Hatcher Pass Avalanche Center

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, January 16th, 2021 - 7:00AM
Expires
Sun, January 17th, 2021 - 7:00AM
Forecaster
HPAC Staff
The Bottom Line

The avalanche hazard is LOW today for persistent slabs on all aspects, at all elevations.

Human triggered and natural persistent slab avalanches are unlikely today, however, triggering a persistent slab in isolated or extreme terrain is not impossible.

Wind speeds are forecasted to increase today. With very little snow available for transport, these winds should not increase the avalanche hazard today.

HP received a couple inches of new snow on Friday. Conditions continue to be a mixed bag of dust on supportable and breakable crusts, and weak sugary snow in isolated, wind protected locations.

The snowpack depth is highly variable, often varying from bare ground to 6 feet deep in a 50 foot spread. Coverage is generally thicker on West to North aspects, and thinner on East to South aspects.

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Sat, January 16th, 2021
Upper Elevation
Above 3,500'
Low (1)
Avalanche risk
Mid Elevation
2,500'-3,500'
Low (1)
Avalanche risk
Low Elevation
Below 2,500'
Low (1)
Avalanche risk
Upper Elevation
Above 3,500'
Avalanche risk
Low (1)
Mid Elevation
2,500'-3,500'
Avalanche risk
Low (1)
Low Elevation
Below 2,500'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

No avalanches observed or reported 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

The avalanche hazard is LOW today for persistent slabs at all elevations and all aspects.

Even though the overall hazard for persistent slab avalanche is rated at Low, it is still worth some discussion.

Low hazard does not mean no hazard, and we expect there to be isolated locations where human triggering a persistent slab may still be possible. Given the poor structure of the snowpack,  it’s impossible to completely rule out any possibility of triggering an avalanche.

Unfortunately triggering this type of avalanche is not likely to be small, but should be expected to be large in size, 1-5 feet deep, with an average depth of 1-2 feet. Combine this with a generally shallow snowpack with exposed rocks on almost every slope, means taking a ride in an avalanche has the added hazard of collision with rocks. A smooth ride is one thing, but a serrated ride is quite another.

The best advice we can offer is to prioritize travel protocols and slope choices to minimize the risk. We are being careful in this time to avoid complacency, and to focus on our systematic use of travel protocol, communication, and decision making within our team. Choose slopes with smooth runouts, lacking terrain traps and rocks. Only one person on slope at a time. Use safe zones to reduce the number of people in harms way at a single time. Spot your partners from safe zones, and wait your turn. Double check communications and plans are clearly laid out and understood. Take that extra moment to slow down, don’t rush it. At the trail head, make sure everyone in your party has a beacon, shovel, and probe on them, and are practiced in their use.

Looking towards the future. We don’t see any major storm systems delivering the goods, but when they do, we are preparing our mentality to be extra cautious. We know that our current snowpack is rotten, and that any significant loading event will result in avalanches.

Weather
Sat, January 16th, 2021

Yesterday we observed 2-3″ of new, low density snow at 3500′.

Possibly a trace of new snow overnight.


Overall the weather has been fairly uneventful in the forecast area this week.

At low elevations temperatures have been hovering in the upper twenties to just breaking 30°F, with a high of 36°F on 1/10. At mid elevation temperatures have been hovering in the 20’s with a high at Independence Mine of 32°F on 1/10. At the upper elevations the temps have been hovering in the upper teens to lower 20’s°F.

Winds at the upper elevations spiked on 1/11-12 and then again on 1/14, however with so little snow available for transport, this has not contributed significantly to avalanche problems.


Marmot Weather Station 1/14-16

Last 24 hours


Independence Mine last 24 hours

1/14-16 Temps


NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

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