Turnagain Pass

No new avalanches are known of in our forecast zone from yesterday. The last avalanches were skier triggered sluffs on Monday and small sluffs during Tuesday’s 4-6+” of snowfall. The last slab avalanche was almost a week ago when a skier triggered a slab around 2′ deep on a lower elevation rollover on Eddie’s Ridge.

After a quiet day yesterday, last night the first of two fast moving storm systems moved in. This event looks to be more blow than snow and should peak this morning before moving out this afternoon. Only 2-4″ of snow is expected (~6″ in Portage/Placer). The next pulse should be tomorrow with similar snow amounts. The winds will the big player for changing avalanche conditions however. Overnight, ridgetop winds picked up into the 15-25mph range from the east with gusts in the 40’s, which should remain until midday when winds make a 180 and blow 10-20mph from the west by this evening. That said, wind slabs will be the primary concern.

The upper elevations will be the most likely place for wind slabs to develop. Exposed areas in the treeline and below treeline band are also suspect. These are likely to be around a foot deep and fairly soft. If you are headed out today, watching for where winds are actively loading slopes, or did so earlier in the day, will our best tool to avoid triggering a fresh wind slab. Also, feeling for stiffer snow over softer snow and looking for any cracks that shoot out from you will be key. Expect any fresh wind slab to be touchy, simply by definition. There is also a chance wind slabs could be forming on a new crop of surface hoar, making them even easier to trigger. All in all, the good news is the avalanche concerns now are mainly focused on the top of the snowpack, we call these surface instabilities. They are much easier to see and assess than the hidden buried weak layers we have been dealing with all season.

CNFAIC intern Megan Guinn holds up a chunk of soft surface snow from the Valentine’s Day storm with a new crop of surface hoar sitting on top yesterday. 2.16.23.

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There are a couple older layers in the snowpack that we are continuing to monitor. These are the storm interface from Feb 5 (1.5-2.5′ deep) and the 1/10 buried surface hoar (2-5′ deep). With new snow and wind today, a wind slab or other surface avalanche could possibly step down to the Feb 5 interface and create a larger avalanche. Something we’ll be watching for. We have not seen any avalanche activity on the 1/10 buried surface hoar for almost a month, it would be highly unlikely an avalanche would release on this layer at this point.

The last known avalanche breaking in one of these older layers was on Saturday (6 days ago) when a skier triggered a ~2′ deep slab at 1,600′ on a lower steep roll on Eddies’s Ridge. This avalanche likely failed at the Feb 5 storm interface where at these lower elevations (2,000′ and below) the bed surface is a crust formed on 1/25.

Our snowpit from the front side (SE face) of Seattle Ridge yesterday. We did not find any weak layers in the top 3 feet of the snowpack. Good news. This includes the Feb 5 storm interface (~2.5′ deep). 2.16.23.

For areas with a thinner snowpack (Silvertip, Summit Lake), the weak layers near the bottom of the snowpack are still a factor in our terrain choices. This includes the weak snow around the Thanksgiving crust, as well as faceted snow at the bottom of the snowpack. Luckily these layers do not seem to be a factor in our core advisory area, but they are still a concern around the periphery.