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Archived

Avalanche Forecast

Apr 14th, 2018–Apr 15th, 2018
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

Snow and wind will continue to build wind slabs in alpine lees and exposed treeline features. These slabs may be poorly bonded to the underlying crust. Watch for sluffing in steep terrain and loose, wet releases on sunny and low elevation slopes.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

TONIGHT: Mostly cloudy, flurries. Accumulation 5-10 cm. Ridge wind moderate to strong, southwest. Alpine temperature near -5. Freezing level 1200 m.SUNDAY: Cloudy, flurries. Accumulation trace. Ridge wind light to moderate, southwest. Alpine temperature near -3. Freezing level 2000 m.   MONDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind moderate to strong, southeast. Alpine temperature near -4. Freezing level 1800 m.TUESDAY: Mostly cloudy, flurries. Accumulation 5-10. Ridge wind light to moderate, northwest. Alpine temperature near -5. Freezing level 1600 m.

Avalanche Summary

Friday several skier-triggered, size 1.5 wind slab releases were reported on north aspects at 2300 m. As well as a few solar-triggered storm slab releases (size 1.5) on steep, unsupported. west-facing features at 2200 m.Wednesday there was a report of an icefall-triggered size 1.5 wind slab (50 cm deep and 50 m wide) on a north aspect at 2400 m. On Tuesday a skier triggered a size 1 wind slab 20 cm in depth on an east facing feature at 2400 m. And on Monday wind loading produced natural wind slab avalanches to size 2 on north facing terrain around 2400 m. Solar radiation also produced natural storm slab and loose wet avalanches to size 2.5 on various aspects between 1700 and 2600 m. We received the following information second hand, and not all details may not be accurate. Last Sunday six riders were involved in an avalanche up Doctor Creek. One was stuck, the second went to help and also got stuck, a third rode up to help and triggered an avalanche that buried all three, "up to their faces." The riders credit airbag packs with saving their lives and although one sled was wrecked, was able to extricate themselves. The slope was reportedly north facing and failed as a wet slab.

Snowpack Summary

About 5-15 cm on new snow overlies a crust on all aspects to at least 2000 m (and possibly higher on south-facing slopes), while 20-30 cm can be found at higher elevations (and up to 50 cm in some areas in the northwest of the region). There are now a few different crusts within the top 50 cm of the snowpack, with only the mostly recently buried crust posing a concern in wind-loaded areas.There is some lingering concern around the mid-March Persistent Weak Layer (PWL) in the alpine where it is found 50 to 90 cm below the surface. This buried crust/surface hoar interface was widely reactive but has produced only isolated avalanche activity in last week. It is likely trending towards dormancy, but we need to keep it in the back of our minds as it is capable of producing large avalanches should it be triggered (think step-down from a surface avalanche or cornice collapse)Deeper persistent weak layers from December and January are considered dormant at this time.

Avalanche Problems

Wind Slabs

New snow and ongoing southwest winds at ridgetop will continue to build wind slabs in leeward areas in the alpine and at treeline. These will likely remain sensitive to human triggers on Sunday.
Be very careful with wind loaded pockets, especially near ridge crests and roll-overs.Sluffs may be easy to trigger in steep terrain that is sheltered from the wind

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2

Loose Wet

Warming temperatures and a bit of sun may destabilize surface snow and initiate loose wet avalanche activity, especially on steep south facing features. The likelihood of cornice failures also increases with sun and warming.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Cornices become weak with daytime heating, give them a wide berth when traveling above or below.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2