Cornice falls have been the most prevalent avalanche problem during the past several days. Wind slabs on the other hand have been relatively small and from what we know, triggered predominantly by cornice falls. If you are just tuning in now, take a look at the past few days of observations (several close calls and one person who did go off with a cornice but is alright). A few inches of new snow in the past 24-hours, sustained moderate to strong winds and relatively mild temperatures all contributed to growing cornices yesterday. If skies open for travel into the Alpine and along ridgelines, take stock of the cornices around you and give them an extra wide berth, why not? Also, watch for who’s above you, could they inadvertently trigger a cornice that sends debris over you?
WIND SLABS: Expect to see some fresh wind slabs from yesterday’s winds, even if new snow amounts are low, there is plenty of snow to transport left over from the Solstice Storm. Wind slabs are likely to be shallow, up to a foot thick, and could be touchy as the underlying surface could be loose snow or surface hoar in cases. Watch for shooting cracks, hollow sounding snow and be especially aware of the terrain – if a wind slab does release where will you go?
Recent cornice fall triggered small windslab and loose snow below on SW face of Magnum on Monday – also note glide cracks below rocks.
Surface hoar that formed on Sunday and Monday is now covered by 2-5″ on new snow, maybe more.
Slab avalanches breaking in weak layers deeper in the snowpack? If you are headed to areas south of Turnagain, keep in mind triggering a large slab avalanche is possible. Buried weak layers, roughly 2′ below the snow surface, have been found in the Summit Lake zone and possibly as far south as Lost Lake. We suspect the snowpack may be similar around Johnson Pass, Lynx drainage and Twin Peaks/Silver Tip. These weak layers are composed of facets associated with crusts and have been showing signs they could be reactive enough a person could trigger a large avalanche. Listen and feel for whumpfing (collapsing of the snowpack) and look for avalanche activity from the storm that may have steeped down into the deeper layers.
On Monday two glide avalanches (actual releases, not just cracks) were observed in the Lynx Creek drainage. One of these clearly visible in the photo below as a brown streak. Observers have reported the glide cracks on Sunburst and in Warm-up (-1) Bowl are opening and people continue to see new cracks throughout the region. It is important to remember glide cracks can release into full-blown avalanches at any time and are not associated with human triggers. Keep your eyes peeled for cracks and limit travel underneath them.
Glide avalanches in Lynx Creek drainage. The slide in the middle of the photo is located in a very common zone to snowmachine.
Yesterday: Mostly cloudy skies were over the region with light rain up to 500′ and light snow above this. Turnagain Pass saw 2-4″ of new snow, while Girdwood looks to have picked up around 5″ (mid-elevation snow stations). Ridgetop winds averaged 20-30mph for the past 24-hours from the east. Winds have quieted down to ~10mph as of 6am. Temperatures are steady in the 20’sF along ridgetops and 32F at 1,000′
Today: Instability showers will be over the region with mostly cloudy skies and a chance for a trace of snow above 1,000′ and rain below this. There is also a chance for clearing skies and some blue holes if the front parked over the Kenai and Girdwood area heads north during the daylight hours (keep track on the satellite). Ridgetop winds are expected to be generally light, in the 5-15mph range from the east. Temperatures should remain in the 20’sF along ridgetops and 32F at 1,000′.
Tomorrow: Another low-pressure system will move in for Thursday, this one wrapping in some warm air. Timing and temperature with this storm is still uncertain, however it looks like snow might fall to 1,000′ but not to make it to sea level. Precip amounts at his point are in the 0.5″ of water range. Stay tuned.
*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′)||30||3||0.2||58|
|Summit Lake (1400′)||30||0||0||12|
|Alyeska Mid (1700′)||31||5||0.33||36|
|Temp Avg (F)||Wind Dir||Wind Avg (mph)||Wind Gust (mph)|
|Seattle Ridge (2400′)||27||*N/A||*N/A||*N/A|