Avalanche danger is on the rise with strong wind and snowfall beginning today and into the weekend.
After 6 glorious days of sunny skies and cold weather – a pattern change is arriving. Starting today, Friday, clouds will push in, temperatures will rise, winds will increase and yes, precipitation is starting to fall. This storm is expected to peak early tomorrow morning and last through tomorrow evening (Saturday). Snowfall totals by tomorrow night should be in the 6-12″ range for both Girdwood and Turnagain Pass (mid-elevations), a bit less in the interior Kenai and Summit Lake zone. The rain/snow line should creep just above sea level and keep precipitation well into the form of snow at the road on Turnagain Pass. A chance for a second pulse of moisture is developing for Monday, and other midweek; cross your fingers!
What is this going to do for our avalanche conditions? That depends on how much snow falls and what the winds do. We can pretty much bank on the winds cranking along the ridgetops, which are forecast to be in the 40-50 mph range with stronger gusts from the east/southeast. Currently, the snow cover is thin, just 1-3′ thick in the mid and upper elevations. Large facets with a crust compromise the bottom of the snowpack and small ‘near surface facets’ with surface hoar sit on the top. This sets us up for some concerning avalanche issues in places seeing significant snowfall and/or wind loading.
Wind Slab avalanches: Any slope harboring fresh wind deposited snow is suspect to slide. There is plenty of older loose snow available to be blown into slabs. Combine this with some warmer temperatures and a bit of new sticky snow and you have a touchy wind slab.
Storm Slab avalanches: In areas lucky enough to get close to a foot of snow or more, that new snow may not want to stick well to the current sugary surface. Watching for cracking and using hand pits to see if the new snow wants to slide off the old surface are great ways to assess this. The bottom line is, any rapid loading of new snow will be an avalanche concern.
Persistent Slab avalanches: This the most concerning avalanche and if one occurs it will, by definition, release in the facets at the base of the pack and create a much larger avalanche than those mentioned above. How likely this is depends how much load is placed on the pack. This storm may not tip that balance, but we need to have our guard up as it’s nothing to mess with. Collapsing (whumpfing) has been prevalent lately and this is a sure sign these facets are still failing.
RED FLAGS: Remember recent avalanches, whumpfing (collapsing) in the snowpack and cracks is the snow that shoot out from you are all signs an avalanche could be triggered.
A Snapshot of the snowpack on Sunburst from Wednesday 11/18/20
Sunburst, Wednesday 11/18. You can almost see the surface hoar in the undisturbed snow.
Tincan on Sunday, Nov 15th (Photo: Tony Naciuk).
Seattle Ridge on Sunday 11/15. (Photo: Troy Tempel)
Manitoba on Sunday, Nov 15th (Photo: Peter Wadsworth).
**Thank you to all those that have submitted observations this season! Keep them coming. It’s an incredible community service and so valuable for the forecast centers.
QPF (Quantitative Precipitation Forecast), which is meteorological speak for how much precipitation in water is expected. Of course we hope this is all in the form of snow. Using a 10 to 1 ratio, that would mean Turnagain Pass at 0.53″ of water would equal around 5-6″ of snow. This is for 1,000′ in elevation and more snow is expected in the higher terrain.
Avalanche Center Operations: We will continue to provide conditions updates and are planning on issuing the first forecast midweek (week of Thanksgiving).
Avalanche Education SCHOLARSHIPS are available and the deadline is December 1st. Please see the ‘Scholarships’ page for more details and get your application in!!
A big thank you to all who join us last night for our annual FUNdraiser, SNOW STORIES III !! If you missed this event, good news – it was recorded! Check our FB page soon for more information on how to watch.
December 1, 15, 29:
CNFAIC Forecaster Chat Series – VIRTUAL! Time: 7-8pm, Cost: FREE
Forecasters will hold a series of online chats. These will begin with a recap of last season, an outlook for the coming year, and move into an in depth discussion on the various avalanche problems and how they impact the Turnagain Pass region. These are a great opportunity to ask questions about specific avalanche conditions and decision-making.