Avalanche Advisory for 2015-12-23 07:04:47

Observations from the field yesterday are limited to what was reported from Mt Shasta Ski Park Ski Patrol (a big "Thank You" for sharing information).  Close to a foot of new snow fell on Monday forming storm slabs that were easy to trigger in steep rocky outcroppings in areas of the Ski Park such as the "Staircase" near Highland Glide.  Mondays storm started cold and warmed as it passed.  This allowed for slightly lighter, less dense snow under heavier, denser snow (think hard slab over soft).  The continued relatively warmer temperatures on Tuesday helped the new snow to settle a bit and the crystals at the interface with the old snow to begin to round and bond.  Storm slabs may become more of a problem if we receive the forecasted amount of new snow late today into early Thursday (6-9 inches).   

Wind slabs are still a factor to consider.  Wind slabs that were formed during the storm on S-SE-E-NE-N aspects may have grown due to continued high winds during the last 24 hours.  Ridge tops remain scoured and firm. Small to medium size cornices may have formed on some ridge tops near treeline and may be easy to trigger.  If traveling along a ridge where cornices have formed give them plenty of room.  There is a slight chance that a cornice fall my trigger a storm slab or wind slab avalanche on slopes underneath on leeward aspects. Easterly aspects have shown the best wind loading.  Continued high winds and additional storm activity will add more snow weight and stress on the leeward slopes listed above. Wind slabs are guaranteed and near and above treeline travel will call for careful route planning, if you can even see at all, let alone stand upright. 

We've been keeping close track of the persistent weak layer problem digging snow study pits where the layer might exist and continuing to conduct stability test in areas where we know the layer exists. The PWL has not been observed on any new aspects or elevations, however it still exists in areas where already observed beginning on December 13th. Stability tests have shown results indicating a gradual strengthening within the PWL as partially faceted snow crystals melt and round.  Has the added weight of heavy snow and the effect of warmer temperatures eliminated the hazard presented by this layer?  There is still some uncertainty, but snow study pits today will hopefully shed more light on the question.  If triggered, the snow above the PWL is only getting deeper with Mondays snow fall and more on the way. So, the bottom line: Human triggered avalanches on this layer are again unlikely today. In the locations where this weak layer is known to exist, a snow pit stability test would shed some light on any lingering sensitivity.  Avoid multiple people clustered together on open slopes and consider the weight of your snowmobile (400+ lbs) when high marking in suspect areas. Consider the influence of the weight of the new snow plus a skier/rider or snowmobile adding more stress to the snowpack. Snow does not like rapid change!

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The Sand Flat cross country ski trails are snow covered and ready for your cross country skis or snow shoes. These are backcountry trails marked with blue diamonds on trees. Trails are not groomed.  Snow shoers, please blaze a parallel trail to cross country skiers staying out of the skin track. Thank you, and Enjoy!

The Pilgrim Creek Snowmobile Park is open! Trails are being groomed currently. Head to our "Education" tab on our website and find the snowmobile section for trail information, grooming status and other sledder resources!

The Five Red Flags of Avalanche Danger any time of year include:  1) Recent/current avalanche activity  2) Whumpfing sounds or shooting cracks  3) Recent/current heavy snowfall  4) Strong winds transporting snow  5) Rapid warming or rain on snow.