Turnagain Pass

Avalanche activity from yesterday:

Yesterday’s heavy rain below 2,000′ and wet snow above 2,000′ combined with very warm temperatures induced a widespread natural avalanche cycle. This extened to the Summit Lake area as well. We were able to get video footage of one natural slide in Portage Valley – video below. Additionally, the AK DOT Avalanche Program was able to trigger several large avalanches along the Seward Highway – one these can be seen in a video HERE.

The start zones for much of yesterday’s activity was in the dry snow above 3,000’. These slides turned wet as they descended due to entrainment of wet snow below treeline. You can see in the video below from Portage Valley how the powder cloud dissipates as the debris encounters the wet snow.

The slightly cooler temperatures along with breaks in cloud cover overnight will help limit any natural acitivity today. Much of the pack below treeline was draining water rapidly yesterday and today there may be a slight refreeze on the surface. The main areas of concern for wet avalanches will be near and just below treeline or in a gully at sea level elevations where debris can be funneled.

The shock of up to 3” of water weight in 24-hours yesterday did a number to the pack – as can be seen in the above videos and in our field day HERE. At the upper elevations this has added around 2′ of new snow along with rain on snow below treeline. The weak snow near the base of pack that is the culprit for many of our large avalanches is once again being overloaded. Though visibility was limited yesterday, it is likely that many of the debris piles seen occurred by an avalanche breaking near the ground and propagating across slopes at the mid to upper elevations. 

For today, the weather has abated but don’t count on the weak snow near the ground to have adjusted to the new load yet. There is much uncertainty going into today but the fact remains that during the past 24-hours we have had a significant avalanche cycle and there are slopes likely teetering on the edge just needing a human trigger.

At the upper elevations – above 3,000′ – temperatures were cold enough for around 2′ of snowfall during yesterday’s storm. Storm snow instabilities, mainly in the form of wind slabs are likely to be found and potentially triggered. With the warm temperatures these are likely to settle out within the 24-hour window – however, this is relegated to the storm snow and not the persistent slab issue mentioned above.

There is also the potentail for any storm snow avalanche to step down and trigger a larger slide breaking in the weak snow at the base of the pack.