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Avalanche Forecast

Archived

Jan 17th, 2020–Jan 18th, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Lizard-Flathead.

Give the snow a few days to settle and stabilize before pushing into bigger terrain. Storm slabs remain sensitive to human and solar triggering.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Friday night: Mostly clear. Light to moderate west to southwest winds. Alpine low around -15 C.

Saturday: Mix of sun and cloud with scattered flurries bringing 5-10 cm of new snow. Light to moderate southwest winds. Alpine high around -8 C.

Sunday: Mix of sun and cloud with scattered flurries bringing a trace of new snow. Light southwest winds, strong at ridgetop. Alpine high around -3 C.

Monday: Mix of sun and cloud. Light southwest winds, strong at ridgetop. Alpine high around 0 C.

Avalanche Summary

Reports of avalanche activity over the past couple weeks have been steady, with each substantial snowfall accompanied by storm slab activity. On Friday, a widespread natural storm slab cycle was observed size 1.5-2.5 on the north end of the Lizard range, while only very thin 5-10 cm slabs were observed to have run during the storm at the south end of the range.

Looking forward, solar triggering of new snow can be expected amid sun exposure and warming temperatures, especially on steep south facing slopes. Rolly balls are a good indicator of impending solar induced avalanche activity.

Snowpack Summary

The recent storm snow is deep, soft and settling in the mild temperatures. Slight wind affect may be observed in exposed alpine features.

Several crust layers exist in the mid snowpack as a result of previous warming and rain events. These have not been identified as bed surfaces or failure planes in recent avalanche activity.

The bottom 10-20 cm of the snowpack consists of faceted snow and decomposing crusts. Although inherently weak, this basal layer has not been an active avalanche problem in our region for several weeks.

Terrain and Travel

  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Give the new snow time to settle and stabilize before pushing into bigger terrain.
  • Brief periods of sun could quickly initiate natural avalanche activity.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.