|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.
The combination of warm temperatures and sunny skies yesterday were causing loose snow avalanches to release on steep southern aspects. Tincan Proper and the Library are perfect examples of terrain that receives strong solar warming where loose snow avalanches release from exposed rocks and then entrain more loose snow on the way down. These loose snow avalanches were increasing in size throughout the day yesterday with the largest being big enough to fully bury a person (D2).
|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
It was eerily warm in the mountains last night, with the full moon lighting up the slopes and temperatures hovering around 35 F at upper elevations. Today we are expecting conditions to be very similar to yesterday. Except the temperature inversion is expected to be even stronger, potentially reaching 40-45 F between 3500-4500′. Despite the warm temperatures, the clear skies overnight probably allowed the snow surface to re-freeze after the surface melting yesterday. Wet loose avalanches releasing near rocks or trees and entraining loose snow below should increase in size throughout the day as the surface snow softens. These could become large enough to bury a person later in the day and are likely to be releasing naturally on steep southerly slopes receiving direct sun. Human triggered wet loose avalanches are also likely and it is helpful to have a plan to manage them by carefully choosing your terrain. Due to the unusually warm temperatures human triggered wet loose avalanches or roller balls are also possible on aspects that are not receiving direct sunshine.
To manage this avalanche problem it is important to monitor the snow surface conditions on a variety of aspects and be aware of any steep south facing slopes above you that could be heating up quickly. Wet loose avalanches can run a surprising distance down slope and if they pick up enough loose snow on the way down they can pack a serious punch. Typically you can switch to a shadier aspect to avoid wet loose avalanches, but with the unusually warm temperatures today it is possible that wet loose avalanches or roller balls could occur even on shady slopes.
Cornice fall is more likely with warm temperatures and strong sunshine, so it is important to be aware of any cornices overhead and try to give them a wide berth if you are travelling along a ridgeline. A big chunk of cornice falling also has the potential to trigger a slab avalanche on the slope below.
Glide cracks have been opening up over the past several weeks and the rapid change in temperature could make them more likely to release. These things have a mind of their own and can really release under any conditions, so it is important to be aware of any glide cracks overhead and try to minimize time spent underneath them.
The rapid warming of the snowpack over the past few days could be enough to cause an avalanche on a buried weak layer or an old lingering wind slab. We have several weak layers in the upper 2-3′ of the snowpack the have been unreactive for several weeks now, but it is feasible that the rapid warming or a loose snow avalanche on the surface could trigger a deeper avalanche in an isolated area. These weak layers are more prominent in areas of the forecast zone that have a thinner snowpack, like near Crow Pass and Johnson Pass Trailhead, so extra caution is recommended if you are travelling in one of those areas.
Yesterday: Sunny skies with a strong temperature inversion leading to warmer temperatures at upper elevations. Ridgetop weather stations are reporting temperatures of 30-35 F throughout the last 24 hours. Weather stations below 2000′ elevation saw somewhat colder temps over the past 24 hours ranging from the teens overnight to 40 F during the heat of the day. Winds have been averaging 0-10 mph over the past 24 hours with gusts up to 15 mph.
Today: Sunny skies and warm temperatures will continue today, with temperature possibly reaching 40-45 F from 3500 to 4500′! At lower elevations the temperatures should be slightly lower but still expected to remain above freezing. Valley bottoms could have cold air pooling into them, causing winds along Turnagain Arm. Wind speeds should be 0-10 mph with gusts to 15 mph. Today should be the warmest day of this high pressure temperature inversion.
Tomorrow: Wednesday looks like the last day of this stable and warm weather pattern. Conditions will be very similar to today with some high clouds possible but otherwise sunny and warm. Wednesday night winds are expected to shift to NW and increase slightly to 5-15 mph. These increased winds will move the temperature inversion out of the area overnight Wednesday and return us to more normal seasonal temperatures.
PRECIPITATION 24-hour data (6am – 6am)
|Temp Avg (F)
|Snow Depth (in)
|Center Ridge (1880′)
|Summit Lake (1400′)
|Alyeska Mid (1700′)
|Bear Valley – Portage (132′)
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