Turnagain Pass

A strong Southerly flow will continue to bring us showery conditions today; 3-5” of new snow is expected. Easterly ridgetop winds 20-30mph will continue to transport snow in the upper elevations and load leeward aspects. This is in addition to 28”of new snow that has fallen in the last two days, a total of almost 9’ of snow since Christmas. Rain/snow line has fluctuated between 1500’ to 800’ this weekend causing wet saturated snowpack below Treeline. Wind slabs in the new snow could be as thick as 6′ in places. 

If you are thinking of heading to Turnagain Pass today, keep in mind the ‘rapid loading’ is a Red flag and warrants extreme caution. Avoid all avalanche terrain including putting yourself under steep slopes where a natural avalanche from above could run into flat terrain.

Many different avalanches are possible today:

1) Wind slab: Triggering a wind slab 2-6’ thick is likely on steep wind loaded slopes. Winds are forecast to remain from the East in the 20mph range. If this is the case, fresh and sensitive wind slabs will remain through the day. 

2) Cornices: With such strong winds and warm snow at the ridgetops, we can expect cornices to be tender! Not only can these trigger an avalanche below, but may also trigger a slide breaking deeper in the snowpack – creating a very large avalanche. 

3) Wet loose avalanches: Rain and wet snow has saturated the snowpack below 1500’ in Turnagain (up to 2000’ in Girdwood and Portage.) This is more of a concern in areas with terrain traps and in steep channeled terrain where an avalanche from above will be impossible to escape. Cooler temps today will be helping this part of the snowpack drain.

Be aware that plow drivers are working hard to keep Turnagain Pass clear of snow. With heavy wet snowfall like yesterday many of the parking areas may not be plowed. Please try to park in places that allow the plows to continue working. 

Yesterday in Summit Lake a snowboarder triggered an avalanche on Tenderfoot in an area many perceive as safe terrain. In the last two days Summit Lake has received 2’ of new snow, which is sitting on several different layers of weak snow including buried surface hoar. Human triggered slabs 3-4’ deep are likely in the Summit Lake area today and may be triggered on slope angles less than 30°. Obvious signs like wumpfing should not be ignored.

A weak layer sitting on a hard bed surface is buried under 5’ of settled snow. Many large avalanches have been observed naturally in channeled terrain along Turnagain Arm and Portage this weekend, but due to poor visibility it is unknown if avalanches have occurred on these older layers. Periods of rain have saturated areas of the snowpack below 2000’. Several large avalanches (D3’s) were triggered yesterday morning with artillery at Alyeska. One of these large avalanches triggered a large wet slab at 1800’ likely on the Thanksgiving crust bed surface. Snow pit tests at Tincan have demonstrated good stability this weekend, but due to limited information we don’t want to make any assumptions. Buried surface hoar is also lurking in the snowpack.

The bottom line is poor structure exists in the snowpack and a 10 day loading events (snow, rain and wind) have created a high consequence avalanche problem. More time and stable weather conditions are needed before it will be safe to go into avalanche terrain.