Avalanche Canada cgarritty, Avalanche Canada

Lizard Range and Flathead Avalanche Forecast

Jan 11th, 2020 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs.

Reports suggest our low density snow is settling and bonding rapidly, with instability focused in wind affected areas. A steady supply of new snow and wind suggests more of the same for Sunday. Be prepared to dial back your terrain selection if snowfall exceeds forecast amounts.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Saturday: Cloudy with continuing flurries bringing 15-20 cm of low density new snow. Moderate southwest winds.

Sunday: Cloudy with continuing scattered flurries bringing 10-15 cm of new snow, increasing overnight. Light to moderate south winds. Alpine temperatures falling to about -15.

Monday: Mainly cloudy with easing flurries bringing about 5 cm of new snow, continuing overnight. Light to moderate southwest winds. Alpine high temperatures to about -17.

Tuesday: Cloudy with continuing flurries bringing 5-10 cm of new snow. Light to moderate southwest winds. Alpine temperatures around -18

Avalanche Summary

Reports of avalanche activity over the week have been steady, with each substantial snowfall accompanied by observations of natural, skier triggered, and explosives controlled storm slabs generally reaching size 2 (large) with a few examples up to size 3 (very large). North to east aspects and higher elevations have figured most prominently in reports as a result of recent winds.

Notably, two larger recent results involved the weak basal snowpack by either stepping down to this layer or failing on its reloaded surface.

Looking forward, a continuing supply of low density snow and elevated winds are expected to maintain active avalanche conditions. Avalanche danger is expected to continue to be focused in exposed areas where wind redistributes new snow into deeper and more reactive slabs.

Snowpack Summary

Another 30-40 cm of low density new snow fell in the region over Friday night, bringing storm snow totals from last week to 70-110 cm.

This recent snow is reportedly settling rapidly, with surface instabilities generally limited to the most recent accumulations, especially where winds have redistributed snow into reactive slabs in leeward features.

Several crusts layers exist in the mid to upper snowpack as a result of recent warming and rain events. These have not been identified as bed surfaces or failure planes in recent avalanche activity.

The bottom 10-20 cm of the snowpack consists of faceted snow and decomposing crusts. Although inherently weak, this basal layer has not been an active avalanche problem in our region for several weeks.

Terrain and Travel

  • Be alert to conditions that change with elevation and wind exposure.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Problems

Storm Slabs

An icon showing Storm Slabs

Likelihood

Likely-Very Likely

Expected Size

1 - 2.5

The forecast calls for a steady supply of new snow, coupled with bouts of moderate to strong wind. New snow in sheltered areas may react as dry loose sluffs, but keep eyes open for signs of instability such as shooting cracks or recent avalanches showing that a reactive slab has formed. Southwest winds may focus instability toward higher elevation, north through east aspects.

Aspects:

All aspects.

Elevations:

All elevations.

Valid until: Jan 12th, 2020 5:00PM