|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.
This week has brought much welcomed new snow to the area. Snowfall amounts have been variable, with greatest amounts near Turnagain Arm and lesser amounts in the Girdwood Valley and as you head South along Turnagain Pass. Winds have been in the moderate range. What this leaves behind is a high degree of variability in the newest slab.
A layer of very weak snow below this slab is much more uniform throughout the forecast area. A 3 week dry spell created this layer of mostly facets. This layer is sitting on a stout crust in the lower and mid elevations.
On Turnagain Pass you will encounter soft slabs 6-10” in depth depending on location. Yesterday skiers remotely triggered slabs from up to 100 yards away. Tests yesterday showed the potential for avalanches to propagate across slopes (see video below).
In the Girdwood Valley older wind slabs (4-8” thick) which formed almost a week ago sit on this weak layer. These older wind slabs are concealed by 6” of storm snow. This makes it more difficult to detect these slabs.
While slabs are not very thick, they do have the ability to connect across terrain features and produce enough volume to injure or bury a person. This issue becomes more pronounced on broad, open and complex terrain.
What does this all boil down to? Staying off of terrain over 35 degrees including slopes connected to steeper terrain will be the best way to avoid triggering slabs today.
Warm temperatures, occasional sunshine and loose surface snow will combine to make wet loose avalanches another snowpack issue to manage today. Avoiding steep sunlit slopes will be the best way to manage this concern. While volume may be low initially, steep sustained slopes hold the potential to produce higher volume far running wet loose avalanches capable of carrying or injuring skiers and riders. This issue becomes even more pronounced when terrain traps such as cliffs, gullies, glide cracks or trees are below.
Rollerballs and shallow wet loose avalanche activity on Lipps yesterday (Feb 11, 2015). Expect more of the same today.
Over the past 24 hours we have seen temperatures on the rise with ridgetop stations averaging in the mid to high 20s F. Winds have kicked up on Seattle ridge into the 15 mph range in the early morning hours with other stations showing light winds. A trace to an inch of snow fell on Turnagain Pass.
Today expect showery conditions, with periods of flurries and occasional clearing. Snow accumulations will be light, in the 1-2 € range. Rain/snow line should hover around the 1000′ level. Temps will remain mild as warm air pushes up from the South, keeping ridgetop temps in the high 20s to low 30s F range. Winds will be out of the East at 10-15 mph.
The extended outlook is calling for continued unsettled weather. A broad area of circulation around the Gulf of Alaska will deliver generally light precipitation and warm temps through the weekend.
|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