Turnagain Pass

Outflow Winds… Strong northwest winds are seeping through from the interior and sending cold air over Southcentral. Where, when and how strong these winds will be are the driving factor for avalanches today and tomorrow. The one bit of good news is the winds are mostly splitting around Turnagain Pass. The Lost Lake and Seward zone is expected to see much stronger wind and Girdwood and Summit Lake are a bit of an unknown, yet could also see strong wind at times. Many of our ridgetop weather stations don’t pick up the northwest flow direction very well and it can be tough to determine areas impacted and areas that are not. For example the AKRR MP 43 weather station that sits near Bench Peak, above and to the west of Grandview, was gusting into the 40’s mph for a brief period last night. This location is just south of the advisory area.

Wind Slabs:  For today, skies should be clear enough to easily see if winds are transporting loose surface snow, loading slopes and sending any plumes off peaks or ridges. Keep in mind terrain can force the wind to swing around and blow from any direction. Other than witnessing active wind loading, watching for previous wind loading, stiff snow over softer snow and cracking in the snow around you are good ways to suss out wind slabs. A layer of buried surface hoar may be sitting under wind slabs, making them easier to trigger and possibly propagate further above or to the side than expected. 

This graphic shows forecast wind for 2pm today at the 4,500-5,000′ level (ridgetops). The color bar shows wind speed per color. Note how the winds are ushered down Cook Inlet and are less intense over Turnagain Pass. 

Cornices:  Small fresh cornice falls from winds today are possible in areas seeing significant wind. Most likely outside of the forecast zone.

Loose snow avalanches:  In areas out of the wind, sluffs are possible in steep terrain.

Sun effect:  The wind and cold temperatures should overrule any sun effect today.

Deeper in the snowpack and under all this wind slab business still sits various forms of weak faceted snow from January. These layers are buried between 3-6 feet deep and remain a concern for a person to trigger a very large and dangerous avalanche. As time goes by, the likelihood of triggering is decreasing, but we can’t assume we are out of the water yet. Areas outside our forecast zone to the south, with a shallower snowpack, are more likely to find one of these large slabs. Also, areas with little traffic this season are suspect. We need to keep our guard up and consider our terrain selection if getting onto steep slopes.