Avalanche Forecast

Issued: Mar 18th, 2016 10:33AM

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.

ghelgeson, Avalanche Canada

South Rockies.

All bets are off this weekend with regard to stability as the region heats up in a big way. Stick to simple terrain and avoid overhead hazard.

Summary

Confidence

Moderate

Weather Forecast

An upper ridge is expected to cross the province this weekend ushering in warm spring like temperatures on both Saturday and Sunday. By Monday the ridge should be loosing strength, which will open the door to cool and unsettled weather going into Tuesday. SATURDAY: Freezing level starting at valley bottom then rapidly climbing to around 2000 m by lunch time, moderate west/southwest winds, no precipitation, clear skies. SATURDAY NIGHT: Freezing level holding around 2500 m. SUNDAY: Freezing level staying around 2500 m, moderate southwest winds at ridge top, no precipitation expected. Increasing cloud cover may trap warm air leading to a greenhouse effect. MONDAY: Freezing level hovering around 2100 m for most of the day, light rain possible in the afternoon, light variable winds and broken skies.

Avalanche Summary

On Thursday avalanche observations were limited to small loose dry releases running in the storm snow. On Wednesday 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 were 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 subsequent slab avalanches being triggered when falling cornices impacted slopes below.

Snowpack Summary

On Thursday there was around 15 to 25 cm of new snow at 1700 m. There has been a touch of northeast wind over the last 48 hours which is forming 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. The early 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, where 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 many are likely teetering on the brink of failure.

Problems

Wind Slabs

A touch of wind out of the northeast has likely created fresh thin wind slabs in upper elevation terrain which may fail naturally as the temperature rapidly rises on Saturday.

Use ridges or ribs to avoid pockets of wind loaded snow.>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

Large unstable cornices overhang countless ridge lines and many of these cornices are teetering on the brink of failure. The weight of an approaching rider, rising temperatures or direct sun could easily induce collapse.

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

Forecast strong solar radiation and warming daytime temperatures will likely result in loose wet avalanches releasing from steep terrain.

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 19th, 2016 2:00PM