Avalanche Forecast

Issued: Mar 3rd, 2016 7:25AM

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

pmarshall, Avalanche Canada

Cariboos.

Storm slabs are highly reactive to human-triggering and conservative terrain selection remains critical for the next few days. Extra caution is required on south-facing slopes in the afternoon if the sun pokes out.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

FRIDAY: Cloudy with sunny breaks and light precipitation starting late in the day. Freezing levels reaching 1600 m late in the day with strong southwesterly ridgetop winds. SATURDAY: Periods of snow bringing another 5-10 cm. Freezing levels steady around 2000 m with moderate to strong southwesterly ridgetop winds. SUNDAY: Periods of snow. The freezing level is around 1600-1800 m and ridge winds ease to light and variable.

Avalanche Summary

On Wednesday, there were reports of a few natural slab avalanches up to size 2.5 failing on the late Feb. sun crust/surface hoar combo. These slides were from S-E aspects at treeline and showed impressive propagation. Reports from Tuesday include more evidence of the widespread natural avalanche cycle early Monday, with avalanches up to Size 2.5. These fresh storm and wind slabs should increase in size and sensitivity and become much more widespread as they build throughout the week.

Snowpack Summary

30-60cm thick storm slabs are bonding poorly to a crust on previously sun-exposed slopes and surface hoar on shady and sheltered slopes. Thicker and touchier wind slabs are lurking throughout exposed terrain at and above treeline. A couple sun crusts might exist in the upper 50-70cm on southerly aspects. The surface hoar and/or crust layer which was buried February 10 is now down around a metre and is still producing isolated hard sudden results in snowpack tests. Large cornices will be getting weak with warmer temperatures.

Problems

Storm Slabs

Fresh storm slabs are primed for human triggering. Particularly touchy wind slabs are lurking below ridge crests, behind terrain features and in cross loaded gullies.

Choose well supported terrain without convexities.>Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Cornices

Warm temperatures, strong winds, and possible sunny breaks are all factors that could weaken large droopy cornices.

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

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Mar 4th, 2016 2:00PM