Turnagain Pass

Triggering a slab avalanche 1-2+ feet thick continues to be our main concern. Today 3-5” of new of new snow and moderate winds (Easterly becoming Westerly) may add stress to the overall snowpack, but not enough to elevate the danger rating. Several weak layers are buried within our snowpack at varying depths and elevation bands. A layer of buried surface hoar from Jan. 21st continues to show signs of reactivity in test pits above 2000’, and we’re also tracking a layer of facets over a melt-freeze crust in the mid elevations. Persistent slabs are becoming more difficult to trigger with time, but a large and unmanageable avalanche is still possible. Today watch for active wind loading on all aspects and be aware that red flags such as “whumpfing” may not be present before a slope releases. The most likely place to find this avalanche problem are slopes that have not seen significant traffic this season. 

Deep Persistent Slabs: Keep in mind that there are deeper persistent layers that could ‘wake up’ if you find the wrong spot above 3,000′ in the Alpine. At these high elevations, old weak layers of facets and buried surface hoar sit in the bottom half of the snowpack. This structure is most pronounced in places with a thin overall snow cover, such as the South end of Turnagain Pass, the Summit Lake area and Crow Pass. 

 Propagation on buried surface hoar and facets was found in several location on Eddies earlier this week. 

New wind slabs will depend on how much snow we see today and if winds are activity moving snow around. Ridgetop winds from the East are expected to change to a Westerly direction this afternoon and remain in the 20’s mph. Not much old snow is available for transport, and only a few inches of new snow is forecasted. Expect wind slabs to be small, but they could be tender should you see any obvious clues like blowing snow or shooting cracks. If this is the case steep leeward aspects and cross loaded terrain features will be suspect.   

Sunshine:  Although the sun is unlikely today, be aware it’s that time of year when we need to pay attention to the sun. Following a storm the sun can heat up Southerly aspects and melt surface snow and cause point releases. This heating can also cause a slab sitting on a weak layer to become more reactive. Keep this in mind should a clearing trend behind today’s storm happen sooner than expected. 

Surface conditions before today’s weather consisted of an inch of loose surface snow on top of variable surfaces (wind affected snow and patches of loose settled snow.)