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Wednesday April 5, 2017

April 5, 2017 at 04:54AM

This Bulletin Valid Until: Friday April 7, 2017 @ 6 pm. 

DANGER RATINGS (Make sure you understand the danger level meanings)
 
Outlook Wednesday Thursday Friday
Alpine HIGH HIGH CONSIDERABLE
Treeline CONSIDERABLE CONSIDERABLE CONSIDERABLE
Below Tree line MODERATE MODERATE MODERATE

Confidence:  Moderate-  high variability between forecast wind and precipitation amounts on Friday  

Main Concerns: (Avalanche problems)

Wind Slab-   Moderate to strong south east winds and up to 70 cm of new snow during this forecast period will form dangerous wind slabs in both the alpine and at tree line. Wind slabs will be found on lee aspects (North west thru to North east) and located in terrain features such as at the base of steep cliffs, below any cornice features, 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 snow fall amounts continue to increase and winds persist. 

Loose Wet-   Upper surface snow will begin to lose cohesiveness as rain is forecast to fall at lower elevations, forming loose wet avalanches. These avalanches can be found on all aspects but especially solar and at all elevations tree line and below. Loose wet avalanches when triggered may gain mass as they travel and have the potential to be large in size (size 2). Expect upper snow pack loose wet avalanches to be near certain to occur during warm storm periods and when rain falls on new snow. Loose wet avalanches are likely to be touchy to light human triggers in steep, thin, and unsupported terrain features and when exposed to either rain or sun will become increasingly unstable and very touchy to triggering.

Storm Slab-   Moderate to strong snowfall amounts are expected to deliver up to 70 cm of snow throughout the forecast period and will likely form storm slabs in both the alpine and at tree line. Storm slabs will be found on all aspects and expect to find these dangerous avalanches in areas that offer protection from the wind. Avalanches from storm 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 and travel in avalanche terrain is not recommended and should be avoided. If user choose to travel in to avalanche terrain, choose simple terrain that avoids over head hazards.

Past Weather: Warm temperatures, followed by a cooling trend with near sea level freezing levels has developed a supportive melt freeze crust. Beginning Tuesday new snow fall had buried this new crust.

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

Snowpack Description  New snow has buried an upper surface crust that is up to 10 cm thick and was supportive to foot penetration. This new snow is settling under moderate temperatures and displaying slab properties, initial testing yesterday indicated a moderate bond between the new snow and this recently buried crust. Below this new crust 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 80 to 100 cm deep on lee aspects.This crust continues to produce 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 120 cm plus under dense well settled snow. The mid February persistent weakness can be found down up to 200 cm in isolated lee terrain in the alpine and is now likely dormant as numerous snow pack tests produced either no results or hard non planar results.The mid and lower snow pack are well settled and very dense snow pack conditions are found. 

Surface- New snow has buried a well developed surface crust.

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

Mid-  Well settled.

Lower- Well settled.

Weather Forecast: A cavalcade of moderately strong pacific lows will continue to pass thru the region with Tuesday night and Wednesdays system looking to be packing the greatest punch. Forecast models predict much higher precipitation amounts on the western edge of the forecast region and throughout the region expect generally milder temperatures, moderate wind and rising freezing levels.

Wed-  up to 20 cm new snow 10 mm of rain. Winds SW to 40 km/hr.                                            Freezing level to 1500 m.

Thur-  up to 20 cm new snow 5 mm of rain. Winds SE to 50 km/hr.                                              Freezing level to 1100 m.

Fri-   up to 25 cm new snow 15 mm of rain. Winds E to 40 km/hr.                                              Freezing level to 1200 m. 

 

Prepared by Jesse Percival

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