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ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, March 8th, 2021 - 7:00AM
Expires
Tue, March 9th, 2021 - 7:00AM
Forecaster
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

The avalanche danger is LOW at all elevations. Triggering a large avalanche is unlikely. Use caution on very steep, rocky, wind-affected slopes where an old wind slab pocket might be lingering. Be aware of fast moving ‘sluff’ in terrain where getting knocked over could have high consequences. Sunny slopes will be crusty this morning, but be ready to head for colder slopes if you see signs of heating like roller balls, small wet loose avalanches and wet, mushy snow.

Good travel habits are important, even during ‘green light conditions’. This includes exposing only one person at a time on a slope, watching your partners closely and having an escape route planned in case the snow moves.

Mon, March 8th, 2021
Alpine
Above 2,500'
1 - Low
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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. Dangerous avalanche conditions. 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.
Avalanche Problem 1
  • Normal Caution
    Normal Caution
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.

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

Happy Spring Break!  There is another day of sunshine on tap and the avalanche danger is LOW today. Wait for it…

LOW danger does not equal NO danger. We hope this doesn’t equate to people flocking to avalanche terrain with reckless abandon. Read the discussion below carefully to understand our buffet of normal caution avalanche concerns. Folks were out enjoying the snow over the weekend without incident. We think triggering a large avalanche is unlikely today but there is a slight chance of triggering a small avalanche, especially in complex or extreme terrain i.e. very steep unsupported slopes. Even the definition of LOW danger states “Watch for unstable snow on isolated terrain features.” Please factor this into your travel plans today. As always use good travel protocol and watch for other parties in the same terrain.

Wind Slabs: Pay attention to any recent wind-loading and be aware of old hard wind slabs. Smooth pillowed snow on steep unsupported features or in rocky areas will be the most suspect places to initiate an old wind slab.

Dry and Wet Loose Snow Avalanches (Sluffs): Dry sluffs on steep slopes are probable and although small have been slowly gaining volume on shady slopes, as cold temperatures facet the surface snow.  Keep terrain choices and potential consequences in mind when managing sluff. On sunny slopes, if crusts soften watch for roller balls and small wet loose avalanches both natural and human triggered, especially in steep rocky areas. If you see this start to happen and/or if the snow you are traveling on starts to get wet and mushy, move to a shadier slope.

Persistent Slabs: A couple layers of buried surface hoar and/or facets sit 1-3’ below the surface. Below 2000′ there is a melt-freeze crust  just below a weak layer of snow. With the amount of time that has passed since these weak layers were buried and due to the lack of significant loading over the last month, these weak layers seem to be in a ‘dormant stage’.  We haven’t had a reported avalanche in the forecast area on one of these layers in over a week and even those observed avalanches were small.  Because of the uncertainty that comes with persistent weak layers in the snowpack although unlikely, a small avalanche breaking on one of these layers on a slope 35° or steeper, especially below 2000′, isn’t completely out of the question today.

Glide Avalanches: Glide cracks continue to slowly open. These may release at any time.  Minimize exposure time spent under visible cracks.

Cornices: Cornices should always be given an extra wide berth if traveling along a corniced ridge.  Like glide cracks, minimize your exposure time spent under these backcountry bombs.

An example of terrain to watch for wet loose activity today. The Library 3.7.21. Note the glide crack and cornice hazard as well. 

Wind transport on the Pastoral ridge, 3.7.21. Watch for lingering wind slab pockets today in steep Alpine terrain.

 

 

Weather
Mon, March 8th, 2021

Yesterday: Skies were sunny with high temperatures in the upper teens to low 30°Fs and light westerly winds.  With an inversion setting up overnight lows were in the single digits at low elevations and mid teens in the Alpine. Winds were light and variable.

Today: Skies will be mostly sunny with calm winds and highs in the mid 20°Fs to mid 30°Fs. Clouds will build overnight and winds will become easterly 10-15 mph with gusts into the 20s. Temperatures will be in the 20°Fs.

Tomorrow: Skies will be cloudy with snow showers throughout the day. Temperatures will be in the 20°Fs and winds will be easterly 10-20 mph with gusts into the 30s. Snow looks to continue through Wednesday. There is still a bit of uncertainty about storm track and snowfall amounts. Stay tuned!

PRECIPITATION 24-hour data (6am – 6am)

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 17 0 0 110
Summit Lake (1400′) 13 0 0 45
Alyeska Mid (1700′) 18 0 0 112

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 17 W 8 19
Seattle Ridge (2400′) 18 NE 2 9
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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.