Avalanche Forecast

Issued: Mar 17th, 2016 8:35AM

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

pmarshall, Avalanche Canada

Northwest Coastal.

Take a conservative approach when the sun is beating down or it feels balmy, especially if you're not sure about the existence and sensitivity of buried persistent weaknesses.

Summary

Confidence

High

Weather Forecast

FRIDAY: Mainly sunny. The freezing level should jump to around 1700-1900 m and ridge winds are moderate from the E-SE. SATURDAY: Increasing cloud with a chance of flurries. The freezing level dips to 1300 m but climbs back to 1700 m late in the day. Winds should be light. SUNDAY: A mix of sun and cloud. The freezing level is near 1800 m and winds are light or moderate from the east.

Avalanche Summary

There were numerous reports of natural and rider triggered wind slabs on northerly aspects and cross-loaded gullies on Wednesday. Most of these were small (size 1-1.5) with a few up to size 2. There were also reports of loose wet snow with the 20-40 cm of new snow moistening and sliding on a buried sun crust. In addition, a couple natural cornice falls to size 3 were observed with numerous cornice falls being reported in the past few days.

Snowpack Summary

We've seen variable amounts of new snow but an average of 30-40cm has accumulated over the last few days in sheltered areas. Variable winds have redistributed the surface snow forming wind slabs and adding mass to cornices. On south aspects, the recent storm snow may have buried a sun crust. Lower elevations and south aspects are going through daily melt-freeze cycles. A layer of surface hoar or melt-freeze crust buried on March 3 is down 70-100cm and has been recently reactive in the areas north of Stewart. An older crust/facet layer buried in early February can now be found down over a meter but this layer has been dormant for several weeks.

Problems

Wind Slabs

Variable and shifting winds may have created fresh wind slabs on a variety of aspects in exposed terrain. Sun and warming could increase the sensitivity of triggering this problem.

Minimize exposure to sun exposed slopes when the solar radiation is strong. >Be cautious as you transition into wind affected terrain. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Cornices are reported to be large and weak. Natural cornice releases are possible with sun exposure and warming.

Extra caution needed around cornices with current conditions.>Cornices become weak with daytime heating. >

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 5

Persistent Slabs

Lingering persistent weaknesses can still be found in the top 100 cm of the snowpack in parts of the region. Triggering is more likely with a heavy load (cornice fall) or warming and solar radiation (expected).

Dig down to find and test weak layers before committing to a big slope. >Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Mar 18th, 2016 2:00PM