|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.
Today marks one week of elevated avalanche danger due to continuous stormy weather following a cold and dry March. A fast moving warm front will impact Southcentral, Alaska this morning, causing Easterly ridgetop winds to build into the 40’s (mph) with gusts in the 60’s (mph). Up to 6” of snow is forecasted to fall above 2000’; this is .45” of rain at lower elevations. Natural wind slab avalanches up to 1-2’ thick are likely today in the alpine due to blowing snow overloading steep slopes.This is on top of 2-4′ of snow that has incrementally fallen across our region over the last week. These storm related wind slabs have the potential to step down to an older layer in the snowpack, and run further than expected. (More on this below.) Avoiding all avalanche terrain, slopes steeper than 30 degrees, is the only way to manage this problem today. This includes giving run out zone plenty of space, and avoiding trails like Johnson Pass and Lynx Creek, where an avalanche could cross the trail.
One of the many debris piles along the East face of Seattle Ridge over the last few days. This is a good example of how far things have been running in Turnagain, and reminder that today’s strong winds could be creating bigger slabs – increasing their run out distance.
On Saturday rain falling on dry snow caused a cycle of wet slab avalanches below 1500’. Over the last two days an additional 6-12” of snow fell across our region insulating a layer of wet snow. Today another cycle of rain, up to a half an inch of water is forecasted below 2000’. This is a perfect recipe (rain falling on dry snow) to intiate another round of natural wet avalanche activity. To compound this, an avalanche in the alpine has the potential to run into the lower elevation band and intiate a wet slab avalanches – increasing the overall volume. Again it will be important to avoid steep terrain and maintain a conservative distance from all runout zones.
A wet slab that occurred between 1 and 2pm on Eddies on Saturday, 4/1/17. It was roughly 1-2′ thick and 300′ wide. The crown is near ~1500′ and was triggered by rain on the new snow from this week. However, if you look closely, it almost seems like it could have broken in an old weak layer that was not near the top of the pack. Photo by Wendy Wagner.
Snowpit at 1500′ yesterday on Sunburst shows about 3″ of wet saturated snow perserved below yesterday’s new snow.
Several old layers of weak snow (near surface facets and surface hoar) sit buried in the snowpack. Avalanches releasing in the storm snow have the potential to ‘step down’ into them. Snowpack tests are still showing propagation potential in these layers and today’s strong winds and precipitation are likely to tip in the balanche in the upper elevations. An avalanche occuring in one of these older layers could be as deep as 3-5′, and run the entire length of slide path.
A persistent slab avalanche triggered by a skier on Manitoba yesterday in Summit Lake. Luckily no one was cuaght or injured. Photo by Matteo Calcamuggi
A snowpit at Sunburst yesteday shows several weak layers (buried surface hoar and the March facets) that are sitting under this week’s snow. Snow totals in the alpine are estimated to be closer to 3-4′ where the snow has remained dry.
Yesterday rain/snow line moved from 200′ to 700′ late afternoon with daily warming. Scattered showers dropped an additional .4 € of H20 fell, 4 € of snow, along Turnagain Pass. Daytime temperatures reached a high of 41F mid day at Center ridge weather station. Skies were obscured and ridge top winds averaged around 20mph from the East. Overnight temps cooled to freezing, causing light rain to become snow again at sea level.
Today a warm front extending from a low pressure system in the Gulf of Alaska is quickly approaching South-central Alaska. Easterly ridge top wind are expected to build this morning from 20mph to 40mph by early afternoon, gusts could reach the 60mph’s. Warming temperatures will cause rain at lower elevations today and rain/snow line may reach 2000′ my mid day. Rain and snow showers are expected to pick up intensity by late afternoon, and a total of .45 € of water is expected by 6pm.
Tonight precipitation should intensify, with an additional 1 € of H20 forecasted. Warm temperatures will likely keep precip as rain below 1000′ overnight. Strong Easterly winds are expected to last through tomorrow morning. Expect a similar pattern of low pressure systems to continue to impact our region through the week.
|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: Bertha Creek
|Schauer/ Cullen Forecaster
|Observation: Magnum & Cornbiscuit
|Moderow / St. Clair
|Observation: Tincan Backdoor
|APU Snow Science I
|Observation: Silvertip Creek
|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