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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, January 28th, 2021 - 7:00AM
Expires
Fri, January 29th, 2021 - 7:00AM
Forecaster
Jake Kayes
Conditions Summary

Today’s avalanche problem will be dry loose, human triggered avalanches are possible at all elevations and on all aspects. These avalanches will be small in size. Natural avalanches are unlikely. 

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

Riding conditions have improved with last weeks new snow, coverage is still thin in many areas especially near ridgetops. 

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Thu, January 28th, 2021
Recent Avalanches

On 1/24 two human triggered slab avalanches occurred on the Tsunami wall west 3500’. Click this here for more info.

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

Cold temps and light winds this week have caused snow surfaces to lose density and begin to facet. This low density sugary snow will be capable of producing dry loose avalanches on all aspects and at all elevations. Expect to find this avalanche problem in terrain that is 40° or steeper. Human triggered avalanches are possible and will be small in size. Natural avalanches are unlikely.

Natural dry loose on Idaho Peak, south face.

Human triggered dry loose on Marmot, lodge run, west aspect.

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

Two human triggered avalanches on 1/24 are a good reminder that persistent slabs are still possible to trigger in isolated areas. The beginning of the week saw a lot of backcountry travelers covering multiple aspects at the mid to upper elevations without any more persistent slab avalanche activity beyond the ones from 1/24. This is a pertinent negative, confirming the persistent slab problem for isolated locations, and not a widespread problem. Any persistent slab avalanche triggered will likely fail at or near the ground. This is concerning due the high likelihood of hitting an obstacle and sustaining a traumatic injury if you are caught in an avalanche.

Debris from 1/24 human triggered avalanche on the Tsunami Wall west 3500′.

Weather
Thu, January 28th, 2021

New snow totals 1/24-28: Independence Mine 1″ of new snow.

Cold, clear and light variable winds have been the trend this week. On sunday 1/24 temperatures were in the mid 20s and began to drop into the teens. While temps began to drop the sky began to clear and light variable winds began. These conditions have persisted this whole week. With these weather conditions widespread surface hoar has begun to form and snow surfaces have begun to facet.


NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.


Marmot 1/24-28:


Independence Mine 1/24-28:

 


Frostbite 1/24-28:

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