Avalanche Forecast
Issued: Feb 5th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Wind Slabs and Loose Wet.
rbuhler,
Avalanche Canada
Wind slabs, loose avalanches, and weak cornices are all expected Sunday.
There is a lot of uncertainty about how buried weak layers are going to react to the sun and warming. Use a conservative approach to terrain selection and watch for signs of instability.
Summary
Confidence
Weather Forecast
A ridge of high pressure brings dry and sunny conditions for Sunday with a layer of warm air expected to reach the alpine and the potential for a temperature inversion in the valleys.
Saturday Night: Mainly clear, light to moderate W wind, treeline temperature around -6 °C.
Sunday: Mainly sunny with a chance of valley cloud, moderate W wind, freezing level reaching near 2000 m in the afternoon with a possible temperature inversion.
Monday: A mix of sun and cloud, moderate to strong SW wind, freezing level around 1800 m with an inversion.
Tuesday: Mainly sunny, light to moderate W wind, freezing level reaching around 1800 m.
Avalanche Summary
An early report from Saturday includes a natural cornice fall triggering a size 2 storm slab failing down 30 cm.
On Friday, ski cutting triggered one size 1 storm slab which failed on the January 30 surface hoar as well as several shooting cracks. On Thursday, this MIN report described a snowmobile-triggered size 1 slab on an east aspect below treeline failing down 30 cm on the January 30 surface hoar.
Snowpack Summary
Up to 50 cm of settling snow now overlies the January 30 interface which consists of a melt-freeze crust at lower elevations and on solar aspects extending into the alpine, widespread surface hoar in sheltered areas at and below treeline, and small facets in some areas. Prior to the weekend warming, the surface storm snow was cold and mainly unconsolidated, and had not formed a slab in most places except for where it was wind loaded. With warming and sun this weekend, rapid settlement is possible and this may result in the formation of a more widespread reactive slab over the weak interface.
Periods of strong wind over the past week has formed reactive wind slabs in exposed terrain at higher elevations and ongoing wind on Friday and Saturday, mainly from the southwest through northwest, has likely continued to develop wind slabs.
The widespread January 18 rain crust is now around 50-70 cm deep with weak faceted snow above. This layer has not produced any recent avalanche activity but will get tested this weekend with warming and sun.
The early December crust/facet persistent weak layer is now 100-200 cm deep. This layer produced numerous large avalanches in January but is now considered dormant. See this forecaster blog on how to manage this layer as it may come into play again later this season.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
- The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
- Cornices become weak with daytime heating.
Problems
Persistent Slabs
Up to 50 cm of relatively unconsolidated snow sits over the January 30 surface hoar. With warming and sun this weekend, this snow may settle into a reactive slab. There is a lot of uncertainty regarding the timing and spatial extent of this scenario so extra caution is recommended, especially around open slopes at and below treeline where the buried surface hoar is most prominent.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Wind Slabs
Recent strong winds from the SW through NW have formed reactive wind slabs in exposed terrain at higher elevations. These slabs are particularly reactive where they overlie buried surface hoar.
Cornices may become weak with sun and warming.
Aspects: North, North East, East, South East, South, South West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Loose avalanches should be expected on steep sun exposed slopes during the heat of the afternoon.
Aspects: South East, South, South West, West.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 6th, 2022 4:00PM
