Avalanche Forecast

Issued: Mar 19th, 2016 9:23AM

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

bcorrigan, Avalanche Canada

South Rockies.

Danger ratings may go higher than forecast in areas affected by the combination of warming temperatures and solar radiation. Stay well clear of terrain affect by cornices. Conservative terrain choices are essential now.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

The high pressure ridge over the interior of the Province will remain through most of Sunday. Southerly winds will continue, with the freezing level forecast to climb to 2700 m late Saturday afternoon and continue through Sunday, then begin to drop late on Sunday afternoon to around 2200 m. No overnight freeze and temperature recovery expected. Flurries are forecast for Tuesday that should to bring 10mm of rain at lower elevations, and a chance of 10 to 15cm above 1200m. Tuesday night the freezing level is forecast to lower to 500 m then climb again on Wednesday to the 2000 m level. No precipitation is forecast for Wednesday.

Avalanche Summary

Recently the reports of avalanches have been limited to small loose dry, or loose wet releases running in steep terrain on the storm snow. Earlier in the week, explosive control work in the far north of the region produced numerous large to very large persistent slab avalanches on north through east facing features between 2200 m and 2400 m. Cornices are reported to be very touchy and sensitive to triggering. Over the course of the last week we have received many reports of cornice failure (some of them quite large), but no reports of avalanches being triggered when falling cornices impacted slopes below.

Snowpack Summary

Earlier in the week, 15 to 25 cm of new snow above 1700 m. Northeast wind over the last 48 hours has formed soft wind slabs in upper elevation wind exposed terrain. These wind slabs may be sitting on the mid-March crust, which is down around 20 cm below the snow surface. An earlier March crust can be found down around 50 cm below the surface. Both of these crusts are reported to be present from valley bottom to around 2300 m, after which they begin to disappear. There are thin snowpack areas in the South Rockies region where deeply buried weak layers near the ground remain sensitive to triggering. Huge cornices still hang over many ridge-lines and with solar radiation and warming temperatures may now be on the brink of failure.

Problems

Wind Slabs

Recent winds from the northeast have contributed to building wind slabs on lee ( southeast and southwest) features at treeline and above. These wind slabs may be easily triggered by a skier or rider.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>The new snow will require several days to settle and stabilize.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Cornices

Large cornices have formed on high ridge features in many places. These cornices present a real danger to skiers and riders. As temperatures warm up, cornices become weak and may fail, potentially triggering a large, destructive avalanche.

Do not travel any where near cornices this weekend! These behemoth chunks of dense snow could collapse at any moment, and you don't want to be underneath one when it fails.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 4

Loose Wet

Strong solar radiation and warm temperatures may result in loose wet snow releasing naturally from steep terrain. A skier or rider may also trigger a loose wet avalanche that could affect buried weak layers and trigger a large destructive avalanche

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 20th, 2016 2:00PM