Wednesday March 6, 2019

Wednesday March 6, 2019
Thursday March 7, 2019
Friday March 8, 2019
Confidence: Moderate - Good field data, wind and temperatures agreed on but precipitation amounts uncertain in forecast weather models.

Main Concerns

Persistent Slab, Storm Slab - view Avalanche Problems for detailed information.

Travel & Terrain Advice

Keep track of how much new snow actually falls in the zone you enter and adjust your decisions/actions for smaller or larger avalanches compared to the forecast precipitation amounts.

The persistent slab issue of weeks previous (weak crystals over the crust) has reduced in avalanche potential but should not be forgotten just yet. Avoid shallow areas in the snow pack where your weight can penetrate down to this layer easier and increase avalanche triggering potential.

Avalanche Summary

No new avalanches reported in the past couple days.

Avalanche Problems

Persistent Slab

The weak layer (facet crust combo) that was very active in the week previous has for the most part stabilized. Although it is unlikely, this layer may still be triggered with human activity and produce avalanches up to size 2 on all aspects and elevation bands. Avoid shallow areas where triggering is more likely, use cautious route finding and investigation (tests) to explore the potential.

Storm Slab

New snow that falls during this forecast period has a good chance of failing on a widespread preserved weak layer of surface hoar that has formed over the past few days. This new snow will be easily triggered by human activity and will very likely result in loose dry avalanches and likely cause storm slab avalanches up to size 1.5 on all aspects and elevations. High likelihood low consequence.

Snowpack Summary

Generally benign weather patterns over the past few days have steadily settled our snow pack. Clear cold nights with light winds have resulted in the growth of a weak layer of surface hoar crystals on the top of the snow, so the future forecast snow will mainly fall on an easy sliding layer. Steep solar aspects have warmed during the past couple days at treeline and below, resulting in a thin sun crust, while sheltered shaded areas have preserved soft snow. Open alpine zones have some wind affected surface conditions.

Snowpack Details

SurfaceWidespread growth of weak surface hoar crystals especially in areas sheltered from the wind and sun.
Upperwell settled 30-40 cm of old snow from the last storms with some weak layers present in between.
Midthe weak facet layer crust combo that resulted in all that unstable avalanche activity in previous weeks.
Lowerwell settled

Past Weather

Generally cool temps, light winds (mainly from the east) and no new snow.

Weather Forecast

Some new snow will fall over the next few days with light winds and cool steady temps. Should make for some fun times in the hills!

Wednesday - 0 to 2 cm of new snow, light NE to W winds, temps -7 to -3, freezing levels 0 to 900 m.

Thursday - a trace to 10 cm of new snow (lower amounts to the north, moderate to the west and greatest in the east), winds light NW to SW, temps -8 to -4, freezing levels 0 to 800 m.

Friday - trace to 12 cm of new snow (as above for zones of most and least accumulation), winds light NW to SW, temps -8 to -4, freezing levels 0 to 800 m.

Posted on Wednesday March 6, 2019 by Bill Phipps

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