Turnagain Pass

After a brief break between storms yesterday, yet another warm ‘fire-hose’ of sub-tropical moisture will be pumping our way today. Easterly winds are just picking up this morning and should reach gale force (or up to a 10 on the Beaufort Scale) by noon on the ridgetops. Precipitation has just begun as well and we can expect 1″ of rain below 1,300′ and around a foot of snow in the Alpine (another 1″ is expected tonight with a rain/snow line dropping to ~600ft). What this all means is another day of HIGH avalanche danger in the mountains.

Avalanche issues today will be similar to those seen since Christmas Eve when this series of storms began. These are: WIND SLABS, STORM SLABS and CORNICE FALLS. Most of the activity we have seen so far has been initiated in the dry snow above treeline. Several slides have been big enough to deposit large amounts of debris at the bottom of the path. Today’s storm is just as likely to create large avalanches and until we see a true break in weather, sticking to gentle slopes and areas well away from slide paths will be key. 

Just because you are in the trees and out of the wind doesn’t mean the pack is stable; especially in the Summit Lake zone. Here the pack is shallower and harbors more weak layers under the recent storm snow. We went out to look at a snowboarder triggered avalanche from Saturday on Tenderfoot yesterday. What we found was a layer of buried surface hoar existing right around treeline (2,000-2,400′) that was responsible for this avalanche. More details on that HERE and HERE. 

With another spike in temperatures, rain up to 1,300′ and wet snow to 2,000′, we may see additional natural wet avalanche activity below 2,000′. Many of the gullies along the Seward Highway and Seattle Ridge have slide over the past week, wet debris can be seen in the bottom of these. Although most of these slides start as dry avalanches in the Alpine and run into wet snow on the descent, some do initiate below 2,000′ as true wet avalanches. Needless to say, steering clear of runout zones is advised.

Sitting under 5-7′ of settled storm snow is a layer of old faceted snow over the Thanksgiving Rain Crust. As we pile more and more load on top of this facet/crust combo, we could see very large avalanches. Some of the large avalanche activity seen during this past week may have ‘stepped-down’ into this deeper layer. And, just one more reason to let the mountains be as these storms roll through.