Hatcher Pass Avalanche Center

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, February 13th, 2021 - 7:00AM
Expires
Sun, February 14th, 2021 - 7:00AM
Forecaster
HPAC Staff
The Bottom Line

The avalanche hazard for today is MODERATE for Dry Loose avalanches (sluffs) on steep slopes 40° and steeper, on all aspects, at all elevations.

New low density snow from last week and this week have improved conditions, in addition to increasing the potential to trigger sluffs.

Route choice and sluff management will be integral to not getting sluffed into a terrain trap or somewhere you don’t want to go. We recommend practicing safe travel protocol, skiing/riding one at a time, spacing out, and using appropriate safe zones.

An additional concern for human triggering small persistent soft slabs failing 0.5-2 feet deep exists in isolated, previously wind effected areas, on all aspects, at mid to upper elevations.

Ill bet you a HPAC Square Pow IPA that you hit a rock too, sorry.

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Sat, February 13th, 2021
Upper Elevation
Above 3,500'
Moderate (2)
Avalanche risk
Mid Elevation
2,500'-3,500'
Moderate (2)
Avalanche risk
Low Elevation
Below 2,500'
Moderate (2)
Avalanche risk
Upper Elevation
Above 3,500'
Avalanche risk
Moderate (2)
Mid Elevation
2,500'-3,500'
Avalanche risk
Moderate (2)
Low Elevation
Below 2,500'
Avalanche risk
Moderate (2)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

Numerous small, natural and human triggered dry loose avalanches (sluffs) were observed this week in much of the terrain at hatcher pass.

2/12 – Microdot, S, 4250′. Unintentional human triggered loose dry avalanche. Rider escaped. Note that having been caught in this slide, the rider could have been swept into rocks and over a small cliff band.

 

2/11-12 – Gold Chord, SE, 4000′. Natural, small, dry loose avalanches.

 

Few, small, isolated natural and human triggered soft slabs and wind slabs were observed this week.

2/10 – Marmot, SW, 4000′. Intentionally triggered, small, fresh wind slab avalanches.

 

2/9-10? – Martin Mine, E, 4250′. Natural slab avalanche, D2

 

2/10-11? – Cable Valley, SW, 4900′. Small, Natural storm slab avalanche.

 

Avalanche Problem 1
  • Dry Loose
    Dry Loose
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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

Dry loose sluffs will be possible to human trigger today only on slopes 40° and steeper, on all aspects, at all elevations. HP received 4″ of new snow on 2/10-11, adding to last weeks 6-10″ of low density snow. This snow combined with old weak facets (Square Pow) will increase the size and consequence of any sluff. Terrain choice and sluff management will be integral to not getting caught or tweaking a knee today. Unfortunately, despite the increasing snow coverage, nearly everyone is still hitting rocks. We are continuing to dial it back a notch due to these hazards.

Some small natural loose dry avalanche activity is possible on south to west aspects at all elevations, on steep slopes with direct solar gain. These will be more likely near rock bands where dark rocks absorb heat from the sun and melt nearby snow, triggering loose dry avalanches.

Additional Concern
  • Persistent Slabs
    Persistent Slabs
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.
More info at Avalanche.org

Small, isolated persistent slabs 0.5-2 feet deep may be possible to human trigger in upper elevation terrain on aspects where wind effected, stiff snow at ridge tops and on cross loaded features exists. Anywhere you encounter stiff snow, you can be assured it is sitting on weak facets, a potential set up for slab release. Stiff, smooth, hollow snow over weaker snow, combined with cracking or collapsing is a red flag for this problem.

Weather
Sat, February 13th, 2021

New snow totals Feb 7th -11th:
Independence Mine: 4″ of new snow

Temperatures at 4500′ since 2/11 have warmed from the teens into the lower 20º’sF. Its 19°F at Marmot, 18°F at Independence Mine, and 5°F with clear skies at the Palmer Airport this morning at 6am. For today the Rec Forecast is calling for inversion with warmer temps up high, possibly reaching 29°F at 3000′ this afternoon with a temp of 22°F at 1000′, however models seem to be indicating slightly cooler temperatures by a few degrees.

Calm winds have persisted along with clear skies since 2/11, and today is no different. However we are looking at a pattern change starting Monday as the Yukon high pressure migrates southward and allows for low pressure systems to enter southcentral from the Bering. We may see some clouds as early as tomorrow with the next chance for snow Monday night into Tuesday.


Marmot 4500′ Last 24 hours


NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

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