Monday February 15, 2021

Wednesday February 17, 2021
Tuesday February 16, 2021
Monday February 15, 2021
Confidence: Moderate - Numerous observations and reports from a wide variety of the zones within the forecast area. Excellent field data and good agreement between weather models.

Main Concerns

Persistent Slab, Wind Slab, Storm Slab - view Avalanche Problems for detailed information.

Travel & Terrain Advice

Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding and conservative decision-making is essential

Avoid convex roll features.

Seek terrain that is well supported.

Caution when transitioning from areas scoured by the wind into areas with recent wind loading.

Avalanche Summary

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Saturday: Numerous new slab avalanches reported thought the storm period, up to size 1.5 mostly north aspects, between 1800 and 1200 meters.

Sunday: No new avalanches have been observed or reported.

Avalanche Problems

Persistent Slab

This problem has now become stubborn to triggering. It continues to provide results and is currently being tracked by a number of our observers.

Location: This problem is widespread, however isolated areas such as convex rolls and unsupported terrain is where it is most concerning.

Possibility: Triggering of this avalanche problem from light loads such as skiers are unlikely. Natural avalanches are very unlikely.

Size: If triggered, expect these avalanches to be large size 2.

Wind Slab

This problem is being buried by new storm snow, however it remains a concern and should be considered prior to route planning and decision making in avalanche terrain.

Location: Specific to South aspects in areas lee of ridgetops. Reverse winds on Sunday began to develop new wind slab on North aspects.

Possibility: Triggering of this avalanche problem from light loads such as skiers are possible to likely. Natural avalanches are possible.

Size: If triggered, expect these avalanches to be small size 1 but in specific terrain with available fetch zones to be large up to size 2, in isolated terrain features very large up to size 3.

Storm Slab

This new problem overlies in areas protected from the wind and sun, surface hoar. In other areas, expect this new slab problem to overlie, smooth and faceted surfaces. Overall the new snow has had a chance to warm slightly and is exhibiting slab properties. The poor bond with the old surfaces is a combination for a sensitive storm slab problem.

Location: Widespread, all aspects and elevations.

Possibility: Triggering of this avalanche problem from light loads such as skiers are likely to very likely. Natural avalanches are possible to likely.

Size: If triggered, expect these avalanches to be large up to size 2, in isolated terrain features very large up to size 3.

Snowpack Summary

Past wind slabs predominantly on South aspects are now buried and will continue to be buried with the current storm snow.

New snow has buried surface hoar from size 10 to 20mm found at Tree line and below in specific areas protected from the wind and sun. During travel take the time to observe where this fragile layer is and its sensitivity to testing. Many areas prior to this past storm had time to both facet and become smooth and hard over the extended period of cool , clear and windy conditions, expect this new snow to take time to bond to these surfaces and expect the new storm slab to remain unstable and easy to trigger from light loads.

The Jan 23, 2021 Persistent weak layer can be found between 60 and 100 cm deep and over the past forecast period, was reactive to testing.

Snowpack Details

SurfaceNew snow overlies and variety of surfaces including surface hoar and faceted smooth surfaces.
UpperFacet and low density snow overlies a dense and strong layer of well bonded and settled snow.
MidAn eroding crust with facets at its base ( JAN 21 PWL).
LowerWell settled.

Past Weather

Past precipitation amounts where highly variable over the forecast areas with up to 30 centimeters in the southern zones and the north western zone receiving 15cms.

Beginning Sunday, a trough of low pressure associated with a weak front approached the region bringing to the forecast area, rising temps and freezing levels. Initially precipitation was in the form of snow, but slowly transitioned to rain at elevations below 500 meters.

Weather Forecast

A frontal system will enter the region Monday and will deliver over a 48 hour period precipitation combined with rising freezing levels and temperatures . Expect on Wednesday clearing sky and cooling temperatures.

Monday: 15 to 30 cm , Winds Light to Moderate from the South East, Freezing levels at 500 to 800 meters.

Tuesday: 5-10 cm, Winds Light to Moderate from the North West, Freezing levels 600 to 1000 meters.

Wednesday: No new precipitation Winds Moderate from the South East, switching to North West, Freezing level from sea level rising to a daytime a high of 400 meters.

Posted on Sunday February 14, 2021 by Jesse Percival

Past Bulletins