Good morning. This is Kevin Wright with the Chugach National Forest Avalanche Information Center on Saturday, December 17th 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).
Thanks to everyone who joined the benefit showing of Teton Gravity Research films at the Sitzmark on Wednesday. Thanks to Wild Alpine for organizing. Your support makes these forecasts possible.
The avalanche danger is (still) MODERATE for new storm snow. Shallow 1-2 foot storm slabs have been failing occasionally over the last 2 days. This trend will continue today with more snowfall in the weather forecast. Watch for tender wind loaded pockets above 1500 feet, especially on West and South aspects.
Over the last 2 days we have seen evidence of small natural and human triggered avalanches breaking in the new storm snow from Thursday. These seem to encompassing only that storm layer, but the pockets can be up to 2 feet in depth, and have the capability to run 1000 feet or more. Above treeline the surface snow is variable and wind affected, and this is generally where you will find the triggerable pockets.
The type of problem we’re dealing with is relatively simple and manageable if treated correctly. The primary concern is the Thursday storm layer, so pay attention to the top 1-3 feet of the snowpack. The wind has been blowing consistently since the snow fell. Certain areas will be pillowed deeper. This is an easy problem to track as you travel, monitoring the depth of the slab with a ski pole. The smaller avalanche sizes can be safer, but don’t get too confident in high consequence terrain. You might consider ski cutting short, low consequence test slopes on your way down to see if they break into slabs.
These slabs are sitting on top of a weak layer of older light density stellar crystals. This is not considered a “persistent” weak layer, so it will likely bond over time. Yesterday we found easy to moderate and clean shears with the stiff wind slab breaking over weak light density snow. Expect these slabs to become less likely to trigger as time passes.
The CNFAIC Staff concern today is new storm snow forecasted to fall today. Weather models are showing inconsistent predictions but the National Weather Service has snow in the forecast for Turnagain Pass and higher elevations of Turnagain Arm and the Kenai. This snow could build quickly and become a problem of its own. Watch the weather this weekend while you are in the backcountry and make decisions according to what you are seeing.
The most recent significant snowfall was Thursday when 8-12 inches fell through the region. Strong wind blew the snow into deeper pockets on West and South aspects. Today up to 7 inches of snow is forecasted. Expect moderate Southeast wind at the ridgetops. Warmer air is moving into the region, so temperatures above freezing at sea level and a rain line up to 1000 feet are possible.
CNFAIC Weather Page and the NWS forecast
Wendy will issue the next advisory Sunday 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.