Good morning and Merry Christmas. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Sunday, December 25th 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).
Placer river valley and the Skookum valley opened yesterday for motorized use. Be aware of thin snow conditions and areas of thin ice over water. 20 mile will remain closed until we get more snow cover at sea level.
The avalanche danger is MODERATE for fresh wind slab avalanches and new snow sluffing. Increasing winds today are expected to form soft wind slabs that could be triggered by a person. Watch for these on all steep slopes with recent wind deposited snow. Sluffing in the loose snow will also be possible on steeper slopes.
Yesterday, the most seen and reported avalanche activity was minor sluffing in the 2-6” inches of light snow (from mainly Thursday night). These were shallow and not packing much punch. However, there were some locations where the light winds picked up enough to blow the low density snow into soft wind slabs. These were in isolated areas but when found, easily triggered. Report HERE.
Today, wind slabs are the primary concern. Winds are forecast to pick up into the 20-30mph range from an easterly direction. This is will be enough to move and deposit the new snow, as well as the older loose snow from Thursday, into soft sensitive slabs. The key today will be to watch for any increase in wind and how the snow is being affected. Cracking from your sled or boards will be your main clue that you have hit a wind slab. These are most likely to be found just off the ridgelines, on the steepest part of a roller and the sides of gullies.
Many areas near and above treeline have a hard winded surface under the several inches of loose snow. This will allow for a slick sliding surface. From what we saw yesterday, if the wind slabs and sluffs are big enough to gain momentum, they could run farther than expected.
CNFAIC Staff than the previously mentioned instabilities in the new and loose snow on the surface, the deeper layers in the snowpack continue to show good bonding and a good set up so far this season.
Under mostly cloudy skies yesterday, intermittent snow showers added around an inch of snow to most locations. Winds were light and variable and temperatures in the teens. Overnight, around 4 inches of light snow has fallen in the Girdwood Valley with the Turnagain Pass SNOTEL reading only 1 inch. Winds have been light to calm from an easterly direction with temperatures dropping to the teens near sea level and single digits above 1500′.
Today, the cloudy skies, light snow showers and cold temperatures will persist. We will likely see around 2-3” of light snow through the day with temperatures in the teens. The easterly winds look to pick up a bit, into the 20-30mph range on the ridgetops.
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.