Turnagain Pass

The most recent observed avalanche activity was a widespread cycle of natural avalanches that occurred during Wednesday and Thursday. It is likely there was another natural cycle during last night’s snow and wind.

Another round of stormy weather last night brought around 12″ snow to Girdwood and 6-8″ to the rest of the forecast area and surrounding zones. The rain level made it up to around 600-800′ last night, and the storm was accompanied by intense easterly winds with the Sunburst ridgetop station recording 8 hours of sustained winds around 40-60 mph and gusts as high as 105 mph last night. For today, our main concern will be avalanches failing within the new snow. Following last night’s winds, there is potential to see some very big human-triggered avalanches today even though the weather should be fairly quiet during the day.

Travel cautiously if you head into the mountains today. With temperatures warming through this storm, we’ve seen yet another upside-down storm with warmer, dense snow sitting on top of cold fluffy snow. This is a setup that can make new snow avalanches more reactive. This includes wind slab avalanches as well as storm slabs failing in steep terrain that was sheltered from the winds. Approach steep terrain with skepticism today, especially in areas that were on the high end of the storm totals from last night, or on slopes where last night’s winds formed a fresh round of reactive wind slabs. With speeds that strong, be on the lookout for slabs forming further downslope from ridgelines than ‘normal’.

With 15.8” Snow Water Equivalent, we are currently tracking well above previous El Niño seasons at Turnagain Pass and at 148% of median SWE for Dec 17 over the past 30 years. Data: NRCS, 12.17.2023

This latest round of snow and wind is adding stress to the weak layer of faceted snow buried near the crust that formed during the Thanksgiving storm, now buried around 3-5′ deep. This is the third major loading event over the past week. We’ve been tracking this layer for the past few weeks, and we know it exists across the forecast zone. For now the layer has been on the unreactive side of stubborn, with only two known avalanches failing on this layer since the crust was buried three weeks ago.

Avalanche problems associated with crusts like this are notoriously difficult to predict, and we don’t want anyone to be caught off guard. The likelihood of triggering an avalanche on this layer is low, but if you were to trigger something it could be very large. With high uncertainty and severe consequences, we are being just a little more conservative than we would be if we were only dealing with the types of new snow avalanches mentioned in Problem 1 above. All slopes above 1000′ should be considered suspect, since we’ve seen the same suspicious structure in virtually every snowpit that has been dug over the past two weeks on all aspects across the advisory area.

This structure on Raggedtop is similar to what we’ve seen across the advisory area. Photo shared anonymously, 12.15.2023.