Avalanche Forecast

Issued: Jan 14th, 2014 9:47AM

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

slemieux, Avalanche Canada

South Coast.

Local avalanche conditions differ greatly across the region. In areas where until recently the snow pack has been unusually thin, it is possible to trigger large and destructive avalanches.

Summary

Confidence

Good

Weather Forecast

Tonight and Wednesday: An inversion will bring fog patches over the low lands and clear conditions up high. Later, a trace to light precipitation is expected with the passage of an unstable airmass with moderate to strong winds from the W shifting from the NW. Freezing levels should lower back to 1300 m. overnight and rise back up again tomorrow to 2000 m. Expect a bit of sun over the region during the day. Thursday: A ridge of high pressure is well in place. Sunny skies and continuing rising freezing levels starting at 2000 m until 3000 m on Friday. Light winds from the W. Friday overlook: Ridge is still dominating the pattern with clear skies and warm temperatures.

Avalanche Summary

A significant natural avalanche cycle happened yesterday with the morning heating. In the Northern part of the region, avalanches up to size 3.5 released in the depth hoar basal layer many of which were remotely triggered or naturally triggered. These mostly occurred on N and E facing slopes. Numerous natural avalanche up to size 2.5 are suspected to have released in the late November persistent weak layer. Around the Coquihalla area, numerous natural up to size 2.5 were also reported.

Snowpack Summary

Wind event from the SW-NW have redistributed the older storm snow and created thick winds slabs extending far into lee features. These windslabs and the old storm snow in sheltered terrain could possibly become more reactive and create moist avalanches as freezing levels rise up tomorrow. This is especially the case for steep slopes getting hit by solar radiation. North of the region, the snowpack is still showing a very weak structure with a basal facet/depth hoar problem at the bottom of the snowpack that is producing some scary snowpack test results. This makes for a low probability high consequence avalanche scenario that is more commonly associated in the interior of the province. South of the region, where the early season snowpack was deeper these persistent weak layers do not seem to be as prevalent. I suspect a wide range of surface conditions depending on altitude. Moist snow, crust and windslabs are part of the mix. Developping windslabs lee of winds in the alpine and moist snow avalanches at lower elevations and on South facing aspects are the most concerning for tomorrow.

Problems

Deep Persistent Slabs

Yesterday's avalanche activity confirms that weak layers are lurking deep in the snow pack particulary in the north. Avoid slopes that were shallow and rocky before the last storm.

Whumpfing is direct evidence of a buried instability.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Choose the deepest and strongest snowpack areas on your run.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Wind Slabs

Buried and developping windslabs could weaken tomorrow with rising temperatures and solar radiation. In the north, windslabs and recent storm snow may be sitting on a buried surface hoar layer.

Enter your line well below ridge crests to avoid wind loaded pillows.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Jan 15th, 2014 2:00PM