Hatcher Pass Avalanche Center
Hatcher Pass

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ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, November 28th, 2023 - 7:00AM
Expires
Wed, November 29th, 2023 - 7:00AM
Forecaster
Allie Barker
Avalanche risk The Bottom Line

The avalanche hazard is CONSIDERABLE for STORM SLABS at all elevations and MODERATE rising to CONSIDERABLE by end of day for WIND SLABS at upper elevations on slopes steeper than 35º.

A sneaker storm hit Hatcher Pass depositing 10 inches of new snow with 1.2″ of SWE  at 3550′ in the past 30 hours accompanied by winds gusting S 22-30 mph at 4500′.  Winds are forecasted to increase throughout the day which will increase the likelihood of triggering a wind slab at upper elevation on west to north aspects.

Below 3000 feet expect new storm slabs to be reactive and not bond well with firm frozen rain crusts from earlier in the week.

Low angle protected terrain and tree skiing will be a safer option for recreating today.

Heads up! The road at Hatcher Pass has been treacherous and resembles an ice skating rink. Drive safely!

Special Announcements
Wednesday, November 29, 6:00PM
Bearpaw River Brewing Company Taproom (Palmer-Wasilla Hwy)

Join HPAC as we host local guide, avalanche instructor, and author Joe Stock for a presentation marking the release of his newest book, “The Avalanche Factor.” Joe will talk about the book and dive into one of its topics, luck and avalanches.

Tue, November 28th, 2023
Upper Elevation
Above 3,500'
3 - Considerable
Avalanche risk
Mid Elevation
2,500'-3,500'
3 - Considerable
Avalanche risk
Low Elevation
Below 2,500'
3 - Considerable
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 Conditions

10 pm 11/27 Intensity of snow and wind are increasing at mile 15

 

Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

Small storm slabs 6-10″ thick will be likely to human trigger at all elevations and all aspects. Natural avalanches are possible. Expect storm slabs to fail easily below 3000′ and not bond well to firm bed surfaces from the rain event 11/24.

Expect the storm slab instability to improve within 24-48 hours.

Avalanche Problem 2
  • 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

Expect winds to increase throughout the day and build wind slabs 4-6″ thick on leeward aspects , mostly west to north, at upper elevation. Although wind slabs will be small in size, it will be possible for wind slabs to step down into the persistent slab at upper elevation, increasing the size and consequence of an avalanche.

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

 

 

 

Weather
Tue, November 28th, 2023

IM reported 10″ new snow with 1.2″ SWE at 3550′ since 11/26 at 1pm.

Frostbite station reported 9″ new snow with 1.6″ SWE at 2700′ in the last 24 hours.

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