Hatcher Pass Avalanche Center

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, January 4th, 2024 - 7:00AM
Expires
Fri, January 5th, 2024 - 7:00AM
Forecaster
Ryan Lewthwaite
Avalanche risk The Bottom Line

The avalanche danger is MODERATE for WIND SLABS on southwest through north aspects at upper elevation. Strong winds on January 2nd have transported snow from windward locations to these aspects where triggering slabs up to 3 inches thick is possible. While the danger remains LOW below 3500 feet, small avalanches in isolated and extreme terrain are possible.

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Thu, January 4th, 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
Fri, January 5th, 2024
Upper Elevation
Above 3,500'
1 - Low
Avalanche risk
Mid Elevation
2,500'-3,500'
1 - Low
Avalanche risk
Low Elevation
Below 2,500'
1 - Low
Avalanche risk
Fri, January 5th, 2024
Upper Elevation
Above 3,500'
1 - Low
Avalanche risk
Mid Elevation
2,500'-3,500'
1 - Low
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

No Recent Avalanches.

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

Overnight moderate winds gusted on Marmot and Hatch peaks for 3 hours before tapering off in the upper elevations, which may contribute to the buildup of cohesive wind slabs. Throughout today expect winds to decrease as we accumulate a dusting of new snow. It will be possible to trigger a small wind slab avalanche in isolated locations near and just below ridgelines on SW to N aspects above 3500 feet. Although this avalanche problem may be stubborn in its sensitivity and unlikely to propagate, you may find specific locations where the slabs are thicker, more cohesive and rests on weak sugary snow. 

Strong winds on the evening of January 2nd transported older soft snow onto leeward aspects, building thin and breakable wind slabs. These 1 to 3 inch soft slabs are easily penetrated by skis and boots and are mostly sitting on weak sugary snow on top of firm surfaces. For a period of 17 hours during this event Marmot weather station recorded winds of 28-34 mph while on Hatch Peak winds were 34-48 mph. 

On or just below SW to N ridgelines it will be easy to find scoured and wind drifted snow surfaces. Recent wind has created more variable snow surface conditions including scalloping and sastrugi. Small near-surface facets formed during the last cold clear spell of weather creating a potential weak layer for future avalanches to slide upon. 

To identify wind slabs look for hard snow sitting over weak snow, smooth and rounded or lens shaped features. They may sound hollow or crack out from your ski tip or snowmachine as you travel across them. Shooting cracks and whumphing are signs of instability and indicators of this avalanche problem.

 

Wind Sculpted Snow on Windward Ridgeline; Hatch Peak 3800 feet southeast Aspect 1/2/24

 

Hatch Peak Ridgeline 1/2/24

Hatch Peak Ridgeline 1/2/24

 

1-3 inch Wind Slabs on Skyscraper ridgeline 1/3/24

 

Cornices forming on Leeward Aspects in the Upper Elevation facing SW to N

Weather
Thu, January 4th, 2024

Strong winds recorded at Marmot Weather Station on 1/2-1/3/24

Strong winds recorded at Hatch Weather Station on 1/2-1/3/24

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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