Turnagain Pass Avalanche Forecast

Clear skies following a big storm is a red flag warning for human triggered avalanches. Over the last three days rain, snow and strong winds impacted our region with an additional 2-3’ of snow in the upper elevations on top of 2-3’ that fell over the weekend. Rain/snow line reached around 3000’ on Tuesday and slowly dropped to ~1300’ yesterday morning as temps cooled near the end of the storm. There was a widespread natural wet avalanche cycle observed on Tuesday in steep channelled terrain from Girdwood to Summit Lake.  

STORM TOTALS above 2,500′ (1/15-1/17)

Turnagain Pass     20-30″  (2.3” of snow water equivalent)
Girdwood Valley    20-30”  (2.1” of snow water equivalent)
Summit Lake         6-10”  (0.6” of snow water equivalent)

Don’t Forget!!! This was the second storm in one week. Basically 4-6+’ of snow is sitting on old weak surfaces (surface hoar and facets) from last week. In between these two storms, several human triggered avalanches occurred on Seattle Ridge  and Eddies, without incident, and stability tests were showing propagation potential in older layers of the snowpack.  More time and lots of patience is required for all of this new snow to adjust. If you are headed out – keep these points in mind

1. Slabs triggered will be deep (2-3+ feet) and could step down to a deeper layer. These are dangerous and unmanageable avalanches
2. Due to the depth of the storm snow, no signs of instability may be present before someone triggers a slab
3. Remote triggering an avalanche from below, or near a slope is possible
4. Cooling temperatures will be forming a crust at lower elevation and stabilizing the snowpack below 1500’- don’t let this fool you into thinking the upper elevations are stabilizing quickly

Dry snow is covering and insulating a wet layer of snow within the new storm snow. Until this wet layer freezes, triggering an avalnche will remain possible in mid elevations. 

Most of the gullies along Seattle Ridge are full of new debris from a wet snow avalanche cycle that occured on Tuesday. 

Weak layers within the snowpack have the potential to re-activate with the added load of this week’s new snow (5” of water weight). Additionally, avalanches in the storm snow, discussed above, could step down to these deeper layers and produce a very large avalanche depending on the size of the slope. In short, two layers of buried surface hoar and near surface facets sit roughly 4-8’ deep at this point and is a concern at elevations above 2,000′. Basal facets, near the ground, remain a concern at elevations above 3,000′. At this point very little is known about reactivity of these weak layers, and its going to take time and patience for the snowpack to adjust. 

*Giving the snowpack time to heal from these storms is key. Sticking to low angle terrain with nothing steeper above is recommended. Remember, it’s the first 2 days after a storm where most avalanche fatalities occur. Although there is nice powder at the upper elevations that can lure us, now is not the time to be sampling it.

A natural avalanche near Bertha Cr on the Southern end of Seattle Ridge (SE aspect) that broke into older layers of the snowpack. 

Cornices have been growing and were unstable in between the two storm cycles this week. Triggering a cornice is likely if you get too close.  A cornice fall could trigger a very large avalanche on the slope below. Give these features lots of space and remember they can break further back from a ridge than expected.