Hatcher Pass Avalanche Center

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, January 4th, 2020 - 7:00AM
Expires
Sun, January 5th, 2020 - 7:00AM
Forecaster
HPAC Staff
Avalanche risk The Bottom Line

Our stale avalanche paradigm has shifted, and the avalanche hazard has increased.

It will be likely to human trigger numerous small dry loose avalanches on upper elevation, northerly aspects, on slopes 40° and steeper. It will be less likely, but possible to human trigger dry loose avalanches on all other aspects at mid to upper elevations.

It will be possible to human trigger slab avalanches at mid and upper elevations today.

Expect sensitive soft slabs up to 12″ thick to be possible to trigger on West to North aspects, on slopes above 35°.

 

 

Special Announcements

Saturday, January 11 from 11 am-1:30 pm. Come practice your companion rescue skills at our Annual Rescue Workshop , sponsored by the HP Snowriders, HPAC, CNFAIC, and Black Diamond Anchorage. Location: Gold Mint Lot at Hatcher Pass.

Don’t miss our favorite party of the year. Come support HPAC at our 11th Annual Cabin Fever Reliever and Fundraiser at the Moose Lodge in Palmer, Saturday, Feb 8 at 5:30 pm. Buy your tickets online NOW at: https://cabinfeverreliever.bpt.me

How about a New Year’s resolution to stay safe in avalanche terrain? Ski one at a time? Read the avalanche advisory or submit an observation? Help us help you be more informed. Support your community funded avalanche center by donating today. Thank You!

Sat, January 4th, 2020
Upper Elevation
Above 3,500'
3 - Considerable
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.
Recent Avalanches

Avalanche Activity 12/29/19- 1/3/20

2019 ended on a WINDY note, blowing SE 15-28 mph, gusting SE 25-63 mph at 4500′ on 12/29 to 12/31.

The New Year arrived bringing approximately a foot of new snow this week.

Natural wind and slabs were observed on leeward aspects, mostly north, at mid and upper elevation, on slopes steeper than 35º up to D2.

Small human triggered soft slabs were observed on 1/2 and 1/3 on steep slopes on northerly aspects, approx. 12” deep. These slabs were sensitive and easy to trigger in the right location.

Numerous natural and human triggered small dry loose sluffs were observed on steep southerly aspects this week. Larger dry loose sluffs were observed on steep northerly aspects. These sluffs were fast and capable of capturing a person, and not out-run-able. This hazard will remain today. Sluff management skills are key to avoiding this hazard in steep northerly terrain.

1/2 – Human triggered slab avalanches

 

12/31-1/1 – Marmot, Rae Wallace, NNW, 3800′-4500′, numerous natural slab avalanches, with white arrows showing crown faces, 6″-12″ deep, D1-2. Note that the second one from the right is older with more new snow obscuring the crown face. Also of importance is that slabs have failed well below ridgeline, so take this into account and do not let down your guard down expecting the hazard to only be present at the top of starting zones.

 

12/31-1/1 – Microdot, Nosebleed, NNW, 4000-4800′, natural slab avalanches, approximately 1 foot deep, D2

 

1/1-1/2 – Skyscraper, S, 4200′, natural loose dry avalanches

 

Avalanche Problem 1
  • 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

Dry loose avalanches (sluffs) will be likely to human trigger and small in size at upper elevations, on northerly aspects, on slopes 40º and steeper. Dry loose avalanches will be possible to trigger at mid to upper elevations on all other aspects, also on slopes 40° and steeper.

Loose dry avalanches will have the ability to injure and/or carry you into additional hazards. In isolated locations they will be large enough to bury a person in specific terrain traps. Useing sluff management skills to mitigate this hazard will be necessary today.

Natural activity is not expected, but may be possible with direct solar near rock heat sinks.

On northerly aspects, where the new snow is deeper, we have seen 12″ or more of newer snow sitting on weak facets over a smooth wind crust, which is helping to increase the speed and volume of sluffs. Yesterday, sluffs were running fast, entraining snow, and could have buried a person in specific terrain traps. We expect this hazard to continue today through the next few days as the weather remains, cold, clear and calm.

Sluffing may be large enough to injure a person, especially if you are caught and carried into additional hazards, such as cliffs and rocks.

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

It will be possible to trigger 6-12″ soft slabs sitting on faceted, weak snow on west to north aspects, at mid to upper elevations. These slabs may also trigger loose dry avalanches which could add to the volume of any slab avalanche triggered.

More likely locations for triggering these avalanches are convex rollovers, steep sidewalls, and on slopes 35° and steeper.

Slabs are expected to have limited propagation, and remain small in size, however, plan for uncertainty and the possibility of finding isolated locations where triggering a large slab, capable of burying, injuring, or killing a person is possible.

You may not encounter warning signs, such as cracking or collapsing before triggering a persistent slab. Also note that slab avalanches have and will fail mid slope. Do not let your guard down thinking slabs will only fail at the upper most portions of any slope or starting zone.

Ski cutting touchy, small, soft slabs will be an effective technique as long as the depth of the slab remains below 12″. Take the time to plan ski cuts properly, using safe zones, and limiting your exposure to larger, open terrain. Use spotters. Build in margins for error by choosing more manageable, smaller slopes and terrain, with less exposure.

Additional Concern
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.
More info at Avalanche.org

Glide Avalanches

The last observed glide avalanche release that we know about was on December 7 on the southeast face of Hatch Peak. This activity is almost a month old, and seems to be in dormancy. However, glide cracks are still present and could release at any time. Many glides are now barely visible from this week’s new snow. Caution should be taken to not ski/ride into these terrain traps. It’s important to note that glide releases can happen in warm or cold weather, are not temperature dependent, and predictability is next to impossible. Any glide avalanche will be large and capable of burying, injuring, and/or killing a person. We recommend avoiding being on or under any locations with glide cracks.

Cornices

Due to plentiful snow this season and strong wind events, cornices are overhanging and large. Cornices are difficult to predict the timing of natural release. There have already been a few releases this season involving people and old cornice debris and large chunks are present at the base of some slopes. If traveling under cornices, limit the time of your exposure. If you are approaching cornices from behind, use extreme caution, gain a safe viewpoint to identify safe entries onto slopes below, and do not step out on overhanging cornice features.

Cornice failures may be large, and the mass of a cornice may be large enough to injure or kill a person. Cornices may also entrain more loose snow, which could carry you into additional hazards.

1/3 – Cornice teetering, Rae Wallace ridgeline

1/3 – Cornice along the Rae Wallace ridgeline

 

 

Weather
Sat, January 4th, 2020

An interior Alaska high pressure ridge is resulting in cold temps, light winds, and relatively clear skies which will persist through the weekend and into early next week. Weak northerly outflow is creating the cold temps, clear skies, and light winds, but may also allow for low pressure systems in the gulf to influence Hatcher Pass with some cloud clover this afternoon and overnight. Some discrepancies in the forecasting models bring some uncertainty to the development and strength of a low pressure system that could bring clouds to HP Monday and Tuesday.

The avalanche hazard will likely remain the same, and stability should incrementally improve through the week.


NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

Observations
Recent Observations for Hatcher Pass