Good morning. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Sunday, February 26th at 7am. This will serve as a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas).
The avalanche danger will rise to CONSIDERABLE today due to the onset of heavy snowfall and wind. Storm snow avalanches, in the form of loose snow, wind slab and soft slabs, will all be likely to be triggered by a person and natural avalanches are possible. It is a storm day and expert level route-finding and terrain management skills will be required for safe backcountry travel. (Remember there is a Sunday Summit Lake advisory.)
It was a fairly busy Saturday at Turnagain Pass with several folks soaking up the sun in the morning until high clouds began moving in ahead of today’s storm. Those getting a close look at the snow surface may have noticed some very large stellar crystals on top shining in the sun. Avalanche activity that was seen/reported was confined to human triggered sluffs on the steeper slopes that initiated in, and entrained, the top several inches of loose powder. A few of these were medium sized and ran quite far. There was also a report of a large cornice break on the far end of Magnum ridge – report HERE.
The loose powder that was sluffing from our snowmachine or board(s) yesterday is now covered with 4-6 inches of new snow overnight, with anCNFAIC Staff 8-16 inches on tap. Bonding of the new snow with older loose snow (including those nice stellar crystals) will likely be poor initially – enhancing all avalanche activity through the storm. Furthermore, how the new snow will bond within itself will also be concern.
Wind slab avalanches – near and above treeline:
The current moderate to strong winds above treeline are, and will be, moving and depositing the new snow into slabs onto the leeward sides of slopes. These are most likely to form off ridgelines, over rollovers and cross-loading on the sides of gullies. Expect these to be quite sensitive, dangerous, and easy to trigger. It is possible to trigger one of these from the side or below with the poor bonding expected with the older snow.
Loose snow and soft slab avalanches – all elevations:
Sluffing in the new storm snow will be likely today, both human triggered and natural. Watch for these to run fast and far with the new and loose snow sitting on top of a harder sliding surface. Soft slabs are also possible today on all slopes at all elevations. Watch for the temperatures to increase. If this happens slightly denser new snow will fall over lighter new snow and slabs can pop out even in areas without wind.
High clouds moved in throughout the day yesterday, after a sunny morning, signaling the approach of a storm heading our way from the southwest. Winds were light from the east in most areas, but picked up on the northern end of Turnagain Pass where they were gusting near 20mph (This can be seen on the SEATTLE RIDGE weather station – which is now back up and running!). Temperatures were chilly, in the teens.
A large low pressure system in the Bering is currently pushing a front over our area now from the west and will continue to move easterly today. Overnight, around 4-6″ of snow has fallen on Turnagain Pass with similar amounts in both the Girdwood Valley and the Summit area. We can expect anCNFAIC Staff 8-16″ to fall through the day with close to 1” of water weight. Temperatures are expected to remain just cold enough, low 30’s, for snow at sea level and increase a few degrees from where they sit currently: 22F at 2000′ and the mid-teens 4000′. Easterly winds have picked up overnight and are averaging ~30mph with gusts between 40 and 50mph where they are forecast to remain.
CNFAIC Weather Page and the NWS forecast
I will issue the next advisory Monday morning. If you get out in the backcountry we want to know what you are seeing. Please send us your observations using the button at the top of this page or give us a call at 754-2369. Thanks and have a great day.