Hatcher Pass Avalanche Center

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, January 14th, 2021 - 7:00AM
Expires
Fri, January 15th, 2021 - 7:00AM
Forecaster
Jake Kayes
Conditions Summary

Today’s avalanche problem will be persistent slab, avalanches are unlikely at all elevations and all aspects. Triggering an avalanche in isolated or extreme terrain is still possible. 

Rocks and other hazards are sitting just below the surface, even a small avalanche could have high consequences.

In isolated wind protected areas some soft riding conditions can be found.

Special Announcements

AMDS and BRP continue to support avalanche safety in Southcentral AK at HPAC with the newest and very best mechanized tools for access. This week we picked up the 2021 AMDS loaner machine. Thanks to everyone @akmining!

Thanks to our sponsors.
Thu, January 14th, 2021
Recent Avalanches

There have been no natural or human triggered avalanches observed this week.

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    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

Persistent slabs will be unlikely to trigger at all elevations and aspects. Large avalanches are unlikely but still possible in VERY isolated or extreme terrain. 

The snowpack is gaining strength very slowly. Without any significant loading events tipping the balance, the weak sugary layers have had time to adjust to the load. West to Northwest to north aspects have significantly thicker coverage 3-6’ deep, due to wind events this season. In contrast, East thru south aspects are significantly shallower 0-2.5’. Human triggered avalanches are more likely in areas with a thinner snowpack(east thru south aspects).

Looking towards the future, our widespread weak snowpack will not handle large loads. Any big snow dump (load) will likely result in natural avalanches. See this observation to get a better idea of the snowpack’s structure.

Coverage is still thin, very thin, and this will increase the consequences for any avalanche triggered. Rocks and other hazards increase your chances of traumatic injury if you get caught in an avalanche.

Under the current conditions we will be continuing to practice safe travel procedures. We recommend ascending and descending avalanche terrain one at time, spreading out, using safe zones to regroup, and avoiding any terrain traps. Remember to always carry a transceiver, probe and shovel, and be practiced in their use. 

Martin Mine showing signs of some wind scouring

Boulders and vegetation sticking out of the snowpack is a common site in Hatcher Pass right now.

Marmot SW face showing signs of extreme winds last week.

Weather
Thu, January 14th, 2021

1” of new snow this week

Overall the weather has been fairly uneventful in the forecast area this week. On Jan 10th both Independence Mine and Frostbite weather stations were well above freezing for most of the day. On Jan 11th strong to extreme winds blew from the east for approximately five hours. As the week progressed winds began to taper and temps began to cool off. While we did have strong to extreme winds from the east this week, there was little to no snow available for transport. 


NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.


Marmot 1/10-1/14

 


Independence Mine 1/10-1/14

Changes in snowpack height reflects settlement in the snowpack.


Frostbite 1/10-1/14

 

Observations
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