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Avalanche Forecast

Apr 12th, 2018–Apr 13th, 2018
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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
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
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: South Columbia.

Wind slabs can be found in leeward areas near ridge crests, while moist or wet snow is a concern on sunny and lower elevation slopes. Also be wary of large cornices that can become weak with warming.

Confidence

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

Weather Forecast

TONIGHT: Flurries, clearing. Accumulation 2-5 cm. Ridge wind light to moderate, northwest. Alpine temperature near -6. Freezing level 500 m.FRIDAY: Increasing cloud and flurries. Accumulation trace. Ridge wind moderate to strong, southwest. Alpine temperature near -5. Freezing level 1700 m. Flurries or snow overnight.SATURDAY: Mostly cloudy, flurries. Accumulation 5-15 cm. Ridge wind moderate to strong, southwest. Alpine temperature near -5. Freezing level 1600 m.SUNDAY: Mostly cloudy, flurries ending. Accumulation 2-4 cm. Ridge wind light to moderate, southeast. Alpine temperature near -4. Freezing level 1600 m.

Avalanche Summary

Thursday there were reports from Glacier National Park of a loose wet size 2 on a south aspect at 2100 m,  and a size 4 wind slab that occurred overnight and is thought to have been cornice triggered on a north aspect at 2800 m.On Wednesday there were reports of wind slab activity on northerly aspects limited to the recent storm snow as well as loose wet activity on south-facing slopes.Tuesday there was a report of a natural size 2 wind slab avalanche that was observed on a north facing feature at 2800 m.On Monday natural loose wet avalanches to size 2 were reported on all aspects with the exception of north between 1500 and 2500 m. A skier triggered size 1.5 storm slab was reported from a west/northwest facing feature between 1800 and 2200, failing on a crust. And riders near Blue Lake also triggered a size 2 slab avalanche on buried surface hoar on a north aspect at 2000 m. Read MIN report here.

Snowpack Summary

A thin surface crust is now present on all aspects to at least 2300 m. This crust likely goes even higher on south facing aspects, while 5-15 cm of cold snow can be found on high elevation north facing aspects. There are now a few different crusts in the upper 50 cm of the snowpack, with only the most recently 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 60 to 110 cm below the surface. This buried crust/surface hoar interface was widely reactive last week, but has not produced any avalanche activity in the last few days. 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 larger triggers such as; sleds, step-down from a surface avalanche or, a cornice collapse).Deeper persistent weak layers from December and January are dormant at this time.

Avalanche Problems

Wind Slabs

Recent snow and wind have formed touchy wind slabs immediately lees near ridge crest on northerly alpine terrain.
Sluffs may be easy to trigger in steep terrain that is sheltered from the windBe careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Loose Wet

Warming temperatures and a bit of sun may destabilize the snow surface and initiate loose wet avalanche activity, especially on steep south facing features. The likelihood of cornice failures also increases with sun and warming.
Use caution above cliffs and terrain traps where loose avalanches may have severe consequences.Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Large cornices become weak with daytime heating, avoid traveling on or underneath them.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 2