|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.
We heard of one human triggered avalanche yesterday. This was in Turnagain Pass on a SSW facing slope of Sunburst. It was triggered by a skier that was ski cutting the slope. The avalanche ran to the valley floor – around 1,000ft. A photo of the crown is below. A few more details HERE.
Photo: Corky Still
It has been just over two days now since we received a foot of heavy snow on top of a 10″ thick layer of faceted snow. There was widespread avalanching during and right after the storm on Friday along with one skier triggered avalanche on Tincan. The culprit weak layer was the Nov 10 faceted snow. Facets are a common persistent weak layer and hence the use of the ‘persistent slab’ icon above. From the report on Sunburst, it sounds like this was a classic case of a wind slab over facets.
Image below is the Tincan skier triggered slide from Friday, Nov 22nd. (more details with the above link)
Though the snowpack is stabilizing, it is doing so slowly. The addition of 1-3″ of new snow should not tip the balance but any recent wind loading could. For anyone getting out today onto the steeper slopes, I’d suggest having your escape route planned in case the slab releases. Steering clear of any recent wind deposited snow will be a good bet as well. The poor structure is there in most locations above treeline – as you can see by the snow profile below – and though the slab is slowly deteriorating, making it harder to trigger, it is still there for now.
Winds are slated to kick back up today from the east/southeast – blowing moderate (15-30mph). This, combined with a possible 3″ of new snow as well as existing snow to transport, should be enough factors to form fresh wind slabs. These likely will be shallow and sitting on a variety of surfaces. As always, be suspect of areas with wind deposited snow. These often have the tell-tale signs of a smooth rounded surface and hollow feeling.
A somewhat weak weather system will be moving over us today from the southeast. Cloud cover has set in and between a trace to an inch of snow has fallen as of 6am this morning. Temperatures have increased overnight with mountain tops approaching 20F and sea level areas are in the low 30’s. Winds have increased from the east/southeast and are blowing ~15mph with gusts to 30mph.
Today we are expecting 1-3″ of light snow (up to .3″ water) above treeline. Temperatures should remain in the mid 20’s at treeline and winds continue to blow in the 15mph range with gusts to 30 from the east. Basically, a mild snow/weather day with limited visibility. A chance for freezing rain exists at sea level.
Monday, we should see skies clear up as we have a break between systems. Winds should continue from the east but settle down and temperatures remain mild in the 20’s.
|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