Turnagain Pass

• Turnagain Pass: Magnum, N face – Crown from either 12.9 or 12.10.21 at ~2900′ on N aspect, observed from center ridge lot. Could be an old glide crack, but appears more likely to be a new avalanche that was partially filled in by wind blown snow. Appears to have broken into deeper faceted layer, but really difficult to tell with combination of cloud cover and only seeing it from a long distance away.

Photo 12.10.21

• Turnagain Pass: Cornbiscuit N face – From either 12.9 or 12.10.21 on N aspect at ~2,700′. Another potential new crown seen from a long ways away during a short break in cloud cover. Appears to be similar terrain character, aspect, elevation, and depth as release on Magnum.

Photo 12.10.21

• Turnagain Pass: About a mile NW of Peak 4940 along ridgeline (labelled 4650 on Cal Topo map) – From either 12.9 or 12.10.21 on SW aspect at ~4000′. Likely a release in the new snow or a wind loaded pocket of new snow.

Photo 12.10.21

• Summit Lake: Fresno Ridge – Small human triggered avalanche at 2000′ on SSW aspect along Fresno ridge in Summit Lake area.

Small human triggered avalanche in Summit Lake area. Photo Mr. Savoona 12.10.21

• Seward: We received a report of a small human triggered wind slab that released remotely on Mt Alice. The group also reported lots of collapsing and whumphing along their route and strong winds transporting snow.

As the skies start to clear today it may be tempting to venture into more consequential avalanche terrain, but with moderate winds from 10-25 mph and lots of light snow available for transport we expect wind slabs to be sensitive to human triggering anywhere from 1 to 3′ deep. We are entering another period of outflow winds from a cold airmass in the interior, and during our last weather pattern like this the Seattle Creek drainage saw higher winds than the rest of Turnagain Pass. In addition we are still very concerned about the potential for triggering very large avalanches 3 to 6′ deep on a layer of buried facets (see problem 2 for more details). Conservative decision-making and terrain selection is essential today, keeping slope angles low and being aware of potential active wind loading along ridgelines.

During the last storm (Thursday through Friday morning) 12 to 24″ of snow fell with wind speeds from 20-35 mph out of the east. We saw evidence of wind transport during a brief break in the clouds yesterday that indicates wind slabs are likely to be lingering along ridelines and in cross loaded gullies. Today the winds are forecast to blow out of the northwest and could create new wind slabs in different terrain features compared to the winds during the storm. Look for fresh cornices, texture on the surface of the snow, hollow feeling snow, and smooth pillow features to identify areas with wind slabs.

Wind affected snow along the ridgeline of Cornbiscuit yesterday. Photo 12.10.21

Human triggered avalanches on a layer of facets buried 3 to 6′ deep are still likely today and would result in very large and destructive avalanches. This layer has been the culprit of many near misses in the past week and has shown the potential for remote triggering and very wide propagation. We heard reports of collapsing and whumphing across the region yesterday which indicate that this buried weak layer is still reactive. During a brief break in the cloud cover we saw a few potential new avalanches on this layer at about 2800′ on the north faces of Magnum and Cornbiscuit. The only way to manage this type of avalanche problem is through conservative terrain selection and avoiding areas underneath steep slopes.

Snowpack structure for faceted weak layer. All the snow from the past several weeks acting as a slab on top of a thick layer of sugary facets on top of a firm bed surface. Photo 12.8.21