December 17, 2001

Canadian Avalanche Association Bulletin

ROCKIES REGION

WEATHER: Between 30-60 cm of new snow fell across the Rockies over the
weekend. Greatest amounts fell along the Continental Divide with a gradual
tapering of depth moving east - a typical pattern during a SW flow.
Temperatures fluctuated and generally winds were light until Sunday when a
stronger SW wind. Expect this week to be less dramatic, with cool
temperatures prevailing and waves of snow flurries moving through.
SNOWPACK: This weekend's storm snow appears to be bonding well to previous
surfaces, with the exception of areas with wind effect. Lee and crossloaded
terrain has seen windslab formation that has been failing within the new
snow. A prominent instability remains in the lower meter of the snowpack,
presenting as a crust/facet combination. The strength of this layer varies
greatly, but in many places the facets are weak and the potential for human
triggering is significant. The next few days should see a gradual
strengthening of the surface layers.
AVALANCHES: Limited observations due to poor visibility, but ski resorts all
reported explosive controlled avalanches on Sunday, mostly in the size 2
range. Several larger avalanches were observed to have slid on the November
crust/facet layer.
FORECAST OF AVALANCHE DANGER UP TO MONDAY THURSDAY (DEC 20)
		ALPINE: Considerable
		TREELINE: Considerable
		BELOW TREELINE: Low
TRAVEL ADVISORY: Coming out of a big storm is a tricky time. Storm snow
instabilities may disappear rapidly, but the November crust/facet layer is a
significant concern right now. This last storm has proven to overload this
weakness in a number of locations - it won't heal quickly so don't forget
what's down there and do lot's of snowpack tests to help with your decision
making.