Turnagain Pass

Updated @ 9am: We had a report of a snowmachine triggered slab avalanche near the Johnson Pass area yesterday. Reported as ‘a slab on a smallish slope near the Johnson pass trail’. Heads up in areas like this with steep avalanche terrain above you.

Cold Arctic air is spilling in from the north this morning and along with clearing out the skies, it’s also expected to wreak some havoc with the snow. As of 6am this morning, the northwest ridgetop winds have bumped up to the teens with gusts in the 20’s at the Sunburst weather station. They are expected to reach averages near 20-30mph with stronger gusts and even stronger winds are expected south of Turnagain Pass. Although the snow surface was affected by Wednesday night’s winds, there is still plenty of loose snow available for transport. This flow direction can funnel through Crow Pass near Girdwood and the Kenai mountains in interesting patterns, loading different aspects on the same pieces of terrain, and can also split around and spare certain zones.

For anyone headed out today, keep a close eye out for where the winds are transporting snow, building cornices and loading slopes. Plumes are likely to be visible if the winds verify. As always, feel for stiff snow over softer snow and any cracks that shoot out from you. These are signs you’ve likely found a wind slab. Avoid being under cornices, these could form in unusual places. Additionally, buried weak layers hide 2-3+’ below the surface and freshly wind loaded slopes could overload these, creating a much larger avalanche. It’s a day to avoid any slope that has recent or active wind loading.

The animation below is from windy.com and shows the general forecast wind pattern along ridgetops, around 5,000′ in elevation. Blue is light wind and orange/red is strong (color legend is on the bottom of the image). Note: weather model data is useful for a general pattern and not always accurate for a specific point.

As we saw yesterday with the brief period of visibility, several avalanches occurred during the winds on Wednesday night and many of these were suspect to have released on the old weak snow that developed during the first part of January. Even in areas out of today’s winds, don’t forget there are facets and buried surface hoar hiding 2-3+’ under us. As the 2-3′ of low-density snow from the past week settles and stiffens, these layers are still something that could catch us off guard and triggering a persistent slab avalanche remains possible. Sticking to lower angle slopes, with nothing steeper above us and the flats are good ways to manage this risk.

This photo was shown yesterday and is taken of the northerly aspect of Sunburst. Note the wide propagation of the slab avalanche that released sometime Wednesday night (1.29.20) in conjunction with the bump in easterly winds. 

Loose Snow Avalanches:  On steep slopes that are spared the wind and in the lower elevations, watch for easily triggered sluffs.