Avalanche Forecast

Issued: Apr 14th, 2016 9:10AM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold. Known problems include Storm Slabs and Cornices.

ghelgeson, Avalanche Canada

Northwest Coastal.

A storm crashes into the NW Coast Friday forcing the freezing level down to about 1000m and is expected to generate significant snowfall through the weekend. Approach the mountains as if the calendar says January, not April.

Summary

Weather Forecast

Cloud developing overnight. Light snow and strong southwest winds by Friday morning with freezing levels at 1000 m. Strong southwest winds on Friday with 10 to 15 cm of new snow above 1000 m in near coastal areas of the region. Another 10 to 15 cm is expected on Saturday with strong southerly winds and freezing level at 1500 m. More snow on Sunday, 15 to 20 cm expected overnight and during the day with strong southerly winds. This storm is coming from the south and may not push very far inland as a blocking ridge steers the moisture towards the north.

Avalanche Summary

On Wednesday loose wet avalanches were reportedly running naturally to size 1 on north through west facing terrain between 1300 and 1600 m. On Tuesday loose wet/"moist" avalanches to size 2 were observed from steep rocky terrain. On both Sunday and Monday, loose wet avalanches up to size 2.5 were reported in the far north of the region. With the arrival of spring, field observations and data have become quite limited in the region.

Snowpack Summary

5 to 20 cm of new storm snow has fallen at higher elevations in the last 48 hours. Strong winds have generally been out of the south, but some wrap around east/southeast winds have also been reported. These winds have redistributed the recent storm snow in exposed alpine terrain and likely formed wind slabs in leeward features. The new snow has buried a widespread melt-freeze crust. With the exception of high elevation shaded terrain, the region likely returned to melt-freeze conditions on Wednesday allowing the surface to melt during the day resulting in crust formation overnight. The snowpack's strength is directly related to the thickness and strength of these surface crusts. A widespread crust/facet layer from early February and depth hoar at the bottom of the snowpack (primarily in northern & inland areas) are dormant. Cycles of melting and refreezing have limited the reactivity of these old layers. However these layers, or the ground, could potentially be the layer for an isolated yet large avalanche with prolonged periods of warming.

Problems

Storm Slabs

New storm snow combined with strong southwest winds are expected to generate fresh storm slabs Friday. These storm slabs rest on a crust in many locations which will likely make them quite sensitive to human triggering.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Be alert to conditions that change with elevation.>The new snow will require a day or two to settle out.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Cornices

The timing of failures is unpredictable. Unsupported sections are extra suspicious. Dropping chunks are a hazard in themselves and they may also trigger a slab avalanche on the slopes below. Watch and limit your exposure to overhead hazards.

Give cornices a wide berth when traveling on or below ridges. >Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Apr 15th, 2016 2:00PM