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Avalanche Forecast

Archived

Jan 18th, 2020–Jan 19th, 2020

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

Regions

Lizard-Flathead.

Give the storm snow a few days to settle and stabilize before pushing into bigger terrain. Storm slabs may remain sensitive to human triggering, especially near ridge crest.

Confidence

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

Weather Forecast

After a very stormy period the outlook is rather dry as temperatures begin to warm though the weekend.

SATURDAY NIGHT: Freezing level at valley bottom, moderate to strong west/southwest wind, trace of snow possible.

SUNDAY: Broken cloud cover, freezing level at valley bottom, moderate to strong south/southwest wind, 1 to 5 cm of snow possible.

MONDAY: A few clouds, freezing level rising dramatically, perhaps as high as 2000 m, light southwest wind at lower elevations, strong southwest wind at ridgetop, no significant precipitation

TUESDAY: Overcast, freezing level lowering to about 1000 m, light southwest wind, 1 to 5 cm of snow possible.

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. Roller balls and pin wheeling are good indicators of impending solar induced avalanche activity.

Snowpack Summary

The region has received about 65 cm of snow in the last three days and almost 120 cm of snow in the last week. 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.