Avalanche Forecast

Issued: Apr 19th, 2017 3:57PM

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

Avalanche Canada mbender, Avalanche Canada

Forecast snowfall amounts for Thursday may vary greatly due to the convective nature of the weather system passing through.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

THURSDAY: Cloudy with isolated flurries / Light west wind / Alpine temperature -1 / Freezing level 1700mFRIDAY: Mix of sun and cloud / Light to moderate northwest wind / Alpine temperature 0 / Freezing level 1900mSATURDAY: Cloudy with sunny periods / Light south wind / Alpine temperature 2 / Freezing level 2200mNOTE: 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

Recent reports from Tuesday indicate natural loose wet activity to size 1.5 and 2.5 in the alpine and tree line elevation bands on all aspects except north. Additionally a few wet slab avalanches to size 2.5 have been observed at tree line on southerly aspects. Reports from Monday indicate a few loose wet avalanches running on solar aspects at tree line and a cornice fall triggering a deep persistent weakness on the slope below to size 2.5 from very steep north facing terrain in the alpine. 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. Cornices remain large and continue to become more overhanging.

Problems

Cornices

An icon showing Cornices
The likelihood of cornices triggering increases with intense sunshine and/or during the warmest parts of the day.
Cornice failures could trigger large avalanches on sugary facets near the bottom of the snowpack.Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Wind Slabs

An icon showing Wind Slabs
Convective flurries and moderate southwesterly winds may create small wind slabs in lee features below ridgetops.
Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 20th, 2017 2:00PM