Good morning. This is Chris Engelhardt with the Chugach National Forest Avalanche Information Center on Friday, March 23nd 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).
There is a MODERATE avalanche danger for the core advisory area today. The upper part of the snowpack continues to harbor persistent slabs with weak layers such as surface hoar and sun crusts/facet combinations that can produce slab avalanches.
Conditions have not changed much as of late with persistent weak layers residing in our upper snowpack including touchy buried surface hoar and sun crusts that have weak faceted snow forming on both the top and bottom of them. The danger level may very well be ramped up if we get a lot of wind and new snow deposited on these layers. Additional weight of new windslab may prove to be the tipping point for increased possibility of natural and human triggered slab avalanches.
Avalanche Concerns for today:
Triggering a slab avalanche on buried surface hoar still remains a possibility. Areas most likely to find this problem are northerly aspects around Girdwood, Placer Valley, 20-mile, and Johnson Pass. Yesterday, we investigated a skier triggered slab that occurred last week on the lower north facing flank of Orca mountain just outside of Girdwood. Check out this observation and video on how the slab is still reacting to the buried surface hoar layer.
We also continue to get easy to moderate failures in test pits on southerly aspects. On Tuesday, we decided to stay off a steep upper slope on Cornbiscuit because of easy failures and clean shears on the persisting faceted suncrust layer that is around 2 feet below the surface.
Storm Snow: Wind Slab and Loose Snow
If conditions degrade rapidly today and it starts blowing and snowing, take note to be diligent with safe travel plans and provide yourself with alternative routes. There is a variety of conditions on the surface of the snowpack such as surface hoar, low density powder and hard sun crusts that will easily shed newly deposited snow or wind slabs today. If winds increase to the 20-30mph range they are going to start transporting the existing light layer of powder and will start to form sensitive new windslabs on the leeward side of ridges. This can happen very quickly so be prepared to potentially alter course. Loose snow sluffing continues to be noteworthy on all aspects and should be taken into consideration when dropping into or riding committing terrain.
Wet Snow Sluffing and Slabs
Alternatively, if warm and sunny conditions prevail throughout the day today, then once again be on the lookout for loose snow shedding on sunny and warming aspects. Avoid traveling on or underneath south facing slopes late in the day.
I surely love a beaming spring Alaskan sun, and it was all about bright rays and moderate temp’s yesterday afternoon. Winds remained calm and temps stayed in the teen’s on ridge tops throughout the day. Overnight the winds continued to remain calm and temperatures were in the 10-14F range on higher elevations. Today may be a different story as conditions are supposed to drastically change with the weather service issuing a blizzard warning for Turnagain arm this evening. Easterly to southeasterly winds are supposed to pick up to 20-35mph through the day and there is a good chance for snow today with increasing amounts tonight.
CNFAIC Weather Page and the NWS forecast
Kevin will issue the next advisory Saturday 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.