Turnagain Pass

There were a few small skier triggered wind slabs yesterday on Sunburst (pictured below) and Tincan. These were in the 6-8″ deep range and around 30′ wide and composed of Monday night’s 3-6″ of snow.

Small skier triggered windslab off the Sunburst ridgeline, with light snow transport occurring. Photo Andy Moderow, 2.15.22.

Heavy snowfall began early this morning in most of Southcentral. Although this storm is favoring Hatcher Pass and the Anchorage area, our forecast zone should pick up anywhere from 6-15″. The higher snowfall amounts will be in Girdwood/Placer and Portage Valleys where 10-15″ is expected, between 6-10″ is expected for Turnagain Pass with a bit less further south in Summit Lake. Ridgetop winds have increased with the onset of the snow and should continue in the 20-30mph range with stronger gusts until this evening when the storm tapers off. All three weather factors are in play today, along with precipitation and wind, temperatures will be rising and rain could reach as high as 1,000′ by this afternoon, creating a rain on snow situation for those lower elevations.

With that said, we can expect all the storm snow avalanche problems out there. These will be storm slabs where over 8″ of snow falls, wind slabs, sluffs, and cornice falls. The size of avalanches will depend on the amount of new snow. In areas seeing a foot or more, expect avalanches to be big enough to be quite dangerous and may run further than expected. Today is a day to play close attention to new snow amounts and winds. This should be in conjunction with the usual red flags (recent avalanches, cracking in the snow and collapsing/whumpfing). If in doubt, sticking to areas that are outside of avalanche terrain will be a good way to have fun in the snow without worrying about triggering an avalanche or being in the way of a natural avalanche occurring above you.

Storm Slabs:  In areas with over 8″ of snow, and especially in places with a foot or more, expect to see slab avalanches in the storm snow. These could be on sheltered slopes as well slopes seeing a little wind effect. Adding to this problem will be today’s rising temperatures, which causes denser snow to fall over lighter snow (upside down storm).

Wind Slabs:  New wind slabs are being formed as we speak with the moderate to strong easterly ridgetop winds over the region. These could be anywhere from 8″ to 2′ deep or more depending on how much new falls. Wind slabs could also pull out older wind slabs from yesterday, making them a bit larger.

Sluffs (loose snow avalanches):  On steep slopes without wind effect, sluffs could occur naturally and will be easy to trigger. They could also trigger a larger storm slab further down the slope.

Wet Avalanches:  Unfortunately the rain/snow line could creep up to 1,000′ today. In this case, rain on snow has a good shot at causing wet loose avalanches in the lower elevations.

Snow total graphic courtesy of the National Weather Service, Anchorage Office. The snowfall numbers are slightly lower for Turnagain Pass due to some rain forecast to fall at 1,000. 

We are continuing to track the snowpack as a whole and the various layers of buried crusts that, in places, have weak snow associated with them. As we’ve been mentioning, shallow snowpack zones are the most concerning for an avalanche breaking in these deeper layers. These areas are on the far north and south of our forecast zone and extend into the interior Kenai. This includes the Summit Lake area (just to the south of our forecast zone).

Glide Avalanches:  A few reports of new glide cracks have filtered in. The photo below by Andrew from Tincan yesterday shows Seattle Ridge with a crack on the south end of the ‘Repeat Offender’ slide path, which is near the common up-track. Cracks have also been seen on Tincan’s south face.

Glide crack on Seattle Ridge, to the looker’s left of the common up-track. 2.15.22.