Avalanche Forecast

High

Recent avalanche up to sz 2.5 have been observed from Alpine and treeline terrain on primarily SE-NE aspects failing down to the Basal interfaces. A large slide off the N Face of Mt Smith dorrien took out previous tracks in a commonly skied run on the north face of Heros knob.

10-15cm of recent snow is overlying the Boxing day crust that is close to 1cm thick and found up to 2100m. In the alpine the recent snow is forming thin windslabs along ridgelines that are reactive yo a skiers weight. The main concerns in the snowpack all involve the deeper weak layers such as the early november surface hoar and the november 25th face interface. In some areas (mainly treeline) these layers can be identified as two seperate layers while in shallower terrain, the facetting process has weakened the snowpack into an overall weak base with not to many discernable layers. Where the snowpack is deeper (over 130cm) the layers are beginning to settle and strengthen. The problem is though that the snowpack depths are so variable at this time of year that thin weak areas are all over and a skiers weight is very easily able to trigger these deep persistent facet layers in these locations that will propagate to deeper areas. The whumpfing and cracking from this terrain is the snowpack telling you this information. Stick to low angle terrain where the consequence of getting a weak spot to fail wont cause a large avalanche. When stability is the question, terrain is the answer and now is the time to stick to conservative terrain.

Forecast for Friday at 4 AM PST:

 

Increasing cloud in advance of the next Pacific system.  Scattered flurries are possible from Jasper National Park (JNP) to the U.S. border early in the morning with minimal accumulations. West ridgetop winds of 40-60 km/h south of Highwood Pass to the U.S. border.  Elsewhere, expect west winds of 20 to 40 km/h.  

Forecast for Friday at 4 PM PST:

 Another wave from the Pacific enters the Range Friday evening bringing snow to all regions especially along west facing slopes.  The highest accumulations are expected in the Little Yoho region where up to 5 cm is possible.  Strong west ridgetop winds continue with winds of 60 km/h expected south of Highwood Pass to the U.S. border. From Little Yoho and Banff to Highwood Pass, expect west winds of 40 km/h.  And finally 20-30 km/h southwest winds are forecast from Jasper to Kakwa. Freezing levels remain at valley bottom north of Highway 3 and fall to valley bottom in WLNP.

 Forecast for Saturday at 4 AM PST:

 Flurries continue across all regions Saturday with 2 to 4 cm of accumulation expected in the Little Yoho region, elsewhere minimal accumulations are forecast.  Strong west winds of 60 km/h are forecast to start the day Saturday from Highwood Pass to the U.S. border before weakening through the day to 40 km/h.  Elsewhere, west winds are forecast to be 30 to 40 km/h.  Freezing levels are expected to remain at valley bottom with the exception of Waterton Lakes National Park (WLNP) where freezing levels are expected to approach 1400 m during the afternoon.

 

 

Forecast for Saturday at 4 PM PST:

 

Flurries continue across most regions but will weaken through the night as an upper ridge begins to build in.  No accumulations are expected.  Ridgetops winds in Kakwa begin the evening west 30 km/h before building through the night to northwest 50 km/h.  Elsewhere west to northwest winds near 30 km/h continue.  Freezing levels will fall back to valley bottom during the evening in WLNP and remain at valley bottom elsewhere.

More details can be found in the Mountain Weather Forecast.

• Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
• Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.