Avalanche Forecast

Issued: Apr 15th, 2018 4:43PM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs and Loose Wet.

jmcbride, Avalanche Canada

South Columbia.

It might be spring but it's still winter up high. Touchy storm slabs exist at treeline and above. Loose, wet avalanches are a concern at lower elevations. Minimize your exposure to avalanche terrain during periods of heavy snow, wind or rain.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TONIGHT: Mostly cloudy, flurries. Accumulation 2-5 cm. Ridge wind moderate to strong, southeast. Alpine temperature near -3. Freezing level 1100 m.MONDAY: Cloudy, flurries. Accumulation 10-20 cm. Ridge wind moderate, southeast. Alpine temperature near -3. Freezing level 1700 m.TUESDAY: Cloudy, flurries. Accumulation 10-15 cm. Ridge wind light to moderate, northwest. Alpine temperature near -5. Freezing level 1600 m.WEDNESDAY: Mix of sun and cloud. Ridge wind light, southeast. Alpine temperature near -5. Freezing level 1600 m.Â

Avalanche Summary

Saturday saw widespread avalanche activity with natural, cornice, skier, and explosive triggered storm slab releases (size 2-2.5) on all aspects in the alpine and in immediate lee areas at treeline.Friday there were reports of several natural and skier-triggered storm snow releases (size 1) in steep and leeward alpine terrain. As well as several natural storm slab releases up to size 2 on alpine, northeast through southeast aspects.Thursday pockets of reactive wind slab up to size 1 in alpine lees were reported, as well as skier-triggered, loose, wet avalanches to size 1.5 up to 2100m on solar aspects and below 1900m on north aspects. There were also reports from neighboring Glacier National Park on Thursday of a loose wet size 2 on a south aspect at 2100 m, and a size 4 slab that is thought to have been cornice triggered on a north aspect at 2800 m.Tuesday there was a report of a natural size 2 wind slab avalanche that was observed on a north facing feature at 2800 m.

Snowpack Summary

About 20-40 cm of new snow overlies a crust on all aspects to at least 2300 m (and possibly higher on south-facing slopes), while 50-60 cm of storm snow can be found at higher elevations. There are now a few different crusts in the upper snowpack, with only the most recently crust posing a concern for the recent storm snow.There is some lingering concern around the mid-March Persistent Weak Layer (PWL) in the alpine where it is found 80 to 120 cm below the surface. This buried crust/surface hoar interface was widely reactive but has not produced any avalanche activity in the past week. It is likely trending towards dormancy, but we need to keep it in the back of our minds as it is capable of producing large avalanches should it be triggered (think larger triggers such as; sleds, step-down from a surface avalanche or, a cornice collapse).Deeper persistent weak layers from December and January are considered dormant at this time.

Problems

Storm Slabs

New snow and strong winds have formed widespread, touchy storm slabs. Avoid wind-loaded and cross-loaded slopes at treeline and above where, these slabs sit on buried crusts and are especially deep and reactive.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid steep lee and cross-loaded slopes

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Loose Wet

Warming temperatures, rain, or a bit of sun may destabilize surface snow and initiate loose wet avalanche activity, especially below treeline and on steep south facing features. The likelihood of cornice failures also increases with sun and warming.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Cornices become weak with daytime heating. Avoid traveling on slopes below them.

Aspects: North, North East, East, South East, South.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 16th, 2018 2:00PM