The problem with the MLK buried surface hoar sitting 2-3′ below the surface is the potential consequences and the uncertainty. It was the culprit in all of the scary avalanches on the Seattle Ridge side. The most recently triggered avalanches were four days ago and snowpack tests on Saturday showed that the layer still has the potential to be triggered on that side of the road. On the non-motorized side there haven’t been avalanches triggered. The buried surface hoar has been found in snowpits but recently has not shown the same potential for triggering. We don’t have a lot of data on this side. The fact that the MLK buried surface hoar is so widespread above 2000′ in the advisory area is concerning. Is there still a chance of triggering a large unsurvivable avalanche on both sides of the road? Or up Lynx or in Placer? At this point we are still saying YES. This the type of weak layer that can’t be underestimated. Additional snow fall and wind loading also could add stress to a layer like this.
What to keep in mind:
1- Around 2-3 feet under your feet or snowmachine sits a weak layer
2- The weak layer may or may not be reactive, this is the tricky part
3- If an avalanche is triggered in this deeper weak layer, it can be very large and propagate across the entire slope.
4- No obvious signs of instability are likely to be seen before a slope releases and it may be the 1st track on the slope or the 20th…
5- Remotely triggering a slab from the ridge, sides or below is possible
6- Use safe travel protocol and assess the consequences if the slope slides. The larger the terrain = the larger the potential avalanche!
To complicate matters the Girdwood Valley has another weak layer of facets associated with a crust. This is now roughly 2-3′ below the surface. All this said, it’s important to keep in mind that the snowpack harbors buried weak layers.
Buried surface hoar at 3200′ on Sunburst, 2-4-19.
Large avalanches on the backside of Seattle Ridge, 2-2-19.
Both the winds last night and on Sunday were enough to move the soft new snow around. Look for signs of wind loading in the Alpine. Fresh wind slabs maybe tender. Watch for cracking in the surface snow and stiffer snow over softer snow. Although wind slabs are likely to be shallow, they could be more dangerous if they were to step-down and trigger a large slab that breaks in the buried surface hoar discussed above.
Loose snow sluffs: Sluffs on steep slopes within the new snow should be expected.
Cornices: We had a report of a large cornice fall in upper Seattle Creek drainage over the weekend. Give cornices an extra wide berth as they continue to grow.
Cross-loading and wind texture on Seattle Ridge, 2-4-19. Photo: Nikki Champion
Glide cracks are opening again. We know of one glide avalanche that has released recently in the Summit zone just north of Manitoba. Look out for glide cracks and limit exposure under them!
Yesterday: Mostly clear skies with valley fog between 1000-2000′ decreasing throughout the day. Easterly winds were light during the day but increased to 10-15 mph overnight with gusts into the 20s. Clouds moved in late in the day.
Today: Mostly cloudy skies and light snow showers starting early this morning are expected to continue on and off throughout the day as a front pushes in from the southwest, 1-3″ of snow forecast. Easterly winds 10-15 mph with gusts into the 20s. Temperatures should remain in the 20Fs at upper elevations, and continue to hover near 30F at sea level.
Tomorrow: Mostly clear skies and calm winds with temperatures in the 20Fs. The next chance for snow looks to be over the weekend. Stay tuned!
*The Seattle Ridge anemometer (wind sensor) was destroyed. We have a replacement on the way and it should be operational by mid February.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||28||1||0.1||59|
|Summit Lake (1400′)||25||1||0.1||28|
|Alyeska Mid (1700′)||25||2||0.2||53|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||25||*N/A||*N/A||*N/A|