|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.
If this is your first day reading the advisory this winter it is important to know that deep slab avalanches have been a concern in the advisory now for two weeks. If you have been following along all season we are not trying sound like a broken record but the message is the same. This snow pack set-up continues to warrant elevated caution and respect. It is a high consequence avalanche problem that is impossible to outsmart. The ingredients for a deep slab avalanches have been found in the upper elevations of our forecast zone, above 3000’ on slopes that did not avalanche in the early December storm cycle. There is a hard slab, 3-5+ feet thick sitting on top of weak sugary snow (basal facets) near the ground. Observations over the last few weeks indicate this poor structure is widespread across our region in the alpine elevations.
When dealing with a deep slab avalanche problem, keep in mind:
An avalanche on the NW face of Pastoral was triggered one week ago by a party of two skies traveling on the low angle terrain below. They were very lucky and were able to get out of the way of the debris. This avalanche also triggered a second avalanche on an adjacent slope over 1000 feet away. Deep slabs can linger for long periods of time and warrants extra caution in places that have not avalanched.
A view of the North facing terrain of Corn Biscuit taken yesterday from Magnum. Some old debris can be seen on looker right side, lower North Chutes, but much of the upper elevation terrain of Corn Biscuit and Super Bowl are still intact and didn’t have evidence of much avalanche activity from mid December.
As we move further away from a wind event that ended on Dec.24th wind slabs are becoming more difficult to trigger. Cold temperatures are making the snow more brittle, and instead of seeing high energy shooting cracks we’re seeing wind boards crumble underfoot. Triggering an old wind slab is still possible in very steep terrain with more potential in the alpine zone. Places you might trigger an old wind slab will be in steep couloirs, large unsupported terrain features, or in thin rocky areas. Triggering a wind slab in the Treeline zone is becoming less likely, but isn’t out of the question on isolated features. The tricky part about this problem is that it will be hard to evaluate a steep slope before committing to it. The other big risk is the possibility of initiating a much larger and more dangerous avalanche if you are above 3000’. Identify features that have fat, smooth, pillow-type shapes and be suspect of any slope that may harbor a more dangerous deep slab problem.
Steep wind loaded gullies adjacent to thin rocky areas on a SE aspect on Seattle Ridge. This is one example of where triggering a wind slab is possible.
Yesterday skies were clear and temperatures along ridgetops averaged in the teens with pockets of single digit (F) temps found at valley bottoms. Winds were light from the East. No precipitation was recorded.
Today looks similar with mostly clear skies, light and variable winds, and temperatures averaging in the teens to low 20F’s. No precip is expected.
A pattern change is in the forecast for this weekend beginning Sunday with a series of low pressure systems moving into our region. This storms should bring warmer temperatures, precipitation (snow and possible rain) and strong winds. At this point it is uncertain how these storms will track across the region, but stay tuned for more info as we move closer to the weekend.
*This 1″ recorded at Summit Lake is likely from ice crystals in the air and not from snow falling from the atmosphere.
|Temp Avg (F)
|Snow Depth (in)
|Center Ridge (1880′)
|Summit Lake (1400′)
|Alyeska Mid (1700′)
|Temp Avg (F)
|Wind Avg (mph)
|Wind Gust (mph)
|Seattle Ridge (2400′)
|Observation: Seattle Ridge
|John Sykes Forecaster
|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