Avalanche Forecast
Issued: Dec 23rd, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Deep Persistent Slabs.
JMinifie,
Avalanche Canada
Managing a hard slab on top of weak sugary snow can be tricky. Avalanches are getting harder to trigger but now is not the time to become complacent. Hard slab can be unpredictable so think in terms of consequences as you travel through terrain just in case you get surprised.
Summary
Confidence
Weather Forecast
The cold continues with north winds. Protect yourself against frostbite!
THURSDAY NIGHT: partly cloudy, winds from the north up to 30km/hr gusting to 40km/hr, trace precipitation, temperature -20 C.
FRIDAY: partly cloudy, winds from north up to 50km/hr, no new precipitation, temperature -22 C. Chance of reindeer sighting!
SATURDAY: HoHoHo! mostly clear skies, winds from the north up to 40km/hr, no new precipitation, temperature dropping to -30 C!
SUNDAY: mostly clear in the morning skies clouding over in the afternoon, wind 20km/hr from the north changing to 20km/hr from the southwest in the afternoon, up to 5cm of new snow starting in the afternoon, temperature -30 C in the morning rising to -14 C in the afternoon.
Avalanche Summary
On Wednesday our field team observed several natural avalanches up to size 2 on Log Cabin and above Fraser Chutes. These avalanches were on cross-loaded east and south east facing slopes above treeline.
During extreme winds on Tuesday night, a size 2 natural avalanche reached the highway during a closure.
The most likely place we will see avalanche activity on Friday will be on south through east facing slopes where wind slabs have not yet bonded well to the layer below due to cold temperatures.
Snowpack Summary
Exposed alpine and treeline areas in places such as Paddy Peak and Powder Valley have been scoured to ground on north aspects and ridges. Wind impacted snow also exists well down into treeline in these places.
In the White Pass, all but sheltered, south facing slopes have been impacted by the wind. Firm wind slabs exist on south aspects and east facing gully features. Softer snow does still exist in sheltered treeline areas.
On the weekend two MIN reports here & here mention surface hoar at and below 1300m, which could be buried just below the recent windslab.
The middle snowpack is supportive to travel but snow depth still varies greatly with aspect and elevation.
The lower snowpack is made up of weak sugary snow. An avalanche at this interface is most likely to be triggered in shallow areas or with a large impact like a cornice fall or surface avalanche.
Terrain and Travel
- Watch for areas of hard wind slab on alpine features.
- Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
- Keep your guard up at lower elevations. Wind slab formation has been extensive.
- This avalanche problem is difficult to trigger but if so, consequences are serious.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Wind Slabs
At the moment, there may be a temptation to ride in areas where the snow has been deposited by the wind. Be aware that in these areas wind slabs could remain reactive longer than usual due to the extremely cold temperatures. Keep in mind that firm slabs can be triggered farther down slope than you might expect. Don't get surprised! As you transition from sheltered areas into wind affected areas, pay attention to ski and track penetration and consider backing off if you encounter firm drum-like slabs or cracking.
Aspects: East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Although the curst associated with this layer has all but disappeared, the weak sugary crystals at the base of the snowpack remain. The bridging affect of the wind hammered upper snowpack is making it harder to trigger this layer but now is not the time to become complacent. When managing hard slab on top of facets I try to think in terms of consequences just in case I get surprised. "If I trigger an avalanche here, what are the consequences? Will the avalanche be large? Are there terrain traps?"
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 24th, 2021 4:00PM
