|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. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential.
|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.
|Size (D scale)
|Unlikely to bury a person
|Can bury a person
|Can destroy a house
|4 & 5
|Can destroy part or all of a village
Although unlikely, there remains a chance that a person could trigger a deep slab avalanche 6’ deep or deeper, failing on weak snow at the ground at elevations above 2500’. Before stepping out into bigger terrain today, consider the consequence of triggering a large avalanche. These avalanches are difficult to predict for a few reasons:
At some point– hopefully sometime soon– we will be able to tuck this problem away as an additional concern. For now, we are still finding weak snow at the ground, and we are actually getting some stability tests to fail in this layer, making this our primary concern for today. Be aware that the most likely places to trigger a large avalanche failing near the ground will be in the areas with the thinnest snowpack. This could be on slopes that have been wind scoured at some point this season, or in steep and rocky terrain. The total snow depth also gets thinner as you head south from Turnagain Pass. Be aware that if you trigger a deep slab avalanche in a shallow spot on a slope, it can propagate into deeper snow.
Tincan. This avalanche occurred almost two weeks ago, but similar avalanches are still a concern for now. Photo: Matthew Howard. 12.04.2020
As always, use safe travel protocol to minimize your risk while you are out. Be on the lookout for clear signs of unstable snow like shooting cracks or whumpfs, only expose one person at a time to avalanche terrain (including runout zones), and keep an eye on your partners from a safe spot if you do choose to ski or snowmachine in steep terrain. You will also want to be aware of lingering wind slabs from the past few days, and continue to give cornices plenty of space. The mountains closer to Girdwood have received 6-8” of low-density snow since Monday morning, and although that will not be enough to bump up the avalanche danger, it may be enough snow to create loose dry avalanches that could knock you off your feet.
Yesterday: Yesterday brought 4” new snow to Alyeska and 1-2” at Turnagain pass, with winds staying around 5 mph or lower. Temperatures reached into the mid- to upper 20’s F with lows in the high teens at upper elevations and the low 30’s F with lows in the mid- to upper 20’s F at lower elevations.
Today: Mountain temperatures are expected to drop throughout the day, reaching the high teens F by this afternoon at upper elevations and staying in the mid 20’s F at lower elevations. Low temperatures tonight will be around 10 F at upper elevations and 20 F in the valleys. Skies will be partly cloudy, with clouds clearing throughout the day. We are expecting light westerly winds around 5-10 mph, with little or no precipitation.
Tomorrow: We have a chance of light snow tomorrow, with 1-4” possible in the mountains. Temperatures should stay cold enough to keep snow at sea level. Easterly winds are expected to pick up slightly to 10-15 mph, with high temperatures around 20 F at upper elevations and 30 F at low elevations.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)
|Snow Depth (in)
|Center Ridge (1880′)
|Summit Lake (1400′)
|Alyeska Mid (1700′)
*Last update at 1:00 a.m.
RIDGETOP 24-hour data (6am – 6am)
|Temp Avg (F)
|Wind Avg (mph)
|Wind Gust (mph)
|Seattle Ridge (2400′)
|Observation: Kickstep NE Bowl
|Observation: TinCan Backdoor/ Center Ridge
|AAS L1 Turnagain
|Avalanche: Lynx Creek
|Observation: Turnagain, Seattle, Mt Ascension
|Silverton Mountain Guides
|Observation: Tincan Trees
|Dalpes/Thamm/ Schauer Forecaster
|Observation: Seward Highway across from Johnson Pass TH
|Avalanche: Base of Seattle Ridge
|Troy Tempel, Thomas Lees, .Josh Bollaert, Damian Naquin
|Observation: Lynx creek