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Monday April 3, 2017

April 3, 2017 at 06:21AM

This Bulletin Valid Until: Wednesday April 5, 2017 @ 6 pm. 

DANGER RATINGS (Make sure you understand the danger level meanings)
 
Outlook Monday Tuesday Wednesday
Alpine MODERATE MODERATE CONSIDERABLE
Treeline LOW MODERATE MODERATE
Below Tree line LOW LOW LOW

Confidence: Good, moderate for alpine, some discrepancies with forecast models in regards to precipitation amounts and freezing level on Wednesday.

Main Concerns: (Avalanche problems)

Loose Wet-  These avalanches can be found on all aspects but especially solar and at all elevations tree line and below. Loose wet avalanches could be large in size and will be very touchy to human triggers during warm storm periods and when temperatures rise. Loose wet avalanches are likely to be touchy to human triggers in steep, thin, and unsupported terrain features and when exposed to sun will become increasingly unstable and very touchy to triggering.

Cornice- In the past week, new snow, wind and moderate temperatures have provided ideal conditions to form cornices.These hazardous snow features can be found on primarily north west thru to north east aspects and in both the alpine and at treeline.As temperatures rise and load increases cornices can be unpredictable and once failing will deliver a heavy load to slopes below and may trigger a much larger avalanche (size 3). Give these hazardous features a wide berth when deciding to travel either above or below them.

Wind Slab-   Forecast moderate south east wind and up to 35 cm of new snow will likely form wind slabs late Tuesday and Wednesday in both the alpine and at tree line. Wind slabs will be found on lee aspects and located in features such as ridge top areas and steep convex rolls. Avalanches from wind slabs could be large (size 2) and will be touchy to very touchy to light human triggers as storm snow fall amounts increase. 

Travel/Terrain Advice:  Dangerous avalanche conditions exist on specific terrain features. Evaluate snow pack and terrain carefully and identify routes that avoid hazardous features and areas of concern. Be very aware of the intensity of solar effect as short periods of clear sky and sun will begin breaking down the upper snow pack and decrease stability. When the sun appears, loose wet avalanches, failing cornices, and storm slab instabilities may become a concern within a very short period of time.

Past Weather: Light precipitation, warm day time temps followed by clear and cool overnight temps. These past conditions have formed an upper surface crust and helped to promote upper snow pack settlement and increased stability within the upper snow pack.

Avalanche Summary: No new avalanche activity reported in the last 72 hours.

Snowpack Description The upper snow pack has settled and the diurnal cycle has seen swings from minus four to plus two. This has created an upper surface crust that is up to 10cm thick and in many places supportive to foot penetration. Day time warming has been able to break that upper crust on direct solar aspects and in most areas remain supportive with only the very upper surface losing any cohesiveness. Below this a variety of both sun crust and wind crust have been observed and are dependent on orientation to both the sun and wind.

  The March 23 crust is between 60 to 80 cm deep on lee aspects.This crust is currently producing hard resistant planar results when isolated and tested.The mid March rain crust is prevalent on all aspects and elevations, up to 20 cm thick and buried down 100 cm plus under new dense well settled snow. That crust is bonding well with continuing hard resistant planar results when tested. The mid February persistent weakness can be found down 150 cm and possibly up to 200 cm in isolated lee terrain in the alpine and is becoming dormant as numerous snow pack tests produced hard non planar results.The mid and lower snow pack remain well settled and dense snow pack conditions are found. 

Surface- Becoming moist in the pm and firm in the am.

Upper-  Numerous melt freeze crusts exist in the upper snow pack.

Mid-  Well settled.

Lower- Well settled.

Weather Forecast:  A short lived high pressure will bring clear conditions to the forecast region. Beginning Tuesday, the ridge will get the push out and a warm and wet westerly flow will follow.The westerly flow will bring increasing wind, warm temps,rising freezing levels and moderate precipitation amounts.

Mon-  no new snow 2 mm of rain. Winds SE to 20 km/hr. Freezing level to 1000 m.

Tues-  up to 15 cm new snow 4 mm of rain. Winds SE to 50 km/hr. Freezing level to 1000 m.

Wed- up to 25 cm new snow 10 mm of rain. Winds SE to 60 km/hr. Freezing level to 1500 m. 

 

Prepared by Jesse Percival

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