Avalanche Forecast

Issued: Apr 20th, 2017 4:38PM

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

jsmith, Avalanche Canada

Cariboos.

Sunshine and rising freezing levels will elevate the potential for cornice failures resulting in large avalanches on Friday.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

FRIDAY: Mix of sun and cloud / Light northwest wind / Freezing level 2100mSATURDAY: Cloudy with sunny periods and isolated flurries / Light to moderate southeast wind / Freezing level 2000mSUNDAY: Cloudy with flurries / Moderate south wind / Freezing level 1800mNOTE: Convective flurries, which are common this time of year, can result in widely varying snowfall amounts. These spring squalls routinely drop 20+ cm of snow in one valley while the adjacent drainage remains dry. For this reason, the distribution of avalanche problems associated with new snow vary greatly within a region.

Avalanche Summary

Numerous natural loose wet avalanches to size 2.5 on a variety of aspects were reported on Wednesday. Exposure to large overhanging cornices remains a significant concern.

Snowpack Summary

Recent new snow tree line and above has been redistributed by west and south winds. Cornices remain large and continue to become more overhanging. The middle of the snowpack is generally well settled and continues to transition into a spring melt/freeze regime except for high elevation northerly aspects. Expect the entire thickness of the snowpack to be moist or wet at lower elevations. At upper elevations a deep persistent layer consisting of facets sitting on a crust that was buried back in November has been sporadically reactive to heavy loads i.e. a cornice fall or the weight of a smaller avalanche running.

Problems

Cornices

The likelihood of cornices failing increases with intense sunshine and/or during the warmest parts of the day.

Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.Minimize exposure to cornices and sun exposed slopes when the solar radiation is strong.Cornice falls have the potential to trigger deeply buried weak layers.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 4

Wind Slabs

Convective flurries and moderate winds may have formed fresh wind slabs on lee features tree line and above.

Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.Pay attention to changing conditions with elevation.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

Loose wet avalanches may trigger deeply buried weak layers, resulting in large avalanches.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Pinwheeling snow below cliffs is a common sign that loose wet avalanches are becoming more likely.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Apr 21st, 2017 2:00PM