Turnagain Pass

There were no known avalanches yesterday and not many folks out in the backcountry. We did investigate the large avalanche that was skier triggered two days ago in Summit Lake (outside of the forecast area to the south of Turnagain Pass). That report will be updated later today, but a video can be seen here.

Another round of snow and wind has moved in overnight. This event comes with a Blizzard warning for the road system from Girdwood to Seward and an Avalanche Warning for the mountains. Similar to last weekend’s event, we can expect many natural avalanches to occur through the day as the storm is peaking from ~9am to 3pm. Up to 18″ of snow could fall by 6pm and more in favored areas like Portage and Placer Valleys. Ridgetop winds are easterly averaging in the 30’s and gusting near 70mph.

Just like last Saturday, it’s a day to hunker down as we strongly recommend staying out of avalanche terrain. If deciding to brave the roads and parking, be sure to avoid being on, or under, steep slopes (more than 30 degrees). Natural avalanches are likely to be of various sizes and types, but some could be large enough to run much further than we may expect. As we saw from last weekend, debris ran into the flat terrain.

With this storm the most common avalanches should be wind slabs releasing under ridgelines and in cross-loaded gullies (like the road side of Seattle Ridge). These are often triggered by parts of cornices that break off from above. We also could see storm slabs in mid elevation treed areas that are sheltered from winds. This means slabs composed of the new snow from today, which will be somewhere in the foot to 18″ range. Temperatures are warming slightly during the day, which will makes storm slabs more likely as heavier snow falls on lighter snow. All in all, mid-March is not disappointing for snow lovers, but could test our patience.

If we think back to the evening of March 14th (3.14, pi day), that’s when the stormy weather started after a 2-week dry spell. Those old surfaces from early March were sun crusts on solar aspects and weak, faceted snow on shaded slopes. As of yesterday, there was roughly 3-6′ of settled storm snow from the past week on this old early March surface. That interface remains a cause for concern. It was the culprit layer is many large avalanches last Saturday. It was also the weak layer in the large Summit avalanche that was skier triggered on Monday, mentioned above. Today, another 12-18″ will be adding stress and if avalanches break on that old layer, slabs will be in the 4-7′ range and surely able to send debris into the flats below.

Additionally, on the southern edge of the forecast zone (Johnson Pass area) to Summit Lake (outside of the forecast zone), even larger avalanches may occur. Here, there are even older weak layers buried deeper in the pack. A lot of uncertainty exists for Johnson Pass area, but Summit Lake has already seen avalanche breaking in deeper layers. That said, for the next couple days we should let the mountains do their thing and not be in the way. Yet when skies clear, we’ll be wary of these layers.