Turnagain Pass

A very warm, wet and windy storm impacted the Kenai and Western Chugach mountains yesterday. Heavy rainfall was seen as high as 2,000′ in places along with sustained hurricane force winds out of the East. In fact, the Sunburst wind sensor blew apart after recording a record gust of 129mph! This is an ALL-TIME high gust for the Sunburst weather station since 2008 when it was installed – the last strongest gust was 121mph in December of 2011. 

Total precipitation amounts during this cycle, which began Sunday evening and ended last night, add up to over 2″ of water in the Girdwood Valley, ~1.5″ on Turnagain Pass and just under an inch in the Summit Lake zone. Snow amounts at the higher elevations can be estimated at 1.5-2′ with larger amounts North of Girdwood and in Portage and smaller amounts at Summit Lake. 

As one might expect, widespread natural avalanche activity was seen with this event. Most of the activity began as dry slab avalanches above 3,000′ that entrained heavy wet snow on the descent. Due to the thin snowpack to start with and no snow below 1,000′, these slides only reached sea level in certain channeled paths; most areas did not have enough volume to run full length. Below are a few images of what we were able to see with yesterday’s low visibility. 

Matt Murphy with the ADOT&PF Avalanche Program (and former CNFAIC avalanche forecaster) gets the winning picture yesterday with this large avalanche in motion – you can see the powder cloud clearly in the left photo. This is at Mile 52, Moose Mtn, just South of the Hope Y. On the right is the debris after the avalanche.
  

Here is one more picture of an avalanche that made it to sea level – this is Peterson #2 slide path just a few miles South of Girdwood.

Today’s Avalanche Problem and Advice:
With yesterday’s storm moving off, winds dying down and skies clearing, natural avalanche activity will decrease as well. However, this is the prime time for human triggered avalanches. The snowpack needs time to adjust – especially where the snow is the best at the upper elevations! Under the past week of snowfall, around 2-3′ deep now, there sits a widespread layer of weak (sugary) faceted snow. This weak layer is keeping the new snow from, essentially, sticking to the mountain sides – nothing any of us want to deal with, but it is there nonetheless.

Red flags such as cracking and collapsing are likely to be found along with the ability to trigger an avalanche remotely or from below that can slide on top of you. It is not rocket science as Fitz pointed out yesterday, avoiding slopes over 35 degrees or steeper is again the take home for today.  

With wet and soggy snow at the treeline elevations below 2,500′, wet loose avalanches will be possible to trigger on steep slopes and gully sidewalls. There may be a bit of a re-freeze limiting this type of avalanche, but considering the danger at the higher elevations in the dry snow and uninspiring wet snow below, it’s a good day to save your gas $, stay in town and not cash in your powder sick day yet.