we have observed have been large and have traveled several hundred vertical feet. 

These dry loose avalanches will be able to entrain surrounding snow and gain speed quickly. Good sluff management will be important if you decide to enter steeper terrain. Terrain traps will also compound the risk of any dry loose avalanche that is triggered. Know what is below you when riding in steep terrain. 

Large dry loose avalanches on Idaho Peak. Southwest aspect 3000′. These avalanches traveled hundreds of feet and traveled into a terrain trap.

Weather
Thu, February 16th, 2023

NWS is call for 8-12 inches of snow on Friday Feb 17th


NWS AVG Forecast here.

NWS point forecast here.

Marmot Weather Station here.

Independence Mine Snotel here.

Frostbite Bottom Snotel here.

State Parks Snow Report and Motorized Access information here.

XC trail grooming report for Mat-Su, Anchorage, and Kenai here.

Observations
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