Good morning. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Monday, February 20th 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).
If you are between the ages of 12 and 18 you won’t want to miss Alaska Avalanche School’s Know Before You Go Backcountry 101 course on Friday February 24th and 25th. It is a 1 1/2 day course specifically geared for this age group and targets the basics of avalanche safely. For more details contact the Alaska Avalanche School.
The avalanche danger is rising to CONSIDERABLE due to the onset of heavy snowfall and high winds over our area today. Natural avalanches will be possible and human triggered avalanches are likely. Avoiding slopes with wind deposited snow is advised as wind slab avalanches can be dangerous and unmanageable if triggered. Conservative route-finding is essential for backcountry travel today.
The most avalanche excitement seen yesterday were small, energetic wind slabs in areas above treeline where a few inches of new snow fell and winds were blowing around 15-30mph. These were most common on the northern half of Turnagain Pass. CNFAIC Staffwise, it was fairly quiet day in the backcountry.
We have a storm day on tap which means an increase in avalanche danger. Avalanche activity for today is expected to be confined to the amount of new snow (around 12-18″) and how well the new snow is bonding to the old surface layers.
Primary concern – storm snow instabilities:
Wind slab avalanches
Fresh wind slabs are, and will be, forming today with the expected strong winds. These are likely to be quite sensitive, dangerous, and easy to trigger. Even in locations seeing less than a foot of new snow, winds will be capable of forming deep slabs. These slabs often release right at a person’s foot or snowmachine, but they can also be triggered from the side or below making an escape difficult.
Soft slab avalanches
These avalanches will be a concern today as the temperatures are expected to rise slightly during the storm. This can cause slightly denser snow to fall over lighter snow and slabs can pop out even in areas without wind.
Loose snow avalanches
Sluffing in the new storm snow will be likely today, both human triggered and natural. These typically do not pack as much punch as slab avalanches, but nonetheless, if they gain enough momentum they can entrain a lot of snow to become a legitimate problem.
The weak system that moved through yesterday brought 2-4″ of snow to Tunrnagain Pass and the Girdwood Valley with only a trace in the Summit area. Moderate easterly winds with higher gusts (into the 40-45mph range) accompanied the snow. Temperatures have remained mostly steady at all elevations – mid 30’s at sea level and ~20F at 4000′.
A more intense storm has ushered in overnight and should peak during the late morning to mid-day. Snow has begun to fall in earnest with roughly 4-8″ reported since midnight and anCNFAIC Staff 8-12″ expected today. The easterly winds have just begun to increase and are expected to average near 40-50mph with gusts to 70mph. Expect snow at sea level this morning, transitioning to a rain/snow mix by the afternoon and 4000′ temperatures to remain ~20F. This system is expected to move through fairly quick with light snow showers and moderate winds tonight and into tomorrow.
CNFAIC Weather Page and the NWS forecast
Graham will issue the next advisory Tuesday 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.