Avalanche Forecast

Issued: Mar 15th, 2014 10:58AM

The alpine rating is high, the treeline rating is high, and the below treeline rating is considerable. Known problems include Storm Slabs, Persistent Slabs and Deep Persistent Slabs.

Avalanche Canada ghelgeson, Avalanche Canada

A conservative approach is critical as Sundays storm increases the load on a variety of weak layers in our complex snowpack.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain on Sunday

Weather Forecast

Synopsis: Snow should start falling in earnest around supper time Saturday evening. Look for it to snow through Sunday night accompanied by strong SW winds. In the wee hours of Monday morning the flow begins to take a more northwesterly tilt which eventually leads to ridging and clearing on Monday/Tuesday. Saturday Night: Freezing Level: 1400m - 1900m; Precipitation: 6:12mm - 6:20cm; Treeline Wind: Moderate, SW | Extreme SW at ridgetop.Sunday: Freezing Level: 1300m - 1800m; Precipitation: 3:8mm - 4:15cm; Treeline Wind: Moderate, SW | Strong SW at ridgetop.Monday: Freezing Level: 1200m; Precipitation: 0:3mm - 0:5cm; Treeline Wind: Light, NW | Moderate NW at ridgetopTuesday: Freezing Level: 1500m; Precipitation: Nil; Wind: Light, SW

Avalanche Summary

On Friday we received a report of storm snow failing as a fast moving size one avalanche that ran on the March 13th crust on a steep north facing slope at treeline. There was also a report of a size two avalanche that was triggered accidently on a North facing slope, again at treeline, on the early March surface hoar/crust combo. On Thursday explosive control produced avalanches to size 3 on both SE & NE facing slopes in upper treeline and alpine elevations. A skier remote triggered a size 3 avalanche from 100m away on a NE facing slope at 2200m. The avalanche was triggered from low angle terrain and resulted in a very large avalanche with a crown up to 150cm in depth. Last Saturday's avalanche fatality occurred in the Keefer Lake area northeast of Cherryville. The avalanche, which occurred in a cut block at about 1700m, involved 3 sledders who were in a party of 6. Two of the men were able to inflate their airbags and were partially buried. The deceased was reportedly not able to inflate his airbag, and was buried approximately 5m below the surface.While not in this region, it's worth taking a look at last weekends incident from the Cariboos.

Snowpack Summary

The surface is currently a mix of 3 - 6mm surface hoar and crust. Last weeks storm snow has settled into a 50 - 100 cm slab that rests on the early March interface consisting of small grained surface hoar in sheltered areas and a sun crust on solar aspects. In upper elevation wind exposed terrain the new snow has been pushed into deep wind slabs by moderate SW winds.The last week featured an average daytime freezing level around 1800m which resulted in a daily melt freeze cycle that left many features wet and sloppy by the afternoon. This setup resulted in some serious incidents recently.Ridgetop cornices remain large and unsupported.The February 10th surface hoar/facet/crust combo is 80cm - 250cm below the snow surface and widespread throughout the region. Surface avalanches in motion and cornice fall still have the potential to initiate an avalanche on this deeply buried weak layer. Remote triggering on this layer is ongoing. The mid and lower snowpack are strong and well consolidated.

Problems

Storm Slabs

An icon showing Storm Slabs
New snow accompanied by strong SW winds is all coming to rest on yet another suncrust/surface hoar combo. Be advised that avalanches running on the surface may provoke deeply buried weak layers into action.
Conservative terrain selection is critical on Sunday.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid exposure to overhead avalanche terrain, large avalanches have the potential to reach down into run out zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
The early March suncrust/surface hoar combo should not be underestimated. While there's a lot of uncertainty surrounding this layer, I suspect that the new storm snow is going to increase it's sensitivity to human triggering.
The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches. >Given all the uncertainty surrounding this slab, I advise against stepping out into terrain with any kind of consequence.>Watch for terrain traps where avalanche debris can accumulate into deep deposits.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
The early February Persistent Weak Layer is still active and has produced some stunning avalanches recently. Very large avalanches may result from a surface avalanche in motion, a cornice fall or a rider finding the sweet spot.
Be aware of the potential for large, deep avalanches due to the presence of deeply buried weak layers.>Avoid rock out croppings, large convexities and anywhere the snowpack is thin and/or variable.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 16th, 2014 2:00PM

Login