Avalanche Forecast
Issued: Apr 16th, 2019 4:55PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Loose Wet.
cgarritty,
Avalanche Canada
Overnight winds are expected to keep slab problems firmly on the radar for Wednesday. The crust under our new snow hasn't been a great bonding surface and wind loading won't help matters.
Summary
Confidence
Moderate -
Weather Forecast
Tuesday night: Increasing cloud with a chance of isolated flurries. Winds increasing to moderate or strong from the southwest. Freezing level remaining near 1700 metres.
Wednesday: Mainly cloudy with isolated wet flurries with a possible trace of new snow above 1800 metres. Light rain below. Moderate to strong southwest winds. Alpine high temperatures around +1 with freezing levels peaking at 2200 metres and rising overnight.
Thursday: Mainly cloudy. Moderate to strong southwest winds. Alpine high temperatures around +6 with freezing levels rising to 2800 metres, remaining elevated overnight.
Friday: Cloudy with showers bringing 5-10 mm of rain to mountaintop. Strong southwest winds. Alpine high temperatures around +6 with freezing levels dropping from 2800 to 2500 metres over the day
Avalanche Summary
On Sunday skier triggered avalanches were widespread on north through east facing slopes in the alpine and down into treeline too.
A natural avalanche cycle occurred Saturday night, the highlights were storm slabs up to size 2 on northeast facing alpine terrain around 1700 m. A natural cornice failure was observed from a north facing ridgeline which subsequently triggered a size 2.5 storm slab involving the new snow. Control work produced storm slabs to size 2. We received a great MIN report of a small storm slab from Saturday morning, and this was well before the storm really kicked into gear.
Snowpack Summary
The Fernie Factor really kicked in late Saturday into early Sunday. The region picked up about 30 cm of snow (and 53 mm of water). Check out this great MIN report from Sunday. This snow sits above a widespread supportive crust. Steep, north facing, alpine terrain may still hold a cold, dry, snowpack where fresh storm slabs are thought to be widespread. Steep north facing terrain is also harboring a deeply buried layer of facets. Although unlikely, human triggering of persistent slabs on this layer may still be possible, especially in rocky alpine terrain with a shallow or highly variable depth snowpack.
It looks like it is going to warm up this week and all the new snow will likely produce a widespread and powerful loose wet cycle. During the heat of the day, especially under direct sun, the snow surface will become moist or wet almost everywhere (except for high elevation north) and loose wet avalanches could run far.
Below treeline the snowpack has melted or is isothermal.
Problems
Storm Slabs
About 30 cm of storm snow rests on a widespread crust. The "crust free" exception may be high elevation north facing alpine terrain. Storm slabs may remain sensitive to human triggering, especially in wind loaded terrain.
- Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- Forecast strong winds will promote the formation of new wind slabs on leeward (north to east) slopes
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Sunny breaks combined with recent storm snow may allow for continued loose wet avalanche activity. The likelihood of loose avalanches increases as temperatures warm throughout the day and/or if the sun comes out for an extended period of time.
- A moist/wet snow surface, pinwheeling and natural avalanches all indicate a weakening snowpack.
- Areas sheltered from wind but exposed to sun will be the most prone to loose wet activity.
- Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.
Aspects: East, South East, South, South West, West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 17th, 2019 2:00PM
