Good morning. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Monday, December 12th 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 will no advisory issued tomorrow. The next advisory will be issued Wednesday, December 14th, at 7am.
Don’t miss Wednesday nights big double premiere and CNFAIC benefit!! “The Continuum” along with “One For the Road” will be playing at the Sitzmark Bar & Grill. More details are on our training and calendar page. Come on out!
There is a CONSIDERABLE avalanche danger today for wind slab avalanches at all aspects and elevations. Wind loaded slopes, from hurricane force winds and intense snowfall yesterday, have not had time to adjust and human triggered avalanches are likely. High winds produce unusual loading patterns and create avalanche hazards in unexpected areas. Avoiding areas with wind drifted snow on steep slopes is advised. Also, watch for small fresh slabs to form as moderate westerly winds are forecast today.
Yesterday’s storm rapidly intensified more than forecast. Along with that, the avalanche hazard increased more than forecast as well with a natural avalanche cycle likely occurring in the afternoon. Hurricane force winds hammered the mountains. Sunburst weather station set a record gust of 121mph. Details HERE. Snowfall rates intensified also with an estimated 24hour snow total between 20 and 30+ inches in the Turnagian Pass area (Girdwood looks to have seen slightly more with Summit Lake a bit less). As the storm tapers today, skies should break up enough to assess the damage.
Wind slab avalanches are the primary concern for today. With the uncertainty of how this quick and intense storm affected the snowpack, conservative backcountry travel is advised along with expert route finding skills. Keep in mind, unusual wind loading patterns can create avalanche hazards in unusual places. Slabs and drifts are likely to be quite deep and stiff at all aspects and elevations. Steering clear of wind loaded terrain will be prudent as the slabs could break above you, creating an unmanageable situation.
Though temperatures have cooled off, helping to lock the snow in place, don’t count on it yet. Additionally, a few inches of snow has fallen without much wind early this morning, dusting the wind hammered slopes. Watch for new fresh wind drifts today on scoured areas as the winds have now shifted around to the west and are forecast to be 30-40mph.
There remains faceted snow in the middle of the snowpack that may have been reactive with the significant added weight. A wind slab triggered today has the potential to ‘step’ down into the weaker faceted snow and produce a larger slide. This is most pronounced in steep terrain above treeline and in the Summit Lake area.
Primary concerns for Tuesday will remain similar to today. It will have been 48 hours after the storm and avalanche conditions will slowly improve as the snowpack has more time to adjust to the new load. Though no precipitation or significant wind is forecast at this time, if the weather does change, any new snow and wind will raise the avalanche hazard.
East winds tore through south central Alaska yesterday as a low pressure system in the Western Gulf rapidly intensified through the morning. Sunburst weather station (3800′) saw sustained wind speeds of 85 and 90mph during the early afternoon (Category 1 Hurricane). Snowfall rates also intensified during the afternoon, up to 5” per hour. Estimated storm totals this morning look to be: Turnagain Pass (1800′)- 25-30”, Girdwood valley (3000′)– 30-35” and Summit Lake (1400′) ~15”.
Today, snowfall should diminish, with a few inches falling this morning, and skies break up as the low pressure system heads out to the northeast. Winds have shifted to the northwest this morning and are expected to pick up into the 30-40mph range. Temperatures will begin to cool off through the day, to mid 20’s at 1000′ and around 20F at 3000′.
Tuesday’s weather looks to be relatively uneventful at this time. Light to moderate winds, no precipitation and dropping temperatures (into the teens) are expected for most locations above 1000′.
CNFAIC Weather Page and the NWS forecast
We will issue the next advisory Wednesday morning at 7am. If you get out in the backcountry we want to hear what you are seeing! Please send us your observations using the button on the right of this page or give us a call at 754-2369. Thanks and have a great day.