Turnagain Pass

The solstice sleeper storm of 2018, which dropped an impressive 4-5′ (yes feet) of very low-density snow from December 19 to 20, has settled an impressive 20″ in the past two days. Light snowfall overnight as added another 3-4″ to the pack and another 2-4″ is expected today – and winter begins! In the Turnagain Pass area all signs are pointing to good bonding between the new and old snow. Reports yesterday spoke of “No obvious signs of current instability“. Although there were several natural avalanches during the storm (photos below), no avalanche activity has occurred, that we know of, in the past two days. The catch is, winds picked up yesterday, continued overnight and are forecast to remain – this will be the main concern for today.

WIND SLABS:  Sustained easterly winds along ridgelines and peaks are likely having their way with all the new loose snow. Add to this warming temperatures to help stick the snow together, and we are set up for a classic wind slab problem. Keep your eyes peeled for areas winds have deposited snow, pillowed surfaces and stiffer wind packed snow. Shooting cracks are likely in this case and triggering a wind slab from below, while ascending, is also likely. These issues should be easily seen if we are looking for them. 

LOOSE SNOW AVALANCHES:  Triggering a loose snow avalanche could be large and unmanageable in steep terrain with so much new snow. Below 1,000′ we could see damp or wet sluffs as temperatures reach above freezing.

SNOW IMMERSION SUFFOCATION:  Getting caught in a tree well, stuck head down in a depression and other means of snow immersion are all possible with so much snow. Watch your partners and be aware of this hazard that claims lives in the US each year.

 Natural ‘storm slab’ avalanche occurring near the end of the storm on Tincan at treeline. Photo: Aleph Johnston-Bloom.

 Another shot of natural ‘storm slab’ avalanches occurring near the end of the storm on Tincan’s CFR ridge near treeline. Photo: Aleph Johnston-Bloom.

Areas south of Turnagain Pass, such as Johnson Pass, Lynx drainage, Twin Peaks/Silver Tip, the Summit Lake zone and possibly Lost Lake are all very suspect for harboring buried weak layers under the storm snow. Triggering a large and dangerous avalanche cannot be ruled out and is considered possible in these zones. Weak layers consist of a facet/crust combination between 2,000-3,000′. The addition of 4′ of new snow clearly overloaded these and several natural avalanches were seen Thursday on the far northern end of Summit Pass. Look out for whumpfing, cracking, and recent avalanches if you head to these areas. 

Natural avalanche that may have released in buried weak layers. This is across the street from Twin Peaks at 62 mile. South facing terrain.

Heads up – Lost Lake zone harbors buried weak layers – be aware of triggering a slab 2-3′ thick. This picture was taken Thursday and the timing of this avalanche is unknown and may be a natural avalanche from a different day. Photo and observation courtesy of Iron (iii) Oxide.

Glide cracks are opening as we speak all over the mountains. Notable locations are Tincan’s SW face, Sunburst’s SW face under the weather station, Gold Pan area (behind Cornbiscuit/Magnum) and Johnson Pass. These cracks can release at any moment. They are not associated with human triggers and the best way to manage the hazard is to avoid being on or beneath slopes with cracks. 

Crazy cracks… Yesterday cracks were found opening in the 4′ of new settling snow. These are not glide cracks, but similar. There is not an avalanche hazard associated with them, but they could trip you up.