Avalanche Forecast

Issued: Apr 13th, 2019 4:39PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs and Loose Wet.

ghelgeson, Avalanche Canada

South Rockies.

If we wake up to more than 20 cm of storm snow, then these danger ratings should all be bumped up one level, so moderate becomes considerable. New snow and wind Saturday night may produce a natural avalanche cycle if we get more snow than expected.

Summary

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain on Saturday

Weather Forecast

A frontal system should track into the region late Saturday into Saturday night.Â Were expecting it to be quite convective which makes it hard to pin down total snow amounts, but right now it sounds like the storm could produce up to 10 cm by Sunday Morning.SATURDAY NIGHT: Freezing level around 1500 m, moderate to strong west/southwest wind, trace to 6 cm of snow.SUNDAY: Scattered cloud cover initially building to broken cloud cover in the afternoon, freezing level around 1800 m, moderate to strong west wind, 1 to 3 cm of snow expected. MONDAY: Scattered cloud cover initially building to broken cloud cover in the afternoon, freezing level around 1800 m, light west/southwest wind, trace of snow possible. TUESDAY: Scattered cloud cover clearing to just a few clouds around lunch, freezing level rising to around 2000 m, light variable wind, no significant snowfall expected.

Avalanche Summary

No new avalanche activity reported from this region, the following is from the Lizard Range:On Friday small loose wet natural avalanches were reported from steep south facing terrain.On Thursday, explosive control was able to initiate a few loose dry avalanches up to size 1.5 which failed in the recent storm snow. In the afternoon skier controlled loose wet avalanches were easily triggered at treeline and below up to size 1.5 on sunny aspects. No natural avalanche activity was reported and no new avalanches were noted in alpine elevations.

Snowpack Summary

20-35 cm of recent snow has accumulated in the last week above a supportive crust at treeline and in the alpine. During the heat of the day, especially under direct sun, the snow surface becomes moist or wet almost everywhere. The exception being high elevation north facing features. Steep, north facing, alpine terrain may still hold a cold, dry, snowpack where isolated reactive wind slabs may exist and a well settled slab rests on weak facets (sugary snow). Although unlikely, human triggering of persistent slabs on this layer may still be possible, especially in rocky alpine terrain with a shallow or highly variable depth snowpack.Below treeline the snowpack is becoming isothermal.

Problems

Storm Slabs

Watch for fresh slab development, especially in high elevation north facing features where human triggering is most likely near ridgecrest. High elevation south and west slopes could produce sluffing as the new snow slides on a crust.

Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.Recent new snow may be hiding windslabs that were easily visible before the snow fell.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 1.5

Loose Wet

Sunny periods Sunday combined with fresh storm snow will likely initiate loose wet avalanche activity. The likelihood of loose avalanches increases as temperatures warm throughout the day and/or if the sun comes out for an extended period of time.

Brief periods of sun could quickly initiate natural avalanche activity.A moist/wet snow surface, pinwheeling and natural avalanches all indicate a weakening snowpack.Loose avalanches may start small but they can grow and push you into dangerous terrain traps.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 14th, 2019 2:00PM