Avalanche Forecast
Issued: Jan 6th, 2019 4:33PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
ghelgeson,
Avalanche Canada
The storm snow is settling out below treeline, but there's been a ton of wind over the last 72 hours and we have limited alpine observations. Factor the potential for large human triggered avalanches at above treeline into your travel plans.
Summary
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Someone or something is playing with the storm switch, flipping it back and forth. Storm on, storm off, storm on. We get a brief respite Monday which may even offer a bit of sun. Another storm approaches the coast moving through the interior on Tuesday/Wednesday.SUNDAY NIGHT: Freezing level at valley bottom, moderate to strong west/southwest wind, 2 to 5 cm of snow possible.MONDAY: Broken cloud cover, freezing level at valley bottom, light west wind at most elevations, strong west wind at ridgetop, a few centimeters of snow possible.TUESDAY: Clear skies at dawn with cloud cover steadily increasing through the day, freezing level at valley bottom, light variable wind, no significant precipitation expected.WEDNESDAY: Overcast, freezing level at valley bottom, light variable wind at most elevations with strong south/southwest wind at ridgetop, a few cm of snow possible.
Avalanche Summary
As skies cleared on Saturday we received reports of a widespread natural storm slab avalanche cycle. The large (size 2 to 3) avalanches likely ran on both Thursday and Friday.Also on Friday, there was a report of a snowmobile triggered avalanche at Allan Creek south of Valemount. The avalanche was size 2 (40 cm deep) on an east aspect at 2100 m.Prior to the storm, several small human triggered avalanches were reported in the region, including small slabs (30 cm thick) on buried surface hoar at Sugar Bowl (see this MIN report for details). This layer is now buried much deeper, and at this point it's uncertain whether it could still be reactive.
Snowpack Summary
An intense storm delivered 50 to 90 cm of snow between Wednesday and Friday. The new snow is rapidly settling at lower elevations, while at higher elevations it continues to get blown around into fresh wind slabs.Prior to the storm, a widespread layer of surface hoar was reactive around treeline elevations. This layer is now 50 to 100 cm deep, and there is some uncertainty about whether or not it remains reactive.Another layer buried 150 to 200 cm composed of weak facets, surface hoar, and a sun crust is believed to be gaining strength. Places that might still challenge this assumption would be steep north and east facing slopes between 1900 and 2300 m and steep south-facing slopes in the alpine.The probability of triggering other deep layers in the snowpack is low, but the most suspect areas would be shallow spots in steep rocky terrain.
Problems
Storm Slabs
Wind effect is widespread in the alpine and wind has made it's way into isolated features at treeline too. Potentially deep wind and storm slabs may remain sensitive to human triggering. Slopes immediately lee of ridgecrest are the most suspect.
Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.Back off if you encounter whumpfing, hollow sounds, or shooting cracks.Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 7th, 2019 2:00PM
