Good morning. This is Graham Predeger with the Chugach National Forest Avalanche Information Center on Tuesday, March 27th 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 is MODERATE today for the core advisory area. Human-triggered avalanches will be possible due to a variety of buried weak layers in our upper snowpack along with fresh wind slabs.
We haven’t seen any large avalanches recently in our forecast area but there have been several class 1 and 2 slides on all aspects. These have not been large and destructive snow slides though many are big enough to bury, injure or kill a person. The common denominator with these avalanches is proving to be buried weak layers (surface hoar and facet/ crust combinations) persisting in the upper snowpack.
Concern #1 – Wind Slabs and Soft Slabs
Winds appear to have picked up again overnight blowing in the 20 to 40 mph range from the east and southeast. Expect to find tender wind slabs on west and northwest aspects especially below ridges today. These newest of wind slabs are likely not bonding well to underlying layers yet. Yesterday we found anCNFAIC Staff sun crust on solar aspects and sporadic pockets of surface hoar. These future weak layers were being buried by light snowfall and are now overlain by a fresh wind slab in problem areas.
Concern #2 – Persistent Slabs
Several weak layers have been buried over the previous 2 weeks. Some of these have healed up nicely and are of no concern today. CNFAIC Staffs however are lingering, waiting for a trigger. It is worth the time to dig into a slope you intend to ski or snowmachine and try to identify the presence of weak layers. An obvious weak layer will show itself as a uniform grey line in your snowpit wall. These weaknesses and overlying slabs have been found recently, lurking in our snowpack from Girdwood to Summit Lake.
Concern #3 – Wet sluffing
It’s unlikely we will see much direct sunlight over the next several days but daytime temperatures do appear to be rising as we near April. Wet sluffs, when initiated will have the potential to step down and pull out some of these deeper buried weak layers over the coming days. Pay attention to areas where the surface won’t support your weight as you step off your skis or machine. This is an easy test that is indicative of the upper snowpack weakening, if you are able to post-hole up to your mid-thigh or crotch.
Sunday’s bluebird day gave way to clouds and light precipitation over south central Alaska yesterday. It was snowing lightly most of the day from Girdwood to Turnagain pass with just a few inches of accumulation to cover up some of the most recently deposited surface hoar from the weekend.
With a warmer unsettled air mass digging in, we can expect mostly cloudy skies and gusty east and southeast winds in the 25-40 mph range at ridge top levels today. Precipitation looks to be mainly in the form of snow (1-3″), but may be mixed with rain at lower elevations. Overnight, temperatures will be significantly warmer (high 20’s) than we have seen recently.
CNFAIC Weather Page and the NWS forecast
Kevin will issue the next advisory Wednesday 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.