Avalanche Forecast

Issued: Apr 10th, 2018 4:17PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Loose Wet and Persistent Slabs.

ghelgeson, Avalanche Canada

North Columbia.

Watch for wind slabs immediately lee of ridge crest, pay attention to cornices and remember that we're still dealing with a persistent slab problem. Choose well-supported lines and travel early to take advantage of the overnight re-freeze.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Wednesday

Weather Forecast

Temperatures are expected to be slightly cooler Wednesday as we move into a pattern across the province that remains quite "winter-like." WEDNESDAY: Scattered cloud cover with potential for some clearing in the afternoon, freezing level beginning around 600 m rising to about 1700 m, light southwest wind, trace of precipitation possible.THURSDAY: Broken cloud cover, freezing level beginning around 600 m rising to about 1500 m, light southerly wind, 2 to 5 mm of precipitation possible.FRIDAY: Clear skies in the morning building to broken cloud cover in the afternoon, freezing level beginning near valley bottom rising to about 1600 m, moderate southwest wind, no significant precipitation expected.

Avalanche Summary

Loose wet avalanches to size 2 were reported from all aspects between 1000 and 2300 m Monday. In the neighboring Glacier National Park, loose wet avalanches to size 3 were reported from solar (south and west) aspects to size 3 between 2000 and 2300 m. A size 1.5 storm slab was ski cut from a northwest facing feature at 2400 m illustrating that isolated storm/wind slabs are still in play at upper elevations.On Sunday natural loose wet avalanches to size 2 were reported from all aspects (including north) as high as 2800 m.

Snowpack Summary

5 to 10 cm of new snow fell Saturday with moderate southerly wind. This snow rests on a crust that is present on all aspects below 2000 m, and extends up to about 2500 m on south facing aspects. The storm snow be be sitting on surface hoar on polar aspects (north and east) at upper elevations. The main concern is the mid-March Persistent Weak Layer (PWL) which is now 60 to 110 cm below the surface. This layer is composed of a crust on all aspects at low elevations. At upper elevations the layer presents as a crust on solar aspects (those that face south and west) and buried surface hoar on polar aspects. The reactivity of this interface has been steadily decreasing and while the likelihood of triggering a deeper persistent slab avalanche is lowering, the consequence of doing so remains high. Persistent slab avalanche activity on polar (north and east) aspects has dramatically decreased and solar (south and west) aspects are expected to be the most suspect over the next few days.Deeper persistent weak layers from January and December are still being reported by professional observers, but are generally considered dormant.

Problems

Loose Wet

Warming temperatures and a bit of sun may destabilize the snow surface and initiate loose wet avalanche activity which will likely be most pronounced on steep south facing features. The likelihood of cornice failure also increases in the afternoon.

Large cornices become weak with daytime heating, avoid traveling on or underneath them.Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Use caution above cliffs and terrain traps where loose avalanches may have severe consequences.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

A buried persistent weak layer consisting of surface hoar and crust is now 60 to 110 cm below the surface and may remain sensitive to human triggering in the alpine, especially on steep solar aspects in the afternoon.

Pay attention to overhead hazards like cornices which could trigger persistent slabs.Be aware of the potential for large, deep avalanches due to deeply buried weak layers.Use caution on open slopes and convex rolls where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Apr 11th, 2018 2:00PM