Hatcher Pass Avalanche Center
Hatcher Pass

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, February 11th, 2024 - 7:00AM
Expires
Mon, February 12th, 2024 - 7:00AM
Forecaster
Allie Barker
Avalanche risk The Bottom Line

A CONSIDERABLE avalanche hazard exists for wind slabs where triggering a slab up to 16 inches thick will be LIKELY on southwest to northeast aspects above 3000ft.  Triggering an avalanche below 3000 ft is unlikely. Natural avalanches are unlikely today.

Winds tapered as of late Saturday night prior to 4 inches of new snow reported early Sunday morning.

Our low avalanche paradigm has changed. Dangerous avalanche conditions exist in specific locations and will require being on top of your game today to avoid triggering an avalanche or getting caught and carried.

Sun, February 11th, 2024
Upper Elevation
Above 3,500'
3 - Considerable
Avalanche risk
Mid Elevation
2,500'-3,500'
3 - Considerable
Avalanche risk
Low Elevation
Below 2,500'
1 - Low
Avalanche risk
Mon, February 12th, 2024
Upper Elevation
Above 3,500'
2 - Moderate
Avalanche risk
Mid Elevation
2,500'-3,500'
2 - Moderate
Avalanche risk
Low Elevation
Below 2,500'
1 - Low
Avalanche risk
Mon, February 12th, 2024
Upper Elevation
Above 3,500'
2 - Moderate
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

Several slab avalanches were reported on Saturday. Natural avalanches were reported and likely occurred during the night Friday or early morning Saturday on Frostbite (see photo below) and N Frostbite aka Moon Bowl.

One avalanche was reported and preliminary information is available about a wind slab that was human triggered on the north side of 4068′ on Saturday that caught, carried, and partially buried two people. No injuries have been reported.

Natural wind slab avalanche that likely occurred late night, early morning 2/9-10 on Frostbite NNE 3600′, Photo: Lynn Whitcomb

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 southeast winds persisted on and off over the past 24 hours gusting 33 to 53 mph for 13+ hours at 4500′. Expect strong to extreme gusts to have transported low density snow and built new wind slabs on leeward aspects.  Evidence of these new wind slabs was observed and reported on Saturday in several locations above 3000ft. Winds tapered late last night prior to receiving 4 inches of new snow with 0.4 inches of SWE at 3500 ft.

Expect wind slabs, 12 to 16 inches thick to be LIKELY to human trigger on southwest to northeast aspects above 3000 ft today on slopes 35º and steeper.  Winds were considerably stronger above 3000 ft and evidence of this avalanche problem will be more obvious at upper elevation. It will be unlikely to trigger a wind slab below 2500 ft. In some locations, wind slabs will be harder to identity because of new snow that fell early this morning. Natural avalanches are unlikely today. Most natural avalanche activity likely occurred during the peak intensity with winds on 2/10.

Marmot snowstake during the beginning of the storm last night

Pay close attention to wind transported snow and avoid steep wind drifted terrain. Shooting cracks and audible collapses are indicators of instability. Look for hard snow sitting over weaker snow, smooth and rounded or lens shaped features.

If you head into avalanche terrain today, utilize strict safety travel protocols, travel one at a time from safe zone to safe zone, only have one person on slope at a time, ensure all members of your party are carrying and know how to use beacons, shovels and probes, and avoid slopes with terrain traps.

 

 

Weather
Sun, February 11th, 2024

Since 2300 on 2/10:

4″ new snow with 0.4″ SWE @3550′ IM 

3″ new snow with 0.3″SWE@ 2700′ Frostbite

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.

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