Hatcher Pass Avalanche Center

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, February 10th, 2024 - 7:00AM
Expires
Sun, February 11th, 2024 - 7:00AM
Forecaster
Allie Barker
Avalanche risk The Bottom Line

A MODERATE avalanche hazard exists for WIND SLABS on Southwest to Northeast aspects above 3500 ft.

The avalanche hazard is LOW below 3500 ft. where triggering an avalanche will be unlikely.

Avalanche stability and general conditions have been excellent for several weeks AND a shift is on the horizon.

Expect strong winds to persist throughout the day followed by precipitation Saturday evening into Sunday morning with up to 10 inches of new snow.

Special Announcements

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Sat, February 10th, 2024
Upper Elevation
Above 3,500'
2 - Moderate
Avalanche risk
Mid Elevation
2,500'-3,500'
1 - Low
Avalanche risk
Low Elevation
Below 2,500'
1 - Low
Avalanche risk
Sun, February 11th, 2024
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
Sun, February 11th, 2024
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

Two small human triggered wind slabs were reported on Hatch Peak and Marmot on Friday as a result of increasing wind throughout the day. No other significant slab avalanches have been observed or reported since January 19th.

2/9 Human triggered wind slab on Hatch Peak N 4400′

 

2/9 Small human triggered wind slab, Marmot SW 4200 feet Photo Katie Warren

Numerous natural and human triggered dry loose avalanches (sluffs) were observed in steep terrain greater than 40º on all aspects this week. Most of the avalanches were small and inconsequential with a few large sluffs observed in isolated and extreme terrain. Most of the activity occurred earlier in the week during the spell of cold temperatures.

Dry loose avalanches on Arkose Ridge from earlier in the week SW 3500′

 

2/8 Sluffs from earlier in the week and highmarking up Archangel Valley

 

2/8 Sluffs and tracks on Divide ridge NW 3500′

 

Recent Conditions

2/8 Strong winds gusting on top of Arkose ridge on Friday 4000′

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Aspect/Elevation
  • 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.

Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.

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

Strong wind at upper elevation was observed by numerous backcountry users and increased throughout the day on Friday, transporting just enough snow to build small wind slabs.  As predicted , Southeast winds have increased overnight and at 6 am are reporting 30-37mph gusting 44-53 mph at 4500ft over the past 7 hours. Winds are expected to remain steady throughout the day and contribute to today’s avalanche problem.

After nearly two weeks of mostly low danger with very few avalanche problems, the paradigm is shifting.  5 to 10 inches of new snow is expected by early Sunday morning. If we receive the higher end of precipitation expect to see an increase in avalanche activity on Sunday.

Wind Slab

It will be possible to human trigger wind slabs up to 12 inches thick on Southwest to Northeast aspects above 3500 ft. Expect wind slabs to grow in size and sensitivity throughout the day as winds persist. Winds are expected at to be strongest at upper elevations.  Pay attention to specific terrain features like leeward aspect gaps, passes, and cross loaded slopes where triggering a wind slab will be more likely today. Triggering a wind slab below 3500 ft is unlikely.

Use hand pits and pole probes to identify wind slabs. Look for hard snow sitting over weaker snow, smooth and rounded or lens shaped features.  Shooting cracks or whumping are signs of instability and indicators of 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 we travel in avalanche terrain. This means spreading out when ascending slopes, descending one at a time, and regrouping well outside of the runout zone.

Loose Dry

Triggering small to large sluffs was more likely earlier in the week during the cold spell of weather.  Over the past several days temperatures have warmed up considerably. Temperatures in the mid-twenties combined with warm storm snow on 2/4 has left snow surfaces more cohesive with a subtle upside down feel. Expect to find more variability with snow conditions today and the best powder on colder protected aspects not affected by the wind.

Triggering a small sluff in isolated locations still remains possible in 40º and steeper terrain on all aspects and all elevations.

Even a small loose dry avalanche may be able to sweep you off your feet and carry you into other hazards.  Small dry loose avalanches can be mitigated safely with appropriate slope cutting techniques.

Weather
Sat, February 10th, 2024

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
Recent Observations for Hatcher Pass