Turnagain Pass

Seward Highway: Multiple small natural avalanches released during yesterday’s warm up. They ran about halfway down the paths, stopping well above the highway.

Winds have returned to the area, and will once again be at work making a fresh round of wind slabs to look out for today. Weather stations are showing sustained westerly winds of 15-25 mph since yesterday evening, with gusts at 30-50 mph near Girdwood and Turnagain, and as high as 72 mph closer to Summit Lake. We are expecting to see similar speeds through the day today. There is limited snow for transport after the strong winds from last week, which will limit the size of new wind slabs forming today. Expect to find these in the typical locations- below ridgelines, on the downhill side of convexities, and in gullies. Clear warning signs like shooting cracks or collapsing are all the info you need to avoid steep terrain. Keep in mind that a relatively small wind slab triggered near the surface has the potential to step down to a deeper weak layer, creating a very large avalanche. More on this in problem 2.

The continued warmup is the wildcard today, and is likely increasing the chances of triggering an avalanche. There were several small natural avalanches yesterday along the Seward Highway near Girdwood, which were most likely a result of continued above-freezing temperatures. With similar warm weather today, we may see some similar activity. There is some uncertainty as to just how tender these surface problems will be today. Whenever we are dealing with a higher level of uncertainty, the safest bet is to increase your safety margins by sticking to lower angle terrain, traveling one at a time, and watching your partners from safe spots out of the way of avalanche paths.

Cornice Fall: Strong winds and above-freezing temperatures will combine to push cornices towards their breaking point today. Be sure to give them plenty of space while traveling at ridgetops, and limit time spent traveling below them. A chunk of cornice breaking off is a big load to drop on the snowpack, and would likely trigger an avalanche near the surface, or possibly deeper.

Loose Wet Avalanches:  Continued warm temperatures may increase the likelihood of loose wet avalanches. While it is unlikely these will bury a person, they can be dangerous if they drag you into terrain traps like trees, alders, rocks, ravines, etc. They also have the potential to trigger a larger avalanche on deeply buried weak layers.

Charts from the Sunburst weather station (3800′ el.). Over 24 hours of above freezing temperatures and continued strong westerly winds may cause issues today. 12.27.2021

The deep persistent weak layer of facets from early November is still giving us cause for concern today. In most places, this layer is buried deep enough that the current warm blast is not having a big effect. This may not necessarily be the case towards the southern end of our forecast area and the Summit Lake zone, where the weak layer is closer to the surface. None of this really changes the way we have been approaching this layer. The potential for a large and unpredictable avalanche requires dialing terrain choices back and avoiding big steep slopes. Keep in mind these avalanches can be triggered remotely from above, below, or adjacent to a steep slope.

In the long run, the current warm spell will actually do a lot of good in helping us put this layer to rest. We are anticipating this layer is going to become really difficult to trigger once temperatures drop again and the snowpack locks up. For now, it is still a concern. Stay tuned in the coming days for more on this.