Avalanche Forecast

Issued: Jan 30th, 2020 1:00AM

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

Ryan Shelly, VIAC

Vancouver Island.

On Wednesday : Several size 1 (ski cut) avalanches reported at Treeline elevation on the recent storm snow interface, remote triggering was also reported (Size 1's) at Treeline elevation.

Summary

Past Weather

Relatively consistent below freezing temperatures at Treeline elevation coupled with consistent moderate snowfall have made for great snowmobiling and skiing. Wednesday's air temperature rose and as a result so too did the avalanche hazard.

Weather Forecast

The weather pattern is about to get dynamic in terms of precipitation, wind and air temperature fluctuation the next several days. Thursday 2- 12 mm Rain, 4 cm - 12 cm Snow, Winds Extreme from the South, Freezing level 2,100 meters.Friday 70 - 130 mm, Winds Extreme from the South, Freezing level 2500 meters.Saturday 2 - 16 cm, Winds Moderate from the West, Freezing level 550 meters.

Terrain Advice

On Thursday, Natural Avalanches possible, Human triggered avalanches likely in Alpine and Treeline on unsupported terrain. There is an extreme amount of precipitation expected Friday. As a result of this major rain event, Friday's forecast Avalanche Hazard is set to HIGH (Human Triggered Avalanches Very Likely, natural avalanches Likely). Be aware as you move through the terrain for shooting cracks, snow "pin wheeling" and signs of instability (including new avalanches) especially at Treeline and Alpine elevation bands. On Friday, it will be wise to avoid all avalanche terrain and allow for cooling air temperatures to settle instabilities that will occur on Friday and into Saturday if the extreme rain event occurs in your area.On Thursday if visible (snow cracking underfoot/adjacent your sled) and/or audible (whumpfing) clues exist in your area, it will be important to find lower angle terrain (generally under 30 degrees) and or ski/sled in more densely vegetated (treed) areas away from these obvious clues of snowpack instability. Check the website ATES PLANNING section for Simple Terrain options on our website. On Friday, avoid all avalanche terrain due to extreme weather (Wind/Rain) forecasted for the majority of Vancouver Island.

Snowpack Summary

Moderate rates of precipitation in the form of snow have occurred on Vancouver Island for the past several days. As a result, the upper snowpack contains several storm snow layers that are consolidating due to favourable air temperature. The mid and lower snowpack are extremely well consolidated due to the below freezing temperatures we have seen throughout the majority of January. The generally high moisture content in the snowpack currently is such that it has allowed for favourable consolidation (rounding).

Snowpack Details

Surface: Multiple storm snow and wind events have created a 30cm-50 cm surface snowpack of rounding snow
Upper: Well bonded and dense moisture laden snowpack
Mid: Well bonded mid-pack that does include two weaker (PWL) layers (Facet layers) both un-reactive to testing
Lower: Well Settled

Confidence

High - Weather models in agreement, sufficient field weather and snowpack observations

Problems

Cornices

Friday’s rainfall will hasten potential for cornice fall. Extreme winds and over 100mm of additional rain at all elevation bands on will increase the probability for cornice failure due to increased load and melting of snow thus decreasing cohesion of snow leading to cornice failures.

Likelihood

Possible

Expected Size

1 - 1

Wet Slabs

Friday’s forecast of extreme rain will also exacerbate stability of the more recent storm snow layers located within the upper 50cm of the snowpack. Extreme Rain will create a majorly over saturated upper snowpack primed for triggering. By Friday, both human triggered and natural avalanches will be likely at Alpine and Treeline elevation bands.

Likelihood

Possible

Expected Size

1 - 1

Loose Wet

On Friday, the forecast models predict over 100mm of rain for all elevation bands (Above mountain-top) Expect natural and human triggered avalanches to occur on steep unsupported terrain and possibly on lower angled slopes as well given the extreme rain event volume.

Likelihood

Possible

Expected Size

1 - 1

Valid until: Jan 31st, 2020 1:00AM