Turnagain Pass

After two days of stormy weather, a break has arrived along with cooler temperatures. Today’s partly cloudy skies should allow for easier travel above treeline and with that, the chance a person could trigger a large avalanche if venturing into avalanche terrain. Depending on location, between 1 and 6 feet of new snow has fallen in the mountains – this is good news for many, but remember, it’s been less than 24-hours since the storm ended.

Storm snow avalanches, such as wind slabs along ridgelines, storm slabs in the sheltered zones, cornice falls and loose snow sluffs should all be viewed as likely today. It’s a day to carefully evaluate terrain and consequences if an avalanche does release. We need to give the mountains time to adjust. Low angle slopes without steep slopes above are great ways to enjoy the new snow without worry. 

Red flags to watch for:
–  Recent avalanches, from today or was there avalanche activity from during the storm?
–  Whumpfing (collapsing) of the snowpack, sure sign to avoid avalanche terrain period.
–  Shooting cracks, likely to be seen near ridgelines where the wind has formed wind slabs.

Storm totals (beginning Thursday night through 6am Sunday morning)

• Turnagain Pass at 1,880′:  1.7 – 2.2″ of water equivalent, roughly 1.5-2′ of snow above treeline
• Girdwood Valley at 1,700′:  3.5″ of water equivalent, roughly 2.5-3.5′ above treeline
• Portage Valley at sea level: ~6″ of water equivalent, roughly 6′ of snow above treeline
• Summit Lake at 1,400′: 0.8″ of water equivalent, roughly 6-8″ of snow above treeline

The good news is the new snow should bond relatively quickly. From what we know, the pre-existing snow surface lacked any persistent type of snow grain and was mainly old wind slab and settled powder. As always however, the snowpack is guilty until proven innocent and there are always surprises out there – it’s the first day after a storm and we can’t get caught being over confident.
 

DEEP PERSISTENT SLAB:
Above 2,500′ there is a thin layer of buried surface hoar anywhere from 2-5′ deep in the snowpack. This layer was buried on Nov 23rd and we are keeping track of it. This storm may have brought it back to life in places – meaning the rapid loading of new snow may have overloaded the layer causing it to collapse and initiate large avalanches. However, that has yet to be determined and something we are focused on. That said, keeping this layer in mind and although the new snow may be bonding well, there is a deeper potential weak layer lurking. 

Turnagain Pass motorized parking lot at 3:30pm yesterday (Saturday). Low visizibility and a few inches of slush at the road.