The Bottom Line: The overall hazard is moderate above treeline due to a challenging snowpack structure and recent wind loading.
The snowpack has been settling since the last major round of storms that ended Dec 19th. Above 4000' the snowpack averages over 300cm deep and has good strength and structure. Below the rain line from the historically warm and wet October the snowpack is significantly shallower and has more problem layers: facet-crust combos and basel facets.
Problem 1: Wind Slab.
Location: all aspects above treeline. Size: small. Likelihood: possible. Sensitivity: stubborn. Wind Slabs up to 2' thick have formed predominantly lee to the NE. Winds slab can be identified by dense, cohesive snow, cracking, and a hollow or drum like feel. Look for wind slab below ridge lines and close to Thompson Pass. Stiff wind slabs can lure riders well onto the slab before failing. Stick to wind-protected areas where the surface snow is still soft and fluffy (better riding conditions usually anyway).
Problem 2: Persistent Slab.
Location: all aspects below 4000' and possibly even higher near shallow parts of the snowpack such as rock outcroppings. Size: small to large+. Likelihood: unlikely. Sensitivity: stubborn-unreactive. There are multiple rain crusts layered with facets throughout the region (reported only up to 4000'). There are also basel facets (weak sugar snow) at the bottom of the snowpack . . . These problem layers are gaining strength and potentially either dormant or waiting for a large load such a big storm or snow machine hitting a sweet spot. If you choose to ride on slopes over 35deg choose slopes with clean run-outs and careful selection of group spacing and safe zones.
Additional Concern: Glide Avalanches.
There are open cracks from the port to 40 mile between 3500-4000' on multiple aspects. The current list of open glides cracks from West to East: Mile High Pk SE, Stone Mtn NE, Loveland S, Catcher's Mit S, Goodwill's S, Python NE, Crudbuster NE and NW. It is important to remember glide cracks can release into full-blown avalanches at any time and are not associated with human triggers. The best way to manage this problem is to limit travel underneath and beside them.
1 large avalanche was reported on Dec 23rd: a slab avalanche near the ridgeline of RFS, below the cornice. It was reported as possibly a size 2.5, persistent slab that ran 800-1000'.
Over the past few days several small wind slabs released near Thompson Pass from human triggers and several more small cornices released naturally, south facing 3-4000'.
The most up to date NWS Rec Forecast can be found HERE:
315 PM AKST Fri Dec 28 2018
The Thompson Pass Mountain Forecast covers the mountains (above
1000 ft) surrounding Keystone Canyon through Thompson Pass to
Temp at 1000` 22 F 25 F
Temp at 3000` 26 F 25 F
Chance of precip 80% 80%
(above 1000 FT) 0.25 in 0.24 in
(above 1000 FT) 3-4 in 3-4 in
Snow level sea level 500 ft
Wind 3000` ridges E 5-20 mph E 5-15 mph
If you get out riding, please send in an observation!
Do a rescue practice with your partners. Always carry a beacon, shovel, and probe, and KNOW HOW TO USE THEM.
Practice good risk management, which means only expose one person at a time to slopes 30 degrees and steeper, make group communication and unanimous decision making a priority, and choose your terrain wisely: eliminating unnecessary exposure and planning out your safe zones and escape routes.
The overall hazard is moderate and all 3 zones have the same forecast. Click 'full forecast' to get more info.
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