|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
After a month with very little precipitation, weather models are showing potential for a snowy week ahead of us. This is good news for powder hungry folks, but we can’t forget about our current state of the snowpack. As we have been discussing for some time, there are several weak layers in the pack that continue to show signs of reactivity. Hard wind slabs formed by last week’s wind event are, in some cases, overlying these buried weak layers. A human triggered avalanche in the Summit Lake area was proof of this last week. Hence, finding and triggering a slab avalanche remains a concern.
Persistent slabs: Buried 1-2 feet deep are facets sitting on a crust at the mid-elevations and 1-3′ deep is a buried surface hoar/facet combo at the higher elevations. The mid-elevation faceted layer seems to be the culprit for many reported ‘whumpfs’/collapses lately and is the layer responsible for the Summit Lake avalanche. Although the heart of Turnagain Pass has these layers, they are more pronounced and developed on the Southern end of Turnagain Pass and in Summit Lake where the snowpack is shallower. Areas to the North, such as Crow Pass, could also be suspect along with those that have not seen much traffic this season. Until we receive a significant load (hopefully this week), triggering these layers are becoming more and more stubborn with time. Continuing to use safe travel protocol and assessing consequences if a slab does release will be key in choosing terrain. The snowpack we have now will likely let us get away with a lot – but probably not everything.
Hard wind slab on faceted snow – Summit Lake/Tenderfoot avalanche that was human triggered last Tuesday (2/27).
Valley fog up to 2,500′ limited visibility along some mid-elevations yesterday.
Partly to mostly sunny skies were found above thick valley fog yesterday; fog lingered late in the day and up to 2,500′. Ridgetop winds were light (5-10mph) from the West and North. Temperatures stayed cool, in the teens along ridgetops, but warmed up in most valley bottoms to ~30F.
Today, Monday, we can expect mostly cloudy skies with a few snow flurries in the afternoon. Only a trace of accumulation is expected. Ridgetop winds will stay light from the Northwest (5-10mph). Temperatures plummeted to the single digits last night in valley bottoms and should bounce back to the 20’sF today. Along the ridgelines, temperatures will remain in the teens.
For tomorrow, Tuesday, cloudy skies and increasing Southeast winds will be over the area as a quick moving front moves through. Snowfall is expected Tuesday night. This flow direction is not ideal for Turnagain but we could see up to 6 inches. A series of storms will follow Tuesday night’s event, the next system moving in Thursday/Friday. Stay tuned!
|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