Very strong winds and 3+’ of new snow over the last three days has created a variety of storm related avalanche problems. Wind slabs may range from 1-4+’ thick on leeward and cross loaded features and may be located further down slope than expected. Feel for denser snow on top of weaker snow and be wary of pillowed or hard supportable snow that rolls into steeper terrain. In places where storm slabs may be less wind affected, this snow may also be upside-down with denser snow on top of weaker snow. Surface hoar from last week was buried under this new storm snow and its unknown how these persistent weak layers are adjusting. The size of an avalanche will depend on the size of the terrain, the larger and more connected the slope the more potential for a larger avalanche. Obvious signs like whumpfing and cracking may or may not be present until it’s too late. Remember its only been 24 hours since 70+ mph winds and heavy precipitation were falling. This is your first red flag of the day.
Storm totals (6am Dec.31 – 6am Jan.2)
CORNICES: High winds and blowing snow will have added to already large cornices. These may be very sensitive, and a cornice fall could trigger a large avalanche on the slope below. Remember these can break further back than expected.
Cross loading and some natural storm triggered slabs on specific terrain features was observed in between storms on Monday at Tincan.
Buried surface hoar found in a pit on Monday was 14″ below the surface. Expect this layer to be at 2-4′ below the surface in some places.
Under all this new snow are hidden glide cracks. They are looming over popular ski and snowmachine terrain and may be tricky to identify with new snow covering them. Several glide cracks have avalanched this week and it’s possible more will release in the coming days. The best way to manage this problem is to avoid being under slopes with cracks opening up. They can release at any time and are not typically associated with human triggers. Glide avalanche have occurred in Lynx Creek, on Lipps, and Seattle Ridge this week.
Most recent known glide avalanche was seen on Monday on an East facing slope of Seattle Ridge near Bertha Creek.
South of Turnagain: A shallow and poor snowpack structure exists in the Summit Lake zone. Buried weak layers of facets associated with crusts sit near the base of the snowpack. An observation from Lynx Creek on Friday also found a reactive layer of facets mid pack and this area is also suspect. Summit Lake did receive strong winds the last few days as well as a foot of new snow at road level, likely more in the alpine. Do not forget the possibility of triggering a larger avalanche that could release near the ground. Check out the Summit observations HERE for the most current information.
Yesterday: Strong Easterly winds decreased from 50mph yesterday morning to 15-30mph for the remainder of the day. A wintery mix of rain and snow was observed along Turnagain Pass with rain/snowline around 900′. Several additional inches of snow fell yesterday following an intense period of heavy snow and rain before 6am. Temperatures hovered around 32F at 1000′ and ridgetops were in the mid 20F’s.
Today: Skies are expected to be mostly cloudy with scattered snow showers and a few inches of new snow possible. Rain/snow line is expected to drop in elevation from 500′ this morning to sea level by this afternoon with cooling temperatures. Expect temperatures near sea level to drop into the mid 20Fs overnight and teens in the mid elevations. Ridgetop winds from the East will be moderate 10-25mph transitioning to light from the Southwest later in the day.
Tomorrow: A cooling trend is expected tomorrow as high pressure moves into our region through the end of the week. Expect clearing skies and temperatures to continue to drop into the single digits.
*Seattle Ridge weather station was heavily rimed and the anemometer (wind sensor) was destroyed.
|Temp Avg (F)||Snow (in)||Water (in)||Snow Depth (in)|
|Center Ridge (1880′)||31||1||0.1||66|
|Summit Lake (1400′)||33||5||0.4||22|
|Alyeska Mid (1700′)||31||1||0.16||51|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||28||*N/A||*N/A||*N/A|